posted 12-09-2007 04:09 AM               

The mission management team is scheduled to meet soon to discuss whether to proceed with tanking. Should they decide favorably, then fueling will begin as the countdown lifts from a planned T-6 hour hold at 5:55 a.m.

At 6:41 a.m., the four low level fuel sensors should become immersed in liquid hydrogen, providing the first opportunity to test the system and assess whether the countdown will continue. [See STS-122: December 6, SCRUB! for discussion]

posted 12-09-2007 06:04 AM               

However, per the launch commit criteria for today's attempt all four sensors must be working, thus today's attempt is not expected to proceed.

posted 12-09-2007 07:42 AM               

"We've got two things we look at," explained Lyons, "the voltages on the circuit and those were all good on all four circuits. Then we also look at the [sensors], whether they are indicating 'wet' or indicating 'dry'. And all of them went wet as expected.

"And then once we were in fast fill for about 10 minutes or so, we went and did the system checkout. That's when we send simulated dry commands sequentially, and see if they go from wet to dry. If they do operate in that manner, that's what we were expecting and that's a good checkout.

"So we were watching of course, with great interest in the firing room and we had a lot of the [mission management team] members on and we started the test. Sensor Number 1 went dry; Sensor Number 2 went dry; Sensor Number 3, and if you recall, 3 and 4 were the ones that failed last tanking, 3 went dry; and 4 went dry. So it appeared, and I should say also that all the voltages were reading good values as well, so it looked like we had a good system.

"We continued to monitor the system and two or three minutes after this test was run, they were all dry and we were keeping them in that condition. Then we saw sensor Number 3 go from dry to wet, which was a failure.

"At that point, based on our revised [launch commit criteria], which called for four or four sensors, we were scrubbed for the day," said Lyons.

According to Lyons, a troubleshooting plan is in place, though what happens next is still under discussion.

posted 12-09-2007 08:11 AM               

And as installed in the external tank:

posted 12-09-2007 10:19 AM               

"If you look what this means moving into January from a big picture standpoint, it's not that big an impact to us overall. It won't impact the next mission, the February flight will be able to accomplish that on time as its planned. There is also some schedule time between that February flight and the April flight, there's a couple weeks of margin in there, so that can slip to the right. So from a big picture standpoint, it is really not an impact to us overall from a mission assembly standpoint or an assembly of space station standpoint. There is enough margin in the system that we can accommodate this move into January without a big impact," said Gerstenmaier.

"We're taking full advantage of the opportunity to gather some data here for a failure that has been very hard for us to get to the bottom of," explained Leroy Cain, chair of the mission management team. "The best thing we can hope for is that it can repeat for us, even after today."

"Starting today, we set up what we are calling our short-term KSC troubleshooting team to put together, brainstorm ideas and troubleshooting methods that we might want to go do for the system we have out at the launch pad. They are going to report out for the first time to the program board, the PRCB, on Tuesday of this week. From there, we will determine what steps we take... to include possibly a tanking test, to include a possible look at some of the feed-through connector areas and other connecting and wiring and cabling areas," said Cain.

posted 12-09-2007 10:45 AM               

And is there a reason why there are ECO sensors in the LH2 tank but not on the LOX tank?

Chris.

posted 12-09-2007 10:49 AM               

quote:

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Originally posted by cspg:
I know that everything is on table right now but does the postponement imply a rollback to the VAB?

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quote:

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From a previous post, it was mentioned that if the problem was with defective sensors, a rollback would be done.

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quote:

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And is there a reason why there are ECO sensors in the LH2 tank but not on the LOX tank?

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quote:

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Will the postponement have an effect on the 2008 shuttle schedule and ATV launch (which was planned for Jan. 31)?

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posted 12-09-2007 11:57 AM               

I suppose one result of this delay could result in him coming home on STS-124 instead.

posted 12-09-2007 01:14 PM               

quote:

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Originally posted by ejectr:
Hey, think of Dan Tani planning to spend Christmas with his family.

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posted 12-09-2007 08:33 PM               

Leopold Eyhart will still have about a month to prep Columbus before he comes home and in a sense, it will be no less intense a work schedule then what Tani had with Harmony. Besides, a crewmember who is busy tends to be a happy crewmember.

posted 12-10-2007 08:44 AM               

"If all four of the sensors are working at liftoff," Hale added, "we think there is a good probability that the system will be working late in the ascent when you need it to work. That's kind of the logic behind the whole subject."

posted 12-11-2007 09:12 AM               

The teleconference will follow a meeting chaired by Hale that will lay out options to better understand recurring problems with the low-level engine cutoff, or ECO, sensor system.

posted 12-11-2007 09:39 AM               

quote:

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Originally posted by cspg:
Are the ECO sensors that trigger the shuttle's computers to shut down the engines?

