Air-Launched Space Van

Air launch from a Boeing 747 or an Antonov AN-225 contributes a lot more than just kinetic energy.  In fact early in the trajectory, potential energy is more important than kinetic energy. The combination of potential energy, kinetic energy, reduced gravity losses and reduced drag losses contribute a total equivalent of about 670 m/s when a carrier aircraft launches an upper stage at perhaps mach 0.8 at an altitude of 12 km. Moreover, air launch eliminates the need for the altitude compensating engine that would otherwise be necessary for an unassisted single-stage-to-orbit (SSTO) reusable launch vehicle. The overall benefits of air launch allow consideration of a small reusable orbiter powered by the well proven Pratt & Whitney RL10 rocket engine. Figure 1 below presents our 1982 concept for using a 747 as a carrier aircraft to launch our then-current "Space Van" reusable orbiter.

Rendering of Space Van and 747 Carrier Aircraft over American Samoa © 1982 by Bill Phillips

The air launched Space Van was designed to operate in two different modes: an orbiter mode; and a booster mode. In the orbiter mode, the Space Van could achieve a 450-km orbiter with a pilot and a 300 kg without further staging. In the booster mode, the 747 would fly uprange before launching the upper stages. An unmanned semi-expendable final stage would then be capable of orbiting a 3000-kg payload. The engines and avionics of the semi-expendable stage were then te be recovered on a subsequent flight of the Space Van in the orbiter mode. As attractive as air launch appears to be, it has its problems. One drawback with the 747 approach was the potential fatigue of the 747 vertical tail because of buffeting from the orbiter stage. A twin-tail would solve this problem; however, building a simple pressure-fed reusable rocket booster appeared to be less expensive. The main problem with subsonic air launch appears to be marginal performance for an orbiter that is designed to get to orbit without further staging. Len Cormier, the X Van's project manager, looked at towing and aerial refuling back in the early 1960s and found these approaches  to be basically similar to air launch with respect to performance benefits and limitations. The Antonov AN-225 already has a twin tail an can carry a 250 tonne payload. Nonetheless, even the AN-225 appears to have serious limitations. Because of these and other problems, Third Millennium currently proposes its X Van launch vehicle -- which greatly reduces the initial investment required to start operations. MMI also feels that the X Vam is significantly lower technical risk than our previous concepts. MMI considered a number of variations of the air launched concept during the period 1978 to 1987.  These included droppable liquid oxygen tanks, and variation in the number of RL-10 engines from six to eight engines. One variation appears to be applicable for X Van operations:  i.e. use of a semi-expendable stage for deployment of initial habitats for the orbital assembly facility that Third Millennium Telecommunications (MMI / Telecom) plans to construct in low Earth orbit. This facility would be used for on-orbit assembly of 40-meter diameter antennas for subsequent transfer to geosynchronous orbit.