December 06, 2007
Shuttle Launch Slips to Saturday (at least)
The launch of the Space Shuttle Atlantis was delayed today by mission managers by at least two days. The cause? Troublesome fuel sensors at the base of the External Tank -- the same sensors that have malfunctioned in a few recent launches. The sensors are meant to show when the tank is emptying of fuel, to prevent unexpected shutdown of the engine or a catastrophic failure. The problem now is that two of the four sensors were not working properly when tanking began early this morning.
Interestingly, NASA managers are discussing using the crew as a backup system to the sensors' failure -- potentially enabling them to fly with only two good sensors. In that scenario, the crew could potentially manually execute the Main Engine Cut Off (MECO). That concept will be discussed further on Friday by senior NASA leadership, so stay tuned!
In the current plan, NASA managers are not focused on opening up the shuttle vehicle, rather they are focused on different operational scenarios. That may change on Friday, depending on the latest data and analysis.
I believe (perhaps a reader could confirm my memory) that these sensors have never been actually needed in the history of the shuttle program. I seem to remember that the only time that they were a factor was when one malfunctioned during ascent, and caused premature shutdown of one of the engines. The crew then overrode another sensor that was on its way to malfunction, which could have caused the premature shutdown of another engine and the only abort to land in the history of the shuttle program. Thankfully, mission control and the crew's fast action enabled the vehicle to make orbit.
Posted by george_whitesides at December 6, 2007 10:20 PM