The Space Propulsion Group Inc. carried out a successful 11-sec. test firing of a developmental, 22-in. flight-class hybrid solid rocket motor fueled by paraffin and liquid oxygen on June 29 at its Butte, Mont., Aerotech test facility.

The Sunnyvale, Calif.-based company, which was formed 13 years ago to develop low-cost, lightweight, environmentally friendly sources of space propulsion and power generation, carried out what was the fifth and longest in a series of test firings. The effort started in 2005 to develop hybrid propulsion scaling tools for the U.S. Air Force Research Lab at Edwards AFB, Calif.

“At this point, I think we are at the stage where we can transition this technology to a product,” Arif Karabeyoglu, SPG’s president and chief technology officer, told a post-test news briefing. “We are at a point where we can actually start to build hybrid rocket motors that deliver the thrust forces needed with the required amount of performance.”

The 22-in. composite case hybrid will undergo additional testing to verify a predicted 5,000-lb. thrust capability at vacuum, with a cumulative 100 sec. of operating time. Thrusting can be stopped and restarted.

The company envisions 22-in. and previously tested 10-in. versions of the paraffin/LOX hybrid as suitable for the second stage of at least one existing launch vehicle, the Pegasus, and sounding rockets.

A 40-in. version for more ambitious propulsion assignments appears attainable, Karabeyoglu says.

Testing of the 22-in. version is scheduled to resume in Butte in July.

SPG counts FAA, NASA, Scaled Composites, the U.S. Air Force and Navy and Virgin Galactic among its customers.\