Everything remains on track for an evening launch of shuttle Endeavour on STS-118, as engineers and technicians continue with the countdown with only a few issues being monitored.
Activation of the orbiter’s Fuel Cells was successful – along with the associated coolant pump motor, which continues to be monitored due to previous phase shorting – along with the tanking of the External Tank, which is now in stable replenish mode. A gash on the LO2 feedline inboard strut has been cleared, as has a hatch closure issue.
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Only a handful of Interim Problem Reports (IPRs) have been listed during the first shift this morning, as Endeavour moves closer to her 20th launch – the first in nearly five years for the youngest orbiter of the NASA fleet.
All of the Engine Cut Off (ECO) sensors have passed testing through the tanking process, leading to extra confidence that Lockheed Martin – who build the ETs – have solved the sensor issues that were prominent during the RTF (Return To Flight) countdowns.
‘MPS (Main Propulsion System) Integration: ECO sensor check out, all sensors performed nominally,’ confirmed a MER (Mission Evaluation Room) note, after the tanking process had entered stable replenish mode.
Inspections to check for the formation of ice and frost on the ET have now been completed at the pad. The only issue so far is understood to be a gash in the area of the LO2 feedline inboard strut. This was cleared to fly ‘as-is’ by the Mission Management Team (MMT).
‘3” Long X 0.25” Wide Crack Found in Feedline Support Bracket Base Fitting at Station XT1973,’ noted one memo. ‘3” long x 1/4” wide crack was found in the foam at the Inboard Base of the LOX Feedline Bracket Foam Ramp (XT1973).
‘Risk analysis and waiver rationale currently being discussed. Appears to be low risk of losing foam from this area.’
Earlier, an issue with the Passive Thermal APU-1 Fuel Bypass Heater is being monitored, after it showed slightly out of line readings around 11am local time. This is not currently a problem.
‘This heater is cycling in a more narrow band than usual, as seen last week. It last flew on STS-90 APU-304,’ added another countdown memo. ‘The temperature range is nominal.’
Prior to Fuel Cell activation, the LH/O2 Isolation valves were noted as ‘not closed,’ which was a constraint to proceed with the activation of the electricity generating cells. However, a plan to reconfigure and re-perform sampling cleared the problem.
Monitoring of a Coolant Pump, which reside in Fuel Cells 1 and 2, is continuing, although no issues have been found during the key event of Fuel Cell activation.
The issue relates to a ‘single phase – or phase to phase – shorting’ concern in the pump, which is also related to the issues associated with the anomaly of Atlantis’ Fuel Cells during STS-115. This appears to be the main area of conversation by engineers during the countdown.
‘Because OV105’s (Endeavour’s) Fuel Cell 1 and 2 cooling pumps are from the same manufacture lot as STS-115’s Fuel Cell 1. The launch team (KSC and JSC) has put together a data retrieval, review and troubleshooting plan to monitor and react between fuel cell activation through launch,’ noted a shift report today.
‘A critical time for the anomaly was during Fuel Cell activation therefore no cockpit lighting or seat adjustments were made during that timeframe.
‘The Fuel Cell LCC console engineer (CFCP) notified the Electrical Systems LCC console engineer (CEPD) just prior to start of each Fuel Cell pump and when the load was transferred to the buses. No problems with the Fuel Cell pumps were noted. The required data will be recorded via the KSC Record and Playback System (RPS) and provided to the team for review.
‘If a problem is observed later in the countdown and there is adequate time remaining to accomplish the troubleshooting and understand the situation, then the appropriate actions could occur to proceed with launch.
‘Example: If the short is understood to be within only one of the phases of the coolant pump and not a phase to phase short, the associated coolant pump phase circuit breaker on panel L4 would be opened by either an Astronaut Support Personnel (ASP) or the STS-118 commander and launch would proceed. Also the appropriate LCC deviation (FCP-04) would be required to be processed by the launch team.’
‘This would be the same type of configuration as was flown for STS-115.’
Meanwhile, one of the issues that is normally the main constraints to launch, the weather, remains very favorable for launch.
‘Launch and RTLS (Return To Launch Site) weather looks very good. No issues at this time. There is a chance of isolated showers, which is typical for KSC at this time of year. Winds are not a concern.’
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