For all of humanity’s impressive innovations, sometimes, Mother
Nature really does know best. And as such, we’ve learned everything we
can from her, including this latest graphene solar cell breakthrough
inspired by none other than moth eyes. According to new reports,
researchers from the United Kingdom’s University of Surrey carefully
examined these insects’ eyes in order to create graphene sheets that
they say are “the most light-absorbent material ever created.” Best of
all, the graphene based cells won’t have to be outside in order to
harvest the sun’s energy — rather, it’ll be able to absorb indirect
sunlight as well as ambient energy from everyday items found at home. Related: Solar gadgets will make charging less frequent, not eliminate it forever
“We realized that the moth’s eye works in a particular way that traps
electromagnetic waves very efficiently,” Professor Ravi Silva, head of
the Advanced Technology Institute at the University of Surrey, told Newsweek.
“As a result of our studies, we’ve been able to mimic the surface of a
moth’s eye and create an amazingly thin, efficient, light-absorbent
material made of graphene.”
Speaking with Electronics Weekly,
Silva added, “Moths’ eyes have microscopic patterning that allows them
to see in the dimmest conditions. These work by channelling light
towards the middle of the eye, with the added benefit of eliminating
reflections, which would otherwise alert predators of their location. We
have used the same technique to make an amasingly thin, efficient,
light-absorbent material by patterning graphene in a similar fashion.”
The incredibly thin sheets of graphene are actually just one-atom
thick and are comprised of carbon atoms arranged in a honeycomb lattice.
But don’t let the delicate arrangement and rubber-like flexibility fool
you — the material is 200 times stronger than steel and is also more
conductive than copper. The hope is that graphene and these moth
eye-inspired sheets will be able to unlock new possibilities within the
Internet of Things, or power a host of different devices. As Newsweek
notes, everything from flexible smartphones to artificial retinas could
benefit from the new material.
“For many years people have been looking for graphene applications
that will make it into mainstream use,” said Silva. “We are finally now
getting to the point where these applications are going to happen. We
think that with this work that is coming out, we can see an application
very close because we’ve done something that was previously thought
impossible: optimizing its incredible optical properties.”
GE has a crazy new plan to harvest CO2 from the atmosphere and use it to store solar energy
http://www.digitaltrends.com/
By Lulu Chang
7 hours ago
If there’s one “resource”
the planet has too much of, it’s carbon dioxide. One of the primary
components to the greenhouse gases thought to be responsible for climate
change, CO2 has long been the bane of our environment’s health. But
now, GE thinks
it may have found a way to repurpose this gas into a useful energy
source — harvesting CO2 to actually create new solar batteries. It’s the
ultimate 180 on carbon dioxide’s harmful effects, and while scientists
have long captured and stored CO2 emissions, it’s been unclear as to how
best to utilize these massive reserves. That is, until now.
Effectively, GE hopes to use the CO2 as an enormous battery whose chief purpose would be to store solar energy.
Although the sun is a great source of energy, it’s rather undependable —
after all, the sun has to be out in order for us to capture its rays.
“That’s the grand challenge,” Stephen Sanborn, senior engineer at GE
Global Research said in a statement. “We need to make renewable energy
available to the grid when it is needed.”
And that’ll happen with the help of the significant CO2 reserves
scientists have been storing for ages. The process would work in two stages
— first, solar energy would be captured and kept in a liquid of molten
salt. Then, extra energy from the power grid would cool CO2 into dry
ice. When power is needed, the salt would turn the dry ice CO2 into what
is known as a “supercritical” fluid, which is matter that does not have
specific liquid or gas phases. The supercritical fluid would in turn
flow into a CO2 turbine called a sunrotor, whereupon energy would be
disseminated as needed. Related: Alaska Airlines delays flight so passengers can see solar eclipse at 37,000 feet
It sounds plenty complicated, but according to Sanborn, it’ll
actually be incredibly cost-effective. “It is so cheap because you are
not making the energy, you are taking the energy from the sun or the
turbine exhaust, storing it and transferring it,” he says. The scientist
claims that sunrotors could operate with 68 percent efficiency, which
is significantly better than today’s most effective gas power plants,
which are only 61 percent effective. “The result is a high-efficiency,
high-performance renewable energy system that will reduce the use of
fossil fuels for power generation,” Sanborn says.
We’re still around five to ten years away from seeing these babies in
action, but don’t despair, environmental activists — there is a way to
fight greenhouse gasses. And in a way, it’s with greenhouse gases
themselves.
If there’s one “resource” the planet has too
much of, it’s carbon dioxide. One of the primary components to the
greenhouse gases thought to be responsible for climate change, CO2 has
long been the bane of our environment’s health. But now, GE thinks
it may have found a way to repurpose this gas into a useful energy
source — harvesting CO2 to actually create new solar batteries. It’s the
ultimate 180 on carbon dioxide’s harmful effects, and while scientists
have long captured and stored CO2 emissions, it’s been unclear as to how
best to utilize these massive reserves. That is, until now.
Effectively, GE hopes to use the CO2 as an enormous battery whose chief purpose would be to store solar energy.
Although the sun is a great source of energy, it’s rather undependable —
after all, the sun has to be out in order for us to capture its rays.
“That’s the grand challenge,” Stephen Sanborn, senior engineer at GE
Global Research said in a statement. “We need to make renewable energy
available to the grid when it is needed.”
And
that’ll happen with the help of the significant CO2 reserves scientists
have been storing for ages. The process would work in two stages
— first, solar energy would be captured and kept in a liquid of molten
salt. Then, extra energy from the power grid would cool CO2 into dry
ice. When power is needed, the salt would turn the dry ice CO2 into what
is known as a “supercritical” fluid, which is matter that does not have
specific liquid or gas phases. The supercritical fluid would in turn
flow into a CO2 turbine called a sunrotor, whereupon energy would be
disseminated as needed.
It
sounds plenty complicated, but according to Sanborn, it’ll actually be
incredibly cost-effective. “It is so cheap because you are not making
the energy, you are taking the energy from the sun or the turbine
exhaust, storing it and transferring it,” he says. The scientist claims
that sunrotors could operate with 68 percent efficiency, which is
significantly better than today’s most effective gas power plants, which
are only 61 percent effective. “The result is a high-efficiency,
high-performance renewable energy system that will reduce the use of
fossil fuels for power generation,” Sanborn says.
We’re
still around five to ten years away from seeing these babies in action,
but don’t despair, environmental activists — there is a way to fight
greenhouse gasses. And in a way, it’s with greenhouse gases themselves
These Solar Farms Help—Not Harm—Birds and Bees
By Taylor Hill | Takepart.com
6 hours ago
TakePart.com
These Solar Farms Help—Not Harm—Birds and Bees
In the United Kingdom, threatened animals need all of the habitat they can get—even if it’s under solar panels.
That’s the idea behind a joint project by
conservation group Royal Society for the Protection of Birds and
alternative energy firm Anesco that aims to create and restore natural
habitats at solar farm sites in the U.K.
By planting wildflower
meadows and restoring natural grasslands in the “unused” margins between
solar panel rows, the team hopes to attract insects, bees, and
butterflies to the sites and provide food and nesting spots for birds.
It
could be a boon to the region’s threatened bird species, which have
seen marked declines in the last 40 years, with tree sparrow populations
dropping 93 percent, turtledoves declining 89 percent, and skylarks
falling 51 percent.
The U.K. has lost nearly 44 million breeding birds since the late 1960s, according to the British Trust for Ornithology’s The State of the UK's Birds 2014 report. And populations for 60 percent of all native species have declined over the last 50 years, the RSPB reported.
One reason is the continued loss of habitat because of agriculture and urbanization.
Solar farms—while providing emission-free renewable power—aren’t
known for protecting wildlife. Placing thousands of photovoltaic panels
in rows along the ground will inevitably affect wildlife, says
Stephanie Dashiell at the Nature Conservancy. RELATED: U.K. Renewables Beat Coal Power for the First Time Ever
But the size of the project and the amount of land clearing and grading is a big factor.
“For
smaller facilities [less than 50 megawatts], such as the facilities
that Anesco develops, this type of mitigation is a promising way to
minimize impacts to wildlife from the development of solar facilities,”
said Dashiell, who is an energy associate project director for the
conservancy in California. “However, the success of such measures
greatly depends on the size of the facility, the ability to install
panels without grading and fencing the land, and the ecosystem in which
the facility is being sited.”
Dashiell has researched the impacts
of large-scale photovoltaic facilities in California that have displaced
thousands of desert tortoises in the Mojave Desert and kit foxes and
giant kangaroo rats in the San Joaquin Valley. She said there haven’t
been any good examples of habitat restoration in California sites,
noting that solar companies often make up for wildlife impacts by
restoring habitat elsewhere.
Anesco operates more than 500
megawatts’ worth of ground-mounted solar panels across the U.K. and
Wales, meaning thousands of acres of habitat could soon be restored. In
the first phase of the project, RSPB experts are visiting solar farm
sites to help identify habitat restoration measures that would benefit
animals deemed to be under the most serious threat.
“Over the next
few years, we will be working with Anesco to further improve the
habitats created at their solar farm sites across the U.K.,” Darren
Moorcroft, RSPB’s head of species and habitats conservation, said in a
statement. “It is an excellent opportunity to develop habitats for
nature in need of our help, showcasing how a renewable energy business
and wildlife conservation can be delivered in unison.”
The
recommendations by RSPB’s research team will also be implemented in
Anesco’s biodiversity management plans for future solar farm sites.
“It’s
promising to see this type of collaboration occur for smaller-scale PV
projects in wetter ecosystems that can easily be restored,” Dashiell
said, adding that she hopes monitoring is done to compare the wildlife
differences between sites that are restored and those that are not.
In California, which has half of the United States’ entire solar capacity,
the arid landscapes aren’t as easy to restore once they’ve been
disturbed and would require water—a scarce resource in the region.
“Due
to the difference in ecological conditions, and the difference in the
scale of the solar PV projects in the U.K. versus California, the Nature
Conservancy continues to support an approach to solar energy
development that directs projects to locations that have the least
impact to wildlife, thus avoiding the greatest impacts to wildlife,”
Dashiell said.
http://www.takepart.com/
This European Country Is Set to Get Half Its Electricity From Renewables in 2016
Scotland is showing how other nations can ramp up carbon-free energy
without compromising the power grid.
Wind turbines at Whitelee Wind Farm in East Kilbride,
Scotland. (Photo: Jeff J. Mitchell/Getty Images)
Jan 28, 2016
Emily J. Gertz is an associate editor for environment and wildlife at TakePart.
Scotland
is poised to generate more than 50 percent of its electricity from wind
power and other renewable sources this year, according to a government
report released Thursday.
The report—Energy in Scotland 2016—confirmed
that the country generated 49.7 percent of its energy from onshore wind
and other renewable sources in 2014 and saw a 16 percent increase in
energy from those sources between January and September of 2015.
October to December figures were not included in the report. But the
trend suggests that Scotland has surpassed the government’s official
target of generating half its annual electricity consumption, or about
19 thousand gigawatt hours, from carbon-free sources by 2015—averting
the emission of more than 12 million tons of greenhouse gas pollution in
the process. Scotland’s
renewable energy production has surged since 2013—when renewables made
up 44.4 percent of the electricity supply—in parallel with three years
of sustained economic growth. Four of Europe’s 10 biggest land-based
wind farms are located in Scotland.
That puts the United Kingdom’s northernmost country among the top producers of renewable energy in the European Union. Norway
is powering its grid almost exclusively with hydropower and is a net
exporter of wind energy, while Austria and Sweden each generate more
than 60 percent of demand from renewables. Germany,
the world’s fourth-largest economy, produces about a third of its
annual electricity supply from wind, solar, and other renewables. Denmark last week announced that wind power supplied 42 percent of its electricity in 2015—a world record for wind.
“What we’re finding from countries like Scotland, Denmark, and
Germany is that you can have a high percentage of renewable generation
on your grid, and it won’t affect reliability,” said Scott Clausen, a
policy and research associate at the American Council on Renewable
Energy.
Scotland has pledged to generate the equivalent of 100 percent of its
electric power demand with renewables by 2020, and 30 percent of
overall energy demand, including transportation and heat.
Lang Banks, director of World Wildlife
Fund-Scotland, noted that Scotland’s renewable energy growth was at risk
of stalling in 2016 because policy shifts in London have created
uncertainty among investors.
U.K. Prime Minister David Cameron last year effectively canceled
government subsidies meant to encourage solar and wind power
investments. “The impact has been an unnerving of the industry,” Banks
said
“That’s not the way to reassure investors who are trying to invest
millions of pounds in renewable energy development,” he added. “You add
to that a government that is hell-bent on imposing nuclear power on the
U.K., and it’s like they’re looking two ways at the same time. They say
renewables are too expensive but are willing to use taxpayer money to
support even more expensive nuclear power.”
Clausen sees lessons for the United States in Scotland’s renewable
power progress, as well as a cautionary tale of how shifting government
policies might slow it down. The U.S. now gets about 17 percent of its
electricity from renewables. Wind, solar, geothermal, and other sources
generate about 10 percent, while hydropower supplies the rest.
“I think Scotland, even though they have crafted their goal in an
interesting way, sent a signal that got their market going,” Clausen
said. “It demonstrates the effectiveness that policy can play in
encouraging renewable energy development.”
Noting that in 2015 Congress extended two important tax credits for
green energy development, Clausen said the U.S. is poised for “very big
gains in renewable generation.”
Renewable power is growing faster than either natural gas or coal in
the U.S., with the federal Energy Information Agency forecasting a 9.5
percent increase in green energy in 2016.
With 29 states, Washington, D.C., and Puerto Rico enacting mandates
for renewable energy, the costs for both solar and wind power have
dropped sharply in the past five years, Clausen said. These “renewable
portfolio standards” require utilities to increase the percentage of
wind, solar, and other carbon-free sources of power by anywhere from 10
to 30 percent. California has set a target of 33 percent by 2020, and it aims to get half its electricity from renewables by 2030.
Efforts in state legislatures to roll back
renewable energy requirements, spearheaded by conservative groups such
as the American Legislative Exchange Council, have been largely
unsuccessful, although Nevada recently slashed incentives for solar energy.
But a big expansion of solar and wind energy in the U.S. would likely
pay for itself when taking into account the jobs and tax revenue
created by new power projects, as well as the public health benefits of
reducing air pollution and cutting the carbon dioxide emissions driving
climate change, Clausen said.
“We now get to make the low-cost argument,” he said. “You want to save money? You should build renewables.” This post has been revised to reflect the following correction: Correction 1/29/16: An earlier version of this
article misstated how much of Scotland's annual electricity demand is
likely to have been met by renewables in 2015. That amount is 19
thousand gigawatt hours.
Government-Backed Solar Plant Producing Only a Fraction of the Energy Promised
A solar power plant in California, built with a $1.6 billion
taxpayer-guaranteed loan, is in danger of being shut down entirely
because it is producing only a fraction of the energy that the owners
promised. The plant only generated 45 percent of expected power in 2014
and only 68 percent in 2015, according to government data.
