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Elimination of Cryosystem Removal of the cryomagnet means removal of the cryosystem and all cryogenic fluids. – No nominal venting and significantly fewer potential fault venting locations. – No helium tank and no dewars during ground processing, and one COPV removed. – No requirement to monitor cryosystem health during canister and PCR operations, so LCCs eliminated. – No requirement to open vent valve during ascent. – No sloshing concerns during transfer or ISS ops. – No cryocoolers, so no payload-induced vibrations. – MMOD risk significantly decreased.
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Permanent Magnet Impacts to STS/ISS/MOD
Chris Tutt5 May 2010
Introduction
AMS Project Office has done an initial review of the impacts of replacement of the cryomagnet by a permanent magnet.
Goal of this presentation is to review changes with impacts to STS, to ISS, or to MOD.
Other changes exist, which will be documented in the safety packages and the ADPs, but which are transparent to the programs.
Elimination of Cryosystem
Removal of the cryomagnet means removal of the cryosystem and all cryogenic fluids.– No nominal venting and significantly fewer potential
fault venting locations.– No helium tank and no dewars during ground
processing, and one COPV removed.– No requirement to monitor cryosystem health during
canister and PCR operations, so LCCs eliminated.– No requirement to open vent valve during ascent.– No sloshing concerns during transfer or ISS ops.– No cryocoolers, so no payload-induced vibrations.– MMOD risk significantly decreased.
Power Requirements Changes
Permanent magnet does not require charging, so maximum power draw on ISS drops to 2400W.
No requirement to run vent pumps and valves during ground ops, so 48 VDC and 110 VAC requirements eliminated.
No requirement to keep cryosystem alive during downtime, so load shed requirements simplify.
Payload A and B buses are now completely identical, so contingency EVA to swap power connectors now highly unlikely.
Magnetic Field Strength Changes
Permanent magnet field strength approximately 1/6 of cryomagnet.– Dipole moment reduced to approximately 1400 Am2.– Reduced effect on plasma environment.
Magnet always on, so field effects need to be considered during ground operations, launch/ascent, and transfer operations.– Permanent magnet previously assessed for ground
operations and shuttle operations for STS-91 with no impacts found.
New Magnetic Field Lines
Current operations constraints are based on keep out zones of 300G (EVA) and 10G (EVR).– New 300G field lines do not extend outside the
Vacuum Case, so no special EVA controls should be required.
– New 10G is approximately where the original 300G line was, so EVR impacts should be minimal.
– Field strength at grapple fixtures are 3.89G (FRGF) and 3.28G (PVGF).
New field map has been provided to OZ for assessment by MAGIK team.
New 10G Field Map
New 10G Field Map
Structural Changes
Permanent magnet is significantly lighter than cryomagnet and associated plumbing systems.
Weight savings has been given to structural group as design budget for new magnet support structure and new tracker planes.
Final payload weight and CG location should be similar to current design. Updated numbers will be provided to STS and ISS as design matures.
Stress and fracture analyses will be updated as required based on new loads.
Outer Mold Line Changes
Majority of hardware changes occur inside the Vacuum Case, so AMS-02 outer mold line is generally unaffected.
Two primary exceptions:– Tracker plane 1N will replace the zenith radiator, but
large clearances exist to 87” envelope, so no impact is anticipated.
– ECAL will be lowered by 35mm to allow installation of tracker plane 6, which will violate the PAS Capture Claw Envelope by 19mm. Preliminary assessment by OM7 shows that clearance to claw is acceptable.
Outer Mold Line Changes
Capture Claw Envelope ViolationENVELOPE VIOLATION OF 19mmACTUAL CLEARENCE TO CLAW 24mm
Constants
Many items are not affected by magnet replacement.– Payload checkout on Shuttle and ISS by DDRS
systems still required, although time-criticality is reduced.
– Transfer thermal timeline remains at 8 hours.– Data transfer rate still averages at 6 Mb/s.– Deployment on MCAS still not acceptable to APO or
ISS.
Conclusions
Thermal and structural analysis is ongoing and results will be provided as they become available.
Project Office will review all previously submitted verifications to determine which ones have to be reopened:– STS MIP and ICD verification updates and new exceptions will be
coordinated with MO.– ISS ICD verification updates and new exceptions will be
coordinated with OZ.– MOD procedure/requirement updates will be coordinated with
ACO.– Flight Safety verifications will be coordinated with the PSRP/SRP.– Ground Safety verifications will be coordinated with the GSRP.
