By Tuan Nguyen
Posting in Design
The Skylon space plane, which can take off and land on runways, may be the future of spaceflight.
If you're the type who prefers to think positive, then the last launch of space shuttle Atlantis can just as easily be seen as not only the end of an era, but also perhaps the dawn of a new and possibly even more exciting one.
Here's why: Reaction Engines, a UK-based start-up, has received the support and financial backing of the European Space Agency (ESA) to develop a revolutionary new spacecraft that may eventually emerge as a successor to the soon-to-be-retired space shuttle. The proposed vehicle, called Skylon, is unique in that it can take off and land on runways, making space travel cheaper and more efficient than the current U.S. based fleet.
That's not to say the last 40 years hasn't been a remarkable run. The International Space Station, Hubble Telescope and the launch of some notable satellites were all a direct result of NASA's ambitious efforts to explore the deep mysteries beyond this little planet we call home. Discoveries like the confirmation of dark energy, the age of the universe and, yes, even those ever-ubiquitous memory foam products can all be attributed to the tireless work carried out by the crew at Space Transportation Systems. But such impressive achievements often obscure the fact that the basic technology underlying space shuttles is quite old -- dating back to least a quarter century -- and not to mention exorbitantly expensive to maintain.
Prior to the Apollo moon landing in 1969, the agency had already been drawing up blueprints for the modern spaceships we see today. Originally, NASA's preferred design called for launching a shuttle using a massive manned rocket booster, an idea that was quickly abandoned when the agency discovered it would tack on untenable costs to an already enormously complex undertaking.
Instead, officials eventually opted to go with a design that relied on disposable rocket boosters despite calculations suggesting that, given enough flights, re-usable manned boosters would actually be more cost effective in the long run.
But what the space agency saw as an inexpensive and efficient way to take to the heavens didn't exactly pan out as such in practice. This was partly due to the decision to construct the space shuttle as a dual-purpose vehicle capable of transporting both humans and cargo. Sending astronauts required that equipment and procedures be in place to ensure their safety. Hauling cargo added a tremendous amount of weight, which in turn added to fuel costs. Over the course of 134 missions, which amounted to less than 5 launches per year, the space shuttle program racked up an operating cost that totaled $209 billion dollars.
John M. Logsdon, a professor at the Space Policy Institute in Washington DC, wrote a scathing essay in MIT Technology Review, taking program officials to task for numerous technical and policy blunders that resulted in runaway costs.
Here's an excerpt:
The shuttle was much more expensive than anyone anticipated at its inception. Then-NASA administrator James Fletcher told Congress in 1972 that the shuttle would cost $5.15 billion to develop and could be operated at a cost of $10.5 million per flight. NASA only slightly overran development costs, which is normal for a challenging technological effort, but the cost of operating the shuttle turned out to be at least 20 times higher than was projected at the program's start. The original assumption was that the lifetime of the shuttle would be between 10 and 15 years. By operating the system for 30 years, with its high costs and high risk, rather than replacing it with a less expensive, less risky second-generation system, NASA compounded the original mistake of developing the most ambitious version of the vehicle. The shuttle's cost has been an obstacle to NASA starting other major projects.
Recently, NASA has awarded a number of companies, including SpaceX and Boeing, a total of $269 million dollars to help fund designs they hope can fill the shuttle's void. Meanwhile, the Skylon concept, the brainchild of a lesser known upstart, has started to receive some serious interest within the growing British aeronautics industry.
To them, what makes the spacecraft particularly tantalizing is a groundbreaking technology that enables it to be completely reusable, without the aid of rocket boosters. Another advantage is that it can be readied for missions in just a matter of hours after returning from orbit, rather than months. In a nutshell, it functions very much like an airplane that just so happens to fly into space.
The key to the successful development of the Skylon is its Synergistic Air-Breathing Rocket Engine or SABRE, which you can think of as a hybrid jet/rocket system. Upon takeoff, the engine burns hydrogen and oxygen from air to generate thrust. Once the spacecraft reaches an altitude of 16 miles and soars at five times the speed of sound (mach 5), it switches over to rocket mode. At this point, the engine starts burning hydrogen and liquid oxygen as the aircraft continues its journey into orbit.
The aircraft's ability to tap into the oxygen from the atmosphere as fuel rather than liquid oxygen during parts of the flight frees up a tremendous amount of room for more cargo, not to mention some hefty savings compared to space shuttles that rely on disposable rocket boosters.
'You need an army to put it together," lead engineer Alan Bond told Management Today magazine, in reference to the high cost and maintenance of the boosters. "There's a massive amount of paperwork, and when you do launch it, about one in 50 ends up in the nearest ocean."
With a fully reusable spaceplane, the cost of delivering payloads to the space station and beyond could could drop from $15,000 dollars per kilo to less than $1,000 dollars, according to Reaction Engines.
Still, building a viable space plane isn't cheap either. The company estimates that development of Skylon would cost a total of $12 billion dollars. However, the ESA gave the project a much needed boost back in March when it declared the design to be feasible, citing that investigators didn't find any "impediments or critical items" in the proposal. In addition, the agency donated $1.4 million dollars (1 million euros) in seed money to further its development.