What's
more, it is producing electricity at a cost of $200 per megawatt hour --
six times the cost of electricity produced by a natural gas-fired
plant. The Daily Caller:
These
disappointing results at high prices could be the solar plant’s
undoing. California Energy Commission regulators hoped the plant would
help the state get 33 percent of its electricity from green sources, but
now the plant could be shut down for not meeting its production
promises.Ivanpah — which is owned by BrightSource Energy, NRG
Energy and Google — uses more than 170,000 large mirrors, or heliostats,
to reflect sunlight towards water boilers set atop 450-foot towers that
create steam to turn giant turbines and generate electricity.
The
plant was financed by $1.6 billion in loan guarantees from the
Department of Energy in 2011. When the solar plant opened in 2014, it
was hailed as a great achievement by Energy Secretary Ernest Moniz.
“This
project speaks for itself,” Moniz said when the project went online in
early 2014. “Just look at the 170,000 shining heliostat mirrors and the
three towers that would dwarf the Statue of Liberty.”
“Ivanpah is
the largest solar thermal energy facility in the world with 392 MW of
capacity — meaning it can produce enough renewable electricity to power
nearly 100,000 homes,” Moniz said.
Moniz’s optimism aside, the
project faced huge problems from the beginning. NRG Energy asked the
federal government for a $539 million federal grant to help pay off the
$1.6 billion loan it got from the Energy Department.
NRG Energy
said the plant had only produced about one-quarter of its expected
output in the months after it opened. The company needed an infusion of
cash to help keep the project afloat.
That was only the beginning
of the company’s problems. Environmentalists quickly attacked the
project for killing thousands of birds since it opened. Many birds were
incinerated by the intense heat being reflected off Ivanpah’s
heliostats.
he Associated Press cited statistics presented by environmentalists in 2014 that “about a thousand… to 28,000” birds are incinerated by Ivanpah’s heliostats every year.
“Forensic
Lab staff observed a falcon or falcon-like bird with a plume of smoke
arising from the tail as it passed through the flux field,” according to
a U.S. Fish and Wildlife Service report from 2014.
“Immediately
after encountering the flux, the bird exhibited a controlled loss of
stability and altitude but was able to cross the perimeter fence before
landing,” FWS reported.
There's also the problem that pilots have when flying over or near the plant:
Pilots have also reported seeing a “nearly blinding” glare emanating from Ivanpah
while flying over the solar plant. The Sandia National Laboratory
reported in 2014 Ivanpah was “sufficient to cause significant ocular
impact (potential for after-image) up to a distance of ~6 miles.”
The
reason the owners requested the government-guaranteed loan is because
no investor in their right mind would take a flyer on what amounts to
gigantic experiment. A two billion dollar plant and it's not supposed to
make a profit -- just to demonstrate that solar power can be generated
at industrial levels.
But this turkey of a power plant can't even
do that. I don't mind solar power at all and I can't wait until it
becomes economically viable. The photovoltaic systems are improving in
efficiency all the time and the price is coming down.
But once
again, government is deciding who wins and who loses and it gave the
Democratic Party contributors at Google a taxpayer-guaranteed loan that,
at present, looks like is going to turn around and bite us in our
sustainable buttocks.
When it's time to construct a solar
mega-plant, investors will be beating down the doors looking to get in
on it. That's not happening now, nor is it likely to happen anytime soon
http://www.gizmag.com/
Invelox wind turbine claims 600% advantage in energy output
SheerWind's Invelox wind power generation unit is said to increase energy output by 600 percent.
SheerWind, a wind power company from Minnesota, USA,
has announced the results of tests it has carried out with its new
Invelox wind power generation technology. The company says that during
tests its turbine could generate six times more energy than the amount
produced by traditional turbines mounted on towers. Besides, the costs
of producing wind energy with Invelox are lower, delivering electricity
with prices that can compete with natural gas and hydropower.
Invelox takes a novel approach to wind power
generation as it doesn’t rely on high wind speeds. Instead, it captures
wind at any speed, even a breeze, from a portal located above ground.
The wind captured is then funneled through a duct where it will pick up
speed. The resulting kinetic energy will drive the generator on the
ground level. By bringing the airflow from the top of the tower, it’s
possible to generate more power with smaller turbine blades, SheerWind
says.
As to the sixfold output claim, as with many
new technologies promising a performance breakthrough, it needs to be
viewed with caution. SheerWind makes the claim based on its own
comparative tests, the precise methodology of which is not entirely
clear.
"We used the same turbine-generator (with a
given load bank) and mounted it on a tower as is the case for
traditional wind mills," SheerWind told Gizmag. "We measured wind speed
and power output. Then we placed the same turbine-generator system
(subjected to the same load), again we measured free stream wind speed,
wind speed inside the INVELOX, and power. Then we used the power-speed
relationship over 5 to 15 days (depending on the test), and calculated
energy in kWh. Six hundred percent more energy was for one of the days.
[...] The improvements in energy production ranged from 81 percent to
660 percent, with an average of about 314 percent more energy."
All else being equal, it would seem to be the latter category that is the most useful indicator.
Besides power performance and the fact it can
operate at wind speeds as low as 1 mph, SheerWind says Invelox costs
less than US$750 per kilowatt to install. It is also claimed that
operating costs are significantly reduced compared to traditional
turbine technology. Due to its reduced size, the system is supposedly
safer for birds and other wildlife, concerns that also informed the
designers of the Ewicon bladeless turbine. Finally, the system also makes it possible for multiple towers to network, that is, to get power from the same generator.
Utility-scale availability of Invelox is slated for 2014.
Solar Wind Energy's Downdraft Tower generates
its own wind
That is directed down the hollow tower and through turbines
placed around its base.
When we think of wind power, we generally think of
huge wind turbines sitting high atop towers where they can take
advantage of the higher wind speeds. But Maryland-based Solar Wind
Energy, Inc. is looking to turn wind power on its head with the Solar
Wind Downdraft Tower, which places turbines at the base of a tower and
generates its own wind to turn them.
Described by the company as the first hybrid
solar-wind renewable energy technology in the renewable energy market,
the tower at the center of the system generates a downdraft that drives
the wind turbines positioned around its base. This is done by using a
series of pumps to carry water to the top of a tower standing up to
2,250 ft (685 m) tall, where it is cast across the opening as a fine
mist. The mist then evaporates and is absorbed by hot, dry air, thereby
cooling the air and making it denser and heavier than the warmer air
outside the tower.
This water-cooled air then falls through the
hollow tower at speeds up to and in excess of 50 mph (80 km/h). When it
reaches the bottom of the tower, the air is directed into wind tunnels
that surround the base, turning wind turbines that are contained within
the tunnels. Although the system requires large amounts of water, the
bulk of the water emitted at the top of the tower is captured at the
bottom and recirculated through the system, being pumped back up to the
top with some of the power generated by the wind turbines.
In this way, the company claims the system
can generate electricity 24 hours a day, 365 days a year, when located
in a hot, dry area – although electricity generation would be reduced in
winter. Depending on the tower's geographical location, electricity
generation could also be supplemented through the use of vertical "wind
vanes" that would capture the prevailing wind and channel it into the
tower.
Solar Wind Energy says it has developed
proprietary software capable of determining a tower's electricity
generation capabilities based on the climate in geographic regions
around the globe. Using the software, the company says it can predict
the daily energy outputs of a tower based on its location and size.
Based on the most recent design
specifications, the company says a tower designed for a site near San
Luis, Arizona, would have a peak production capacity on an hourly basis
of up to 1,250 MWh on sunny days. However, when taking into account the
lower generation capabilities during the winter months, the average
hourly output per day comes out to approximately 435 MWh.
The company points out that once built (using
conventional materials, equipment and techniques), its towers are
capable of operating throughout the year independent of wind speeds with
virtually no carbon footprint, fuel consumption or waste generation.
Earlier this year, Solar Wind Energy gained
the necessary local entitlements to pursue development of its first
tower near San Luis, Arizona. The project got a leg up earlier this week
when it announced a financing agreement with JDF Capital Inc., which
will provide up to US$1,585,000 to the company. Solar Wind Energy says
it is also exploring potential sites in Mexico, which along with the
Middle East, Chile and India, would be an ideal location for the
technology in terms of climate.
The video below explains how the Downdraft Tower works.
Source: Solar Wind Energy Inc.
http://www.csmonitor.com/
Recycling sunlight: a solar cell revolution?
Scientists have found a way to recycle sunlight and boost the amount of energy captured from the sun's rays.
Criss Hohmann/Courtesy of St John's College, University of Cambridge
View Caption
The world of solar cells could be on the cusp of a revolution, as
researchers seek to boost efficiency by harnessing the power to recycle
light.
A new study, published Thursday in the journal Science, considers the properties of hybrid lead halide perovskites,
a group of materials already making waves in solar cell technology, and
demonstrates their ability to absorb energy from the sun, create
electric charge, and then churn out some light energy of their own.
Moreover,
the researchers demonstrated that such these cells can be produced
cheaply, with easily synthesized materials, making the proposition much
more commercially viable.
“We already knew that these materials were good at
absorbing light and producing charge-carriers,” says co-author Felix
Deschler of Cambridge University, UK, in a telephone interview with The
Christian Science Monitor. “But now we have demonstrated that they can
also recombine to produce photons again.”
Solar cells work by absorbing the light
energy – photons – from the sun, converting this energy into electrical
charge, and then conveying that charge to electrodes, which take the
energy out into the power-hungry world.
Hybrid lead halide
perovskites were already known to do this task efficiently, but what Dr.
Deschler and his team have demonstrated is an ability to do more: the
perovskites are actually able to emit light themselves after creating
charge – and then reabsorb that light energy.
The result is a
solar cell that acts like a concentrator, able to produce more energy –
to boost the voltage obtained from a given amount of light – than would a
cell made of materials without this recycling ability.
“Why this
is now a big thing is because the current record of photo cell
efficiency rests at 20-21 percent, whereas the absolute limit is 33
percent,” says Deschler. “Our results suggest a route to achieve that
limit.”
The efficiency of a solar cell refers to the percentage of energy, given a certain amount of light, it can harness for use.
According to a widely accepted 1961 paper
by William Shockley and Hans Queisser, theoretical thermodynamics cap
solar efficiency at 33 percent. It is simply impossible to do better,
they argued.
Yet the beauty of this most recent work is not only
the hope of climbing closer to that theoretical ceiling, but the
materials used to do so.
“You wouldn’t expect photon recycling in
our materials because their fabrication is so much simpler than others,”
explains Deschler. “Our materials are very cheap to make, very
versatile.”
The reason for surprise, even skepticism, is founded
in the way these materials are made – via solution. This affords little
control over the way in which the structure forms.
If you have
impurities in a crystalline structure, you are left with a “defect
site”, which makes the material “messier,” in terms of light absorption.
Without such impurities, you have what is known as a “sharp absorption
onset,” allowing efficient and clear absorption of the light.
“So,
while they are very efficient,” says Deschler, “we’re still trying to
understand why and how they’re better than other materials.”
The
researchers expect considerable interest from solar cell producers
looking for a cheaper, more efficient way to harness the power of the
sun.
http://www.computerworld.com/
New solar towers, cubes offer 20X more power, researchers say
Two small-scale versions of
three-dimensional photovoltaic arrays were among those tested by on an
MIT rooftop to measure their actual electrical output throughout the
day.
Credit:
Allegra Boverman
Researchers at MIT have discovered a method of optimizing solar energy collection by arranging photovoltaic (PV) panels on a tower or in a cube shape.
The new forms of solar energy collection offer anywhere from double to
20 times as much output compared with today's common flat-panels using
the same area.
The technology would be most advantageous in northern climates --
further away from the equator -- where the less intensive solar exposure
can be optimized.
MIT's research, the findings for which are based on both computer modeling and outdoor testing of real modules, were published in the journal Energy and Environmental Science.
"I think this concept could become an important part of the future of
photovoltaics," Jeffrey Grossman, an associate professor of Power
Engineering at MIT and lead author of the research paper, said in a
statement.
The cost of the 3D solar towers or cubes exceeds that of ordinary flat
panels. But the expense is partially balanced by a much higher energy
output for a given footprint, as well as much more uniform power output
over the course of a day and over the seasons when panels face less
light and more cloud cover, the researchers stated.
Allegra Boverman MIT's solar towers.
Because solar cells have become less expensive than accompanying support
structures, wiring and installation, the time is right to move forward
with the innovation, the researchers said.
Solar power generation is leading the cost decline in solar systems.
Solar photovoltaic (PV) module costs have fallen 75% since the end of
2009 and the cost of electricity from utility-scale solar PV has fallen
50% since 2010, according to a report from the International Renewable Energy Agency (IRENA).
In a separate report
issued by Deutsche Bank last year, the cost to generate power through
solar means was predicted to drop by 40% over the next three to four
years. Deutsche Bank has also reported that the cost of rooftop solar
power is expected to beat coal and oil-fired plant energy costs in just
two years.
MIT's 3D solar structures' vertical surfaces can collect much more
sunlight during mornings, evenings and winters, when the sun is closer
to the horizon, according to co-author Marco Bernardi, a graduate
student in MIT's Department of Materials Science and Engineering (DMSE).
The 3D solar structure improvements simply make power output more
predictable and uniform, which could make integration with the power
grid easier than with conventional systems, the authors said.
"Even 10 years ago, this idea wouldn't have been economically justified
because the modules cost so much," Grossman said. "The cost for silicon
cells is a fraction of the total cost, a trend that will continue
downward in the near future."
Can Dean Kamen make the Stirling engine part of our energy future?
As New Hampshire contemplates its energy future, maybe we should include a bit of energy past that has never quite succeeded.
That’s the idea behind an intriguing
proposal from Dean Kamen’s research firm, DEKA. It wants to power a
state-owned building with a Stirling engine, a design that has shown
great promise for more than a century but hasn’t been truly
commercialized.
If the proposal is accepted by lawmakers
and if it works, it might save the state a little money on electricity,
might help DEKA turn one of Kamen’s dreams into a real business, and
would go a long way toward burnishing New Hampshire’s credentials as a
place where interesting technology comes to life.
So how likely is it? It’s hard to say,
but since this is Granite Geek, we’ll contemplate the tech stuff before
we get to the lawmaker stuff.
A Stirling engine (named after Robert
Stirling, a Scottish minister who developed one of the prototypes 200
years ago) has two major differences from my car engine.
One is that it uses an external heat
source to create energy and move parts around rather than an internal
heat source created by a spark plug igniting a mix of gasoline and air.
The other is that it is a closed-cycle engine; the internal fluids and
gases stay inside, unlike the exhaust that is released by my car.
In theory, these make the Stirling
engine more efficient, less polluting and more flexible than
internal-combustion engines, since it can use any external heat source.
In reality, issues of heat transfer through materials, sealing fluids
and other engineering problems have kept it from working efficiently on a
useful scale except in a few limited applications.
Enter Kamen, famous for the Segway but
more importantly an inventor of medical devices, a major force in the
rebirth of Manchester’s millyard tech scene and the creator of the FIRST
Robotics Competition. Kamen has long been fascinated with Stirling
engines, creating them in various sizes and configurations to power
various devices. But they haven’t really worked out – until now, maybe.
“We have done a lot of work at DEKA to
make (the Stirling engine) a more viable, a more practical technology,”
said Jim Scott, a DEKA representative.
DEKA has built refrigerator-sized
Stirling engines, powered by natural gas, that it says can generate 10
kilowatts of electricity and 40 kilowatts of heat. (I didn’t even know
you could measure heat in kilowatts; energy units sure are confusing.)
