Vehicle performance tradeoff study for a small size lifting re-entry vehicle

Abstract

A wing-body re-entry vehicle has higher lift-to-drag ratio and enhances the down-range and the cross range of a ballistic vehicle. In the present study, trade-off analysis has been carried out between vehicle performance and flight parameters with variation in burn out angle at suborbital speeds. The vehicle during its re-entry flight is subjected to extreme heat rate and very high dynamic pressures. The re-entry range is maximized for shallow entry angles. Lowering the re-entry angle implies lowering the flight path angle at the burn out point. This results in increase in re-entry range and reduction of free flight range. These two parameters affect the overall range of the vehicle. Longer flight times at shallow re-entry angles also result in an increase of the total heat load. The burn-out angle also affects the g-load required to initiate the initial skip. This paper discusses the sensitivity of total heat load, maximum normal acceleration, range and the flight time once the re-entry trajectory is optimized for maximum down range subject to maximum dynamic pressure constraint of 350 KPa and 3 MW/m2 of heat rate limit for a range of burn-out velocities and burn-out angles. All trajectories within the matrix have been optimized for maximum down range/cross range using hp-adaptive pseudospectral method. The optimal angle-of-attack and bank angle control deflections have also been discussed. It has been found that for a boost-glide wing-body vehicle, the range advantage is of more than 35 percent as compared to bi-conic re-entry vehicle. Near optimal down range is obtained at burn-out angle of approximately 15 degree. The g-loads and angle-of-attack trim control requirements remain within limits. Cross-ranges of the order of 800 to 2000 km can be obtained with in the medium to intermediate range using wing-body re-entry vehicle design.