Atlantis to donate valve for Endeavour troubleshoot

by Chris Bergin

A replacement valve will be taken from Atlantis, after the United Space Alliance finalized a decision that will RandR (Remove and Replace) the cabin relief valve at the center of the failed leak tests on Endeavour.

The culprit, a Positive Pressure cabin Relief Valve B (PPRV B) – one of two valves – will be replaced overnight, in a process that at present will not affect the move to the launch countdown of STS-118, although the timeline is now very tight.

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Testing of the cabin relief valves were completed this morning – via leak checks – which isolated the origin of the leak is PPRV B, after PPRV A passed. Its location is behind the Waste Collection System (WCS).

The results from the leak checks will be discussed at the OPO (Orbiter Project Office) meeting at noon today, with evaluations to consider whether the valve will require replacing. The R&R plan was approved, with NASA now meeting to give the approve the plan.

If replacement is the forward plan, the valve will be removed from Atlantis, to be replaced in Endeavour. Engineers do have other spare valves, which will ensure there is no impact to Atlantis’ processing timeline.

‘The Problem Resolution Team (PRT) recommends change out of the valve using Atlantis to cannibalize the part. This will be going to the Noon board for approval.
‘If the OK is given to R&R (Remove and Replace) the valve, access is needed behind the WMC panel and the anticipated duration is eight hours to perform the R&R.
‘After the R&R, time has to be found in the schedule to perform two cabin leak checks with the vehicle powered down.’

Memos flying around the Kennedy Space Center this morning did point towards an on time call to stations for the August 7 launch attempt. This is still under review.

The forward plan is to remove the valve from Atlantis this evening and R&R in Endeavour overnight.

Leak checks will be conducted on Friday and Saturday morning, ahead of the start of S0007 (launch countdown) on Saturday evening.

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