Tense Tuesday for Shuttle and Station

by Chris Bergin

A crucial element for the upcoming flights of the Shuttle, the CSCS (Crew Shuttle Contingency Support) capability on the International Space Station (ISS), will take a step forward – or backwards – on Tuesday, as ISS crewmembers carry out the repair to the Elektron Oxygen Generator.

Tuesday is also the new date for the rollover of Discovery to the VAB, in preparation for her STS-116 mission.

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It was Thursday’s arrival of Progress M-58 that delivered the vital spare parts for the broken Elektron, which will undergo a series of installation tasks on Monday, before Tuesday’s re-start. The other Elektron on the station – also broken – will return to Earth for refurbishment on STS-116.

‘Update on Elektron: Repair of the Russian electrolysis machine for oxygen generation with the newly arrived spares is scheduled for Monday (10/30), activation for Tuesday,’ confirmed Sunday’s ISS On Orbit Status Report.

How the Elektron performs over the subsequent days will also be under close observation, given previous breakdowns have usually occurred a couple of days after a re-start has been initiated, post troubleshooting.

A successful return to action for the machine will be a timely boost to the consumable status of the O2 supply on the ISS, which in turn will ease pressure on the CSCS timescale relating to the LON (Launch On Need) support required for STS-116, currently tasked to Shuttle Atlantis on LON-317.

At present, NASA documents show a nine day allowance (O2 limit) between current and allowable CSCS levels – a level that needs to stay above the current 60 day target for Atlantis to be ready to launch on a rescue mission, should the unlikely event be required. It does not state if current CSCS levels take into account the current status of the Elektron system.

Very little – if any – contingency remains for the STS-116 flow, although processing is not behind schedule. However, the NET (No Earlier Than) December 7 launch target is still 50/50, with a smooth mating and pad integration required to make the date, added to the on-going negotiations over the availability of the range.

Back on the ISS, some of the fallout from the troublesome docking of the Progress is coming to light, with further notes on the On Orbit Status Report.

‘Update on 23P Docking: The EPS (electrical power system) load shed during the Progress 23P docking delay on 10/26 had some minor impacts to payload operations. ER3 (EXPRESS Rack 3), with the EMCS TROPI (European Modular Cultivation System/Analysis of a Novel Sensory Mechanism in Root Phototropism) experiment was without power for approximately 10 hours.

‘However, this power outage occurred during the ‘dark’ cycle of the experiment and power was restored to the rack just in time to continue the ‘light’ cycle of the experiment. MELFI (Minus Eighty Degree Celsius Laboratory Freezer for ISS)’s Brayton motor was powered off for the docking activities and was down for approximately 9 hours. The dewars experienced very little temperature gain during this time and it is believed there are minimal impacts to the science.

‘ER1 was also powered down during the EPS load shed. The MAMS (Microgravity Acceleration Measurement System) data that were collected during the docking event was lost.’

Interestingly, while the report noted that investigations are continuing into the problems encountered, Russian controllers do not believe the antenna actually retracted ahead of docking, despite before and after photography apparently claiming the possibility that it did actually retract.

‘Flight controllers at TsUP/Moscow believe that the KURS 2AO antenna on the Progress did not retract,’ the report added. ‘Investigation into the exact state of the antenna is ongoing.’

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