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Parachute Problems Plague NASA's Flying Saucer
An anonymous reader writes: NASA's test of a Mars landing system came to a end Monday when the saucer-shaped vehicle's parachute tore away after partly unfurling high over the Pacific Ocean. NASA says they will provide more details at a news conference Tuesday. Another parachute failed during a similar test of a new Mars spacecraft last year. "This is exactly why we do tests like this," NASA engineer and LDSD mission commentator Dan Coatta said after the test. "When we're actually ready to send spacecraft to Mars, we know that they are going to work when that big mission is on the line."
Parachutes don't just unfold, they actually deploy in a very controlled fashion. All it takes is something to initiate the sequence. In human parachutes, a pilot chute is released, which pulls out a deployment bag. The bag in turn does not open until suspension lines are stretched, and once the canopy is released from the bag, it inflates due to the difference in static air pressure within. vs dynamic air pressure outside (Bernoulli's principle). There are further mechanisms to slow down deployment in order to control the deceleration and opening shock (important for human well being). Problems occur if things happen out of sequence, or if the parachute is structurally unsound.
I can't speak for the system NASA is using, but I expect there already is a unit to "unfold" the parachute, and it is all part of the parachute system already.