The first phase of tests of the rocket motor for Virgin Galactic's SpaceShipTwo (SS2) space tourism vehicle has been successfully completed at Mojave, Calif., by Scaled Composites and its subcontractor Sierra Nevada Corp. (SNC).
"The hybrid nitrous oxide system being used is the largest of its kind in the world and will send Virgin's customers up into suborbital space at speeds over 2,500 mph, to heights over 65 miles above the Earth's surface, before the spaceship descends back down through the atmosphere using its pioneering feathered re-entry system," says Virgin Galactic in a statement.
The rocket motor team is led by the former SpaceDev company, which was acquired by SNC in December 2008, and which previously joined forces with Scaled Composites to help refine the hybrid rocket motor for SpaceShipOne between 2001 and 2004. The latest milestone follows the August 2008 signing of a multiyear contract under which SpaceDev announced it would be collaborating with Scaled's internal design team to develop a production-ready hybrid rocket motor for SS2.
The agreement, which is primarily expected to cover work through 2010 but which officially extends to 2012, includes engineering services as well as the development, manufacture and integration of rocket motor system components. SNC also is conducting ground tests on components and is working with Scaled in the full-scale rocket test program both on the ground and during SS2 flight-tests.
The completion of the initial test phase also marks a key milestone in the program's recovery effort from the devastating rocket testing accident at Mojave in July 2007 that killed three Scaled workers and injured several more. Findings by the California Division of Occupational Safety and Health Administration later revealed the explosion was likely caused by an oxidizer tank failure during a cold nitrous oxide flow test.
SNC's hybrid rocket propulsion system uses nitrous oxide as the oxidizer, and hydroxy-terminated polybutadiene (HTPB), or synthetic rubber as the fuel. "The result is a propulsion technology that blends the simplicity of solid rockets with the restart and throttle ability of liquid-fueled propulsion," SNC says. | 
