The Countdown Begins...

The Shuttle launch is Tuesday. And NASA engineers are effectively going nuts - testing like mad to find the problem with the ECO sensors that cancelled the last flight attempt.

The countdown has begun. Can they find the problem in time? It's like watching an Engineering competition of sorts - because I'm not entirely convinced that they are as close to finding the problem as these reports are saying. So many things could go wrong to screw the plan up.

Either way this is interesting:

Some engineers favored another tanking test prior to any additional launch attempts to collect data in the actual operating environment. But the mission management team today ruled out that option and agreed to press on into a countdown.

Maybe I'm getting confused. Months ago, the ECO sensors failed on a fueling test. Some engineers called for a third tanking test to ensure that the problem was solved when they swaped ET tanks. NASA managers decided it was not neccessary. Maybe that's what this article is referring to. Because if not, it means that those same Engineers have requested another fueling test again, only to get shot down again. In which case, this is just a whole new level of ironic.

Basically, the way I'm reading it, there are basically two possible causes Engineers are focusing on. The first is that it's a grounding problem with the ECO sensor wiring. The plan is, switch the wiring around, and see if the sensors keep on malfunctioning.

The other possibility, is that it is a problem with electromagnetic interference from the newly installed heaters could be a cause of the problem.

Engineers plan extensive troubleshooting to identify possible sources of interference and its effects in an electronics unit called a point sensor box, which routes sensor data to the shuttle's computers. Candidates include the circuitry for new post-Columbia heaters added to the shuttle's external tank to prevent ice formation.
...
"In the end, analysis of the circuitry suggested that grounding might be a problem. Testing of the (point sensor) box ... in the lab in Houston suggested electromagnetic interference could interfere with the box. We went looking in the vehicle and we found a discrepancy in the grounding of the vehicle.

"We're going to go in tonight and try to replicate as best we can the electromagnetic environment of launch to see if we can trap the signature of it," Muratore said. "Even if we can't trap the signature, we're going to go make the system good. And then the best way to go and further understand the problem is ... to load the tank up and observe its operation and that's best accomplished in the environment of a launch countdown."

I've had a little experience dealing with grounding issues in a manufacturing environment. I can still remember trying to map out the electrostatics of a room... Not pretty. I can imagine the amount of headaches involved with this system. Not pretty at all.

There's talk of amending the rule that all 4 sensors have to be functioning for a launch... Well that's one way of dealing with a problem.

My gut feeling right now is that there will be another launch attempt on Tuesday. Whether or not the bird gets off the launchpad is another thing altogether.