A couple of these units have been helping
power DEKA’s millyard building at 100 Commercial St. since late 2013 as
part of a test, and the company has several more operating in other
buildings hither and yon. It says they are living up to their promise,
and now DEKA would like to put one in a state building in Concord to
give the project a much higher profile.
A law (Senate Bill 489) has been proposed
to allow the project to go ahead, at no cost to the state. “It’s like
hooking up a generator and a water heater, that’s all,” Scott said.
Scott showed up at a legislative hearing
last Tuesday to answer questions on the proposal, but as it turns out,
there weren’t any questions for him. Lawmakers on the Science,
Technology and Energy Committee mostly talked about whether the issue
should be handled by the Legislature or handled through the Executive
Council, which is usually the body that accepts gifts to the state
government. They’ll discuss the issue again Thursday.
Sen. Jeb Bradley of Wolfeboro, the prime
sponsor, argued that the bill had the potential to give a boost to a
well-known state company, above and beyond its energy benefits. “We have
nothing to lose by doing this,” he said.
Committee member Herbert Vadney, a state
representative from Meredith who is a mechanical engineer, said his
familiarity with Stirling engines made him less than optimistic. “I see
no reason for the state to get involved in an R&D project at this
point – this is a gift to somebody,” he said.
David Murotake of Nashua, another
committee representative with tech background, was more
supportive. “It might build New Hampshire as a skill center for Sterling
engines,” he mused.
Meredith Hatfield, director of the Office
of Energy and Planning, said she was interested in the project as the
state ponders ways to deal with the fast-changing energy universe, where
utilities and power production is being reinvented on the fly.
“We need to be looking at different ways
of doing things,” she told the committee. A natural gas-fired
electricity-producing engine might not be as cutting edge as fuel cells
or solar panels, but adding small-scale power plants could give the
state more flexibility to cope with changes coming down the pike.
Plus, she noted, DEKA’s offer is a
full-scale pilot project for free. “We don’t have the budget to test it
out ourselves,” she said dryly.
(David Brooks can be reached at 369-3313, dbrooks@cmonitor.com or on Twitter @GraniteGeek.)
Russian air-launched winged orbital launch vehicle. The MAKS spaceplane
was the ultimate development of the air-launched spaceplane studies
conducted by NPO Molniya. The draft project for MAKS was completed in
1988 and consisted of 220 volumes, generated by NPO Molniya and 70
sub-contractors and government institutes. Development of MAKS was
authorised but cancelled in 1991. At the time of the cancellation,
mock-ups of both the MAKS orbiter and the external tank had been
finished. A 9,000 kgf experimental engine with 19 injectors was tested.
There were 50 test burns proving the separate modes and a smooth switch
between them. Since it was expected that MAKS could reduce the cost of
transport to earth orbit by a factor of ten, it was hoped in the 1990's
that development funding could be found. However this did not
materialise. MAKS was to have flown by 1998.
In 1976-1981 it was realised that launch of Spiral from a large
transport was feasible and of much lower development cost than the
previous approach using a supersonic launcher. Further it was realised
that a smaller orbital spaceplane would have many advantages compared to
the Buran space shuttle then in development. These included quicker
turnaround, more launch flexibility, and a wider range of achievable
orbits. The MAKS approach would allow launch of payloads into orbit;
working on satellites in orbit; and return of payloads to earth.
The MAKS design was superior to the earlier System 49 and Bizan designs
in several ways. The single-stage-to-orbit allowed the propellant tank
to be dropped safely into the antipodal ocean after launch, whereas the
'49' with separate rocket stages was constrained to launch points where a
first stage impact point 2000 km away was available. MAKS was more
reusable than Bizan since all of the engines would be recovered; only
the propellant tank was expendable. Finally., the availability of the
An-225 transport meant that a larger spacecraft could be designed.
The MAKS draft project used 3 x NK-45 Kuznetsov Lox/LH2 engines with 90
tonnes thrust each. This design had 250 tonne flight mass and a 7 tonne
net payload. Switch during development to the RD-701 tripropellant
engine improved the design. The higher-density propellants allowed a
smaller, lighter tank with an increase of the net payload to 8.4 tonnes.
Studies indicated that the optimum launch angle for MAKS was 45 degrees.
But to attain this with the An-225 transport a rocket engine would have
to be installed in the launch aircraft, which was undesirable from a
development standpoint and would also cut into the gross mass of the
MAKS vehicle. Finally a tank geometry, and engine/orbiter arrangement
was found that allowed the proper release conditions without requiring a
supplemental rocket engine in the transport.
The mix and arrangement of propellant tanks changed during development.
At first the oxidiser cell was placed at the front of the drop tank.
This was aerodynamically stable but resulted in excessive static loads.
Other locations posed insurmountable problems with the vehicle's
aerodynamic moment and separation from the carrier aircraft. Putting the
entire vehicle under the launch aircraft was considered, but this would
require redesign of the An-225. There were finally two choices: either
an unstable design, with the wings of the MAKS orbiter pitching the
vehicle up 45 degrees immediately at release; or three cylindrical tanks
arranged under the orbiter in a 'Siamese' arrangement. This last
solution was favoured by TsAGI Central Hydrodynamics Institute, but the
design bureau felt the weight penalty was too great.
The final layout had a complex form, with the thrust vector running
below the axis of the drop tank. This 'tug' arrangement basically turned
the drop tank into a barge with the orbiter pushing it into orbit. This
solution had the lowest mass, was the best for a variety of abort
situations, produced the best separation of the orbiter from the tank,
and allowed a clear field for use of the crew ejection seats in an
emergency.
The MAKS expendable-tank solution also produced a higher payload
fraction to orbit than competing integrated vehicle approaches (such as
I-HOTOL / MAKS-M or VKS-O). This provided a better margin in case of
vehicle weight growth. The drop-tank / lightweight orbiter approach also
reduced the amount of orbital manoeuvring propellant required, which
allowed heavier payloads to be placed into high altitude orbits than
pure single-stage-to-orbit designs.
The MAKS air-launched manned space system weighed 620 tonnes on takeoff and consisted of three elements:
An-225 Mriya carrier aircraft, the largest in the world,
originally developed to transport the Buran orbiter. The Mriya would
take the 275 tonne MAKS piggy-back a launch position appropriate for the
target orbit. The optimum release manoeuvre involved a dive from 7.8
km altitude to 6.8 km over a 7 km distance. The transport would then
pull up, releasing MAKS at 8.6 km altitude and 900 km/hr. After release
the transport nosed over, reaching a peak altitude of 8.8 km, levelling
out at 8.2 km 20 km from the start of the manoeuvre.
External tank. This carried liquid oxygen, kerosene,
and liquid hydrogen propellants. It was 6.38 m in diameter and 32.1 m
long, with a total mass of 248,000 kg and an empty mass of 11,000 kg.
MAKS Orbiter. This spaceplane, designed for 100
reuses, used on-board systems based on those already developed for
Energia and Buran. The orbiter had an empty mass of 18,400 kg, with a
wingspan of 12.5 m and a length of 19.3 m. The aerodynamic shape was
refined considerably from that of Spiral / 49 / Bizan to accommodate the
main engine installation in the tail. An unmanned version could deliver
9.5 tonnes to a 200 km, 51 degree orbit in a payload bay 2.8 m diameter
x 8.7 m long. The manned version took two crew and a payload of 8.3
tonnes in a bay 2.8 m diameter x 6.8 m long to the same orbit. In the
orbiter's tail were two RD-701 tripropellant engines. These were
designed for 15 re-uses and used dense kerosene and liquid oxygen for
initial operations, then switched modes to a reduced thrust and higher
specific impulse using low density liquid hydrogen and liquid oxygen.
This reduced the size of the huge hydrogen tank otherwise required. The
RD-701 engine assembly in the MAKS had a total mass of 3990 kg and
delivered a total thrust of 400,000 kgf at separation from the An-225.
LEO Payload: 6,600 kg (14,500 lb) to a 400 km orbit at 90.00 degrees. Payload: 9,500 kg (20,900 lb) to a 200 km 51 deg orbit in unmanned configuration in 1985 dollars. Flyaway Unit Cost $: 113.000 million. Stage Data - MAKS
Stage 0. 1 x An-225. Gross Mass: 600,000 kg (1,320,000 lb). Empty Mass: 216,000 kg (476,000 lb). Thrust (vac): 1,387.072 kN (311,826 lbf). Isp: 9,000 sec. Burn time: 3,375 sec. Isp(sl): 8,000 sec. Diameter: 18.07 m (59.28 ft). Span: 88.40 m (290.00 ft). Length: 84.00 m (275.00 ft). Propellants: Air/Kerosene. No Engines: 6. Engine: D-18T. Status: Out of Production. Comments:
Antonov cargo aircraft swept wing. Release conditions: Piggy-back,
275,000 kg, 38.0 m length x 24.0 m wingspan, 900 kph at 9,500 m
altitude. Effective velocity gain compared to vertical launch 270 m/s.
Stage 1. 1 x MAKS Orbiter. Gross Mass: 18,400 kg (40,500 lb). Empty Mass: 18,400 kg (40,500 lb). Thrust (vac): 3,618.771 kN (813,532 lbf). Isp: 437 sec. Burn time: 440 sec. Isp(sl): 396 sec. Diameter: 3.00 m (9.80 ft). Span: 12.50 m (41.00 ft). Length: 19.30 m (63.30 ft). Propellants: Lox/Kerosene/LH2. No Engines: 1. Engine: RD-701. Status: Development 1988.
Stage 2. 1 x MAKS Tank. Gross Mass: 248,000 kg (546,000 lb). Empty Mass: 11,000 kg (24,000 lb). Thrust (vac): 0.0000 N ( lbf). Isp: 437 sec. Burn time: 440 sec. Isp(sl): 396 sec. Diameter: 6.38 m (20.93 ft). Span: 6.38 m (20.93 ft). Length: 32.10 m (105.30 ft). Propellants: Lox/Kerosene/LH2. No Engines: 1. Engine: None. Status: Development 1988.
Status: Cancelled 1988. Gross mass: 275,000 kg (606,000 lb). Payload: 6,600 kg (14,500 lb). Height: 39.00 m (127.00 ft). Diameter: 6.38 m (20.93 ft). Thrust: 3,900.00 kN (876,700 lbf). Apogee: 400 km (240 mi).
Glushko lox/lh2/kerosene tripropellant rocket engine for air-launched
MAKS spaceplane. 4003 kN. Development ended 1988. Isp=415 / 460s. First
flight 2001.
The RD-701 was developed for the 22 tonne MAKS spaceplane, which was to
have been launched at an altitude of 8 kilometres from the back of a
behemoth An-225 Mriya transport. It was planned for 15 re-uses and
featured both first and second stage engine characteristics in one
reusable package. The tripropellant engine used dense kerosene and
liquid oxygen for initial operations, then switched modes to a more
modest thrust and higher specific impulse using low density liquid
hydrogen and liquid oxygen. This reduced the huge hydrogen tank
otherwise required. The state pulled out of the venture in cutbacks
following perestroika but it was an extremely effective engine. A 9,000
kgf experimental engine with 19 injectors was tested. There were 50 test
burns proving the separate modes and a smooth switch between them.
Energomash states that if additional investment could be found use of
the engine would lead to a 10 x cut in payload launch costs and make the
development of a SSTO vehicle possible (VTOVL). Mass: 3990 kg assembly,
1840 kg each dry. Length: 5.4 m extension down, 3.8 m extension up.
Diameter: 2.4 m. Engine Cycle: closed staged combustion. Oxidizer: LOX.
Fuel: mode 1: hydrogen and kerosene. mode 2: hydrogen. Mixture Ratio:
(O/F. mass) mode 1: 5.27:1 kerosene and 13.2:1 hydrogen. mode 2: 6.1:1.
Flow Rate (each chamber, kg/s) mode 1: 388.4 LOX, 29.5 LH2, and 73.7
kerosene. mode 2: 148.5 LOX and 24.7 LH2. Thrust (each chamber, vac):
1960 kN mode 1 and 785 kN mode 2 (throttle 40-100%). Isp: mode 1: 415
sec and 330 sea level. mode 2: 460 sec. Chamber Pressure: mode 1: 290
atm. mode 2: 122 atm. Expansion Ratio: 170 extension down and 70
extension up. Developed 1986-on. Two identical engines with common
booster pump set. Chamber pressure 294 / 124 bar. Specific impulse 415 /
460 sec.
Application: MAKS spaceplane.
Characteristics Chambers: 2. Throttled thrust(vac): 1,588.000 kN (356,996 lbf). Thrust (sl): 1,406.100 kN (316,104 lbf). Thrust (sl): 143,384 kgf. Engine: 3,670 kg (8,090 lb). Chamber Pressure: 294.00 bar. Area Ratio: 133.8. Thrust to Weight Ratio: 111.22. Oxidizer to Fuel Ratio: 6. Status: Development ended 1988. Unfuelled mass: 3,670 kg (8,090 lb). Height: 5.70 m (18.70 ft). Diameter: 2.30 m (7.50 ft). Thrust: 4,003.00 kN (899,910 lbf). Specific impulse: 415 s. Specific impulse sea level: 330 s. Burn time: 440 s. First Launch: 1988-.
Tripropellant motors use high-density kerosene for the boost phase, then
low-density, high-performance liquid hydrogen for the later stages of
ascent. However the propellants are stored in separate tanks. The fuel
density indicated is the average for the MAKS design, which burned
17,850 kg LH2 and 18,698 Kerosene to reach orbit using 175,758 kg of
liquid oxygen oxidiser.
Liquid oxygen, as normally supplied, is of 99.5 percent purity and is
covered in the United States by Military Specification MIL-P-25508. High
purity liquid oxygen has a light blue colour and is transparent. It has
no characteristic odour. Liquid oxygen does not burn, but will support
combustion vigorously. The liquid is stable; however, mixtures of fuel
and liquid oxygen are shock-sensitive. Gaseous oxygen can form mixtures
with fuel vapours that can be exploded by static electricity, electric
spark, or flame. Liquid oxygen is obtained from air by fractional
distillation. The 1959 United. States production of high-purity oxygen
was estimated at nearly 2 million tonnes. The cost of liquid oxygen, at
that time, ex-works, was $ 0.04 per kg. By the 1980's NASA was paying $
0.08 per kg.
Rocket propellant RP-1, or its foreign equivalents,
is a straight-run kerosene fraction, which is subjected to further
treatment, i.e., acid washing, sulphur dioxide extraction. Thus,
unsaturated substances which polymerise in storage are removed, as are
sulphur-containing hydrocarbons. Fuel: Kerosene/LH2. Propellant Formulation: Lox/Kerosene/LH2. Optimum Oxidizer to Fuel Ratio: 4.8. Density: 0.50 g/cc. Fuel Density: 0.133 g/cc. Fuel Freezing Point: -259 deg C. Fuel Boiling Point: -253 deg C.
Tripropellant. Figures indicated are average for RD-701 engine. Specific impulse: 440 s.
Russia Shows Off New Manned Spacecraft To Replace Aging Soyuz
Russia’s RSC Energia launched a creative competition to finally
give a name to this ‘new generation new transport spacecraft.”
(Photo : Russian Federal Space Agency)
A
new generation spacecraft is being developed by Russian scientists to
perform similar functions of and replace an aging space probe.
The manned space transport has not yet been given a name, but has
already been displayed to the public for the first time Monday.
