Flying qualities of the Hermes spaceplane and shape definition process

Abstract

This paper deals with the last Hermes spaceplane shape 1.0 definition and evaluation cycle. It focuses its interest on flying quality aspects to highlight in this important domain the shape definition process, but performance and other main design drivers are also defined and evaluated. After a general description of Hermes critical mission phases, trajectory control principles and flight parameters envelopes are defined. Then we recall the main reasons why Hermes is not similar to the U.S. Orbiter or Buran and that this was again confirmed in a trade-off in 1990. So iteration from 0.0 to 1.0 shape was limited within the same concept. The process of shape definition itself is described including presentation of all the checking points defined. A reduced set of 15 control points have been defined and must be evaluated with the best computational tools for acceptance by the agencies of the proposed shape. The 1.0 shape is presented and compared to its predecessor 0.0. In the second part we define and justify all the criteria concerning trajectory and flight control that were defined in the overall Shape's Requirement Document that was the result of an intensive system and synthesis activity. After computation/estimation of a detailed data base including uncertainties, the 1.0 characteristics are compared to the required ones that are almost all satisfied in nominal conditions and often with margins. Finally, the problem of compatibility of aerodynamically controllable range with respect to layout and overall CoG whose shift can be higher than 1% due to uncertainties is discussed including further work presently planned.