Design of air breathing engine is ahead of schedule

Initial design of a new prototype air-breathing rocket engine for NASA reached a major milestone ahead of schedule last week.

Initial design of a new prototype air-breathing rocket engine for NASA – one that could revolutionise air and space travel in the next 40 years – reached a major milestone ahead of schedule last week.

According to a statement from Boeing, the engine’s design team, the Rocket Based Combined Cycle Consortium (RBC3), completed its first major engine systems requirements review – an examination of the engine’s design and performance parameters – three months earlier than originally planned.

To design the new engine, the consortium combined the propulsion development skills of the Rocketdyne Propulsion & Power business of Boeing; the Pratt & Whitney space propulsion business unit of United Technologies Corp and the Aerojet missile and space propulsion business unit of GenCorp.

The flight-like ground test engine is being developed as part of NASA’s Integrated System Test of an Air-breathing Rocket (ISTAR) program, which intends by the end of the decade to flight-test a self-powered vehicle to more than six times the speed of sound, demonstrating all modes of engine operation.

The engine, dubbed ARGO by its makers, is designed to function as a rocket, ramjet and scramjet. Key among its technical advantages is its ability to use air as an oxidiser. Compared to conventionally powered rocket vehicles, this technology will, according to Boeing, reduce vehicle weight by eliminating a significant amount of its required on-board oxidiser.

The air-breathing rocket engine for the operational vehicle would get its initial power boost from specially designed rockets in a duct that captures air, an arrangement that is said to improve performance about 15 percent above conventional rockets.

Once the vehicle has accelerated to more than twice the speed of sound, the rockets are turned off and the engine relies solely on oxygen in the atmosphere to burn its hydrogen fuel.

When the vehicle has accelerated to more than 10 times the speed of sound, the engine converts to a conventional rocket-powered system to propel the craft into orbit.

Spacecraft powered by air breathing — or rocket-based, combined cycle — rocket engines would be completely reusable, able to take off and land at airport runways, and ready to fly again within days.

The ISTAR contract calls for completion of conceptual system design and subsystem testing by November 2002. Ground testing of the flight-weight, fuel-cooled engine flowpath is scheduled to begin in 2006.