By Guy Norris/Colorado Springs, Colo.

Aerojet is meeting with the US Air Force in a bid to speed development of a US-designed, reusable hydrocarbon rocket engine that could play a key part in plans for an operationally responsive space vehicle.

Dubbed HC Boost, the technology development program is aimed at providing an improved, home-grown alternative to the Russian RD-180, the only other viable current-production hydrocarbon rocket engine. Unlike the RD-180, however, the US engine would be designed to be re-usable for up to 100 missions, have up to 15% better performance and would operate for up to 50 missions between engine overhauls.

More importantly perhaps, says the Air Force Research Laboratory (AFRL) which is leading the program, it would help pave the way for responsive access to space in terms of days and weeks, rather than months. The development would also, it says, free up U.S. dependency from the Energomash-produced RD-180, which is used to power the Atlas V launcher.

Aerojet is currently working on the HC Boost under a $109 million contract spread over almost nine years. The Sacramento, Calif.-based rocket specialist believes that more can be achieved by compressing the schedule and, at the same time, shifting the focus from a pure technology-driven research effort to a demonstration effort. "If we can do it in half the time they'd get a lot more for the money," says Aerojet president Scott Neish.

The last US-designed and produced hydrocarbon engine was the Rocketdyne RS-27, based on 1960s technology and now out of production. The HC Boost engine, on the other hand, is expected to have higher operability, faster turn time, a longer-life thrust chamber, turbopumps and a new design nozzle. To meet its high operational tempo requirements, the engine must also have a cooling system that does not lead to coking over successive flights.

The re-usable challenge is being addressed through several concepts ranging from its use as a main engine for a fly-back launcher to more extreme notions such as detachable propulsion units that para-glide back to a soft landing.