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Discovery Launch Delayed Due To Engine Issue
An anonymous reader writes "The launch of Space Shuttle Discovery was originally slated for February 12th, has now been postponed to February 19th — at the earliest. The change of launch dates were decided by NASA managers during a review of the shuttle's flow control valve in the main engine. The new date is pending further analysis of the flow control valve and everything checking out okay for pre-flight tests. Discovery's STS-119 14-day mission will deliver the station's fourth and final set of solar arrays, completing the orbiting laboratory's truss, or backbone. The arrays will provide the electricity to fully power science experiments and support the station's expanded crew of six in May."
... for 20 now? How many miles on it?
It is dangerous to be right when the government is wrong.
I think the biggest thing is that NASA needs to come up with an actual number for acceptable risk, then make it clear that the public and the astronauts know and understand that number. I believe the current acceptable risk is something like 1% chance of failure and due to the non-replaceable nature of the spacecraft and astronauts that is probably a realistic target to shoot for (if we lose another shuttle it will be virtually impossible to continue our current commitments). If we move to disposable spacecraft, that number should probably be adjusted.
I know it's harsh to say that 5% risk is acceptable when we're talking about human lives, but if they know and understand the risk it is their decision to sign up for a mission. Having a goal of perfect just adds unreasonable amounts of overhead and increases costs faster than savings. Far too much time and effort is wasted in the bureaucracy of NASA, especially considering that the causes of both shuttle losses were brought up by engineers before the accidents occurred but weren't responded to at the upper levels. They need to change the way things are done to identify true risks instead of filling out a mountain of paperwork to change a few bolts out if something is broken.
The vibration problem appears to have been caused by the engines being "steerable" and having a hard time finding their "sweet spot", so they kept adjusting where they were pointing during the firing.
More information here.