- The Washington Times - Monday, November 3, 2014

Federal investigators probing Friday’s fatal crash of a Virgin Galactic private space tourism craft say they now suspect the rocket plane’s descent system deployed prematurely, sending the ship’s tail into a rise and causing the craft to “disintegrate.”

The so-called feathering process, designed to slow down the craft’s descent upon reentry into Earth’s atmosphere, was wrongly applied as the craft was still trying to achieve cruising speed, National Transportation Safety Board investigators believe.

Pilot error is a consideration, but NTSB acting Chairman Christopher Hart said it was still early in the investigation.

The crash of SpaceShipTwo, which occurred after the spacecraft was released by its carrier plane at 45,000 feet above the Mojave Desert, killed co-pilot, Michael Alsbury, 39, while pilot Peter Siebold, 43, parachuted to the ground and is receiving treatment at a hospital for serious injuries.

Virgin Galactic Chairman Sir Richard Branson blasted weekend reports that challenged the safety of the rocket plane’s hybrid liquid-solid engine, as well as stories that questioned why the commercial spaceflight company apparently only tested their newest version of the engine on the ground and not an unmanned test flight first.



Mr. Branson vowed Monday to press ahead with his venture as soon as the problems are identified and fixed.

But Paulo Lozano, director of the MIT Space Propulsion Lab, said in an interview that it would be a mistake to compare testing protocols for traditional NASA rockets to Virgin’s rocket plane, since the latter was only trying to graze past the 62-mile suborbital boundary of space.

“I think the missions are very, very different,” he said. “In the case of NASA, they are sending something into orbit and the conditions are different. … It goes from practically no aerodynamic load to a very high aerodynamic load. They are very different systems and designs.”

He said a better comparison would be to the “X-planes that the U.S. Air Force flew in the 1950s as they tested the supersonic barrier. I think that’s a clearer analogy.”

Jeffrey Hoffman, a former space shuttle astronaut who is also a professor at MIT said that people can get confused since Virgin Galactic refers to its rocket plane as a “spaceship.”

“First of all, SpaceShipTwo is not designed to fly unmanned,” he said. “Many airplanes are in that class — all the new airplanes that the Air Force flies — they don’t fly unmanned. They fly with pilots first and that’s the way they worked SpaceShipTwo.” He added that “the idea of testing a rocket plane with a crew on board doesn’t strike me as particularly unusual.”

Early reports following the crash focused on the hybrid liquid-solid engine that powered SpaceShipTwo.

Virgin Galactic rocket planes use a hybrid liquid-solid engine, which mixes pressurized nitrous oxide with a separate solid fuel source once the engine ignites. The process creates greater risk than engines that use only liquid fuel because liquid fuel engines can regulate their fuel flow and thrust level.

The commercial spaceflight company also recently upgraded the type of hybrid liquid-solid engine it uses from one that burns rubber to an engine that burns plastic. Both the engine and the fuel source received widespread criticism.

On Friday, Richard Osborne, chair of the British Interplanetary Society Technical Committee, told the “New Scientist” magazine that he believed that using the hybrid engine was a “mistake” and that Virgin should convert to using an engine that relies entirely on liquid fuel.

But MIT’s Mr. Hoffman said that so far he does not see evidence that the rocket engine was the cause of the crash, and added that many things can go wrong during such flights.

“When you’re going at transonic or supersonic velocity there’s a tremendous amount of aerodynamic pressure,” he said. “If you’re not careful, it can rip you apart.”

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