SpaceX’s next Dragon mission to the International Space Station (ISS) will involve the delivery of a replacement Extravehicular Mobility Unit (EMU), allowing for the return of a faulty suit on the same vehicle when it returns to Earth. Notably, the returning suit won’t be Luca Parmitano’s EMU, after its water leak issues were resolved via successful troubleshooting efforts.
EMU Status:
Luca Parmitano safely landed back on Earth in the early hours of Monday morning, marking the end of a six month stay on the ISS that included his first two EVAs on the outside of the Station.
It was the second of his spacewalks that became the center of the EMU investigation that has been ongoing for some months now, following the early termination of EVA-23 on July 16.
The problem related to water leaking and building up in his helmet, around one hour into the planned six hour spacewalk.
Despite the issue being extremely serious, Luca’s life was never in immediate danger, thanks to his own, his EVA partner – Chris Cassidy, the ISS and ground control team’s professionalism, as they put into work their extensive training by safely returning the Italian into the safe haven of the Quest Airlock.
Technically, the investigation into what went wrong with Luca’s suit began moments after he egressed the airlock and removed his helmet. However, as per NASA’s tried and trusted methodology in solving problems in space, it was the task of experts on the ground to nail down the root cause.
That investigation was conducted by NASA’s Anomaly Resolution Team (ART) at the Johnson Space Center (JSC) in Houston, in tandem with hands on evaluations into the suit – known as EMU 3011 – by the ISS crewmembers.
The EMU is a highly complex life support apparatus that has proved to be highly reliable during its role of providing safety to astronauts working on the outside of spacecraft.
As such, pinpointing the problem with EMU 3011 was never going to be a speedy process.
Per the ART investigation (full coverage in L2), the initial theory pointed towards a vent loop water leak caused by either a blocked or clogged Water Separator Pitot Tube, a blocked condensate water relief valve, or a blocked condensate water line – causing the water separator loop to allow excessive amounts of water to enter the ventilation loop.
Testing the suit, involving the replacement of hardware elements along the root cause path, gained mixed results, while a plan to send additional hardware uphill was aided by the Station’s continually busy Visiting Vehicle schedule of both Agency and commercial resupply ships.
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The Russian Progress M-20M provided the ISS crew with a collection of troubleshooting tools just a few weeks after the premature end to EVA-23, aided by NASA personnel rushing the equipment over to Moscow in time for the hardware to be manifested and flown to the Baikonur Cosmodrome in Kazakhstan in time for late loading on the Progress.
Additional items also flew with the first Cygnus mission (ORB-D) to the ISS, as Orbital’s new bird provided additional Helmet Absorption Pads (HAPs).
Further investigations with the suits on the ISS resulted in the root cause focusing on the Fan/pump/separator hardware.
After that hardware was replaced on EMU 3011 – following the hardware’s arrival on the Station via Soyuz TMA-10M – results showed that the water leak was no longer present.
The removed hardware then flew back to Earth with Luca on Soyuz TMA-09M, allowing for it to be shipped back to Houston for additional testing and confirmation of the root cause tree.
With EMU 3011 returning to full functionality, the ISS has three working spacesuits (EMU 3010 and 3005 being the others). A fourth suit, EMU 3015 is deemed as faulty and needs to be returned to Earth.
Given SpaceX’s next Dragon mission to the ISS – CRS-3 (SpX-3) – was already on standby to bring EMU 3011 back to Earth, the plan is still on to utilize a specially made rack on the spacecraft, allowing for EMU hardware to be launched and returned to and from the ISS.
The realigned plan – per L2 information – is to launch a replacement suit, known as EMU 3003, to the ISS on the Dragon, before returning EMU 3015 – which also has a faulty sublimator – to Earth via Dragon’s splashdown homecoming in the Pacific Ocean.
A question remains over when this suit relay will take place, based on Dragon’s launch date.
Currently, the CRS-3/SpX-3 Dragon mission is set to launch on February 11, 2014. However, this will be Dragon’s first ride on the upgraded Falcon 9 v1.1.
SpaceX still have two satellite launches to complete via the use of the newly upgraded rocket, following on from its debut launch with the Cassiope mission.
The first of these two satellite missions will be the rocket’s debut from its Florida base at Cape Canaveral’s SLC-40.
Tasked with lofting the SES-8 satellite into a geostationary orbit, the launch date has slipped a few times due to work relating to an issue observed during the Cassiope mission – specifically the restart of the second stage in space.
While the restart wasn’t a mission requirement for Cassiope’s successful deployment, it is required for the SES-8 mission, which has the ultimate goal of reaching a GEO destination.
With the Eastern Range approving a launch date target of November 22, SpaceX lined up their pre-launch tasks, with L2 information noting a Wet Dress Rehearsal (WDR) set for November, 12 – followed by the Static Fire (Hot Fire) on November 14.
However, updated L2 information has noted the WDR was “scrubbed/cancelled”, allowing for it to become part of the Static Fire test. This was soon followed by the launch date moving to a preliminary date of November 25.
Reasons for the latest slip are not fully clear. However, it is understood to include working Range approval for pre-launch events surrounding the upcoming MAVEN launch and ongoing work to complete the upgrades to the SLC-40 launch site for the Falcon 9 v1.1.
The following launch, tasked with launching Thaicom-6, was set to follow one month after the SES-8 mission.
It was previously understood that minimum separation of one month (30 days) was required between launches, and with the Christmas holidays coming into play, resulting in Thaicom-6’s launch was deemed to be “highly likely” to move into a January launch window.
However, SpaceX have since responded, noting they are still targeting a December 20 NET for the Thaicom-6 launch, which points to another feather in the cap of SpaceX, based on an extraordinary ability to turn around their Cape site for two launches in quick succession.
Only when Thaicom-6 is successfully launched will SpaceX be able to finalize their flow schedule for the CRS-3/SpX-3 mission to the ISS, given all three of the next Falcon 9 v1.1 launches will depart from SLC-40 at Cape Canaveral.
Should the February 11 target be impacted by the two preceding missions, Dragon will have to negotiate with the ISS’ Visiting Vehicle schedule to find an acceptable window to be berthed at the orbital outpost.
At present, the CRS-3/SpX-3 launch date remains unaffected.
(Images: via L2’s SpaceX Special Section, which includes over 1,000 unreleased hi res images from Dragon’s three flights to the ISS. Special section also contains presentations, videos, images (Over 3,500MB in size), space industry member discussion and more. Other images via SpaceX and NASA)
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