Masten Space Systems has lost one of its research rockets after a mostly successful test flight this week. Company spokesman Colin Ake told Wired the flight was designed to expand the flight envelope of its Xaero rocket when the incident occurred.

"One of the primary goals was to test how the vehicle would handle at higher wind loads and at higher altitudes," Ake said.

Xaero is part of Masten's development program to build a reusable, sub-orbital rocket that is capable of precision landings. The 12-foot-tall rocket had made 110 flights before this week's accident. The flight at the Mojave Air and Space Port was supposed to fly to an altitude of one kilometer while testing the flight controls at higher ascent and descent velocities and then return to a precise landing point.

With about two-thirds of the flight complete, Xaero was in the descent stage when control was lost.

"As we were throttling up for landing, we had a throttle valve failure, it was essentially stuck," Ake said. "We are entirely dependent on high-precision throttling, that's the core of the handling in the descent stage. The flight was terminated and the vehicle was destroyed."

Photo: Masten Space Systems

Ake says the safety systems worked as they were designed, but could not say whether the on-board system terminated the flight or if the flight was terminated by a person on the ground.

"No one was hurt, that's the most important thing," he added. "Hardware failures happen. Rocket science is a cliche because rocket science is not easy."

Indeed, after more than 220 successful vertical take-off and landing test flights over the past two years, Masten was beginning to make the development of precision-landing rockets look routine. This week's accident is a reminder of the dangers of flight-testing new rocket vehicles.

Xaero flew to an altitude of 444 meters on July 4. Masten is focused on the precision landings that will allow its rockets to fly into space and return to a specific landing spot on the ground, rather than a ballistic reentry with a splashdown in the ocean.

The company already has an updated, larger version of the Xaero standing in its facility in Mojave. Ake would not say when the first flight of the new version was expected to happen.

Masten's Xombie rocket continues its flight test program with a flight last month that included reaching 475 meters in altitude and a 750 meter horizontal distance to a precision landing (video below). Masten believes the August Xombie flight marks the longest horizontal flight ever made on earth by a vertical take-off and landing rocket powered vehicle.

The Apollo moon missions did manage to go a bit further, though Xombie's flight is more analogous to the lunar lander taking off and landing again on the moon. NASA's Jet Propulsion Laboratory is one of Masten's clients and the precision-landing rocket flights could one day be used on a Mars mission.