MMT decide to try for a Sunday launch attempt for STS-122
The Mission Management Team (MMT) have concluded their meeting on flight rationale for proceeding with the launch of Shuttle Atlantis on STS-122, deciding to make a launch attempt on Sunday at 3:21pm Eastern, in a one minute launch window.
The main reason for waiting an extra day would be to finalize Flight Controller procedures for watching the tank closely during ascent, in the event of ECO (Engine Cut Off) sensors were deemed unreliable. The launch could be delayed longer if those procedures are not finalized.
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ECO Evaluations pre and post-MMT:
Currently in a 48 hour launch scrub turnaround, due to the LH2 ECO sensor failures, NASA has two clear options to them: to repair the fault – now thought to be within the External Tank, or fly with rationale that allows the removal of the LCC (Launch Commit Criteria) that requires three of the four ECO sensors to be in full working order.
The second option will rely on a plan being completed by Flight Control staff, who will monitor the tank’s use of propellant during the ride to orbit.
It was the second option which was taken by the MMT, along with a scrub to the countdown if the sensors fail again, with the full LCC (Launch Commit Criteria) of 4/4 working ECO sensors required.
‘The team has a long discussion today. At the end of the day we asked the team to go home and think about it, with another MMT at 1pm on Saturday,’ said shuttle manager Wayne Hale.
‘The flight control team proposal, if accepted, would lead us to go for a launch on Sunday. If not, we will standdown and do something different. We don’t want to get launch fever.’
A memo from the Flight Director Office (DA8) outlined their current work on creating procedures. Presentations have since been acquired by L2, with an article to follow on Saturday.
‘Within MOD that effort is being led by Ascent Flight Director/Norm Knight and Entry Flight Director/Bryan Lunney. Folks from the Booster, DPS and FDOs arenas are also heavily involved,’ noted the memo.
‘The Boosters are working to understand the root cause, possible work-around options, and developing rationale to fly with less than four sensors. The FDOs are helping to develop flight rationale, including an understanding of past flight history and SSME shutdown options.
‘The DPS folks are working with the Boosters to no-op any failed ECO sensors in the flight software, should the community agree that is the proper course of action.
‘The flight software sensor no-op would occur via uplink (i.e., TMBU or GMEM) and be verified via SAIL in conjunction with the Flight Software and Engineering community.’
ET documentation presentated to the MMT gave strong rationale to go ahead with a tanking test to be carried out prior to a launch. However, this was played down before heading to the MMT.
‘Rational for a Tanking test is being developed. The MMT would like to understand if there is any benefit to performing a tanking test prior to a launch attempt. As of now there are no approved plans to perform a tanking test prior to STS-122/1E,’ added information.
‘This 48 hour scrub means the vehicle is being turned around for a launch attempt on Saturday 12/8. The team should remain ready to support launch and flight operations on Saturday, including update of any pre-flight products required to support that date (trajectory, pointing, communications planning info).’
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The MMT was delayed by an hour – to 3pm Eastern – due to the large amount of data being brought to the table. ET Project and JSC Engineering were believed to be against any launch attempt on Saturday.
‘Keep in mind this is a fluid situation and things can change rather rapidly. Ideally we’ll find the problem that is easily fixed and launch shortly after,’ noted the Flight Director’s office.
‘It is our job to maintain a posture to support the early December launch window. If we happen to launch late in this December window, we will potentially fly over the Christmas holiday. Please be patient, we will launch when the vehicle and team are ready.’
The MMT was presented with several possible causes for the ECO sensor faults, which include: ‘Short or open in sensor. Short or open in ET cabling. Short or open in ET connector,’ though all three are classed as improbable.
Downstream with the orbiter, ET claim it could be related to: ‘Short or open in Orbiter cabling. Short or open in Orbiter connector. Intermittent in Orbiter sensor electronics box. Intermittent for Orbiter MDM input,’ though this is believed to have been cleared by engineers.
After the MMT, a root cause was still outstanding.
An 8 inch crack has been reported on one of the LOX Feedline brackets. Photographs are being taken at the pad, with evaluations to take place over the coming hours. PAO claim it is not an actual crack, but scuff (thus not a problem).
L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.
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