MMT outlines their extension day decision – EVA-4 finalizes SARJ tasks
The Mission Management Team (MMT) has decided to extend STS-126 by an additional docked day. This will allow for additional troubleshooting time on the Water Recycling System (WRS) that was carried to the Station by Endeavour. Meanwhile, EVA-4 has concluded the mission’s spacewalk tasks.
Flight Day 11 focused on the fourth and final spacewalk of the mission, which involved the final tasks on the starboard SARJ (Solar Alpha Rotary Joint) – such as work on the final Trundle Bearing Assembly (TBA) that was outstanding from EVA-3, and the clean/lube tasks on the final 30 degrees of the Race Ring.
The spacewalkers – Steve Bowen and Shane Kimbrough – utilized most of the EVA on the port SARJ, as a pre-emptive action of cleaning and lubing, although this SARJ has not suffered the same vibration issues as seen on the starboard side.
Several other tasks were included in the EVA, such as the installation of a GPS antenna on Kibo, along with the P3 truss thermal cover removal and installation of camera system on the truss.
The MMT decided to extend the mission by a day in order to support STS-126′s crew efforts in finding a solution to problems that have been encountered with the hardware that is vital for the six person crew next year.
According to the Flight Day 11 MMT Minutes – available in L2′s expansive coverage of STS-126 – the extension by one day, resulting in a Sunday landing on a nominal EOM (End Of Mission), was always in their back pocket.
“Always planned for extension day and we told folks to plan for it,” noted MMT chair Leroy Cain. “No issues Orbiter is working that would have any issues with staying up another day.
“No concerns with extra day, ISS sleep shift and Progress docking, comfortable with the off duty time that was scheduled,” added Crew Office Brett Jett.
During the MMT, Mr Cain asked for any issues with the extension to aid his final decision. The only reference of note came with regards to the ISS crew’s workload, with the next Russian Progress soon to launch to the Station.
“Some concern for the violation of GGRC (progress launching during docked ops loop hole) hoping to get ISS crew half day off to help ease this concern,” noted Space and Life Sciences (S&LS). “Good from sleep shift and when progress docks at Nadir after crew wake up.”
“ISS supports the half day off and the team should be working towards that,” answered ISS program manager Kirk Shireman.
This led to Mr Cain decision that they would “officially extend a Day and defer the Entry briefing until Friday.”
The problem with the WRS is specific to the Urine Processing Assembly, which shuts down after just a few hours of run time.
Monday’s plan has been to hard mount to structure to see if can isolate the vibration that is understood to be causing the centrifuge to undergo thermal variations – resulting in a shutdown – then refill and restart processing. This has now been completed.
If – in the worst case scenario – the assembly needs to be returned, the MMT noted they are looking at MPLM stowage if required to bring it home.
“Having issues with the distillation assembly of the urine processor. On Spacehab flight a unit flew with no issues hard mounted for four days,” added Mr Shireman at the MMT on Monday. “Working towards success and learn what we can. Appreciate you staying the extra day.
“For REGEN, got a wet indication on a sensor and looking at the nuisance messages. INH wet indication since have other ways to know water on the fan. TOCA had some air bubble issues and we changed some software to clear this up.
“Readiness review for Sunday’s Progress docking. Some open work but ready for docking (6:23 am CST, Sunday).”
The only other new issue that has been discussed relates to a Micrometeoroid Orbital Debris (MMOD) strike to Endeavour’s window 6, reported as 0.5” in diameter to the PLT right window to the thermal pane (estimate 1/32” depth).
Based on analysis the window should have no issues for peak heating M=8.0, but could form cracks but remain intact during peak loading M=0.7. Pilot visibility should not be hindered by this location if it cracks. The MMT concluded that the damage is ok, at present, to re-enter with as-is.
Numerous images, presentations and notes have been acquired by L2, with a round up forthcoming in the next article to be published on site.
L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.