Engineers are working through the opening issues with Discovery at Pad 39A – all of which are expected for a pad flow – as the pace picks up ahead of the May 31 launch date target for the mission that has been extended to 14+1+2 days.
Discovery’s crew – led by commander Mark Kelly – also made their journey from the Johnson Space Center (JSC), arriving on their T-38 jets at the Kennedy Space Center (KSC) Tuesday afternoon.
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Now officially a 14+1+2 mission – due to the addition of an extra docked day to accomodate Battery Changeout ops in the airlock – the shuttle is now into the Shuttle Launch Pad Validation (S0009) procedures.
The newly arrived stack is checked out via connections that have been made between the vehicle and the pad’s GSE (Ground Support Equipment).
The flow is proceeding towards the TCDT (Terminal Countdown Demonstration Test) on Thursday and Friday, ahead of the closure of the payload bay doors the following day – which will be closely monitored in case of problems with the radiator retract hoses.
‘Vac Ion pump run was completed yesterday. Various systems performed hardwire and LDB (Launch Data Bus) safing checks,’ noted processing information on Tuesday. ‘Comm audio hardline verifications are complete.
‘MLP (Mobile Launch Platform/PIC (Pyrotechnic Initiator Controller/Circuit) pad interface and first motion checks are complete.’
As per normal for such a complex operation as the pad flow, a few IPRs (Interim Problem Reports) have been created since Discovery arrived at 39A – which are in various stages of troubleshooting.
‘Had a little work to do, but completed everything planned on weekend. Picked up a few IPRs, mostly associated with ground; understand all of these,’ noted the latest Shuttle Stand-up/Integration report.
‘Will follow with hydraulic operations. Plan TCDT (Terminal Countdown Demonstration Test) Thursday and Friday, close PLBDs (Payload Bay Doors) Saturday.’
‘GSE LOX transfer line main fill valve on side 1 of the MLP stayed open when commanded closed by hardwire safing. Troubleshooting revealed an off nominal wiring configuration in the Safing Rack. This IPR will be upgraded to a PR and the wiring will be corrected,’ added Tuesday processing information.
‘Heated pre-press valve/heater combo stayed off when commanded on by hardwire safing. Troubleshooting revealed the off nominal wiring configuration discovered. Is the same issue which resulted in this IPR condition. Additionally, this IPR will also be upgraded to a PR and the wiring will be corrected.’
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Another issue involves a card inside the Integrated Network Control System (INCS), relating to the Space Shuttle Main Engines (SSMEs). The card will be removed and replaced, ahead of the IPR being removed from the list.
‘During GN2 hardwire functional a channel on a card inside the INCS safing rack was reading 0.5 volts, s/b 0.0 volts. IPR will be transferred to INCS for card R&R,’ noted processing information, which added that SSME Frequency Response Tests (FRT), helium signature test, and fuel/oxidizer ball seal leak checks picked up yesterday and continue today.
Discovery received her payload on Monday without any issues reported, while work continues around her to configure the pad and stack for launch.
‘GO2 and GH2 blank off plate installation to be worked today. S0024 hypergolic propellant loading preps and QD (Quick Disconnect) mates will be worked all week. SRB (Solid Rocket Booster) aft skirt GN2 purge hook-up and validation is complete.
‘HPU (Hydraulic Power Unit) carts were transported from the fuel farm to the MLP 0 level yesterday. OWP’s (Orbiter Weather Protection Systems) will be extended today. Forward and aft Ground Lightning Monitoring System (GLMS) equipment is installed.’
Radiator Retract Hose Update:
Saturday’s payload bay door closure will be monitored with interest, specifically with the radiator retract hoses and their ability to retract back into their boxes without bending – as has been the problem with recent pad flows.
The last time a problem occurred during door closure was with Atlantis’ – ahead of STS-122’s launch – which was solved by an engineer guiding the hose, located in the aft, back into its box, via the use of a special tool on the end of a long pole.
STS-122: Hose related news content (all exclusives): *Issue found/fleet to be checked (December)* – *Atlantis found to have problem* – *Managers discuss forward plan* – *Use of pole to aid retract* – *Successful Retraction*
However, engineers are planning ahead in case the same issue strikes with one of the two hoses located at the forward portion of the payload bay.
‘Plan for radiator retract hose will go to Noon Board Tuesday; will build access to watch operation, will stop if hose binds up and assist hose into box,’ noted the Integrated Flow Status. ‘Risk assessment came back as low yellow. Assured that payload folks are comfortable with this work happening over payload.’
The evaluations for the forward plan in the event of a hose bending have been taking place at Huntington Beach in California, which analyzed procedures via a TIM (Technical Interchange Meeting).
Part of that meeting will try and find a root cause for the issue, which appears to be happening fleet-wide and with added frequency.
‘Assembled a group of the radiator flex hose experts at Huntington Beach for a TIM. Had a few objectives to determine,’ noted JSC’s Orbiter Project. ‘First, trying to develop test plan to support omega bend if one occurs when close PLBDs. Appreciate that the team developed a process to reposition a hose back into the box if needed. Will assess plan.
‘Don’t know if will ever determine the root cause of the bend, but developed a lengthy fault tree, and have various tests that will perform to eliminate branches of the fault tree and narrow down the root cause.
‘Also looked at mitigation plans if can narrow down scope of what problem is. Will start the testing this week, and hopefully will get results back this week or next week.
‘Appreciate the team working on plan to put radiator retract hoses back in box. For forward locations, plan for Saturday is that will review plan and be able to give Go to KSC; won’t hold up unless see something far out of family. This is best posture for flight.’
ISS Ready To Receive Discovery:
Last week saw a compressor in the Russian segment of the International Space Station (ISS) being changed out, following a leak of Freon coolant from the system.
Engineers on the ground have evaluated that the leak is well below allowable levels, and are using the Russian version of the US Trace Contaminant Control System (TCCS) – called the BMP – to remove the contamination from the air.
‘A compressor was changed last week on the Russian segment. One of the air conditioner units leaked Freon 218 (about 600 gm of the 800 gm in system),’ noted JSC’s Mission Operations. ‘The system shut itself down after the leak. Are working to scrub this out of the atmosphere.
‘This is very far below the crew Spacecraft Maximum Allowable Concentration level, and there are no issues for the crew. The engineering teams on ISS will engage the engineering teams on the Shuttle side.
‘Want to understand what the levels may be on STS-124 and ensure there are no impacts. Currently appears this will be okay by time of STS-124.’
Meanwhile, Expedition 17 commander Sergei Volkov, and flight engineer Garrett Reisman have completed their scheduled training for the arrival of Discovery during her always-stunning RPM (R-bar Pitch Maneuver).
During their skill training exercise, the duo practised taking photos with a DCS-760 digital still camera utilizing 400 and 800mm lenses out of Service Module windows 6 and 8, where Discovery will be commanded through a back-flip to have imagery taken of her Thermal Protection System (TPS).
Those images will be downloaded the same day, for evaluation by engineers on the ground.
Notably, STS-123’s post flight review presentations confirmed that Endeavour’s flight (STS-123) was the cleanest ever – following hot in the heels of Atlantis (STS-122), which was the previous cleanest flight.
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