NASA and the United Space Alliance (USA) are in the midst of dual processing flows, required to support STS-118’s scheduled launch attempt next Tuesday.
Endeavour, sat on pad 39A, has a new leak issue being worked, while at the same time her older sister, Discovery, is being finalized for rollover one month later, in time to launch to the International Space Station to pick up a stranded crew in the event of an emergency.
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New Leak Issue:
**NEW ARTICLE – Tuesday Morning – Click here to read**
Engineers are attempting to track down the source of another pressure decay onboard Endeavour, after a leak check failed late last night on the crew cabin and Spacehab module.
The new leak is separate to the failed test at the weekend, which was quickly tracked down to a loose nut on the Probe Assembly related to the Ingress/Egress Hatch. Elements of the pad flow ahead next week’s STS-118 have been delayed, while engineers evaluate the problem.
‘Leak checks failed for the crew module and Spacehab. Cabin leak checks were performed again on Monday evening in the same configuration as (process) requires. Pressure decay failed at 0.047 per hour,’ noted processing information on Tuesday.
‘Five data points were taken every half hour. Leak rate remained the same at 0.023 psi per half hour. GSE (Ground Support Equipment) QD was disconnected from the probe and retightened b-nut on the probe, with no difference in decay rate. Engineering evaluation continues.
‘S5009 Ordnance Installation/Connects, has been postponed to today (Tuesday) to accommodate SRB (Solid Rocket Booster) power up for HPU (Hydraulic Power Unit) fuel isolation valve cycling. S0071 Hyper/MPS (Main Propulsion System) Press/Closeouts operations are scheduled to pick up Wednesday.’
Launch On Need Requirement
To support Endeavour’s mission, Discovery is required to launch within a schedule determined by a timeline known as CSCS (Crew Shuttle Contingency Support) – which is the amount of days the crew of Endeavour – along with the three member Expedition 15 crew – can be sustained onboard the ISS, until the four man rescue crew on Discovery arrive at the station.
While the chances of a LON (Launch On Need) rescue being called are remote at best, the requirement is often under reported. However, the contingency is a key element of post-Columbia safety improvements in the event of serious damage during ascent, or whilst on orbit.
In the event of a LON/CSCS scenario, Endeavour would have to be undocked from the ISS, before Discovery arrived to pick up the crew. The extent of damage to Endeavour would determine whether controllers would attempt to bring her home unmanned – via the available Remote Control Orbiter (RCO) modification, or if she sadly has to be destroyed via the disposal option, a controlled and destructive ‘tail first’ re-entry.
While the exact CSCS timeline is constantly under review – based on consumables onboard the ISS – Discovery is currently targeted to launch on October 5, if a LON rescue contingency was called during STS-118. At present, the ISS is in good shape, with large amounts of consumables, along another Progress re-supply ship due to launch in a couple of days time.
Because of LON/CSCS, NASA’s shuttle schedule reflects this requirement, with the primary launch of Discovery – carrying Node 2 for installation on the station on STS-120, scheduled for October 23 – allowing the orbiter to be processed along a very similar timeline for both requirements.
As with all processing flows, issues can arise which delay the date an orbiter can be launched. Should this arise with Discovery, NASA can use backup options, which include Russian assistance via Soyuz rescue missions.
Looking at Discovery’s processing flow, the orbiter is enjoying a smooth turnaround from her STS-116 mission at the end of 2006. Discovery recently had all three of her SSMEs (Space Shuttle Main Engines) installed, with the OMS (Orbital Manoeuvring System) Pods set to be installed into the business end of the orbiter this week.
‘Payload configuration and bay closeouts continue,’ added the latest processing information. ‘Preparing for RH (Right Hand) OMS pod installation planned later this week. ECO (Engine Cut Off) sensor mod power up retest continues. SSME leak checks completed. Payload testing continues; CEIT (Crew Equipment Interface Test) scheduled later this week.’
The only issues with STS-120 relate to the External Tank (ET-120), which still needs concerns with a couple of its LO2 liquid level ‘loading’ sensors allaying, following out of spec readings during final checkouts at the Michoud Assembly Facility (MAF).
While Lockheed Martin engineers at MAF have worked a plan that gives colleagues at the Kennedy Space Center the option of flying ‘as is’ – or changing out the sensors – further tests are to be conducted on the tank inside the Vehicle Assembly Building (VAB) to help assess the status of the sensors.
‘Resistance checks for loading sensors on ET-120 still scheduled August 1,’ noted processing information. ‘Want LO2 loading sensor resistance check to be performed for ET-120. Hope stability of measurements is good. If resistance shifts further, team is ready to respond.’
Another issue relating to STS-120 and the LON requirement in support of STS-118 was resolved, after a hold in stacking operations for Discovery’s Solid Rocket Boosters (SRBs) inside the VAB. Following the resolution of the issue, the left hand booster completed its build up, as operations moved to the adjacent right hand booster.
‘During the LH (Left Hand) forward segment mate, operations were held while evaluations took place to understand segment drift above the FJAF (Field Joint Assembly Fixture),’ noted ATK processing information. ‘No contact was made with the FJAF.
‘These evaluations determined that the drift was caused by the mate enclosure air conditioning duct (horizontal drift) and expansion of the crane cables (vertical drift) due to sunshine through the high bay doors. There was also a problem where the segment would not lower due to a crane fault. These problems were corrected and the mate was nominal.’
At present, ET-120 will join the boosters for mating on August 20 – although this is under review pending sensor tests – while Discovery is due to rollover and mated to the stack September 6, for rollout to pad 39A a week later.
Endeavour Readiness
Meanwhile, Endeavour, just a week away from the opening launch attempt for STS-118, was back into a smooth pad flow, after the scare of the pressure leak from the crew cabin over the weekend. The new leak issue could become a similar threat to the launch date as the previous pressure decay problem of Saturday and Sunday.
‘Finished propellant load at pad and did leak checks. Completed EMU (EVA Mobility Unit – space suits) functional, and final SRB closeouts are in work,’ added processing information on Monday, ahead of the problem with the new leak check later that evening.
‘Payload bay doors closed for flight. Will recheck after ordnance installation Tuesday (now postponed due to new leak issue). Continuing this week with orbiter aft closeout, flight crew systems stow, hypergol and MPS tank pressurization. Will try to close aft compartment toward end of week.’
Over-viewing Endeavour’s status with just over half a week before the start of S0007 (Launch Countdown), other than the new leak problem, the shuttle appears to be in great shape for her ride uphill to the ISS, as the last remaining items are cleared for flight.
‘Discussed MPS (Main Propulsion System) temperature transducer at FRR (Flight Readiness Review) that was qualified only by similarity to Apollo vintage hardware,’ added Standup/Integration report information, listing off a vast array of items that are being cleared ahead of the launch.
‘Ran test on transducer this weekend for 50 mission duty cycle times four, and it looks good. Doing final NDE (Non-destructive Evaluation) Monday and Tuesday, and should wrap up certification this week.
‘On Fiberglas material around ET disconnect, fire barrier coating was applied on STS-118, and is in good configuration for flight. GRC (Glenn Research Center) completed window testing almost one week early…with good results.’
Managers are meeting on a regular basis to check on Endeavour’s status ahead of launch, following the FRR last Thursday, and the L-10 day bench review last Friday, which ‘went well.’
The next big review will come in the form of the L-2 day meeting of the MMT (Mission Management Team), which checks over items of interest, as Endeavour proceeds with the three day countdown, which starts at T-43 hours and includes over 27 hours of built-in hold time leading, to a preferred launch time at 7:02 pm local time.
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