A prototype vertical take-off and landing sub-orbital launch vehicle under development by Masten Space crashed Sept. 11 during a flight test at Mojave, Calif.

Masten business development director Colin Ake says the Xaero was preparing to make a vertical landing and was around two-thirds of the way through its mission when the accident took place. Although investigations continue, Ake says initial indications are that an engine valve became stuck in the open position. Sensing the situation, the vehicle’s flight termination system was activated. The vehicle was completely destroyed.

Work on a more advanced, larger Xaero B model is now being accelerated, says Ake, who adds that no timescale for first flight has yet been determined. The Xaero is a reconfigured, higher altitude version of Masten’s Xombie which first flew in 2009.

“We have the other vehicle in the works,” says Ake. The loss of the Xaero, which had flown 110 times before the accident, is unfortunate, he adds. “But [this] is at the core of what Masten does - we test and iterate.”

Tests of the Xombie vehicle, meanwhile, continue at Mojave. Recent work included flights with NASA JPL which involved the vehicle flying to an altitude of 475m and translating 750m downrange. The flight “tested algorithms for flight optimization that could potentially be used on a Mars mission,” says Ake. He notes that vertical modes are being closely studied because “precision landing is one of 10 top technical challenges facing NASA.”

Including Xaero and Xombie, Ake says Masten has successfully completed 227 vertical take-off and landing test flights since January 2011.