Flight international, 19 April 1989 (page 19)
By Tim Furniss
A Phase 2 technology development programme could lead to flight demonstration in 1999 of a prototype Sanger reusable two-stage space transportation system, says the West German Federal Ministry of Research and Technology.
MBB is leading the Phase I concept definition study, with a team comprising its two space and two aircraft divisions, MTU, and Dornier. The four-year study, begun in February, will cost DM220 million (£68 million), MBB providing half the DM30 million being contributed by German industry.
Pic.1. Germany's Sanger could boost Europe towards a hypersonic airliner
The West German aerospace research establishment, DFVLR, is providing about DM86 million and Deutsche Forchungsgemeinshaft between DM20 million and DM25 million.
This Phase 1 study could be followed in 1993 by the Phase 2 technology development programme, leading to flight demonstration in 1999. Development of the Sanger vehicle could begin in 1996, when work on the expendable Ariane 5 is complete, providing the logical next step in European launchers, says MBB. A Sanger first flight is possible in 2006.
European autonomy
Dr Dietrich Koelle, Phase I study manager, says that, for real European autonomy— which means the capability to perform launches from Europe —only a horizontal launch is feasible for safety reasons.
The main missions required by Europe are: transfer to the Freedom Space Station, and later autonomous Columbus-based manned platforms, in 28.5° orbit: and launches into geosynchronous orbit, which require a cruise capability of 3,500km, only feasible with Sanger's five first-stage air-breathing turboramjet engines.
In contrast to single-stage concepts, such as Britain's Hotol, the two-stage concept allows the air-breathing propulsion system to be separated from the rocket engine. "The technical risks entailed by a very complex combined propulsion system can be avoided and no dead weight need be carried into orbit," says Ernst Hogenauer, vice-president and general manager of MBB's space communications and propulsion systems division. "Propulsion is the technology that will make or break the plane," he says.
The 300kN-thrust turbo-ramjets on the winged first-stage vehicle offer maximum commonality with potential future hypersonic passenger aircraft, and the synergistic effect will be taken fully into account, Koelle says.
He believes that past experience proves that manned space-flight and unmanned missions should be carefully separated. This requirement is met in Sanger by two different upper stages, the reusable HORUS., a manned hypersonic orbital upper stage capable of carrying 4 tonnes into orbit, and the expendable CARGUS, an unmanned cargo upper stage for payloads up to 14 tonnes.
Koelle also adds that "no major technical breakthroughs are required" to develop Sanger. It is the logical follow-on to Ariane 5 and the Hermes manned spaceplane, he argues. Sanger could make six manned launches a year at $15 million to $20 million each, compared with Hermes' $200 million launch cost and two launches a year. Sanger could save Europe $1 billion a year, he says.
HORUS would have a two-day lifetime in orbit compared with Hermes' proposed 33 days. The upper stage is seen as a transportation vehicle and not a laboratory. The 24-tonne HORUS manned orbiter, with a l,200kN cryogenic rocket engine, "will require more advanced technology than the US Shuttle or Hermes," says Koelle.
The flight profile of Sanger would begin with the first-stage turbojet engines taking the vehicle to 10km altitude before passing Mach 1 under full thrust with afterburner. At about Mach 3.5, and 19.5km altitude, ramjet propulsion takes over, accelerating the vehicle to Mach 4.4 and to 28km.
A Mach 4.4 cruise phase over inhabited areas will extend 3,500km to the south and then due east until the vehicle is accelerated to Mach 6.6 and 37km for staging.
