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Tuesday, December 21, 2010

NASA adds turbojets and rockets to its railgun scramjet launcher

Does more engines equal more awesome? You bet it does. NASA's latest concept for their satellite launching system is getting fleshed out with some extra sources of thrust.
NASA wants to be able to do away with inefficient rockets and launch satellites into orbit using a scramjet spacecraft fired out of a railgun. A system like this is actually realistic in the near future, seeing as both high powered railguns and scramjet aircraft have been successfully tested.
As NASA starts seriously considering how exactly the launching system would work, we're getting more details about just what would be involved, and it looks like there are some thrust gaps that would need to be filled with more conventional technology.
The initial launch is based on a railgun. The vehicle would be fired down a two mile long track using 180 megawatts of electricity, propelling it to Mach 1.5 in about 60 seconds. That's a lot of acceleration, but not enough to turn a human into a pancake. Mach 1.5 (about 1,100 miles per hour) is fast, but not fast enough for a scramjet to function, so the vehicle would fire up a high speed turbojet just before it lifts off from the track to boost itself to Mach 4.
At Mach 4, the turbojet shuts down and the scramjet kicks in, accelerating the vehicle to Mach 10 at 200,000 feet. At that altitude, there's not enough atmosphere left for the air-breathing scramjet to work, so the final piece of the system is a regular old rocket. The scramjet/turbojet vehicle drops away, leaving an upper stage of sorts behind, which uses rockets mounted in its tail to make it the final distance into orbit as the lower stage re-engages its turbojet to fly back to base. After delivering its payload, the upper stage glides back like the space shuttle, and both stages can be ready to go again in 24 hours.
So when is all this going to happen? Well, the technology is basically here, we just have to figure out how to scale it up. As NASA puts it, "we have all the ingredients, now we just have to figure out how to bake the cake." It'll be more than billion dollars or so worth of cake by the time it's finished, but just imagine how tasty it'll be when it's all done.
Via Popular Science

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