Here we are, 26 July 2005, and just about 1 hour til the scheduled launch of the space shuttle Discovery (STS-114). So far, all systems are go. The engineers still don't seem to know what has caused the fuel sensors to fail in the past, but for this launch have relaxed the "GO" requirement. Now, instead of requiring that all 4 sensors on each engine are working, it is only requird that 3 of the 4 sensors on each engine are working. As an engineer, it's a bit disturbing to me that the can't figure out what the problem is. Moreover, I fear that if today's launch is successful, NASA's administrators will be willing to overlook the fact that nobody has a clue as to what is causing the sensors to fail. THAT is bad engineering, plain and simple. I understand the desire to return to flight, but at the same time, some either alternative or work-around for the sensor failure problem should be addressed, and addressed soon. As of right now, 2 of 3 scheduled tests on the fuel sensors have been conducted, and both tests were 100% successful.
Follow all the return to flight coverage via NASA's Return to Flight page.