FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1964
1964 - 0041.PDF
36 FLIGHT International, 2 January 1964 Missiles and Spaceflight ALTITUDE MILES ASPECTS OF THE AEROSPACE PLANE 5,000 Fig I Aerospace vehicle performance 10,000 15,000 SPEED FT/SEC 20,000 This article is based on extracts from "Some Fundamental Aspects of the Aerospace Plane Concept," presented at the recent British Interplanetary Society symposium on aerospace vehicles by C. R. Turner of Hawker Siddeley Aviation Ltd. Other papers from the symposium were abstracted in our issues of December 19 and December 26, 1963. THE major mission envisaged for the aerospace plane is that offerrying supplies and personnel between the Earth and satellitesin near-Earth orbit. For this type of mission an operating height above the Earth's surface of the order of about 200 miles should suffice. This ferrying operation might be used for the assembly of interplanetary missions, or alternatively off-loading them on return to near-Earth orbit, and also for setting up scientific space laboratories. All this implies provision for rendezvous and docking, and to this end the capability of the vehicle for pre-orbital manoeuvre might be an important design factor when assessing the comparative features of a rocket first stage or an airbreathing first stage. Other foreseeable missions include the conducting of scientific experiments and the inspection and possible servicing of communi- cation, navigation and meteorological satellites. For some of these missions the operating heights would have to be greater than 200 miles, unless considerable orbiting manoeuvre is built into these satellites for such a purpose, involving a payload penalty, more severe guidance and control requirements and would in fact imply a more advanced concept. Also, in general, any manned mission where information is required with the minimum of delay might justify an aerospace plane concept. With the assumption that the concept will enable launching from more conventional sites, possibly in Europe, the capability of launch into an orbit other than through its point of launch is a very important aspect of an aero- space plane operation. Could it be used, for instance, to undertake those missions for which an equatorial launching site is considered necessary? It must be realized that this range of missions with corresponding payloads cannot be accomplished economically with a single design. One does not expect one type of civil airliner to be suitable for all operating conditions. These designs will certainly differ radically one from the other. For example, the propulsion combination required for a low-payload mission may differ considerably from that requiring a high payload. Ultimately, and this will be a difficult decision, a choice will have to be made, for the first generation aerospace plane at least, regard- ing the particular missions and payload range on which it is best to concentrate. It has been suggested that the payload might be in the region of about five tons so as to compete neither with payloads associated with large US rockets, nor with the large US spaceplane concepts. Regarding most of these missions, the inclusion of a man in the system seems imperative, in particular for the requirements of rendezvous, docking and landing at a specified site. It is realized that the inclusion of a man in a space system requires additional equipment to provide life support and more duplication than for an unmanned mission. Obviously the man must not be taken along just for the ride, but must be justified as an essential part of the system. Basic Design Considerations Bearing in mind these missions, let us attempt to define the principal characteristics of an aerospace plane. These must be such as to show positive advantages over any existing conventional systems or developments thereof. As it is inconceivable that, on this side of the Atlantic, any project based on this concept will be completed in under ten years, the problem of creating a system that will not be superseded before it is operational is very important. To my mind the basic characteristics of an aerospace plane should be the following:— (a) The vehicle's stages should be recoverable whether rocket or airbreathing. (a) The final stage should be capable of entering an orbit of at least 200 miles in the first instance; this may be extended in the light of experience and requirements. (c) It should be capable of considerable sub-orbital manoeuvre. To attain orbital planes that periodically pass through the launching point, manoeuvrability that would effectively reduce the time delay should be a capability. Regarding orbital planes inclined to the equatorial plane at an angle less than the launching latitude, manoeuvring capability to enter these orbital planes should exist, although this will depend on the latitude of the launching site. (d) It should be capable of a limited manoeuvring capability in orbit. It must be realized that manoeuvring operations such as orbit changing, repositioning in orbit, etc, involve a very large weight penalty. It can be calculated, based on a 5,0001b payload, that even a 1° orbit change can involve a weight penalty of about 3501b, a 30° orbit change about 5,0001b. To "catch up" a 30° lag in a 200-mile circular orbit by direct orbit transfer requires again about 8501b. However, these figures do imply a reasonably quick manoeuvre time, for the weight penalties can often be considerably reduced if a longer time is acceptable. The point, however, is that within the present capabilities the idea that the spaceplane in orbit can enjoy the manoeuvring capabilities of a fighter should be dispelled. Finally, the vehicle should be able to rendezvous and dock as required by the missions. (e) Re-entry should be possible whenever required and the vehicle should have the aerodynamic capability (moderately high hyper- sonic L/D) and good subsonic characteristics to enable it to glide and land, with power when required, to a pre-determined site. The main problems encountered here are high deceleration, heating rates, total heat input, and acceptable landing speeds, etc. (/) The vehicle, in its final form at least, should be manned; this will undoubtedly suggest a minimum orbital weight of at least 4,0001b. (g) To enable reasonably fit, but not specifically trained, personnel to engage in these missions the maximum vehicle acceleration and deceleration should be restricted to a value between 1.5g and 2g, although this will depend on the rate of change of acceleration, and its duration. These requirements represent to my mind the desirable features of an aerospace plane and those which taken as a whole should lead
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