The Russian Space Agency presented photos of this spacecraft at Moscow's MAKS-2015. Along with this new Russian development displayed at the 12th
International Aviation and Space Station at Hall D1 were the Roskosmos
and ACCD built by leading Russian enterprises and 19 other space
industry exhibits.
This "new generation new transportation spacecraft" is being
developed by RSC Energia which has been involved in the rocket-space
industry since 1946. The manned spacecraft is designed to replace
Soyuz-TMA which was issued by the Russian Federal Space Agency and
features changes according the NASA's requirements as well as service
the International Space Station (ISS). Some of the features of the aging
spacecraft include more latitude in the crew's height and weight,
better parachute systems and a glass cockpit.
The new spacecraft which has been under development for about a
decade now will send astronauts to further explore the moon and Mars.
The development is a part of the Prospective Protected Transport System
9PPTS) aimed at replacing not only the Soyuz-TMA but also the Progress
Cargo ships. The long-awaited testing of the capsules will take place
over the next few months. In 2021, this new spacecraft will be test
launched in an unmanned orbital flight atop the new Angara rocket from
the new Russian spaceport Vostochny Cosmodrome, also currently being
constructed.
While space enthusiasts await the new Russian spacecraft's first unmanned test flight, its developer RSC Energia announced the launching of a competition for a name.
The creativity competition will run from Aug. 30 through Nov. 2 this year, with results to be announced Jan. 15 next year.
Deliberations of a judging panel and votes of the public will decide
on the best suggested name and the winner of the competition. If naming
this new spacecraft isn't a prestige enough, the winner will also have
the chance to watch the Soyuz spacecraft take off in the launch of a
manned spaceflight in Baikonur spring of 2016.
A Space Shuttle rocketing into space, just after booster separation.
A spaceplane is an aerospace vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space.[1]
It combines features of an aircraft and a spacecraft, which can be
thought of as an aircraft that can endure and maneuver in the vacuum of
space or likewise a spacecraft that can fly like an airplane. Typically,
it takes the form of a spacecraft equipped with wings, although lifting bodies have been designed and tested as well. The propulsion to reach space may be purely rocket based or may use the assistance of airbreathing jet engines. The spaceflight is then followed by an unpowered glide return to landing.
Only five spaceplanes have successfully flown to date, having reentered Earth's atmosphere, returned to Earth, and safely landed — the North American X-15, Space Shuttle, Buran, SpaceShipOne, and Boeing X-37. All five are considered rocket gliders. As of 2015, only these aircraft and rockets have succeeded in reaching space. Two of these five (X-15 and SpaceShipOne) are rocket-powered aircraft, having been carried up to an altitude of several tens of thousands of feet by an atmospheric mother ship before being released, and then flying beyond the boundaries of the earth's atmosphere under their own power. Three (Space Shuttle, Buran, and X-37) are vertical takeoff horizontal landing (VTHL) vehicles relying upon rocket lift for the ascent phase in reaching space and atmospheric lift for reentry, descent and landing.
The three VTHL spaceplanes flew much further than the aircraft launched
ones, not merely leaving the earth's atmosphere but also entering orbit
around it, which requires at least 50 times more energy on the way up
and heavy heat shielding for the trip back.[2] Also, of the 5 vehicles, three have been piloted by astronauts, with the Buran and X-37 flying unmanned missions.
All aircraft utilize aerodynamic surfaces in order to generate lift. For spaceplanes a variety of wing shapes can be used. Delta wings are common, but straight wings, lifting bodies and even rotorcraft have been proposed. Typically the force of lift generated by these surfaces is many times that of the drag that they induce.[citation needed]
Because suborbital spaceplanes are designed for trajectories that do not reach orbital speed, they do not need the kinds of thermal protection orbital spacecraft required during the hypersonic phase of atmospheric reentry. The Space Shuttle thermal protection system,
for example, protects the orbiter from surface temperatures that could
otherwise reach as high as 1,650 °C (3,000 °F), well above the melting
point of steel.[3]
A spaceplane operates as an aircraft in Earth's atmosphere. Aircraft may land on firm runways, helicopter landing pads, or even water (amphibious aircraft), snow or ice. To land, the airspeed and the rate of descent
are reduced such that the aircraft descends at a slow enough rate to
allow for a gentle touch down. Landing is accomplished by slowing down
and descending. This speed reduction is accomplished by reducing thrust
and/or inducing a greater amount of drag using flaps, landing gear or speed brakes. Splashdown is an easier technical feat to accomplish, requiring only the deployment of a parachute (or parachutes), rather than successfully aviating the atmosphere.[4]
Project Gemini's original concept design was as a spaceplane, with
paraglider and wheels (or skis) attached. However, this concept was
abandoned in favor of parachute splashdowns, because of expensive
technical failures during testing and development. Whereas Project
Gemini's splashdown parachutes took only 5 months to develop in 1963,
Gemini's spaceplane concept failed to materialize even after nearly 3
years of continued development.
Propulsion
Buran orbiter rear showing rocket engine nozzles, for maneuvering in low Earth orbit and thin air
Rocket engines
All spaceplanes to date have used rocket engines with chemical fuels. As the orbital insertion burn has to be done in space, orbital spaceplanes require rocket engines for at least that portion of the flight.
A difference between rocket based and air-breathing aerospace plane
launch systems is that aerospace plane designs typically include minimal
oxidizer storage for propulsion. Air-breathing aerospace plane designs include engine inlets so they can use atmospheric oxygen for combustion. Since the mass of the oxidizer is, at takeoff, the single largest mass of most rocket designs (the Space Shuttle's liquid oxygen tank weighs 629,340 kg, more than one of its solid rocket boosters[5]),
this provides a huge potential weight savings benefit. However, air
breathing engines are usually very much heavier than rocket engines and
the empty weight of the oxidiser tank, and since, unlike oxidiser, this
extra weight (which is not expended to add kinetic energy to the vessel,
as is propellant mass) must be carried into space it may offset the
overall system performance.[citation needed]
Types of air breathing engines proposed for spaceplanes include scramjet, liquid air cycle engines, precooled jet engines, pulse detonation engine and ramjets. Some engine designs combine several types of engines features into a combined cycle. For instance, the Rocket-based combined cycle
(RBCC) engine uses a rocket engine inside a ramscoop so that at low
speed, the rockets thrust is boosted by ejector augmented thrust. It
then transitions to ramjet propulsion at near-supersonic speeds, then to
supersonic combustion or scramjet propulsion, above Mach 6, then back
to pure rocket propulsion above Mach 10.[citation needed]
Harsh flight environment
The flight trajectory required of air-breathing aerospace vehicles to
reach orbit is to fly what is known as a 'depressed trajectory' which
places the aerospace plane in the high-altitude hypersonic flight regime
of the atmosphere. This environment induces high dynamic pressure, high
temperature, and high heat flow loads particularly upon the leading edge surfaces of the aerospace plane. These loads typically require special advanced materials, active cooling, or both, for the structures to survive the environment.
Rocket-powered spaceplanes also face a significant thermal
environment if they are burning for orbit, but this is nevertheless far
less severe than air-breathing spaceplanes.[citation needed]
Suborbital space planes designed to briefly reach space do not
require significant thermal protection, as they experience peak heating
for only a short time during re-entry. Intercontinental suborbital
trajectories require much higher speeds and thermal protection more
similar to orbital spacecraft reentry.[citation needed]
Center of mass issues
A wingless launch vehicle has lower aerodynamic forces affecting the vehicle, and attitude control
can be active perhaps with some fins to aid stability. For a winged
vehicle the centre of lift moves during the atmospheric flight as well
as the centre of mass; and the vehicle spends longer in the atmosphere
as well. Historically, the X-33 and HOTOL
spaceplanes were rear engined and had relatively heavy engines. This
puts a heavy mass at the rear of the aircraft with wings that had to
hold up the vehicle. As the wet mass reduces, the centre of mass tends
to move rearward behind the centre of lift, which tends to be around the
centre of the wings. This can cause severe instability that is usually
solved by extra fins which add weight and decrease performance.[citation needed]
All three of the orbital spaceplanes successfully flown to date utilize a VTHL (vertical takeoff, horizontal landing) design. They include the piloted United StatesSpace Shuttle and two unmanned spaceplanes: the late-1980s SovietBuran and the early-2010s Boeing X-37.
The early-1980s BOR-4 (subscale test vehicle for the Spiral spaceplane that was subsequently cancelled) was a spacecraft that did successfully reenter the atmosphere and fly like an aircraft. But it was not designed to sustain atmospheric flight. It was designed to stop flying, open a parachute and then splash in the ocean.
These vehicles have used wings to provide aerobraking to return from orbit and to provide lift, allowing them to land on a runway like conventional aircraft. These vehicles are still designed to ascend to orbit vertically under rocket power like conventional expendable launch vehicles. One drawback of spaceplanes is that they have a significantly smaller payload fraction
than a ballistic design with the same takeoff weight. This is in part
due to the weight of the wings — around 9-12% of the weight of the
atmospheric flight weight of the vehicle. This significantly reduces the
payload size, but the reusability is intended to offset this
disadvantage.
While all spaceplanes have used atmospheric lift for the reentry phase, none to date have succeeded in a design that relies on aerodynamic lift for the ascent phase in reaching space (excluding a mother ship first stage). Efforts such as the Silbervogel and X-30/X-33 have all failed to materialize into a vehicle capable of successfully reaching space. The Pegasus
winged booster has had many successful flights to deploy orbital
payloads, but since its aerodynamic vehicle component operates only as a
booster, and not operate in space as a spacecraft, it is not typically
considered to be a spaceplane.[citation needed]
On the other hand, OREX[7] is a test vehicle of HOPE-X and launched into 450 km LEO using H-II in 1994. OREX succeeded to reenter, but it was only hemispherical head of HOPE-X, that is, not plane-shaped.
The X-15's rocket engine used ammonia and liquid oxygen.
Other spaceplane designs are suborbital, requiring far less energy for propulsion, and can use the vehicle's wings to provide lift for the ascent to space in addition to the rocket. As of 2010, the only such craft to have successfully flown to and from space, back to earth, have been the North American X-15 and SpaceShipOne.
Neither of these craft was capable of entering orbit. The X-15 and
SpaceShipOne both began their independent flight only after being lifted
to high altitude by a carrier aircraft.
SpaceShipOne Space plane
Scaled Composites and Virgin Galactic unveiled on December 7, 2009, the SpaceShipTwo space plane, the VSS Enterprise, and its WhiteKnightTwo
mothership, "Eve". SpaceShipTwo is designed to carry two pilots and six
passengers on suborbital flights. On 29 April 2013, after three years
of unpowered testing, the spacecraft successfully performed its first
powered test flight.[8] XCOR Aerospace signed a $30 million contract with Yecheon Astro Space Center to build and lease its Lynx Mark II
spaceplane, which would be designed to take off from a runway under its
own rocket power, and to reach the same altitude and speed range as
SpaceShipOne and SpaceShipTwo, due to the fact that Lynx is propelled by
higher specific impulse fuels. Lynx is designed to only carry a pilot
and one passenger, although tickets are expected to be around half those
quoted for Virgin Galactic services.[9] Hyflex[10][11] was a miniaturized suborbital demonstrator of HOPE-X launched in 1996. Hyflex flew to 110 km altitude and succeeded in atmospheric reentry, subsequently achieving hypersonic flight. Though Hyflex achieved a controlledaircraft descent, it was not designed for a planned aircraft landing, the engineers opting instead for a splashdown without a parachute. The Hyflex that flew failed to recover and sank in the Pacific Ocean.
United States Gemini spaceplane concept testing, August 1964.
Various types of spaceplanes have been suggested since the early twentieth century. Notable early designs include Friedrich Zander's spaceplane equipped with wings made of combustible alloys that it would burn during its ascent, and Eugen Sänger's Silbervogelbomber design. Also in Nazi Germany and then in the USA, winged versions of the V-2 rocket were considered during and after World War II, and when public interest in space exploration was high in the 1950s and '60s, winged rocket designs by Wernher von Braun and Willy Ley served to inspire science fiction artists and filmmakers.
United States
The U.S. Air Force invested some effort in a paper study of a variety of spaceplane projects under their Aerospaceplane efforts of the late 1950s, but later ended these when they decided to use a modified version of Sänger's design. The result, Boeing X-20 Dyna-Soar, was to have been the first orbital spaceplane, but was canceled in the early 1960s in lieu of NASA's Project Gemini and the U.S. Air Force's Manned Orbiting Laboratory program.
In 1961, NASA originally planned to have the Gemini spacecraft land on a firm, solid ground runway[12] with a Rogallo wingairfoil,[13] rather than as a splashdown with parachute.[13] The test vehicle became known as the Paraglider Research Vehicle. Development work on both Gemini's splashdownparachute and spaceplane paraglider began in 1963.[14] By December 1963, the parachute was already to undergo full-scale deployment testing.[14] On the other hand, by December 1963 the paraglider spaceplane concept was running into technical difficulties[12] and subsequently became replaced by the parachute splashdown concept.[14] Though attempts to revive Gemini's paraglider spaceplane concept persisted within NASA and North American Aviation as late as 1964,[15] NASA Headquarters Gemini Chief William Schneider discontinued development as technical hurdles became too expensive.[15]
United States STS Space shuttle concepts circa 1970s
The Rockwell X-30
National Aero-Space Plane (NASP), begun in the 1980s, was an attempt to
build a scramjet vehicle capable of operating like an aircraft and
achieving orbit like the shuttle. It was canceled due to increasing
technical challenges, growing budgets, and the loss of public interest.[citation needed] In 1994 Mitchell Burnside Clapp proposed a single stage to orbit peroxide/kerosene spaceplane called "Black Horse".[16] It was to take off almost empty and undergo mid-air refueling before launching to orbit.[17]
The Lockheed Martin X-33 was a prototype made as part of an attempt by NASA to build a SSTO hydrogen-fuelled spaceplane VentureStar that failed when the hydrogen tank design proved to be unconstructable in the planned way. The March 5, 2006 edition of Aviation Week & Space Technology
published a story purporting to be "outing" a highly classified U.S.
military two-stage-to-orbit spaceplane system with the code name Blackstar, SR-3/XOV among other nicknames.[citation needed]
Boeing X-37B being prepared for launch in 2010 on an expendable orbital rocket
In 1999 NASA started the Boeing X-37 project, an unmanned, remote controlled spaceplane. The project was transferred to the U.S. Department of Defense in 2004.[citation needed]
Boeing has proposed that a larger variant of the X-37B, the X-37C could be built to carry up to six passengers up to LEO. The spaceplane would also be usable for carrying cargo, with both upmass and downmass
(return to Earth) cargo capacity. The ideal size for the proposed
derivative "is approximately 165 to 180 percent of the current X-37B."[18]
In December 2010, Orbital Sciences made a commercial proposal to NASA to develop the Prometheus, a lifting-body spaceplane vehicle about one-quarter the size of the Space Shuttle, in response to NASA's Commercial Crew Development (CCDev) phase 2 solicitation. The vehicle would be launched on a human-rated (upgraded) Atlas V rocket but would land on a runway.[19] For the same solicitation, Sierra Nevada Corporation proposed phase 2 extensions of its Dream Chaser spaceplane technology, partially developed under the first phase of NASA's CCDev program.[20] Both the Orbital Sciences proposal and the Dream Chaser are lifting body designs.[21] Sierra Nevada will utilize Virgin Galactic to market Dream Chaser commercial services and may use "Virgin’s WhiteKnightTwo carrier aircraft as a platform for drop trials of the Dream Chaser atmospheric test vehicle"[20][22]
NASA expects to make approximately $200 million of phase 2 awards by
March 2011, for technology development projects that could last up to 14
months.[23]
President Ronald Reagan described NASP in his 1986 State of the Union
address as "...a new Orient Express that could, by the end of the next
decade, take off from Dulles Airport and accelerate up to twenty-five
times the speed of sound, attaining low earth orbit or flying to Tokyo
within two hours..."[24]
There were six identifiable technologies which were considered
critical to the success of the NASP project. Three of these "enabling"
technologies were related to the propulsion system, which would consist
of a hydrogen-fueled scramjet.[24] The NASP program became the Hypersonic Systems Technology Program (HySTP) in late 1994.
