http://www.newscientist.com/news/news.jsp?id=ns99996541
Genesis crash linked to upside-down design
17:18 15 October 04
NewScientist.com news service
Sensors to detect deceleration on NASA's Genesis space capsule were installed correctly but had been designed upside down, resulting in the failure to deploy the capsule’s parachutes. The design flaw is the prime suspect for why the capsule, carrying precious solar wind ions, crashed in Utah on 8 September, according to a NASA investigation board.
The sensors were a key element in a domino-like series of events designed to release the parachutes. When the capsule - which blazed into the atmosphere at 11 kilometres per second - decelerated by three times the force of gravity (3 Gs), the sensors should have made contact with a spring.
"It's like smashing on the brakes in your car - you feel yourself being pushed forward," says NASA spokesperson Don Savage.
The contact should have continued as the capsule peaked at a deceleration of about 30 Gs. Then, when the capsule’s deceleration fell back through 3 Gs, the contact would have been broken, starting a timer that signalled the first parachute to release.
"But it never made the initial contact because it was backwards," Savage told New Scientist.
Wrong orientation
The sensors, which are estimated to be less than an inch (2.5 centimetres) wide, were apparently installed in a circuit board in the wrong orientation - rotated 180° from the correct direction. But the problem stemmed not from the installation but the design, by Lockheed Martin, based in Bethesda, Maryland.
"They still have to find out why that design error was not caught," says Savage. The mission's Mishap Investigation Board will continue to investigate the problem.
"This single cause has not yet been fully confirmed, nor has it been determined whether it is the only problem within the Genesis system," says the board's chairman Michael Ryschkewitsch. "The board is working to confirm this proximate cause, to determine why this error occurred, why it was not caught by the test programme and an extensive set of in-process and after-the-fact reviews of the Genesis system."
So far, Savage says, the design flaw does not seem to be shared by NASA's Stardust mission, which will use a similar parachute system to deliver samples of a comet to Earth in January 2006.
The $264 million Genesis mission launched in August 2001 to study the composition of the early Solar System, which is thought to be reflected in the solar wind.
Maggie McKee
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