STS-400 – NASA draws up their Hubble rescue plans

by Chris Bergin

NASA has drawn up extensive plans for the mission they hope they’ll never have to launch, STS-400 – the rescue mission for next summer’s STS-125 Hubble Servicing Mission.

The unique rescue mission would see Endeavour linking up with a crippled Atlantis on orbit, before transferring and bringing the crew home. STS-125 is the only remaining mission that doesn’t have the “safe haven” of the International Space Station (ISS) available.

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STS-400 is one of many roles Endeavour will be tasked with during her pre-launch flow. While being the last shuttle to sit on launch pad 39B as STS-400, she’ll also provide STS-326 rescue support for STS-124. Endeavour’s primary mission, STS-126, will be the heaviest logistics flight ever, STS-126, carrying supplies – including a new six-crew Galley – to the ISS.

Because of the lack of ‘safe haven’ for STS-125, any major problems on orbit would require the crew to either carry out a repair, or turn Atlantis into a lifeboat until Endeavour arrives.

Due to the restrictions of how long an orbiter can survive on orbit, Endeavour will be sat on Pad 39B at the same time as Atlantis launches from Pad 39A, ready to launch if an emergency is called during STS-125.

The plan is for the LON (Launch On Need) orbiter (Endeavour) to rollout to Pad 39B first. Endeavour would sit on the pad while Atlantis was stacked in the Vehicle Assembly Building (VAB), for rollout two weeks after Endeavour made the trip to 39B.

After the stand-down of the LON requirement is given during STS-125, Endeavour would then be transported from Pad B to Pad A and prepared for her primary mission, STS-126. If a contingency is called, Endeavour would immediately become STS-400 LON, launching one week after Atlantis’ lift-off, to rendezvous on orbit.

The amount of planning that is required for this unique rescue mission is expansive and has been ongoing for around two years. With the mission closing in, NASA now have a set of baseline plans (eight presentations on L2), ahead of final approval and fine tuning.

‘The concept of a Shuttle rescue was examined after the Columbia accident,’ noted an overview presentation on STS-400, which noted that the mission would be flown by a crew from a recent mission, rather than the main crewmembers of STS-126

‘Basic Assumptions: Will be a recently flown crew. Crew is trained for an ISS mission with some HST training. Minimum 3 crew members (though will be four). External airlock will not have an APDS (Androgynous Peripheral Docking System).

‘Stranded Vehicle has attitude control. It is most likely possible to rescue a vehicle without attitude control, but it will take different techniques and be more challenging.’

Rendezvous with Atlantis would be conducted by Endeavour approaching from below, level on the Rbar at 600 feet, as Atlantis holds position – payload bay facing Endeavour – on the Vbar. Endeavour would then close distance.

This is tagged as Rbar Approach 3, and could allow for Endeavour to conduct a RPM (Rbar Pitch Maneuver) – with the stricken Atlantis taking the role normally given to the ISS, with imagery taken of Endeavour’s belly to ensure she has managed to get into orbit without serious Thermal Protection System (TPS) damage.

‘Could be done if STS-125 has the cameras,’ noted one presentation where the possibility was raised. ‘Visual cues would have to be trained. (Other options include): Utilize additional Crew Cabin and OMS Pod surveys to capture those areas normally covered by ISS RPM photos.’

‘MC4 (burn) to Rbar arrival should be the same as ISS/HST,’ added notes on the Manual Phase of the approach to Atlantis. ‘Same DAPs, hitting Rbar around 600 ft. HHL/KU Radar will be as accurate as docking with any payload.

‘(For final approach – 500 ft to 30 ft) Standard Rbar braking gates (R/1000). DAPs A9/B9 for both vehicles. Free Drift for STS-125 at capture. STS-125 in: LO Z. Verns (ALT for VERN Fail instead of PRI). Flight Control power off. Attitude: -ZLV +YVV.’

Several other approaches were looked at including approaching toward the Nose and a Vbar Approach.

Once within the required distance, Endeavour would move her RMS (Remote Manipulator System) robotic arm and grapple with Atlantis’ RMS joint for capture. Other options are being evaluated for fine tuning.

The process of transferring the STS-125 will come in the form of a spacewalk ballet, that will be conducted between the two orbiters, along a transition rope.

‘All crewmember transfers done via EMUs (EVA Mobility Unit). 4 EMUs – HST Orbiter, all in working order. 2 EMUs – launched on Rescue Orbiter. Only 3 EMUs can return on Rescue Orbiter. All 7 entry suits must be transferred

‘HST Orbiter SRMS is not used. EVAs will be performed by the HST crew only. Three crewmembers will not have optimal sizing; simple translations may be difficult. LON crew will be a recently flown crew that requires minimal training for LON support.’

‘Set-up part 1: 3 EVA crew positioned in HST airlock. 2 EMUs pre-positioned in LON airlock for retrieval. Set-up part 2: EV crew installs translation rope on SRMS of LON orbiter. One HST crew ready waiting for transfer in HST airlock.

‘Transfer part 1: EVA crew retrieves 2 empty EMUs for transfer to HST airlock. Part 2: Two empty EMUs transferred to HST airlock. Three crewmembers translate to LON airlock. Part 3: Airlocks are closed and repressed. Final part: Both hatches closed, 3 crew transferred to LON. Two EMUs transferred to HST.’

‘Second transfer part 1: Two crew in HST airlock with 4 entry suits. Three EMUs pre-positioned in LON airlock for transfer to HST. Part 2: EVA crewmembers transfer entry suits to LON. Part 3: Entry suits are store in LON airlock and 3 EMUs picked up for transfer. Part 4: EMUs stored in HST airlock. Part 5: EVA crewmembers transfer back to LON. Final part: EVA crewmembers transfer back to LON. EMUs transferred to HST middeck.’

This process continues through a third transfer, ending with the removal and stowage of the translation rope, along with the transfer crew staying at vacuum, prepared for contingency EVA for un-grapple, should it be required.

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Given the process is such a complex EVA training scenario, it is likely to be fine tuned over the coming months to ensure the best possible and economical transfer is achieved.

‘Scenario is an example of many possible permutations of the transfer concept. In each of the permutations 3 crew transfers are required. Each permutation requires 3 airlock depress/repress cycles,’ added the EVA presentation for STS-400.

‘No individual task is considered overly complex. The specific skill and EMU fit of individual crewmembers may determine the actual order of transfer. A tabletop review of the detailed EVA procedures will be performed with the HST and LON crews late in the flow.’

The STS-400 mission is timelined for seven days (launch to landing), although what will happen to the stricken Atlantis is unclear. Only a few hints were forthcoming in the eight presentations, which pointed towards the possibility of giving Atlantis a chance to land unmanned, a feasible idea as previously reported by this site, though second to the primary choice of a destructive deorbit disposal of the orbiter.

‘Future work: Determine impact of SM4 OA Burn Optimization (Conus Deorbit vs Disposal Burn) on LON Deorbit costs,’ noted one presentation, which appears to be in answer of a question earlier in the document, which asked: ‘Protect Automated Controlled Landing at a Conus Site (Vandenberg?).’

The whole basis of STS-400 is in regard to contingency, and this rescue scenario is highly unlikely to be required. However, without ISS ‘safe haven’, having a back-up plan for the STS-125 crew in case of an emergency is a vital ingredient to ensuring all the bases are covered during this high profile mission.

L2 members: All documentation and quotes – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.

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