HySTP was designed to transfer the accomplishments made in hypersonic
technologies by the National Aero-Space Plane (NASP) program into a
technology development program. On January 27, 1995 the Air Force
terminated participation in (HySTP).[24]
The Soviet Union firstly considered a preliminary design of rocket-launch small spaceplane Lapotok in early 1960s. Then the Spiral airspace system with small orbital spaceplane and rocket as second stage was widely developed in the 1960s-1980s.[citation needed]Mikoyan-Gurevich MiG-105 was a manned test vehicle to explore low-speed handling and landing.[25]
Cosmoplane
In recent times, an orbital spaceplane, called cosmoplane (Russian: космоплан)
capable of transporting passengers has been proposed by Russia's
Institute of Applied Mechanics. According to researchers, it could take
about 20 minutes to fly from Moscow to Paris, using hydrogen and oxygen-fueled engines.[26][27]
United Kingdom
The Skylon spaceplane is designed as a two-engine, "tailless" aircraft, which is fitted with a steerable canard.
The Multi-Unit Space Transport And Recovery Device (MUSTARD) was a concept explored by the British
Aircraft Corporation (BAC) around 1964-1965 for launching payloads
weighing as much as 5,000 lb into orbit. It was never constructed.[28] The British Government also began development of a SSTO-spaceplane, called HOTOL, but the project was canceled due to technical and financial issues.[29]
The lead engineer from the HOTOL project has since set up a private company dedicated to creating a similar plane called Skylon with a different combined cycle rocket/turbine precooled jet engine called SABRE. This vehicle is intended to be capable of a single stage to orbit launch carrying a 15,000 kg payload into Low Earth Orbit. If successful it would be far in advance of anything currently in operation.[30]
The British company Bristol Spaceplanes has undertaken design and prototyping of three potential spaceplanes since its founding by David Ashford in 1991. The European Space Agency has endorsed these designs on several occasions.[31]
France and the European Space Agency
France worked on the Hermes manned spaceplane launched by Ariane rocket in the late 20th century, and proposed in January 1985 to go through with Hermes development under the auspices of the ESA.[32]Hopper
was one of several proposals for a European reusable launch vehicle
(RLV) planned to cheaply ferry satellites into orbit by 2015.[33] One of those was 'Phoenix', a German project which is a one-seventh scale model of the Hopper concept vehicle.[34] The suborbital Hopper was a FESTIP (Future European Space Transportation Investigations Programme) system study design[35] A test project, the Intermediate eXperimental Vehicle (IXV), has demonstrated lifting reentry technologies and will be extended under the PRIDE programme.[36]
Japan
HOPE was a Japanese experimental spaceplane project designed by a partnership between NASDA and NAL (both now part of JAXA), started in the 1980s. It was positioned for most of its lifetime as one of the main Japanese contributions to the International Space Station, the other being the Japanese Experiment Module. The project was eventually cancelled in 2003, by which point test flights of a sub-scale testbed had flown successfully.
Germany
After the German Sänger-Bredt RaBo and Silbervogel of the 1930s and 1940s, Eugen Sänger worked for time on various space plane projects, coming up with several designs for Messerschmitt-Bölkow-Blohm such as the MBB Raumtransporter-8.[37] In the 1980s, West Germany funded design work on the MBB Sänger II
with the Hypersonic Technology Program. Development continued on
MBB/Deutsche Aerospace Sänger II/HORUS until the late 1980s when it was
canceled. Germany went on to participate in the Ariane rocket, Columbus
space station and Hermes spaceplane of ESA, Spacelab of ESA-NASA and Deutschland
missions (non-U.S. funded Space Shuttle flights with Spacelab). The
Sänger II had predicted cost savings of up to 30 percent over expendable
rockets.[38][39] The Daimler-Chrysler Aerospace RLV was a much later small reusable spaceplane prototype for ESA FLPP/FLTP program.
Shenlong (Chinese: 神龙; pinyin: shén lóng; literally: "divine dragon") is a proposed Chinese robotic space plane that is similar to the American Boeing X-37.[42] Only a few images have been released since late 2007.[43][44][45]
Boeing X-37
From Wikipedia, the free encyclopedia
X-37
The OTV-1 X-37B in April 2010, inside its payload fairing prior to launch
The Boeing X-37, also known as the Orbital Test Vehicle (OTV), is a reusable unmannedspacecraft. It is boosted into space by a launch vehicle, then re-enters Earth's atmosphere and lands as a spaceplane. The X-37 is operated by the United States Air Force for orbital spaceflight missions intended to demonstrate reusable space technologies.[5] It is a 120%-scaled derivative of the earlier Boeing X-40.
The X-37 began as a NASA project in 1999, before being transferred to the U.S. Department of Defense in 2004. It conducted its first flight as a drop test on 7 April 2006, at Edwards Air Force Base, California. The spaceplane's first orbital mission, USA-212, was launched on 22 April 2010 using an Atlas V rocket. Its successful return to Earth on 3 December 2010 was the first test of the vehicle's heat shield and hypersonic aerodynamic handling. A second X-37 was launched on 5 March 2011, with the mission designation USA-226; it returned to Earth on 16 June 2012. A third X-37 mission, USA-240, launched on 11 December 2012 and landed at Vandenberg AFB on 17 October 2014. The fourth X-37 mission, USA-261, launched on 20 May 2015 and is in progress.
In 1999, NASA selected Boeing Integrated Defense Systems to design and develop an orbital vehicle, built by the California branch of Boeing's Phantom Works. Over a four-year period, a total of $192 million was contributed to the project, with NASA contributing $109 million, the U.S. Air Force $16 million, and Boeing $67 million. In late 2002, a new $301-million contract was awarded to Boeing as part of NASA's Space Launch Initiative framework.[6]
1999 artist's rendering of the X-37 spacecraft
The X-37's aerodynamic design was derived from the larger Space Shuttle orbiter, hence the X-37 has a similar lift-to-drag ratio, and a lower cross range at higher altitudes and Mach numbers compared to DARPA's Hypersonic Technology Vehicle.[7] An early requirement for the spacecraft called for a delta-v of 7,000 mph (3.1 km/s) to change its orbit.[8] An early goal for the program was for the X-37 to rendezvous with satellites and perform repairs.[9]
The X-37 was originally designed to be carried into orbit in the Space
Shuttle's cargo bay, but underwent redesign for launch on a Delta IV or comparable rocket after it was determined that a shuttle flight would be uneconomical.[10]
The X-37 was transferred from NASA to the Defense Advanced Research Projects Agency (DARPA) on 13 September 2004.[11] Thereafter, the program became a classified project. DARPA promoted the X-37 as part of the independent space policy that the United States Department of Defense has pursued since the 1986 Challenger disaster.
Glide testing
The vehicle that was used as an atmospheric drop test glider had no propulsion system. Instead of an operational vehicle's payload bay doors, it had an enclosed and reinforced upper fuselage structure to allow it to be mated with a mothership. In September 2004, DARPA announced that for its initial atmospheric drop tests the X-37 would be launched from the Scaled Composites White Knight, a high-altitude research aircraft.[12]
On 21 June 2005, the X-37A completed a captive-carry flight underneath the White Knight from Mojave Spaceport in Mojave, California.[13][14] Through the second half of 2005, the X-37A underwent structural upgrades, including the reinforcement of its nose wheel
supports. Further captive-carry flight tests and the first drop test
were initially expected to occur in mid-February 2006. The X-37's public
debut was scheduled for its first free flight on 10 March 2006, but was
canceled due to an Arctic storm.[15] The next flight attempt, on 15 March 2006, was canceled due to high winds.[15]
On 24 March 2006, the X-37 flew again, but a datalink failure
prevented a free flight, and the vehicle returned to the ground still
attached to its White Knight carrier aircraft. On 7 April 2006, the X-37
made its first free glide flight. During landing, the vehicle overran
the runway and sustained minor damage.[16] Following the vehicle's extended downtime for repairs, the program moved from Mojave to Air Force Plant 42 (KPMD) in Palmdale, California
for the remainder of the flight test program. White Knight continued to
be based at Mojave, though it was ferried to Plant 42 when test flights
were scheduled. Five additional flights were performed,[N 1]
two of which resulted in X-37 releases with successful landings. These
two free flights occurred on 18 August 2006 and 26 September 2006.[17]
X-37B Orbital Test Vehicle
On 17 November 2006, the U.S. Air Force announced that it would
develop its own variant from NASA's X-37A. The Air Force version was
designated the X-37B Orbital Test Vehicle (OTV). The OTV program was
built on earlier industry and government efforts by DARPA, NASA and the
Air Force, and was led by the U.S. Air Force Rapid Capabilities Office, in partnership with NASA and the Air Force Research Laboratory. Boeing was the prime contractor for the OTV program.[8][18][19] The X-37B was designed to remain in orbit for up to 270 days at a time.[20] The Secretary of the Air Force
stated that the OTV program would focus on "risk reduction,
experimentation, and operational concept development for reusable space
vehicle technologies, in support of long-term developmental space
objectives."[18]
The X-37B was originally scheduled for launch in the payload bay of the Space Shuttle, but following the 2003 Columbia disaster, it was transferred to a Delta II 7920. The X-37B was subsequently transferred to a shrouded configuration on the Atlas V rocket, following concerns over the unshrouded spacecraft's aerodynamic properties during launch.[21] Following their missions, X-37B spacecraft land on a runway at Vandenberg Air Force Base, California, with Edwards Air Force Base as an alternate site.[22] In 2010, manufacturing work began on the second X-37B, OTV-2,[23] which conducted its maiden launch in March 2011.[24]
On 8 October 2014, NASA confirmed that X-37B vehicles would be housed at Kennedy Space Center
in Orbiter Processing Facilities (OPF) 1 and 2, hangars previously
occupied by the Space Shuttle. Boeing had said the space planes would
use OPF-1 in January 2014, and the Air Force had previously said it was
considering consolidating X-37B operations, housed at Vandenberg Air
Force Base in California, nearer to their launch site at Cape Canaveral.
NASA also stated that the program had completed tests to determine
whether the X-37B, one-fourth the size of the Space Shuttle, could land
on the former Shuttle runways.[25]
NASA furthermore stated that renovations of the two hangars would be
completed by the end of 2014; the main doors of OPF-1 were marked with
the message "Home of the X-37B" by this point.[25]
Most of the activities of the X-37B project are secret. The official U.S. Air Force
statement is that the project is "an experimental test program to
demonstrate technologies for a reliable, reusable, unmanned space test
platform for the U.S. Air Force."[5]
The primary objectives of the X-37B are twofold: reusable spacecraft
technology, and operating experiments which can be returned to Earth.[5] The Air Force states that this includes testing avionics, flight systems, guidance and navigation, thermal protection, insulation, propulsion, and re-entry systems.[26]
Speculation regarding purpose
In 2010, Tom Burghardt wrote for Space Daily that the X-37B could be used as a spy satellite or to deliver weapons from space.[27]The Pentagon subsequently denied claims that the X-37B's test missions supported the development of space-based weapons.[27] In January 2012, allegations were made that the X-37B was being used to spy on China's Tiangong-1 space station module.[28]
Former U.S. Air Force orbital analyst Brian Weeden later refuted this
claim, emphasizing that the different orbits of the two spacecraft
precluded any practical surveillance fly-bys.[29] In October 2014, The Guardian
reported the claims of security experts that the X-37B was being used
"to test reconnaissance and spy sensors, particularly how they hold up
against radiation and other hazards of orbit."[30]
The X-37 Orbital Test Vehicle is a reusable roboticspaceplane. It is a 120%-scale derivative of the Boeing X-40,[6][22] measuring over 29 feet (8.8 m) in length, and features two angled tail fins.[5][31] The X-37 launches atop an Atlas V version 501 rocket with a Centaur second stage.[5][19] The X-37 is designed to operate in a speed range of up to Mach 25 on its reentry.[32][33]
The technologies demonstrated in the X-37 include an improved thermal protection system, enhanced avionics, an autonomous guidance system and an advanced airframe.[10] The spaceplane's thermal protection system is built upon previous generations of atmospheric reentry spacecraft,[34] incorporating silicaceramic tiles.[35] The X-37's avionics suite was used by Boeing to develop its CST-100 manned spacecraft.[36] According to NASA, the development of the X-37 will "aid in the design and development of NASA's Orbital Space Plane, designed to provide a crew rescue and crew transport capability to and from the International Space Station".[37]
The X-37 is independently powered by one Aerojet AR2-3 engine using
storable propellants, providing thrust of 6,600 pounds-force
(29.341 kN).[38] The human-rated AR2-3 engine had been used on the dual-power NF-104A astronaut training vehicle, and was given a new flight certification for use on the X-37 with hydrogen peroxide/JP-8 propellants.[39]
The X-37 lands automatically upon returning from orbit, and is the
second reusable spacecraft to have such a capability, after the SovietBuran shuttle.[40] The X-37 is the smallest and lightest orbital spaceplane flown to date; with a launch mass of around 11,000 pounds (5,000 kg), it is approximately a quarter the size of the Space Shuttle orbiter.[41] In 2013, Guinness World Records recognised the X-37 as the world's smallest orbital spaceplane.[42]
The Space Foundation awarded the X-37 team on 13 April 2015 with the 2015 Space Achievement Award
"for significantly advancing the state of the art for reusable
spacecraft and on-orbit operations, with the design, development, test
and orbital operation of the X-37B space flight vehicle over three
missions totaling 1,367 days in space."[43]
Operational history
As of 17 October 2014, the two operational X-37Bs have conducted
three orbital missions, spending a combined total 1,367 days in space.[44]
OTV-1 sits on the runway after landing at Vandenberg AFB at the close of its USA-212 mission on 3 December 2010.
OTV-1, the first X-37B, launched on its first mission – USA-212 – on an Atlas V rocket from Cape Canaveral Air Force Station, Florida, on 22 April 2010 at 23:58 UTC. The spacecraft was placed into low Earth orbit for testing.[19] While the U.S. Air Force revealed few orbital details of the mission, amateur astronomers
claimed to have identified the spacecraft in orbit and shared their
findings. A worldwide network of amateur astronomers reported that, on
22 May 2010, the spacecraft was in an inclination of 39.99 degrees,
circling the Earth once every 90 minutes on an orbit 249 by 262 miles
(401 by 422 km).[45][46]
OTV-1 reputedly passed over the same given spot on Earth every four
days, and operated at an altitude of 255 miles (410 km), which is
typical for military surveillance satellites.[47]
Such an orbit is also common among civilian LEO satellites, and the
spaceplane's altitude was the same as that of the ISS and most other
manned spacecraft.
