Endeavour enjoying a smooth countdown heading into L-2 MMT milestone

by Chris Bergin

STS-127 is on track for a Saturday launch, with no issues of note being worked on the vehicle. The Mission Management Team (MMT) will meet – as per usual – on Thursday morning, in order to check on the progress of the Launch Countdown which began at 9am local time on Wednesday.

STS-127 Processing Latest:

It’s been a huge achievement by the Kennedy Space Center (KSC) engineering teams to process Endeavour for the June 13 launch target, with schedule realignments – and a healthy dose of smooth processing – working around what has been a flow with no margin for delays.

Up to Friday of last week, the status of making the start of S0007 (Launch Countdown) operations was in doubt, with local weather threatening to delay processing at the pad. Any notable delays may have resulted in the launch date slipping by a day.

“Congratulations to the Ground Ops team. They discussed on Friday that with the weather forecast, they might not be able to make the call-to-stations, but the weather cooperated and the team did a lot of good get-ahead work, so we are on track still with STS-127,” noted the KSC Launch Integration Manager on the latest Shuttle Standup/Integration report (L2).

“It’s a big week for us,” added MMT co-chair Leroy Cain. “There was a lot of really good work over the weekend. Appreciate that for the whole team. A lot going on this week. L-2 on Thursday, and getting ready to go launch on Saturday.”

As with all flows on such a complex vehicle, a few issues still challenged the engineers ahead of the countdown, notably with potential damage to one of Endeavour’s SSMEs (Space Shuttle Main Engines) during vehicle pressurization.

“During S0071 initial pressurization, the pressure on the left RCS (Reaction Control System) fuel tank was not increasing during regulator lock-up,” added engineering notes (L2). “The test team suspected that the left RCS fuel tank quick disconnect (QD) was not mated to the vehicle.

“MPS (Main Propulsion System) pressurization was put on hold to support personnel access to the 107′ level (at the pad). The team verified the QD was not mated, re-mated the QD, and accomplished a pull-test and functional test. Pad-A was cleared of all personnel and S0071 operations resumed.

“Note – Pad Safety observed that there was sufficient slack in the hose that the QD could have made contact with the Engine 1 bell when it de-mated. An inspection by Rocketdyne (SSME contractor) will be completed once S0071 operations are finished.”

Thankfully, the SSME inspections found no damage to the engine bell, as per updated notes on Wednesday.

“Update: Rocketdyne performed an inspection of the SSME 1 bell and verified no damage from the RCS GHe QD that was found de-mated during hyper pressurization.”

e1It’s been a busy week for the Rocketdyne engineers, with a large amount of attention placed on observed corrosion on the tubing associated with SSME nozzles. Two engines required their nozzles cleaning, before leak checks confirmed no underlying damage, allowing for the subsequent clearance for flight – although this will be discussed further by managers at the L-2 MMT meeting.

“Last Thursday and Friday they cleaned the residual contamination off Engine 1 and Engine 3’s nozzle,” noted SSME (Pratt & Whitney Rocketdyne/KSC) on the Standup report. “Then performed a nozzle tube leak check on Friday. No leakage. Got the problem behind them. Will expect to debrief at L-2 this week.”

The only other note of interest related to latch measurements on the crew hatch – which has since been cleared for flight.

“A cycle of the crew hatch was performed yesterday to verify latch measurements; hatch limit switch rigging was successfully completed on 2nd shift last night,” added notes. “Per senior NASA management and the Chief Engineer, the hatch was cycled again on 3rd shift; no issues noted.”

Another issue, that has been troublesome on the entire fleet over the last year, relates to the External Tank umbilical well camera/flash system, used to take photography of the ET – to check and cross reference foam loss – after it is separated just after MECO (Main Engine Cut Out).

Engineers cleared the system for flight last week, but are continuing to work on a root cause of the system’s issues. Initially, the system’s operation on ground power, versus orbiter battery power, was deemed as the likely reason the system was proving to be temperamental. However, Electromagnetic Interference (EMI) has since been included as potentially part of the root cause.

“On the ET umbilical camera, did get it operational on Friday. There are a couple of theories as to why it did not communicate properly the first time with the laptop,” noted the Orbiter Project, based at the Johnson Space Center (JSC).

“In the past, we have had issues with EMI, and at the time that they did the initial check the orbiter RF system was up so we’ve seen that in the lab, and also grounding power. The camera checked out well. Were able to communicate with the flight laptop.”

The ET camera/flash system troubleshooting overview may also be included in the L-2 MMT meeting, although the main focus will be on the latest S0007 processing schedule progress, and the weather – which are both currently favourable for making a launch attempt on Saturday.

“The probability of KSC weather prohibiting launch was reduced from 20 percent to 10 percent on launch morning – our primary concern is only cumulus cloud development,” noted Wednesday’s weather report to shuttle managers, with conditions remaining favorable for the next two launch attempts in the short window.

L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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