Graham Warwick/ATLANTA
PRATT & WHITNEY and Russian rocket-engine manufacturer NPO Energomash are jointly studying a tri-propellant motor for NASA's X-33 reusable launch vehicle (RLV) technology-demonstrator. Near-full-scale combustion tests are being conducted in Russia under NASA contract, says the US Company.
News of the tie-up emerged at the hand-over of the first Energomash RD-120 rocket motor to P&W, which has offered the engine to power Orbital Sciences' X-34 small re-usable launch vehicle. The 835kN (190,000lb)-thrust RD-120 is the second-stage motor from Russia's Zenit expendable launch vehicle.
Compared with the liquid-oxygen/kerosene RD-120, the tri-propellant engine being studied jointly with P&W would burn liquid hydrogen, kerosene and oxygen for lift-off, and liquid hydrogen and oxygen later in the ascent. During tri-propellant operation, liquid hydrogen improves the combustion of kerosene and increases rocket-motor specific impulse.
Energomash is developing the RD-700 tri-propellant-engine series, says Igor Fatouev, chief designer of medium thrust-class engines. A jointly developed engine would combine P&W's experience with liquid hydrogen and Energomash's expertise with kerosene, says Joseph Zimonis, vice-president of P&W Space Propulsion Operations' liquid-rocket programmes.
P&W plans to test fire the RD-120 engine at its West Palm Beach, Florida site later this year. The engine is being offered in competition with the Rocketdyne RS-27 to power the X-34, a small reusable launcher, which will be air-launched from NASA's Shuttle carrier-aircraft.
Modifications required for the X-34 are limited to halving the nozzle length and adding a gimbal, says Zimonis. The RD-120 is designed for one-time use, but can be used up to seven times, says Fatouev. One engine has undergone 17 ground tests, he says.
The RD-120 has been used in 25 Zenit launches since 1985, with two failures, Fatouev says. A total of 481 tests have been conducted using 150 engines, demonstrating a statistical reliability of 0.995, he says.
P&W and Energomash plan to establish an US-based joint venture to market the modified RD-120M worldwide. Fatouev says, that three RD-120s, have already been supplied by Russia to China.
Source: Flight International
