The Feasibility of a Mach 7 Transport Employing Airbreathing Propulsion Systems 610102

Trip time requirements between points on earth can be reduced by use of hypersonic aircraft if the range is sufficiently large so as to minimize the effect on average speed of the time of acceleration and deceleration. See Fig. 1. The objective of this study is to determine if it is technically feasible to use airbreathing propulsion systems to provide an intercontinental vehicle which will bring virtually all major cities of the world within two hours flying time of each other.

An extensive study of various propulsion and performance aspects of a single-stage long range Mach 7 delta wing trans port, Fig. 2, 30,000 lb payload (125 passengers and cargo), has been completed. The study encompasses consideration of the propulsive performance of a hypersonic ramjet design featuring lift augmentation. Particular attention is given to the influence of geometry, equivalence ratio, diffuser recovery characteristics, and boundary layer bleed on this performance. A variety of design charts permitting immediate engine sizing is presented. Next, considerable attention is given to climb and acceleration which is accomplished in two phases; a Mach 0-3.6 turbojet phase, and a Mach 3.6-7.0 ramjet phase. The significance of the number of turbojet engines, ramjet engine size, called-for tangential acceleration, and gross weight at take-off for trajectory characteristics, climb-time, climb-fuel, and climb-range is is presented. Finally, the significance of all these factors for overall trip performance is given.

The results of the study indicate that present state-of-the-art in propulsion, aerodynamics, insulation, cooling, and structures can provide a hypersonic airbreathing transport capability. A 700,000 lb configuration could transport the above payload 3600 nautical miles with a fuel reserve adequate for descent and landing techniques similar to those used in present transport operation. Fully automatic flight control from take-off through landing would provide a means for substantially reducing fuel reserves. 4500 nautical miles would be possible if the fuel reserve requirement could be reduced to zero. The trip times would be 82 and 94 minutes respectively.

These results demonstrate that it is technically feasible to construct a hypersonic transport of intercontinental range. It may be anticipated that continued research in troublesome problem areas will suggest solutions which will increase the ratio of payload weight to gross weight and hence increase the efficiency of hypersonic transport.