MOJAVE - XCOR Aerospace has begun test-firing its 7,500-pound-thrust methane-fueled engine, a prototype of one intended for NASA's next-generation spacecraft. The Mojave-based company is partnered with Alliant Techsystems, or ATK, in the $10.4 million contract for the first phase of developing a rocket engine that runs on liquid oxygen and liquid methane, nontoxic fuels that could help lower the overall cost of spaceflight. XCOR's engine successfully has completed six short-duration test firings at the test site on the northeast end of Mojave Airport, using a new test stand that can handle up to 40,000 pounds of thrust, said Rich Pournelle,...