Saenger joins Hermes and Hotol

Flight international, 13 September 1986 (page 62)

MUNICH

During an ESA Council meet­ing late in June, plans for a proposed German space shuttle and launcher design were officially submitted, and now rank alongside the British Hotol and the French Hermes projects, reports Stefan Geisenheyner.

Announcing the news, the ESA said: "The German dele­gation presented an MBB study on a two-stage space shuttle system named Saenger, which the delegation con­siders to be a contribution, serving together with Hotol, for a joint technology study. The ESA Council has noted the statements on Saenger and Hotol and the additional information submitted by the German and British dele­gations."

Pic.1. Germany's proposed Saenger two-stage shuttle system could take off from any large European airfield to carry payloads into space. The rocket-powered second stage, borne on the back of the hypersonic first stage, will be able to reach an altitude of 300km

The ESA now has three projects to consider. The German proposal comes roughly midway between the French and British projects in terms of technical sophisti­cation. At present the French Hermes project appears to be the most realistic. Proposed by Aerospatiale, it is fairly modest in its technological pretensions. Planned to be ready for launch by an Ariane 5 booster in the mid-1990s, it is basically a large-winged, 16-ton re-entry vehicle with no propulsion of its own. In effect, Hermes will be no more than a payload for the launch vehicle. Both launcher and shuttle have yet to be funded, designed, and built.

Hotol, proposed by British Aerospace, is much more ambitious, not only in size and weight, exceeding Hermes' figures ten times over, but also in representing a new launch concept. Hotol is essentially an aerospaceplane, a trans-atmospheric vehicle, outdoing everything yet airborne or proposed.

The newly presented German project, named after German space pioneer Eugen Saenger, embodies a two-stage space shuttle similar in appearance to an aircraft. In launch configuration it would weigh roughly 400 tonnes and consist of two vehicles, with the actual shuttle riding on the back of the launch air­craft. This piloted and recov­erable delta-winged mothership would be 170ft long and have a span of 82ft. On land­ing it would weigh between 120 and 150 tonnes. Powered by turbojets, this first stage would fly like an aircraft and, upon reaching its ceiling alti­tude of 100,000ft, would attain a speed of Mach 6.0. The space vehicle, resembling the mothership in shape, is to be 82ft long, span 40ft, and have an overall weight of 50 tonnes, of which 35 tonnes will be fuel.

On reaching launch altitude the shuttle would separate from the mothership and ignite its rockets to attain its desired orbit. The first stage would return to earth and land on a runway like a con­ventional aircraft, as would the shuttle after completion of its mission.

If this concept can be realized – the key for success is, without doubt, the avail­ability of very advanced jet engines for the mothership – the Saenger could avoid many of the difficulties inherent in the British project. The first stage would be powered by jet engines using atmospheric oxygen, and the second driven by a rocket engine, thereby avoiding the costly research and development required for Hotol's radically novel hybrid engines, suitable for use both in the atmosphere and in space.

Above all, the first stage of Saenger would have much in common aerodynamically with a hypersonic transport built along Hotol's lines, while the Saenger shuttle vehicle would be able to transport a much heavier payload than the Hermes. MBB claims that it could carry a crew of between two and 12, or a corresponding payload. It is also claimed that payloads could be orbited at only 20 per cent of the cost of using the Hermes-Ariane 5 combina­tion.

The entry of the Saenger project into ESA planning does not imply that the three proposals are now competing. They all have the potential to help Western Europe gain independent access to manned space travel, boosting European space autonomy and thereby reducing reliance on the super-powers.

Hermes does not clash with the Saenger and Hotol concepts. The French shuttle has been designed for the mid-1990s, utilising existing state-of-the-art technology. Hermes is a mandatory step on the road to European manned space travel, which necessarily must involve a learning phase. It is also the least expensive of the three shuttles, though it is expected to cost between £1 and £2 billion to develop, and it is common for estimates of this kind to be greatly exceeded in practice.

The much more ambitious British and German projects would cost at least twice as much, if not three times as much, and it is more than doubtful whether ESA is will­ing and able to allocate the needed funds. Even if the unlikely happens and money begins to flow, the British and German designs could not possibly become available before the turn of the century. By that time the USSR and the USA are bound to have space stations in orbit, being supplied by some sort of shuttle service.

Nonetheless, a decision to go ahead with either Hotol or Saenger, or a combination of the concepts, would open the way for Europe to participate in the quest for hypersonic air travel, now an official goal of the USA. Last spring Washington earmarked $530 million for the development of a national aerospaceplane programme.

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