The U.S. Air Force announced on 30 November 2010 that OTV-1 would return for a landing during the 3–6 December timeframe.[48][49] As scheduled, OTV-1 de-orbited, reentered Earth's atmosphere, and landed successfully at Vandenberg AFB on 3 December 2010, at 09:16 UTC,[50][51][52]
conducting America's first autonomous orbital landing onto a runway;
the first spacecraft to perform such a feat was the Soviet Buran shuttle in 1988. In all, OTV-1 spent 224 days in space.[53] OTV-1 suffered a tire blowout during landing and sustained minor damage to its underside.[23]
OTV-2, the second X-37B, launched on its inaugural mission, designated USA-226,[54] aboard an Atlas V rocket from Cape Canaveral on 5 March 2011.[55] The mission was classified and described by the U.S. military as an effort to test new space technologies.[56]
On 29 November 2011, the U.S. Air Force announced that it would extend
the mission of USA-226 beyond the 270-day baseline design duration.[53] In April 2012, General William L. Shelton of the Air Force Space Command declared the ongoing mission a "spectacular success".[57]
On 30 May 2012, the Air Force stated that OTV-2 would complete its mission and land at Vandenberg AFB in June 2012.[58][59] The spacecraft landed autonomously on 16 June 2012, having spent 469 days in space.[1][60]
OTV-3, the second mission for the first X-37B and the third X-37B
mission overall, was originally scheduled to launch on 25 October 2012,[61] but was postponed because of an engine issue with the Atlas V launch vehicle.[62] The X-37B was successfully launched from Cape Canaveral on 11 December 2012.[41][63][64] The launch was designated USA-240.[65][66]
The OTV-3 mission ended with a landing at Vandenberg AFB on 17 October
2014 at 16:24 UTC, after a total time in orbit of just under 675 days.[3][67]
OTV-4
The Air Force launched a fourth X-37B mission, designated OTV-4 and
codenamed AFSPC-5, aboard an Atlas V rocket from Cape Canaveral Air
Force Station on 20 May 2015.[44][68] The launch was designated USA-261 and is the second flight of the second X-37B vehicle.[21] The mission will test a Hall effect thruster in support of the Advanced Extremely High Frequency communications satellite program,[68] and conduct a NASA investigation for testing various materials in space.[4][21][43] The mission is expected to last at least 200 days,[21] and as of 8 December 2015 the vehicle remains in orbit.[69]
Variants
X-37A
The X-37A was the initial NASA version of the spacecraft; the X-37A
Approach and Landing Test Vehicle (ALTV) was used in drop glide tests in
2005 and 2006.[14][70]
X-37B
The X-37B is a modified version of the NASA X-37A, intended for the U.S. Air Force.[5] It conducted multiple orbital test missions.[63]
X-37C
In 2011, Boeing announced plans for a scaled-up variant of the X-37B,
referring to it as the X-37C. The X-37C spacecraft would be between
165% and 180% of the size of the X-37B, allowing it to transport up to
six astronauts inside a pressurized compartment housed in the cargo bay.
Its proposed launch vehicle is the Atlas VEvolved Expendable Launch Vehicle.[71] In this role, the X-37C could potentially compete with Boeing's CST-100 commercial space capsule.[72]
Specifications
Three-views of the X-37B
X-37B
Data from USAF,[5][34] Boeing,[73]Air & Space Magazine,[70] and PhysOrg.[74]
Skylon is a design for a single-stage-to-orbitspaceplane by the British company Reaction Engines Limited (REL), using SABRE,
a combined-cycle, air-breathing rocket propulsion system, potentially
reusable for 200 flights. In paper studies, the cost per kilogram of payload carried to low Earth orbit in this way is hoped to be reduced from the current £1,108/kg (as of December 2015),[4] including research and development, to around £650/kg, with costs expected to fall much more over time after initial expenditures have amortised.[3] In 2004, the developer estimated the total lifetime cost of the programme to be about $12 billion.[3]
The vehicle design is for a hydrogen-fuelled aircraft that would take off from a purpose-built runway, and accelerate to Mach 5.4 at 26 kilometres (16 mi) altitude using the atmosphere's oxygen before switching the engines to use the internal liquid oxygen (LOX) supply to take it into orbit.[5]:5
Once in orbit it would release its payload of up to 15 tonnes. The
vehicle will be unpiloted, but also be certified to carry passengers.
All payloads could be carried in a standardised container compartment.
The relatively light vehicle would then re-enter the atmosphere and land on a runway, being protected from the conditions of re-entry by a ceramic composite
skin. When on the ground it would undergo inspection and necessary
maintenance. If the design goal is achieved, it should be ready to fly
again within two days.
As of 2012, only a small portion of the funding required to develop
and build Skylon had been secured. The research and development work on
the SABRE engine design is proceeding under a small European Space Agency
(ESA) grant. In January 2011, REL submitted a proposal to the British
government to request additional funding for the project and in April
REL announced that they had secured $350 million of further funding
contingent on a test of the engine's precooler technology being
successful. Testing of the key technologies was successfully completed
in November 2012, allowing Skylon's design to advance to its final
phase.[6][7]
On 16 July 2013 the British government pledged £60M to the project:
this investment will provide support at a "crucial stage" to allow a
full-scale prototype of the SABRE engine to be built.[8]
If all goes to plan, the first ground-based engine tests could happen
in 2019, and Skylon could be performing unmanned test flights by 2025.[1]
It could carry 15 tonnes of cargo to a 300 km equatorial orbit on each
trip, and up to 11 tonnes to the International Space Station, almost 45%
more than the capacity of the European Space Agency's ATV vehicle.[9]
Skylon is based on a previous project of Alan Bond, known as HOTOL.[10] The development of HOTOL began in 1982, at a time when space technology was moving towards reusable launch systems such as the Space Shuttle. In conjunction with British Aerospace and Rolls-Royce,
a promising design emerged to which the British government contributed
£2 million. However, in 1988, the government withdrew further funding,
and development was terminated. Following this setback, Bond decided to
set up his own company, Reaction Engines Limited, with the hope of continuing development with private funding.
The Skylon was developed from the British HOTOL project.
After securing more funding in the 1990s, the initial design
underwent radical revision and, since 2000, Reaction Engines has been
working with the University of Bristol
to develop an engine design vital to the success of Skylon. The
STRICT/STERN designs resulting from this programme were deemed a great
success.[11] The next stage of development will be to construct a full-sized working prototype of the SABRE Engine.[12]
There are several differences compared with HOTOL. Whereas HOTOL would have launched from a rocket sled, to save weight, Skylon uses a conventional retractable undercarriage. Skylon's revised engine design, the SABRE engine, is expected to offer higher performance.[5]:4
HOTOL's rear mounted engine gave the vehicle intrinsically poor
in-flight stability. Skylon solves this by placing engines at the end of
its wings, but further forward and much closer to the vehicle's centre of mass
longitudinally. Early attempts to fix this problem had ended up
sacrificing much of HOTOL's payload potential, and contributed to the
failure of the project.[5]:11
Project brief
A computer-generated image of the Skylon spaceplane climbing to orbit.
REL intends ultimately to operate as a for-profit commercial
enterprise, manufacturing Skylon vehicles for multiple international
customers; these customers will operate their fleets directly, with
support from REL. While REL intends to manufacture some components
directly, such as the engine precooler, other components have been
designed by partner companies and a consortium of various aerospace
firms is expected to handle full production of Skylon.[13] According to Management Today, Skylon has been discussed as a possible replacement for NASA's Space Shuttle.[14]
In service, Skylon could potentially lower satellite launch costs
from the current £15,000/kg to £650/kg, according to evidence submitted
to the UK parliament by Reaction Engines Ltd.[15] Funding for the project from the British government has often been difficult to obtain.[16] Speaking on the topic of Skylon in 2011, David Willetts, the UKMinister of State for Universities and Science, stated:
The European Space Agency is funding proof of concept work for Skylon
from UK contributions. This work is focusing on demonstrating the
viability of the advanced British engine technology that would underpin
the project. Initial work will be completed in mid 2011 and if the trial
is successful, we will work with industry to consider next steps.[15]
Funding and engine development
An unsuccessful request for funding from the British government was
issued in 2000. This involved a proposal offering a potentially large
return on investment.[17] Subsequent discussions with the British National Space Centre (which later became the UK Space Agency) led to a major funding agreement in February 2009 between the British National Space Centre, European Space Agency (ESA) and REL for €1 million ($1.28 million) to produce a demonstration engine for Skylon by 2011.[18][19][20]
The Technology Demonstration Programme will last approximately 2.5 years and will benefit from another €1 million from ESA.[21] This programme will take Reaction Engines Ltd from a Technology Readiness Level (TRL) of 2/3 up to 4/5.[22] The former UK Minister for Science and Innovation in 2009, Lord Drayson,
commented on Skylon in a speech: "This is an example of a British
company developing world-beating technology with exciting consequences
for the future of space."[15]
As of 2012, the funding required to develop and build the entire
craft has not yet been secured, and so current research and development
work is focused on the engines, under an ESA grant of €1 million.[23] In January 2011, REL submitted a proposal to the British Government requesting additional funding for the Skylon project.[15]
On 13 April 2011, REL announced that the Skylon design had passed
several rigorous independent reviews. On 24 May 2011, ESA publicly
declared the design to be feasible, having found "no impediments or
critical items" in the proposal.[24]
The precooler rig that tested the heat exchange system of the SABRE engine.
The major milestone of the commencement of static testing of the
engine precooler and the SABRE engine was achieved in June 2011, marking
the start of Phase 3 in the Skylon development programme.[15]
An REL spokesperson announced that they had secured $350 million of
further funding, contingent on successful completion of the full-sized
precooled jet engine test in June 2011.[25] Engine testing was initiated in June 2011,[26] and was expected to continue to the end of that year.[26] However, testing was delayed until April 2012.[27]
On 9 May 2011, REL stated that a preproduction prototype of the
Skylon could be flying by 2016, and the proposed route would be a
suborbital flight between the Guiana Space Centre near Kourou in French Guiana and the North European Aerospace Test Range, located in northern Sweden.[28] Pre-orders are expected in the 2011–2013 time frame coinciding with the formation of the manufacturing consortium.[15]
On 8 December 2011, Alan Bond, speaking at the 7th Appleton Space
Conference, stated that Skylon would enter into service by 2021-2022
instead of 2020 as previously envisaged.[29]
In April 2012, REL announced that the first phase of the precooler
test programme had been successfully completed. On 10 July 2012, REL
announced that the second of three series of tests has been completed
successfully.[30] The test facilities underwent upgrades to allow the third and final phase of testing to proceed.[31]
On 13 July 2012, ESA Director-General Jean-Jacques Dordain told Space
News that ESA would hold talks with REL to develop a further "technical
understanding".[32]
Following a successful propulsion system test that was audited by
ESA's propulsion division in mid-2012, the company announced that it
would begin a three-and-a-half-year project to develop and build a test
rig of the Sabre engine to prove the engine's performance across its
air-breathing and rocket modes.[6]
In November 2012, it was announced that a key test of the engine
precooler had been successfully completed, and that ESA had verified the
precooler's design. The project's development is now allowed to advance
to its next phase, which involves the construction and testing of a
full-scale prototype engine.[6][33] In June 2013, George Osborne,
The Chancellor of the Exchequer stated on his Twitter account that the
British government would be giving £60 million towards the further
development of the SABRE engine. Osborne's tweet stated: "Just seen
SABRE -a rocket engine that cools air from 1000 degrees to -150 in
fraction of a second. We're backing the future with £60m funding".[34] This grant was later reduced to £50 million and was approved by the European Commission in August 2015.[35]
In October 2015, BAE Systems
entered into an agreement with Reaction Engines where it would invest
£20.6 million in Reaction Engines to acquire 20% of its share capital
and help develop the SABRE engine.[36][37]
The Skylon spaceplane is designed as a two-engine, "tailless" aircraft, which is fitted with a steerable canard.
Skylon is a fully reusable single stage to orbit (SSTO) vehicle, able to achieve orbit without staging.[38]
Proponents of SSTO claim that staging causes a number of problems due
to its complexity that includes being difficult or impossible to recover
and reuse many parts, leading to great expense, and therefore believe
that SSTO designs hold the promise of reducing the cost of space-flight.[38] It is intended for Skylon to take off from a specially strengthened runway, fly to low earth orbit, re-enter the atmosphere, and land upon a runway like a conventional aeroplane.[5]:5
The design of the Skylon C2 features a large cylindrical payload bay, 13 m (42 ft 8 in) long and 4.8 m (15 ft 9 in) in diameter.[5]:12 It is designed to be comparable with current payload dimensions, and able to support the containerisation of payloads that Reaction Engines hopes for in the future.[5]:12 To an equatorial orbit, Skylon could deliver 15 t (33,000 lb) to a 300 km (190 mi) altitude or 11 t (24,000 lb) to an 800 km (500 mi) altitude.[5]:7
Using interchangeable payload containers, Skylon could be fitted to
carry satellites or fluid cargo into orbit, or, in a specialised
habitation module, up to 30 astronauts in one launch.[39][40]
Because the engine uses the atmosphere as reaction mass at low altitude, it will have a high specific impulse (around 2,800 seconds), and burn about one fifth of the propellant that would have been required by a conventional rocket.[41] Therefore, it would be able to take off with much less total propellant than conventional systems.[41] This, in turn, means that it does not need as much lift or thrust, which permits smaller engines, and allows conventional wings to be used.[41] While in the atmosphere, using wings to counteract gravity drag is more fuel-efficient than simply expelling propellant (as in a rocket), again reducing the total amount of propellant needed.[41]
The payload fraction would be significantly greater than normal rockets and the vehicle should be fully reusable (200 times or more).[42]
One of the significant features of the Skylon design is the engine, called SABRE.[5]:4[41] The engines are designed to operate much like a conventional jet engine[citation needed] to around Mach 5.5 (1,700 m/s),[41] 26 kilometres (16 mi) altitude, beyond which the air inlet closes and the engine operates as a highly efficient rocket to orbital speed.[41] The proposed SABRE engine is not a scramjet, but a jet engine running combined cycles of a precooled jet engine, rocket engine and ramjet.[3]
Originally the key technology for this type of precooled jet engine did
not exist, as it required a heat exchanger that was ten times lighter
than the state of the art.[11] Research conducted since then has achieved the necessary performance.[5]:4[43]
Operating an air-breathing jet engine at velocities of up to Mach 5.5 poses numerous engineering problems.[41] Several previous engines proposed by other designers worked well as jet engines but performed poorly as rockets.[41] This engine design aims to be a good jet engine within the atmosphere, as well as being an excellent rocket engine outside.[41]
The problem with operating at Mach 5.5 has been that the air coming
into the engine rapidly heats up as it is compressed into the engine;
due to certain thermodynamic effects, this greatly reduces the thrust
that can be produced by burning fuel.[41] Attempts to avoid these issues typically make the engine much heavier (scramjets/ramjets) or greatly reduce the thrust (conventional turbojets/ramjets).[41] In either case the end result is an engine that has a poor thrust to weight ratio at high speeds, resulting in an engine that is too heavy to assist much in reaching orbit.[41]
The SABRE engine design aims to avoid this by using some of the liquid hydrogen fuel to cool helium in a closed-cycle precooler, which quickly reduces the temperature of the air at the inlet.[41] The air is then used for combustion much like in a conventional jet,[41]
and once the helium has left the pre-cooler it is further heated by the
products of the pre-burner, giving it enough energy to drive the
turbine and the liquid hydrogen pump.[41] Because the air is cooled at all speeds, the jet can be built of light alloys and the weight is roughly halved.[41] Additionally, more fuel can be burnt at high speed.[41]
Beyond Mach 5.5, the air would become unusably hot despite the cooling,
so the air inlet closes and the engine relies solely on on-board liquid oxygen and hydrogen fuel as in a normal rocket.[41]
Fuselage and structure
The fuselage of Skylon is expected to be a carbon-fiber-reinforced polymerspace frame; a light and strong structure that supports the weight of the aluminium fuel tanks and to which the ceramic skin is attached.[5]:11 Multiple layers of reflective foil thermal insulation fill the spaces of the frame.[5]:15
The currently proposed Skylon model C2 will be a large vehicle, with a
length of 82 metres (269 ft) and a diameter of 6.3 metres (21 ft).[44] Because it will use a low-density fuel, liquid hydrogen,
a great volume is needed to contain enough energy to reach orbit. The
propellant is intended to be kept at low pressure to minimise stress; a
vehicle that is both large and light has an advantage during atmospheric reentry compared to other vehicles due to a low ballistic coefficient.[5]:7
Because of the low ballistic coefficient, Skylon would be slowed at
higher altitudes where the air is thinner. As a result, the skin of the
vehicle would reach only 1,100 K (830 °C).[45] In contrast, the smaller Space Shuttle was heated to 2,000 K on its leading edge, and so employed an extremely heat-resistant but fragile silica thermal protection system. The Skylon design does not require such a system, instead opting for using a far thinner yet durable reinforced ceramic skin.[3] However, due to turbulent flow around the wings during re-entry, some parts of Skylon would need to be actively cooled.[5]:15
Wheels and runway
At a gross takeoff weight of 275 tonnes, of which 220 tonnes is
propellant, the vehicle is capable of placing 12 tonnes into an
equatorial low Earth orbit.[46] A reinforced runway will be needed to tolerate the high equivalent single wheel load.[47] It will possess a retractable undercarriage with high pressure tyres and water-cooled brakes.[5]:21
If problems were to occur just before a take-off the brakes would be
applied to stop the vehicle, the water boiling away to dissipate the
heat.[5]:21 Upon a successful take-off, the water would be jettisoned,
thus reducing the weight of the undercarriage, in the C1 design 1200 kg
of water allows the weight of the brakes alone to be reduced from over
3000 kg to around 415 kg.[46] During landing, the empty vehicle would be far lighter, and hence the water would not be needed.[5]:21
Maximum speed: Orbital (air-breathing Mach 5.14, rocket Mach 27.8)[48]:6
Service ceiling:
28,500 m air-breathing, 90 km SABRE ascent, 600 km exoatmospheric
(93,500 ft air breathing, 56 mi rocket ascent, 373 mi exoatmospheric)
A reusable launch system (RLS, or reusable launch vehicle, RLV) is a launch system which is capable of launching a payload into space more than once. This contrasts with expendable launch systems, where each launch vehicle is launched once and then discarded.
