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EUROPE'S NEW CONCEPTS FOR RLV DEMONSTRATORS

The new technologies divisions of various European aerospace companies are currently working on new concepts for RLV demonstrators (reusable launch vehicle). This is not entirely incidental. After ESA has completed its FESTIP study (Future European Space Transportation Program), Europe is now setting the cornerstone for the development of a partial or fully reusable launcher which is to ensure Europe's leading position in the commercial launch market.

The main point of Europe's concern are the various developments of new launchers in the USA. Along with heavily governmental funded new expandable launchers (EELV), there are several other enterprises for reusable launchers on their way as well, the X-33/VentureStar being one example.

Even though there is a big questionmark on the operability and feasibility of some of these new systems, many believe that it is only a question of time until the reusable launch technology will be mature enough so that an RLV will take over the role of expandable rockets.

"We cannot ignore what is going on in the USA", says Bernard Humbert, director for space programs with Aérospatiale. While Europe has made some experience with its recent flight of the atmospheric reentry demonstrator, it has basically no basis of expertise on the reusability aspects of RLVs. Furthermore Europe's spaceflight budget is very limited due to its commitment to ISS and Ariane 5 improvements. One more reason to focus its limited forces.

The next flight opportunity for Europe will be the in the frame of the European participation in the NASA X-38 program for the future crew rescue vehicle for the space station. The flight is planned for 2001.

However, these opportunities are not sufficient for Europe to gain enough expertise to master RLV technology on a system level. For this, a European lead X-vehicle program is needed, such generating the expertise to decide on the feasibility of a reusable launcher in the future.

Along with various national programs, the validation of key technologies on the ground and in-flight will be managed through ESA's FLTP (Future Launchers Technologies Programme), in which the German government, much to the dismal of the German industry, does not want to participate although the German industry has a leading role in Europe for RLV technology programs and for the European participation in the X-38 program.

The goal of the first phase of FLTP from 1999 to 2001 will be to evaluate the various concepts and to make a decision on a flight demonstrator. Various concepts were presented in Arcachon, France, in March at an atmospheric reentry vehicle symposium organized by the French Aeronautics and Astronautics Association.

ESA itself came forward with its European eXperimental Test Vehicle EXTV which was based on the FESTIP study. EXTV has a projected mass of 4,2 tons and is supposed to be used in several flights. The vehicle will be powered by rocket engines and is supposed to take off and land horizontally, reaching speeds of up to Mach 4. Additional booster shall increase the flight regime to Mach 12.

Aérospatiale has come forward with a phase approach involving three different demonstrators. First, it plans to explore the flight regime up to cold hypersonic flight and also focus on guidance and autonomous landings with a slow-speed version of the Ares vehicle. A high-speed version (Ares-H) will then be used to explore the hyperflight envelope. In this mission, the horizontal landing is only secondary and the vehicle will be recovered with a parachute and land in the ocean.

As a next step, the French aerospace company sees the Themis demonstrator which would have four times the size of Ares and focus on key RLV technologies along with the operability of such systems. Themis would be powered by a reusable version of the Ariane 5 Vulcain 2 engine, the vehicle reaching speeds up to Mach 11.

Alenia suggested a stepwise concept using an even smaller demonstrator (approximately 64 percent of Ares), followed by the EXTV and a subscale RLV.

Dassault Aviation suggested the Vehra, which already has a more commercial aspect to it. Vehra is a lifting body design in the 25-ton class. The vehicle would be carried on top of an Airbus A300 airliner currently operated by Novespace for zero-g flights.

Vehra would be released at approximately 10 kilometers altitude and at a speed of about 0.8 Mach. The Airbus would do a zero-g push-over maneuver to ensure safe separation of the craft. Vehra's NK39 engine would fire about five seconds after physical separation. According to Dassault, Vehra could carry a 4-ton second kickstage in a payload bay, allowing to carry a 250-kg payload to be carried to a 500-kilometer low-earth orbit. According to Dassault, Vehra could be built for Euro 300 million and accomplish five flights by 2004.

The German Dasa is suggesting a very much commercially oriented concept. Dasa is looking at the small Phoenix demonstrator which would be used with and without propulsion modules. Within ten years, this small experimental demonstrator would lead via the EXTV to a Full-scale suborbital hopper. The 400 ton launcher is based on the FESTIP design for a suborbital hopper and would carry a second stage with a mass of 6 to 8 tons to carry payloads into low earth orbits, such being complimentary to the Ariane 5 rocket.

The Hopper would be launched horizontally on a sled to reduce the necessity for a heavy landing gear. The sled would accelerate the ship to approximately 600 km/h. Dasa is ready to invest approximately DM 60 million into the Phoenix development. First windtunnel test with a 1:20 scale model are already under way.

The purpose of the FLTP will be to select the right demonstrator concept for Europe. Europe must avoid the mistakes that were made with the Hermes program which was canceled by ESA in 1992 because of the financial and technical risks. According to ESA and the involved industries, a technology validation with experimental vehicles will be the key to be ready for a full-scale RLV development program in 2006. This transporter should then have the potential to significantly lower the launch costs and be commercially successful.

From page 46 of FLUG REVUE 7/1999