But before the technology can even be close to prime time, the team must figure out how to overcome some major challenges. For instance, the intake of oxygen from the air needs to be cooled to roughly minus 238 degrees Fahrenheit for the engine to work efficiently. The problem is that cruising at such high speeds creates friction, causing the surrounding air to be extremely hot.
A static test of an helium precooler system they're hoping would do the trick had been planned for June. But so far, company officials have yet to report any results.
Update: The story was updated to reflect the fact that space shuttle Atlantis launched this morning at 11:30 eastern standard time.
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Jul 7, 2011
Several points: the wings don't look big enough to enable the plane to glide. The nose is too pointed, and of course there are no re-entry tiles as on the shuttle, so how does the bare metal take the vast amount of heat generated by re-entry? Why don't they pre-cool the air using the liquid hydrogen,instead of liquid helium? I wonder why the engine nacelle is bent and not straight. Why don't they make them usable cargo carrying rocket, and then a separate smaller rocket, just carrying crew? Actually come to think of it, that is what the Russians do. Finally, the cargo bay looks very small compared with the size of the fuselage
Nice idea but will it fly? If it can't carry the heavy cargo loads we need into space then what's gained? Then there's a few concerns about how they'll create a material that will support re-entry yet have a return flight just hours later. Lofty ideas that might not be as well grounded as we wish. We need our space program but this looks more like pie in the sky than something we'll actually seeing at our local airport anytime soon. I love the SR71 freshening. All of us space geeks can't get enough of it.
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The biggest problem with their pre-cooler isn't getting the air cool, it's dealing with the inevitable frost build up, especially at lower altitudes. At the high volumes of air it will need to take in, it will also be taking in high volumes of water vapor. This vapor will tend to condense on the cooling vanes, producing a nice insulating blanket of frost, thus defeating your cooling effort. So you need some method to repeatedly heat up some percentage of the cooling vanes (to defrost them) and yet still supply enough chilled air via the active-cooling vanes. You could also combine the defrosting with some physical disruption, e.g. induce sonic booms (or some less exciting sonic disruption) inside the pre-cooler to shake loose the frost. But that would mean making your pre-cooler components stronger (and therefore heavier). And the systems downstream would also need to be stronger. Think about the damage fairly small chunks of relatively low-density foam insulation caused on the Shuttles. Then think about what a supersonic chunk of ice could do in a rocket engine. Ugh. And BTW, oxygen isn't a fuel, it's an oxidizer. Hydrogen is the fuel for this proposed vehicle.
By using a module for the humans, missions without people don't have to carry all the unnecessary paraphernalia to keep the crew alive. The real savings in in the mix of cargo and people.
I've been seeing the Skylon for years. Too bad there is no test vehicle. It's still all just a paper space ship. I wonder if it could work. Reliability? Maintainability? Lift Capacity? Re-entry needs? Operational Launch requirements? Runway length? There are still more unanswered questions than answers from these folks. What they have is a sales presentation. I want to see engineering data.
But at the end of the day, will it be any cheaper on a per-mission or per-lb-transported basis than the Shuttle was? I doubt it.
The simpler design of Burt Rutans SpaceShipOne/White Knight is already evolving with SpaceShipTwo/White Knight Two. The ongoing design process will have him flying far more advanced versions in 10 years. Well before any of these designs get through the prototype stage. His evolutionary design has put Virgin Galactic in a position to evolve into using a plane that can do everything from take off to landing with 1 plane while gaining valuable flight time, operational experience and perhaps more importantly the income to support deploying such a futuristic plane as shown here. Go Burt! Go Virgin Galactic!
I think what you mean is that only the cargo module with people on board would require the complex, expensive and heavy life support equipment. This would make the rest of the vehicle more efficient for non-human missions. But if it's going to have people on board, the while vehicle is still going to have to be "man rated", which is one factor that made the Shuttle so expensive.
it probably will be cheaper. Just launching directly up requires more fuel than flying sideways at a gradual pace.
A shuttle replacement - a spaceplane that will put heavy payloads into orbit at lower cost than an ordinary rocket - will be beyond the capacity of Virgin Galactic to develop. White Knight Two has a 17 tonne payload. A shuttle replacement will likely be around the 140 tonnes that a 747 can carry. The Air Force is already developing a spaceplane to replace the shuttle to put people into space through the X-37B project.
...but the maintenance of the vehicle. Each Shuttle mission cost roughly $1-billion, which was mostly turn-around maintenance required after each flight. It is very difficult to design a reusable vehicle that is "human rated" that can operate in as many hostile regimes as an earth-to-orbit-and-back vehicle has to endure.
It was originally proposed as a lifeboat for the ISS. It has already been scaled up successfully once for SpaceShipTwo. The basic design is very scalable. A larger scale version with half the cargo capacity of the shuttle could be flying years before anything currently on the drawing boards.