Construction of the first parts of Rotary Rocket's Roton commercial space vehicle is under way, kicking off an ambitious development schedule aimed at achieving initial flight tests by the middle of 1999.

The first elements of the Roton, an unpiloted, unmanned, re-useable single stage to orbit (SSTO) launch vehicle, are being built at Mojave, California, by Scaled Composites. These include the large composite propellant tanks. The vehicle is designed to carry up to 3,189kg (7,000lb) to low earth orbit using a 2,225kN (500,000lb)-thrust Rotary RocketJet engine. Unlike previous craft, the Roton is designed to return to the surface using rotor blades fitted with tip thrusters.

"We are in the process of starting construction of the ATV [atmospheric test vehicle], so that we can prove we can fly it and land it," says business development director, Geoffrey Hughes. "We originally intended to autorotate all the way in with heavy tips on the rotors. However, we faced taking all that weight to orbit, so we opted for tip jets," he adds.

The result of that modification is expected literally to provide a boost to the test programme. The powered rotors will be used to "bunny hop" the ATV to altitudes of between 5,000ft (1,525m) and 8,000ft for test flights.

By demonstrating the landing phase using the ATV, the San Francisco-based company does not have to wait for the development of the rocket engine, shaving several months off the schedule. This now calls for full scale flight tests using the "full-up"-powered Roton at the end of next year, with entry into service in 2000 and a target price per flight of $7 million.

The test programme will begin "-with a couple of vertical hops before we head for orbit", according to Hughes.

When complete, the Roton will stand almost 20m tall with a maximum diameter of 6.7m. The rotors, which lie flush with the casing of the liquid oxygen tank during the ascent, will be deployed from a hub which is mounted in the nose of the rocket. The rotors measure about 8m in length.

Source: Flight International