‘Shuttle’ type vehicles

It was the need for a more economical system, which could be used for placing objects into earth orbit and land on a conventional runway which led to the development of the Space Shuttle (Fig. 8.19). This vehicle was launched by a booster rocket and injected into orbit by its own rocket engines. During re-entry it was successively a hypersonic, supersonic, transonic and subsonic glider.

If we examine the aerodynamic characteristics of the shuttle, we find that the lifting surface was a slender delta configuration which had a great deal in common with Concorde’s wing. We have already seen that this type of wing behaves in a progressive and satisfactory manner from subsonic to supersonic speeds. It is, in fact, the landing requirement which was mainly responsible for the overall size of the shuttle wing.

We have already seen (Chapter 1) how separation is used to good effect on this type of wing to produce a pair of well-ordered vortices on the top surface over a large range of incidence. If the angle of attack is increased to extreme values there is a progressive breakdown in the vortex structure until the con­ventional disordered separated wake is obtained. This flow condition is not desirable on a supersonic passenger transport because of the large amount of drag involved. No such economical restriction applies to the re-entry case, though, and it is this flow regime which was used during a large proportion of the hypersonic phase of re-entry.

The provision of substantial amounts of lift enabled flight profiles to be chosen which considerably alleviated the heating problems associated with re­entry. An ablative shield was not required and instead ceramic tiles were used to insulate critical parts of the structure.

The shuttle was placed into orbit using a booster rocket and the shuttle itself formed the second stage of the launch vehicle. In general two stages are always needed to inject a payload into earth orbit if conventional rocket propulsion is used. Thus expensive recovery and refurbishment of the first stage is required and in addition, although a runway can be used for landing, it is necessary to provide a launch gantry and attendant services at the commencement of the mission. From an economical point of view the attraction of a single stage vehicle which can both take off and land from a runway and still inject a payload into earth orbit is obvious.