Accelerators and decelerators for large hypersonic aircraft

Abstract

H YPERSONIC aircraft will be considerably different from subsonic aircraft. They will be very large, deltoid-configured aircraft with needle noses. Thus their shape will be almost the opposite that of subsonic aircraft which have much higher aspect-ratio wings and raindrop-shaped fuselages. A result of these differences is that hypersonic aircraft will have much higher takeoff and landing speeds, and they will be less efficient when flying at subsonic speeds. To overcome their low-speed inefficiency, more powerful subsonic engines would be required. Since noise increases with power, more noise would be created during subsonic operation. And because of their large size, hypersonic aircraft will generate intense sonic booms when flying at supersonic speeds. With these vast differences it is unreasonable to assume that hypersonic aircraft will be operated the same way as subsonic aircraft, i.e., that they will take off with onboard power and land on a long runway at any large airport. On the contrary, hypersonic aircraft, with their onerous characteristics, will probably be over-the-ocean craft, like the historical flying boats. Thus they will take off and land at only seacoast sites where the noise and sonic boom will be generated over an ocean. With takeoffs and landings at only a few sites, it will be economically feasible to have a considerable amount of ground-based equipment at each site. For good economics the operation of hypersonic aircraft must be very reliable. The use of ground-based, rather than airborne, equipment will increase their operational reliability because: 1) Ground-based equipment does not have the severe weight and volume limitations that airborne equipment has; so it can be designed more conservatively with larger margins of safety. 2) Ground-based equipment does not have to endure the vibrations, large temperature changes, and other hazards of flight. 3) Ground-based equipment will be available for maintenance most of the time. It will not be in the air where it cannot be serviced or repaired. Thus the goal should be to minimize the amount of airborne equipment by developing as much ground-based equipment as can be used. To fulfill this goal it is found that: 1) It is possible to design and build a ground-based accelerator that can precisely control the attitudes of very large aircraft while they are accelerated through the speed of sound and then launch them at a speed of Mach 2. 2) It is also possible to design and build a rotatable, groundbased decelerator that can land a large, fully-loaded aircraft that is traveling at a speed of 450 mph. Presented as Paper 90-1986 at the AIAA/SAE/ASME/ASEE 26th Joint Propulsion Conference, Orlando, FL, July 16-18, 1990; received July 30, 1990; synoptic received March 14, 1991; accepted for publication March 28,1991. Full paper available from AIAA Library, 555 W. 57th Street, New York, NY 10019. Copyright © 1991 by Edward Lantz. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. * Consultant. Associate Fellow AIAA.