No completely reusable orbital launch system is currently in use.[citation needed] The closest example was the partially reusable Space Shuttle. The orbiter, which included the Space Shuttle main engines, and the two solid rocket boosters, were reused after several months of refitting work for each launch. The external tank and launch vehicle load frame were discarded after each flight.[1][2] However, several at least partially reusable systems are currently under development, such as the Falcon 9.
Orbital RLVs are thought to provide the possibility of low cost and
highly reliable access to space. However, reusability implies weight
penalties such as non-ablativereentry
shielding and possibly a stronger structure to survive multiple uses,
and given the lack of experience with these vehicles, the actual costs
and reliability are yet to be seen.
In the first half of the twentieth century, popular science fiction often depicted space vehicles as either single-stage reusable rocket ships which could launch and land vertically (SSTOVTVL), or single-stage reusable rocket planes which could launch and land horizontally (SSTO HTHL).
The realities of early engine technology with low specific impulse or insufficient thrust-to-weight ratio to escape Earth's gravity well, compounded by construction materials without adequate performance (strength, stiffness, heat resistance) and low weight, seemingly rendered that original single-stage reusable vehicle vision impossible.
However, advances in materials and engine technology have rendered this concept potentially feasible.
Before VTVL SSTO designs came the partially reusable multi-stage NEXUS launcher by Krafft Arnold Ehricke. The pioneer in the field of VTVL SSTO, Philip Bono, worked at Douglas. Bono proposed several launch vehicles including: ROOST, ROMBUS, Ithacus, Pegasus and SASSTO. Most of his vehicles combined similar innovations to achieve SSTO capability. Bono proposed:
Plug nozzle engines to retain high specific impulse at all altitudes.
Base first reentry which allowed the reuse of the engine as a heat shield, lowering required heat shield mass.
Use of spherical tanks and stubby shape to reduce vehicle structural mass further.
Use of drop tanks to increase range.
Use of in-orbit refueling to increase range.
Bono also proposed the use of his vehicles for space launch, rapid
intercontinental military transport (Ithacus), rapid intercontinental
civilian transport (Pegasus), even Moon and Mars missions (Project Selena, Project Deimos).
In Europe, Dietrich Koelle, inspired by Bono's SASSTO design, proposed his own VTVL vehicle named BETA.
Before HTHL SSTO designs came Eugen Sänger and his Silbervogel ("Silverbird") suborbital skip bomber. HTHL vehicles which can reach orbital velocity
are harder to design than VTVL due to their higher vehicle structural
weight. This led to several multi-stage prototypes such as a suborbitalX-15. Aerospaceplane being one of the first HTHL SSTO concepts. Proposals have been made to make such a vehicle more viable including:
Rail boost (e.g. 270 m/s at 3000 m on a mountain allowing 35% less SSTO takeoff mass for a given payload in one NASA study)[3]
Use of lifting body designs to reduce vehicle structural mass.
Use of in-flight refueling.
Other launch system configuration designs are possible such as horizontal launch with vertical landing (HTVL) and vertical launch with horizontal landing (VTHL). One of the few HTVL vehicles is the 1960s concept spacecraft Hyperion SSTO, designed by Philip Bono.[4]X-20 Dyna-Soar is an early example of a VTHL design,[citation needed] while the HL-20 and X-34 are examples from the 1990s.[citation needed] As of February 2010, the VTHL X-37 has completed initial development and flown an initial classifiedorbital mission of over seven months duration.[citation needed] Currently proposed VTHL manned spaceplanes include the Dream Chaser and Prometheus, both circa 2010 concept spaceplanes proposed to NASA under the CCDev program.[citation needed]
The late 1960s saw the start of the Space Shuttle design process. From an initial multitude of ideas a two-stage reusable VTHL design was pushed forward that eventually resulted in a reusable orbiter payload spacecraft and reusable solid rocket boosters. The external tank and the launch vehicle load frame
were discarded, and the parts that were reusable took a 10,000-person
group nine months to refurbish for flight. So the space shuttle ended up
costing a billion dollars per flight.[5] Early studies from 1980 and 1982 proposed in-space uses for the tank to be re-used in space for various applications[1][2] but NASA never pursued those options beyond the proposal stage.
During the 1970s further VTVL and HTHL SSTO designs were proposed for solar power satellite and military applications. There was a VTVL SSTO study by Boeing. HTHL SSTO designs included the RockwellStar-Raker and the Boeing HTHL SSTO study. However the focus of all space launch funding in the United States on the Shuttle killed off these prospects. The Soviet Union followed suit with Buran. Others preferred expendables for their lower design risk, and lower design cost.
Eventually the Shuttle was found to be expensive to maintain, even
more expensive than an expendable launch system would have been. The
cancellation of a Shuttle-Centaur rocket after the loss of Challenger
also caused an hiatus that would make it necessary for the United
States military to scramble back towards expendables to launch their
payloads. Many commercial satellite customers had switched to
expendables even before that, due to unresponsiveness to customer
concerns by the Shuttle launch system.
In 1986 President Ronald Reagan called for an airbreathing scramjet plane to be built by the year 2000, called NASP/X-30 that would be capable of SSTO. Based on the research project copper canyon the project failed due to severe technical issues and was cancelled in 1993.
This research may have inspired the British HOTOL program, which rather than airbreathing to high hypersonic
speeds as with NASP, proposed to use a precooler up to Mach 5.5. The
program's funding was canceled by the British government when the
research identified some technical risks as well as indicating that that
particular vehicle architecture would only be able to deliver a
relatively small payload size to orbit.
When the Soviet Union collapsed in the early nineties, the cost of Buran became untenable. Russia has only used pure expendables for space launch since.
The 1990s saw interest in developing new reusable vehicles. The military Strategic Defense Initiative ("Star Wars") program "Brilliant Pebbles" required low cost, rapid turnaround space launch. From this requirement came the McDonnell DouglasDelta Clipper VTVL SSTO proposal. The DC-X
prototype for Delta Clipper demonstrated rapid turnaround time and that
automatic computer control of such a vehicle was possible. It also
demonstrated it was possible to make a reusable space launch vehicle
which did not require a large standing army to maintain like the
Shuttle.
In mid-1990, further British research and major reengineering to
avoid deficiencies of the HOTOL design led to the far more promising Skylon design, with much greater payload.
From the commercial side, large satellite constellations such as Iridium satellite constellation
were proposed which also had low cost space access demands. This fueled
a private launch industry, including partially reusable vehicle
players, such as Rocketplane Kistler, and reusable vehicle players such as Rotary Rocket.
The end of that decade saw the implosion of the satellite constellation market with the bankruptcy of Iridium.
In turn the nascent private launch industry collapsed. The fall of the
Soviet Union eventually had political ripples which led to a scaling
down of ballistic missile defense, including the demise of the
"Brilliant Pebbles" program. The military decided to replace their aging
expendable launcher workhorses, evolved from ballistic missile
technology, with the EELV program. NASA proposed riskier reusable concepts to replace Shuttle, to be demonstrated under the X-33 and X-34 programs.
The 21st century saw rising costs and teething problems lead to the cancellation of both X-33 and X-34. Then the Space Shuttle Columbia disaster
and another grounding of the fleet. The Shuttle design was now over 20
years old and in need of replacement. Meanwhile, the military EELV
program churned out a new generation of better expendables. The
commercial satellite market is depressed due to a glut of cheap
expendable rockets and there is a dearth of satellite payloads.
Against this backdrop came the Ansari X Prize
contest, inspired by the aviation contests made in the early 20th
century. Many private companies competed for the Ansari X Prize, the
winner being Scaled Composites with their reusable HTHL SpaceShipOne.
It won the ten million dollars, by reaching 100 kilometers in altitude
twice in a two-week period with the equivalent of three people on board,
with no more than ten percent of the non-fuel weight of the spacecraft
replaced between flights. While SpaceShipOne is suborbital like the X-15, some hope the private sector can eventually develop reusable orbital vehicles given enough incentive. SpaceX is a recent player in the private launch market succeeding in converting its Falcon 9expendable launch vehicle into a partially reusable vehicle by returning the first stage for reuse.
On 23 November 2015, Blue Origin New Shepard rocket became the first proven Vertical Take-off Vertical Landing (VTVL) rocket which can reach space, by passing Kármán line (100 kilometres), reaching 329,839 feet (100.5 kilometers). [6] Previous VTVL record was in 1994, the McDonnell Douglas DC-X ascended to an altitude of about 3.1 kilometers before successfully landing. [7]
Reusability concepts
Single stage
There are two approaches to Single stage to orbit or SSTO. The rocket equation says that an SSTO vehicle needs a high mass ratio.
Mass ratio is defined as the mass of the fully fueled vehicle divided
by the mass of the vehicle when empty (zero fuel weight, ZFW).
One way to increase the mass ratio is to reduce the mass of the empty
vehicle by using very lightweight structures and high efficiency
engines. This tends to push up maintenance costs as component
reliability can be impaired, and makes reuse more expensive to achieve.
The margins are so small with this approach that there is uncertainty
whether such a vehicle would be able to carry any payload into orbit.
Two or more stages to orbit
Two stage to orbit
requires designing and building two independent vehicles and dealing
with the interactions between them at launch. Usually the second stage
in launch vehicle is 5-10 times smaller than the first stage, although
in biamese and triamese[8] approaches each vehicle is the same size.
In addition, the first stage needs to be returned to the launch site
for it to be reused. This is usually proposed to be done by flying a
compromise trajectory that keeps the first stage above or close to the
launch site at all times, or by using small airbreathing engines to fly
the vehicle back, or by recovering the first stage downrange and
returning it some other way (often landing in the sea, and returning it
by ship.) Most techniques involve some performance penalty; these can
require the first stage to be several times larger for the same payload,
although for recovery from downrange these penalties may be small.
The second stage is normally returned after flying one or more orbits and reentering.
Biamese & Triamese (Crossfeed)
Two or three similar stages are stacked side by side, and burn in
parallel. Using crossfeed, the fuel tanks of the orbital stage are kept
full, while the tank(s) in the booster stage(s) are used to run engines
in the booster stage(s) and orbital stage. Once the boosters run dry,
they are ejected, and (typically) glide back to a landing. The advantage
to this is that the mass ratios of the individual stages is vastly
reduced due to the way cross feed modifies the rocket equation.
Isp*g*ln(2MR^2/MR+1) & Isp*g*ln(3MR^2/MR+2) respectively. With
hydrogen engines, a triamese only needs an MR of 5, as opposed to an MR
of 10 for a single-stage equivalent vehicle.
A criticism of this approach is that designing separate orbiter and
boosters, or a single vehicle that could do both, would compromise
performance, safety, and possible cost savings. Compromising maximum
performance to reduce cargo cost however, is the point of the triamese
approach. Stacking two or three winged vehicles can also be challenging.
Optimistically, the lower mass ratios would translate to lower overall
R&D costs, even if two different stage designs. While many aerospace
designs have successfully been modified far beyond the original
designers intentions (Boeing's 747 is perhaps the best example) the slow
and painful birth of the F-35 family demonstrates that it is not always
a guarantee of such flexibility.
Crossfeed is to be an important part of SpaceX's Falcon Heavy - and one of the main reasons it will be able to lift over ~4 times as much cargo to orbit as the Falcon 9 v1.1.
In this case the vehicle requires wings and undercarriage (unless
landing at sea). This typically requires about 9-12% of the landing
vehicle to be wings; which in turn implies that the takeoff weight is
higher and/or the payload smaller.
Concepts such as lifting bodies attempt to deal with the somewhat conflicting issues of reentry, hypersonic and subsonic flight; as does the delta wing shape of the Space Shuttle.
Parachutes could be used to land vertically, either at sea, or with
the use of small landing rockets, on land (as with Soyuz). McDonnell
Douglas DC-X ascended to an altitude of about 3.1 kilometers before
successfully landing. [7]
Alternatively rockets could be used to softland the vehicle on the ground from the subsonic speeds reached at low altitude (see DC-X). This typically requires about 10% of the landing weight of the vehicle to be propellant.
