A huge blast at the Mojave Air and Space Port on Thursday afternoon killed three employees of Scaled Composites, the company that built SpaceShipOne, the first privately funded space vehicle.
Early reports say that the explosion was caused by two nitrous oxide tanks; the workers who died were checking the tanks' flow rate before the disaster, Burt Rutan, who heads Scaled Composites, told reporters.
The company is currently building two highly complex vehicles -- SpaceShipTwo, which will fly two pilots and six wealthy passengers into space, and White Knight 2, a carrier vehicle that will lift SpaceShipTwo to 15 kilometers above the Earth before releasing it into space. Richard Branson's Virgin Group has ordered five SpaceShipOne units to launch its space-tourism business Virgin Galactic. Rutan did not say whether the explosions will set back production of these vehicles.
Stuart Witt, the general manager of the airport -- which is home to several space start-ups -- told the Associated Press: "What we do is inherently risky. These are not the days we look forward to, but we deal with it."