STS-119 FCV performance boosts flight rationale for STS-125

by Chris Bergin

Aiding the requirement of flight rationale for STS-125, engineers have found that the three replacement Flow Control Valves (FCVs) that flew on STS-119 suffered from no cracking, following inspections on the valves after they had been removed from Discovery. The news comes as managers prepare to conduct both the post flight review of STS-119 and the opening pre-briefs for STS-125 later this week.

STS-125 Processing Flow Latest:

Atlantis – preparing for her May 12 launch date to the Hubble Space Telescope – is enjoying a smooth pad flow out at 39A, as she moves into hyper servicing and payload arrival preparations.

“Will continue with S0024 preps. That will lead to a Call-to-Stations Tuesday night, and hyper servicing on Wednesday and Thursday of this week,” noted the latest Shuttle Stand-Up/Integration report on L2. “Next week preparing for the payload delivery on April 18.

“Range Safety System validation (first motion checks) are complete. Helium signature test and Ball Seal Leak Checks are complete and good; GO2 blank off plates removed.”

This week will also kick off the Flight Readiness Reviews (FRRs) for STS-125, opening with the second MOD FRR review – following the previous FRRs last September, before the mission was delayed – outlining the upcoming mission in detail.

This will also coincide with the Mission Management Team (MMT) undergoing a pre-brief, which will be headed by Leroy Cain.

“Folks have a lot of other things to do between now and STS-125, and have a lot of other meetings on the schedule. We won’t do it if it does not look necessary,” noted Mr Cain on the Stand-Up.

“On STS-125, there will be a MMT pre-brief. It will be scheduled this week. It will be a challenge to find a place to put it on the calendar with the meetings we have in place.”

Flow Control Valves:

a24As with STS-119, more discussion will take place on the Flow Control Valves (FCVs), following the incident observed during STS-126’s ride to orbit late last year. This in turn led to a major part of the FRR process being dedicated towards the gaining of Flight Rationale ahead of STS-119.

Click here for articles on the FCV issue since STS-126.

Including two Special PRCBs (Program Requirement Control Board) meetings, the launch date was delayed until managers and engineers were certain they had the right amount of confidence in flying the three FCVs on Discovery – without the requirement to standdown for a redesign, which some engineers had been calling for.

As per usual, the decision to fly with three “cherry picked” valves that had previously flown without issue has been proven to be the correct decision, with no anatomies noted during Discovery’s ascent.

That confidence has been boosted via flight inspections, proving the valves didn’t suffer from cracks – which is the driver for an eventual liberation, as found with one of Endeavour’s valves.

“On OV-103 (Discovery’s) FCVs, did get them out last week and to Vacco over the weekend and inspected,” noted the Orbiter Project at the Johnson Space Center. “Two of the three looked really good, no cracks. The other one picked up a little scratch.

“We will have to figure out where that came from, and how to get it turned around. Right now the first blush is that we might have to do some flow-balance testing on it. Will work through that. It looks like the FCVs came through pretty well.”

Due to the nominal performance of the valves, the sets of FCVs that are set to fly with Atlantis on STS-125, and Endeavour on STS-127 (and STS-400 if required), will be likely to gain the required flight rationale without the need for a major discussion at the FRRs.

a311A proposed metal plate that would “beef up” the most ‘at risk’ area of the downstream plumbing in the Main Propulsion System (MPS) – known as the 90 degree elbow bend – is now unlikely to have a place in future plans, due to the reduced threat of a liberation, which would have to be on a greater magnitude than that observed during STS-126 to cause damage in this area of the MPS.

In fact, the encouraging post flight inspections of the valves, from which no cracks have been found, will aid flight rationale for at least STS-125.

“The FCV data is very important, and getting those three valves off of STS-119 is the first time we’ve had a chance to look at just one flight’s performance in terms of crack growth,” added the Orbiter Project.

“It is good to see that we had no cracks on the valves within our detectability limits pre-flight, and then after flight we don’t see any as well. It is good news for our flight rationale.”

No major issues are expected to be discussed when managers close out STS-119 via what is called the post-flight IFA (In Flight Anomaly) review, to be conducted during Thursday’s PRCB meeting – thanks in part to Discovery’s clean mission.

“On STS-119 MMT debrief, do not have much to talk about. For most of the folks solicited, we really don’t have much to debrief from a MMT standpoint,” noted Mr Cain on the Stand-Up report.

Items likely to be discussed are the usual “squawks” that are noted on most Solid Rocket Booster (SRBs) IFA presentations, along with the problem with the ET Umbilical Well Camera, which failed to properly execute its flash – or download imagery – during post ET-sep.

“Still working on the ET camera off of STS-119. Got it back to JSC. Did some troubleshooting, and had the same indications as on flight with the camera,” added engineering notes. “Sent the camera on command and nothing happened; the laptop couldn’t find the camera. They opened of up the box and couldn’t find anything.”

Any items of interest found during the STS-119 post-flight IFA review will be added to the STS-125 SSP (Space Shuttle Program) FRR documentation.

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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