WASHINGTON — Sierra Nevada Corp. completed two major development milestones under NASA’s Commercial Crew Development (CCDev) program last month, conducting three firings of a hybrid rocket motor designed to power the company’s Dream Chaser reusable crew taxi to low Earth orbit, according to NASA and company officials.

The engine test took place Sept. 21 at the company’s new test facility outside San Diego. NASA officials were on hand to review the motor’s design and performance, including one firing that took place under vacuum-ignition conditions.

“The overall test was to complete three test burns emulating burn missions over two days, but they ended up doing it all in one day because things went so smoothly,” said Valin Thorn, deputy manager of the Commercial Crew and Cargo Program Office at NASA’s Johnson Space Center in Houston.

The Sparks, Nev.-based company garnered the largest award under NASA’s 2009 CCDev competition, receiving $20 million of the $50 million in American Recovery and Reinvestment Act money the agency divided among five industry teams to mature various human spaceflight technologies. The other winners were Kent, Wash.-based Blue Origin, Chicago-based Boeing Co., Tucson, Ariz.-based Paragon Space Development and United Launch Alliance of Denver. Each company signed Space Act Agreements with NASA that fund performance-based milestones that began in February.

Sierra Nevada is using its $20 million award to continue work on Dream Chaser, a lifting-body space plane based on the HL-20 concept NASA pursued into the early 1990s as a safer, lower-cost alternative to the space shuttle for flying astronauts to the international space station. Sierra Nevada has invested millions of its research and development money over the years to mature the spacecraft’s design. Mark Sirangelo, head of Sierra Nevada’s space systems unit, says Dream Chaser is being readied to launch atop a United Launch Alliance Atlas 5 rocket by 2014 and return to Earth for a space shuttle-style runway landing.

“All three of our completed milestones were completed on time and on budget,” Sirangelo said, adding that the company has received $12 million in milestone payments from NASA under the CCDev program.

Sirangelo said Dream Chaser’s on-board hybrid engine is also being used to power New Mexico-based Virgin Galactic’s SpaceShipTwo suborbital space plane.

“We are using a single larger motor for Virgin Galactic and two motors for the Dream Chaser Orbital Vehicle,” he said, adding that the Virgin Galactic engine has been tested twice at Sierra Nevada’s new test facility.

This summer, Sierra Nevada completed its second major milestone focused on developing the primary tooling needed to build the composite structure of the Dream Chaser vehicle. The tooling is now being used to begin fabrication of the first critical aeroshell structures that will be tested in December.

Last month’s propulsion tests, which marked successful completion of the third of four milestones under the 10-month CCDev initiative, were designed to simulate a complete mission profile and demonstrate the engine’s ability to restart multiple times during flight.

Sirangelo said Dream Chaser’s hybrid motor is designed to provide on-board propulsion for the spacecraft, which will carry a crew of seven as well as critical cargo to the space station and potentially other destinations in low Earth orbit, returning crew and fragile experiments to a runway landing.