"ECO's" from the past? December 7, 2007—Okay, bad pun. But, it’s difficult not to try to find some humor in a problem that’s been a thorn in NASA’s side since the Agency started flying Space Shuttle’s again following the Columbia disaster. The engine cut-off, or ECO, sensors are clustered at the bottom of Atlantis’ external fuel tank. Two of them failed on Thursday, which is pushing NASA closer to another "cut-off" situation. It’s the December 13th or 14th deadline after which Atlantis can’t fly at all this year. Okay, one problem at a time.
As for the December 13th or 14th deadlines, that's to make sure the Shuttle isn't orbit over New Year's Day. NASA's not sure how Atlantis' computers might handle the switch from 2007 to 2008. Saturday maybe for the launch. We’ll see you out there if it goes. By the way, I said "bah humbug" during my last entry when everyone was talking about how great the weather forecast was. I’m no "Kreskin", but after a few years of this, you learn the hard way that there’s no sure bet until the Shuttle settles into orbit. More to come. |
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The ECO sensors, pictured here, act like the low fuel light on a car’s dashboard. The Space Shuttle’s main engines run fine, so long as there’s supercold liquid hydrogen and oxygen fuel flowing through them. If, during the trip to orbit, the tank runs out of gas, the turbo pumps on the motors might run wildly out of control and explode in mid-air. The ECO sensors trip when propellant gets low and they signal the Shuttle’s engines to shut down. There were sensor failures on the first and second missions after the Columbia disaster. That prompted engineers to install extra instrumentation on the sensors for Atlantis. The game plan following Thursday’s failure is for NASA to try to figure out how much to trust that instrumentation. Mission managers might choose to launch while keeping on eye on the extra wiring around each sensor. So, if an ECO sensor signals a verifiable emergency, Mission Control can radio the Astronauts to manually shut down the engines and avoid a disaster.