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In fact, the ECO sensors are ignored for most of the ascent, until just before the computers calculate when the fuel should be depleted (referred to as the "arming mass").

If an ECO sensor reads "dry" before reaching arming mass, it is deemed failed and ignored. After arming mass, it requires two or more ECO sensors to read dry before the computers interpret it as fuel depletion and an abort (TAL or ATO) follows as a result.

posted 12-11-2007 09:49 AM               

quote:

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Internal NASA emails from the director of Shuttle Safety at the Johnson Space Center and the Shuttle Program Manager show how they struggled with the potential risk to astronauts’ lives in assessing how to proceed with the launch of Atlantis in the wake of engine cutoff (ECO) sensor malfunctions.

Aviation Week & Space Technology obtained exclusive copies of these emails, which are reproduced largely in full here on AviationWeek.com to retain the context intended by their authors.

The emails were sent to the team by astronaut Bill McArthur, Jr. who heads the Space Shuttle Safety and Mission Assurance Office at the Johnson Space Center and Wayne Hale, shuttle program manager.

McArthur has launched into space three times on the shuttle, a fourth time atop a Russian Soyuz and he also commanded the International Space Station.

The emails were sent Dec. 7. This was a day after the Atlantis countdown was scrubbed Dec. 6 when two ECO sensors failed and managers debated whether they could proceed Dec. 8 or needed more time.

They ultimately slipped the next attempt to Dec. 9 after setting new flight rules that 4 good ECO sensors would be required.

This was a change to the original Atlantis launch rule that said the vehicle could fly with 3 of 4.

The Dec. 9 attempt was then scrubbed when one ECO sensor failed in the countdown, a situation that two days before, would have been "go" for launch.

The emails indicate that some of NASA’s highest managers believe that the design of the total system would enable safe launch of the shuttle, without use of any ECO sensor system at all.

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posted 12-11-2007 05:20 PM               

Elsewhere, the companies that built the sensor system are continuing tests to help determine a cause.

"This is part of broad-ranging effort," shuttle program manager Wayne Hale said.

posted 12-13-2007 07:20 PM               

quote:

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NASA Targets Space Shuttle Atlantis Launch on Jan. 10

NASA's Space Shuttle Program managers have targeted Jan. 10 for the launch of shuttle Atlantis' STS-122 mission to the International Space Station.

"The workforce has stepped up to and met every challenge this year," said Wayne Hale, Space Shuttle Program manager at NASA's Johnson Space Center. "Moving the next launch attempt of Atlantis to Jan. 10 will allow as many people as possible to have time with family and friends at the time of year when it means the most. A lot has been asked of them this year and a lot will be asked of them in 2008."

The liftoff date from NASA's Kennedy Space Center, Florida, depends on the resolution of a problem in a fuel sensor system. The shuttle's planned launches on Dec. 6 and Dec. 9 were postponed because of false readings from the part of the system that monitors the liquid hydrogen section of the tank.

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posted 12-14-2007 09:01 AM               

quote:

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It’s a possibility and it all rests on coming to resolution on the ECO system issue. However, there are contingency days built into the schedule that give us time to adjust launch schedules. It will be tight but it is possible.

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I kinda wished NASA would've never re-scheduled STS-122 for Jan 2nd now that they've pushed it out to Jan 10th. Their stated reason for this new date (the 10th) is so shuttle program employees can spend time with their families for the holidays.

I plan to attend the STS-123 launch in mid-February (my first launch) so I hope it stays on course. But nowadays it seems "scrubs" the word.

posted 12-15-2007 12:15 PM               

Cool pictures of your memorabilia too.

Quality stuff.

posted 12-16-2007 10:20 AM               

quote:

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There is no 'window' per say. The shuttle can launch to the ISS any day of the year except during beta angle cutouts (like the current one of Dec. 14 to 29). In 2008 there are cutouts from around May 10-23 and July 7-21.

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posted 12-18-2007 09:22 AM               

quote:

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Originally posted by Robert Pearlman:
NASA has scheduled a tanking test for Dec. 18...

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NASA commentator George Diller said this morning that two of the four sensors were performing intermittently as the liquid hydrogen tank was filled. Sensors no. 2 and 3 were acting up, while another — sensor no. 1 — failed outright.

Engineers are using a circuit monitoring tool similar to that used by cable television and telephone companies to seek breaks in the lines. The tool is currently being used to monitor ECO sensors 2 and 3.

Data from the failed sensor no. 1 and working sensor no. 4 will be recorded.

Wayne Hale, NASA's space shuttle program manager, will discuss the test during a news conference scheduled to begin no earlier than 3:30 p.m. CST.