A slightly different approach to vertical landing is to use an autogyro or helicopter rotor. This requires perhaps 2-3% of the landing weight for the rotor. Blue Origin New Shepard rocket became the first proven rocket which can do vertical landing after reaching space,[clarification needed] by passing Kármán line (100 kilometres).[6] SpaceX's Falcon 9
rocket became the first orbital rocket to vertically land its first
stage on the ground, after propelling its second stage and payload to a
suborbital trajectory, where it would continue on to orbit. <[9]
The vehicle needs wings to take off. For reaching orbit, a 'wet wing'
would often need to be used where the wing contains propellant. Around
9-12% of the vehicle takeoff weight is perhaps tied up in the wings.
This is the traditional takeoff regime for pure rocket vehicles.
Rockets are good for this regime, since they have a very high
thrust/weight ratio (~100).
Airbreathing
Airbreathing approaches use the air during ascent for propulsion. The most commonly proposed approach is the scramjet, but turborocket, Liquid Air Cycle Engine (LACE) and precooled jet engines have also been proposed.
In all cases the highest speed that an airbreathing engine can reach
is far short of orbital speed (about Mach 15 for Scramjets and Mach 5-6
for the other engine designs), and rockets would be used for the
remaining 10-20 Mach into orbit.
The thermal situation for airbreathers (particularly scramjets) can
be awkward; normal rockets fly steep initial trajectories to avoid drag,
whereas scramjets would deliberately fly through relatively thick
atmosphere at high speed generating enormous heating of the airframe.
The thermal situation for the other airbreathing approaches is much more
benign, although is not without its challenges.
Propellant
Hydrogen fuel
Hydrogen is often proposed since it has the highest exhaust velocity.
However tankage and pump weights are high due to insulation and low
propellant density; and this wipes out much of the advantage.
Still, the 'wet mass' of a hydrogen fuelled stage is lighter than an
equivalent dense stage with the same payload and this can permit usage
of wings, and is good for second stages.
Dense fuel
Dense fuel is sometimes proposed since, although it implies a heavier
vehicle, the specific tankage and pump mass is much improved over
hydrogen. Dense fuel is usually suggested for vertical takeoff vehicles,
and is compatible with horizontal landing vehicles, since the vehicle
is lighter than an equivalent hydrogen vehicle when empty of propellant.
Non-cryogenic dense fuels also permit the storage of fuel in wing
structures. Projects have been underway to densify existing fuel types
through various techniques. These include slush technologies for
cryogenics like hydrogen and propane. Another densifying method has been
studied that would also increase the specific impulse of fuels. Adding
finely powdered carbon, aluminum, titanium, and boron to hydrogen and
kerosene have been studied. These additives increase the specific
impulse (Isp) but also the density of the fuel. For instance, the French
ONERA missile program tested boron with kerosene in gelled slurries, as
well as embedded in paraffin, and demonstrated increases in volumetric
specific impulse of between 20-100%.
Tripropellant
Dense fuel is optimal early on in a flight, since the thrust to
weight of the engines is better due to higher density; this means the
vehicle accelerates more quickly and reaches orbit sooner, reducing gravity losses.
However, for reaching orbital speed, hydrogen is a better fuel, since
the high exhaust velocity and hence lower propellant mass reduces the
take off weight.[citation needed]
Therefore, tripropellant vehicles[citation needed] start off burning with dense fuel and transition to hydrogen. (In a sense the Space Shuttle
does this with its combination of solid rockets and main engines, but
tripropellant vehicles usually carry their engines to orbit.[citation needed])
Propellant costs
As with all current launch vehicles propellant costs for a rocket are
much lower than the costs of the hardware. However, for reusable
vehicles if the vehicles are successful, then the hardware is reused
many times and this would bring the costs of the hardware down. In
addition, reusable vehicles are frequently heavier and hence less
propellant efficient, so the propellant costs could start to multiply up
to the point where they become significant.
Launch assistance
Since rocket delta-v has a non linear relationship to mass fraction due to the rocket equation,
any small reduction in delta-v gives a relatively large reduction in
the required mass fraction; and starting a mission at higher altitude
also helps.
Many systems have proposed the use of aircraft to gain some initial
velocity and altitude; either by towing, carrying or even simply
refueling a vehicle at altitude.
Various other launch assists have been proposed, such as ground-based sleds, or maglev systems, high altitude (80 km) maglev systems such as launch loops, to more exotic systems such as tether propulsion systems to catch the vehicle at high altitude, or even Space Elevators.
Robert Zubrin has said that as a rough rule of thumb, 15% of the landed weight of a vehicle needs to be aerobraking reentry shielding.[10]
Reentry heat shields on these vehicles are often proposed to be some
sort of ceramic and/or carbon-carbon heat shields, or occasionally
metallic heat shields (possibly using water cooling or some sort of
relatively exotic rare earth metal.)[citation needed]
Some shields would be single-use ablatives, discarded after reentry.[citation needed]
A newer Thermal Protection System (TPS) technology was first developed for use in steering fins on ICBM MIRVs.
Given the need for such warheads to reenter the atmosphere swiftly and
retain hypersonic velocities to sea level, researchers developed what
are known as SHARP materials, typically hafnium diboride and zirconium
diboride, whose thermal tolerance exceeds 3600 C. SHARP equipped
vehicles can fly at Mach 11 at 30 km altitude and Mach 7 at sea level.
The sharp-edged geometries permitted with these materials also
eliminates plasma shock wave interference in radio communications during
reentry. SHARP materials are very robust and would not require constant
maintenance, as is the case with technologies like silica tiles, used
on the Space Shuttle, which account for over half of that vehicles
maintenance costs and turnaround time. The maintenance savings alone are
thus a major factor in favor of using these materials for a reusable
launch vehicle, whose raison d'etre is high flight rates for economical
launch costs.[citation needed]
Weight penalty
The weight of a reusable vehicle is almost invariably higher than an
expendable that was made with the same materials, for a given payload.
R&D
The research & development
costs of reusable vehicle are expected to be higher, because making a
vehicle reusable implies making it robust enough to survive more than
one use, which adds to the testing required. Increasing robustness is
most easily done by adding weight; but this reduces performance and puts
further pressure on the R&D to recoup this in some other way.
These extra costs must be recouped; and this pushes up the average cost of the vehicle.
Maintenance
Reusable launch systems require maintenance, which is often
substantial. The Space Shuttle system requires extensive refurbishing
between flights, primarily dealing with the silica tile TPS and the high
performance LH2/LOX burning main engines. Both systems require a
significant amount of detailed inspection, rebuilding and parts
replacement between flights, and account for over 75% of the maintenance
costs of the Shuttle system. These costs, far in excess of what had
been anticipated when the system was constructed, have cut the maximum
flight rate of Shuttle to 1/4 of that planned. This has also quadrupled
the cost per pound of payload to orbit, making Shuttle economically
infeasible in today's launch market for any but the largest payloads,
for which there is no competition.
For any RLV technology to be successful, it must learn from the
failings of Shuttle and overcome those failings with new technologies in
the TPS and propulsion areas.
Manpower and logistics
The Space Shuttle program required a standing army of over 9,000
employees to maintain, refurbish, and relaunch the shuttle fleet,
irrespective of flight rates. That manpower budget must be divided by
the total number of flights per year. The fewer flights means the cost
per flight goes up significantly. Streamlining the manpower requirements
of any launch system is an essential part of making an RLV economical.
Projects that have attempted to develop this ethic include the DC-X
Delta Clipper project, as well as SpaceX's Falcon 9 and Falcon 1
programs.
One issue mitigating against this drive for labor savings is
government regulation. Given that NASA and USAF (as well as government
programs in other countries) are the primary customers and sources of
development capital, government regulatory requirements for oversight,
parwork, quality, safety, and other documentation tend to inflate the
operational costs of any such system.
Avatar RLV - Under development, first scaled-down demonstration flight planned in 2015.[11][12]
Blue Origin is developing a reusable booster system, as of November 2015.[13][7]Blue Origin New Shepard rocket is the first rocket successfully launched and which is proven to be able to land vertically on earth VTVL after reaching space, by passing Kármán line. [6]
As of 2014, China is working on a project to recover rocket boosters, using a "paraglider-type wings" approach. Powered flight tests are in the future, and the process is expect to take until approximately 2018.[14]
Swiss Space Systems is developing launching system including the suborbital spaceplane SOAR. The first 2 stages, an Airbus 300 and SOAR, are completely reusable.[19]
zero2infinity is developing a launching system called bloostar based on the rockoon system, which consists in elevating to the near space the launcher using a high-altitude balloon and once there launch a multi-stage rocket to put a satellite into orbit.[20]
SpaceLiner (a mid-2000s German proposed suborbital, hypersonic, winged passenger transport concept)
Shenlong (spacecraft) (an early 2000s Chinese proposed, scaled model tested at high altitude in 2005)
PlanetSpaceSilver Dart (a 2000s partially reusable spaceplane concept, based on a hypersonic glider design)
As of January 2015, the French space agency CNES is working with Germany and a few other governments
to start a modest research effort with a hope to propose a LOX/methane
engine on a reusable launch vehicle by mid-2015, with flight testing
unlikely before approximately 2026.[22][23]
Baikal French/Russian early-2000s joint-project concept. Cancelled after "CNES
officials concluded that a rocket system with a reusable first stage
would need to launch some 40 times a year" in order to make the project
economically feasible.[23]
Roton Commercial launch vehicle project, cancelled in 2000 due to lack of funds.
Reusability dropped, flown only as expendable
SpaceXFalcon 1
was announced as a partially reusable launch vehicle, and the 28
September 2008 test flight reached orbit, but vehicle recovery was never
demonstrated and the vehicle was retired after 2009.[25
The MAKS (Multipurpose aerospace system) (Russian: МАКС (Многоцелевая авиационно-космическая система)) is a cancelled Soviet air-launched with orbiter Reusable launch system
project that was proposed in 1988, but cancelled in 1991. The orbiter
was supposed to reduce the cost of transporting materials to Earth orbit
by a factor of ten. The reusable orbiter and its external non-reusable
fuel tank, was to have been launched by an Antonov AN-225 airplane, developed by Antonov ASTC (Kyiv, Ukraine). Had it been built, the system would have weighed 275 metric tons (271 long tons; 303 short tons), and would have been capable of carrying a 7-metric-ton (6.9-long-ton; 7.7-short-ton) payload.[1]
Three variants of the MAKS system were conceived: MAKS-OS, the
standard configuration; MAKS-T, with upgraded payload capability; and
MAKS-M, a version that included its fuel tank within the envelope of the
orbiter.[2]
As of June 2010, Russia was considering reviving the MAKS program.[3] In Ukraine this project has developed into other air-launched orbiter projects, such as Svityaz and Oril.
Reusable Military Spaceplane Tops DARPA's Budget Request, Again
By Mike Gruss, Space News |
5
4
0
3
28
MORE
Boeing is
one of three teams designing a new spaceplane for DARPA's Experimental
Spaceplane-1 program, known as XS-1. The program leads DARPA's
space-related budget requests for fiscal year 2017.
Credit: Boeing
WASHINGTON — For the second consecutive year, the U.S. Defense Advanced
Research Projects Agency's top-funded space program is an experimental
spaceplane intended to make frequent trips to orbit.
DARPA asked for $50 million in the Pentagon's 2017 budget request for its Experimental Spaceplane 1, or XS-1 program. That's up from a $30 million the agency asked for during the fiscal year 2016 budget cycle.
XS-1 aims to develop a reusable first stage that could carry an
expendable upper stage capable of placing payloads weighing up to 1,800
kilograms into orbit. DARPA said the vehicle could ultimately fly 10
times in 10 days and boost payloads into low Earth orbit for less than
$5 million per launch. [DARPA's XS-1 Military Space Plane Concept in Pictures]
Three industry teams are working on the program: Boeing and Blue
Origin; Masten Space Systems and XCOR Aerospace; and Northrop Grumman
and Virgin Galactic.
In July, all three teams received funding to continue design work and risk reduction activities in preparation for a production contract.
DARPA said in 2014 it intended to pick one team in 2015 to work toward
demonstration flight in 2018, but now it is unclear when such a
downselect will occur.
DARPA said in budget documents that it plans to complete system and
subsystem designs later this year, as well as coordinate with the
Federal Aviation Administration for preliminary flight test planning.
A critical design review is planned for fiscal year 2017, the documents said.
In October, the Government Accountability Office said none of several
Defense Department efforts to field quick-reaction launch vehicles,
including XS-1, have advanced past the development stage.
In its 2017 budget request DARPA asked for $175 million for its space
programs and technology office, significantly higher than the $127
million budget for 2016.
In addition to $50 million for XS-1, next year's budget would also include:
$45 million for the RadarNet program. an effort to design a deployable
lightweight, low-power and wideband-capable communications antenna for
cubesats.
$33 million for Robotic Servicing of Geostationary Satellites, which
would establish a robotics operation in geosynchronous orbit to perform
servicing tasks.
This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.
- See more at: http://www.space.com/32051-reusable-military-spaceplane-darpa-budget.html#sthash.w5lxIKMB.dpuf
Reusable Military Spaceplane Tops DARPA's Budget Request, Again
By Mike Gruss, Space News |
5
4
0
3
28
MORE
Boeing is
one of three teams designing a new spaceplane for DARPA's Experimental
Spaceplane-1 program, known as XS-1. The program leads DARPA's
space-related budget requests for fiscal year 2017.
Credit: Boeing
WASHINGTON — For the second consecutive year, the U.S. Defense Advanced
Research Projects Agency's top-funded space program is an experimental
spaceplane intended to make frequent trips to orbit.
DARPA asked for $50 million in the Pentagon's 2017 budget request for its Experimental Spaceplane 1, or XS-1 program. That's up from a $30 million the agency asked for during the fiscal year 2016 budget cycle.
XS-1 aims to develop a reusable first stage that could carry an
expendable upper stage capable of placing payloads weighing up to 1,800
kilograms into orbit. DARPA said the vehicle could ultimately fly 10
times in 10 days and boost payloads into low Earth orbit for less than
$5 million per launch. [DARPA's XS-1 Military Space Plane Concept in Pictures]
Three industry teams are working on the program: Boeing and Blue
Origin; Masten Space Systems and XCOR Aerospace; and Northrop Grumman
and Virgin Galactic.
In July, all three teams received funding to continue design work and risk reduction activities in preparation for a production contract.
DARPA said in 2014 it intended to pick one team in 2015 to work toward
demonstration flight in 2018, but now it is unclear when such a
downselect will occur.
DARPA said in budget documents that it plans to complete system and
subsystem designs later this year, as well as coordinate with the
Federal Aviation Administration for preliminary flight test planning.
A critical design review is planned for fiscal year 2017, the documents said.
In October, the Government Accountability Office said none of several
Defense Department efforts to field quick-reaction launch vehicles,
including XS-1, have advanced past the development stage.
In its 2017 budget request DARPA asked for $175 million for its space
programs and technology office, significantly higher than the $127
million budget for 2016.
In addition to $50 million for XS-1, next year's budget would also include:
$45 million for the RadarNet program. an effort to design a deployable
lightweight, low-power and wideband-capable communications antenna for
cubesats.
$33 million for Robotic Servicing of Geostationary Satellites, which
would establish a robotics operation in geosynchronous orbit to perform
servicing tasks.
This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.
- See more at: http://www.space.com/32051-reusable-military-spaceplane-darpa-budget.html#sthash.w5lxIKMB.dpuf
