Discovery Launch Scrubbed - Should It Have Been Scrubbed Earlier?

CNN reports that today's launch of the space shuttle Discovery was scrubbed because of a faulty fuel sensor.

Monday MSNBC reported that there was an ongoing debate among mission manager as to Discovery's readiness. One of the concern's mentioned in MSNB's article was "a review of issues involving unusual data from the external fuel tank's low-level sensors, which engineers saw during recent tests."

If that is related to the scrubbing of today's launch it could be a bad omen indicating NASA even after the loss of Challenger and Columbia doesn't give enough credence to dissenting opinions. I understand space flight is a dangerous. I often rant about the U.S. not being willing to accept enough risk for such a dangerous enterpise. But if the indications were there and not given enough credence .... Of course this is just wild uneducated, and I hope not irresponsible speculation on my part. The good news is that the problem was caught. I just wonder if Discovery's launch should have been scrubbed earlier.

Comments

[cuddihy]

Baloney. Anyone who has ever had to deal with remote sensors(as I have on a submarine) has felt the pain of the intermittent indication. Electrical connections on large machines sometimes develop unexplainable faults. You can replace the sensor, the cable, signal processers, the indicators, only to find out none of them are causing the fault. That possibility is why there are 4 sensors and only 2 are needed to function correctly for the system to function correctly. If the shuttle had launched today and the tank had run dry(which has never happened and would require an off-nominal launch, say with one of the engines underperforming), any of the other three sensors could have failed and the engine still would have shut down.

[rocket scientist]

Here's the lowdown. Originally, they were going to use a different ET, ET-114, for this flight. When they tested it on the launch pad before the original May launch, they had problems with it, other than the ECO. They decided to swap out the tanks, to ET-121, to use instead for this flight. Also, they decided they would only do a tanking test on ET-121 on launch day, not testing it before hand. As a result, we ended up wasting some people's time and money today. I think they've had this problem before.

Also, the flight rules state that all 4 ECO's must be working in order to launch. However, they also say that after liftoff, you can safely fly with only two working. That means that this system has 2 failures before you have to abort. It's just a margin of safety they want to maintain. And also, this was not anything necessarily 'flight critical.' It only would have been used in an abort scenario, which is unlikely, but there is much planning for many scenarios.

[RFTR]

You're forgetting one thingthey were listened to, in the end, and the mission was scrubbed.

Maybe they should have done it sooner, but the fact that the dissent ultimately got through (before a failed launch) would imply to me that the appropriate feedback loops are in place and functioning appropriately.

[Nate]

I'm pretty naive on NASA protocol myself, but the whole thing simply felt rushed to me and I had a bad feeling in my stomach about it. I'm glad to see it grounded right now.

[Woody]

More likely it wasn't a lack of credence, but rather a problem that wouldn't or couldn't correct itself in the push towards the launch window. At this particular point in the countdown, launch parameters for those ECO sensors were finally (one might say "officially") violated, and the scrub decision was made.

The numbers of technical procedures followed by the launch team are staggering. The fact that engineers were indeed aware of a possible problem, and they weren't comfortable with it this far along in the countdown, indicates a willingness to wait until they can get everything right before they commit.

I love to listen to the pre-launch communications at United Space Alliance's website for the few hours just prior to launch. It's amazing just how many "issues" they have to make go-nogo decisions for right up until launch. It's astounding how much ground they cover during the T-9 hold.

Like you, I'm glad they chose to side with caution today.