I often think that these projects suffer from a severe lack of ambition. When it comes to moving things, small has never been better. We need to replace the lifting capacity of the main booster.
In order to do it with a rail based accelerator we need to bring the whole package up to just subsonic before it becomes airborne. It also helps if you are as far up as possible so you do not have to fight the lower denser atmosphere so much when you become airborne.
So we build it in Denver
Our bird is at least the size of the space shuttle and has either a scram jet package able to escape on its own and or a solid booster pack as was used on the shuttle. We expect the scram jet kit to need some evolution time. Either way it is not necessary to lift a huge tank of hydrogen from the ground in order to go from zero to one hundred.
The bird could start on a flat track under external power the same way we launch planes on an aircraft carrier. A tunnel is built upward through the mount to exit at say 11,000 feet or more. There is no curvature in the track for the bulk of the lift and the main turn takes place just as the bird is entering the tunnel and passing one hundred miles per hour.
The tunnel itself is actively evacuated through a parallel relieve tunnel in stages as the bird is passing through the tunnel. The exit speed will be just subsonic and the internal power will be also up to full power as it hits the heavier atmosphere on exit. It may well turn out to be quite practical to have the scram jet initially on cruise while the bird lifts substantially into the upper atmosphere, at which point full power is applied in order to build up speed in order to break out into orbit.
The purpose is to get up to orbital speed and that can be possibly done at a lower altitude were oxygen is still available to the scram jet. Once speed is up, it is easy to punch into orbit and use rockets to maneuver.
The point of all this is to leave all the heavy launch power on the ground. This system can be built today with our present knowledge and the payoff will be a heavy lifter able to fly into space and return under its own power. The scram jet will allow the bird to maneuver and properly slow down for a well controlled reentry, possibly by even dipping into and out of the atmosphere a couple of times to shed velocity.
A well thought out program will make space access routinely available.
| Railway to the Sky? NASA Ponders New Launch System By SPACE.com Staff 14 September 2010 |
Imagine this: A wedge-shaped aircraft attached to a supersonic jet engine is hurtling along an electrified track, carrying a pod or spacecraft destined for orbit.
Sound farfetched? It may not be.
A team of engineers from NASA's Kennedy Space Center in Florida and some of the agency's other field centers are looking into this and other novel launch systems based on cutting-edge technologies.
Scramjet sky launch pads
One early proposal calls for mounting the launching aircraft on scramjets, which are air-breathing jet enginesdriven by supersonic combustion.
The aircraft would fly up to Mach 10, using thescramjets and wings to lift it to the upper reaches of the atmosphere, and then a small payload canister or space capsule similar to a rocket's second stage would fire off the back of the aircraft and into orbit.
After the high-altitude launch, the mother aircraft would return to land on the runway where its trip began.
The launch system would require some advancements of existing technologies, but it wouldn't need any brand-new technologies to work, said Stan Starr, branch chief of the Applied Physics Laboratory at Kennedy Space Center
"All of these are technology components that have already been developed or studied," Starr said in a statement. "We're just proposing to mature these technologies to a useful level, well past the level they've already been taken."
Riding rails to space
The scramjet launcher project could form the foundation of a future Advanced Space Launch System, with elements spread across different NASA centers to make it work, agency officials said.
At the Kennedy Space Center , a 2-mile (3.2-kilometer) test-launch track could be installed between NASA's huge Vehicle Assembly Building
But there are some challenges. To launch on an electrified track, for instance, the track would have to withstand at least 10 times the speeds commonly seen on tracks used for roller coasters, NASA scientists said. Roller coasters typically run about 60 mph (100 kph), they added.
NASA scientists also are looking into other methods of powering a track-launched vehicle.
A study into a rail launcher that uses gas propulsion is under way, with Starr's team applying for more funding through NASA's innovative-technology program to pursue it.
Engineers with NASA's Marshall Space Flight Center in Huntsville , Ala.
As for aircraft launching from a rail, there are some real-world tests for designers to draw on. NASA's X-43A, or Hyper-X, program and the U.S.
In late May, the Air Force's X-51A Waverider scramjet test vehicle set a world record for the longest hypersonic flight. The vehicle flew faster than Mach 5 for more than three minutes, compared with the previous record of 12 seconds by NASA's X-43A craft in 2004.
Commercial scramjet launches ahead?
Scramjet vehicles could be used as a basis for a commercial launch program if a company decided to take advantage of the basic research NASA performed along the way, Starr said.
Starr and his engineering team propose a 10-year plan that would begin with launching a drone similar to those used in the ongoing Air Force tests. More-advanced models would then follow, with the goal of developing a vehicle that can launch a small satellite into orbit.
The Advanced Space Launch System is not geared to replace NASA's retiring space shuttle fleet, or any other manned spacecraft program, Starr said. But if the early unmanned launches were successful, the system could eventually be adapted to carry astronauts, he said.
"It's not very often you get to work on a major technology revolution," Starr said.
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