In addition to rocket and air-breathing propulsion work involving combustion, NASA is beginning to test concepts such as magnetic levitation (MagLev) systems that could hurtle future reusable launch vehicles off their pads with ground-based electrical fields.
NASA MagLev testing is to enter a major new phase next spring. The use of a MagLev launch-assist track would reduce the vehicle size and propellant needed to place a payload in orbit. The work is underway at Marshall Space Flight Center and Lawrence Livermore National Laboratory.
By using a MagLev track to provide the initial 400-600 mph. of velocity at 2g of acceleration, engineers believe they could develop a winged space vehicle 20% smaller than one with a comparable payload using all self-contained propellant, said Sherry Buschmann, Marshall's project manager for Launch Technologies.
The advantage with MagLev is that propulsion for the initial acceleration off the runway is ground-based electricity that does not have to be carried by the flight vehicle.
Marshall engineers believe that a 1.5-mi. MagLev track could be used to accelerate a 120,000-150,000-lb. RLV about the size of an SR-71 using only $75 of electricity. The carriage for the flight vehicle would weigh 60,000 lb. and stay on the track at vehicle liftoff.
The savings in propellant and overall RLV design costs could be significant. And the track would also allow launch-abort advantages. Initial rocket engine start would occur midway down the track. If the rocket propulsion system failed to come up to speed as planned, the remaining 4,000 ft. would be used to slow the vehicle to a safe stop.
Marshall has already run more than two dozen MagLev runs on a 50-ft. proof-of-concept track. This track will be extended to 400 ft. for higher-speed runs that are to begin in March or April. The Navy is interested in MagLev catapults on future aircraft carriers, and a Navy-designed electrical compensator will be used with the 400-ft.