Alpha Magnetic Spectrometer 02 AMS02 Safety TIM Helium Venting and Vacuum Seals

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Alpha Magnetic Spectrometer - 02 (AMS-02)Safety
TIMHelium Venting and Vacuum Seals
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Agenda

• (Re)Introduction to AMS-02
• Certification Plan for AMS-02 Vacuum Seals
• Certification Plan for AMS-02 Mechanical Fittings
  for Pressure Systems
• Puncture of Vacuum Case
• Puncture with Payload Bay Doors Open
• Puncture with Payload Bay Doors Closed
• Micro-Meteoroids and Orbital Debris Penetrations
• AMS-02 Nominal Vent into Payload Bay
• General Discussion

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What is AMS?

• AMS is a high energy physics payload that
  searches for antimatter and darkmatter
• AMS is funded by DOE, NASA, and various high
  energy physics institutes throughout the world
• AMS is an across-the-bay payload that has a
  current ISS manifest weight of 13,500 lbs.
• Experiment is composed of a large annular
  cryogenic super conducting magnet and several
  layers of detectors

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Where has AMS been and where is it going?

• The feasibility study for AMS was performed in
  1994
• The plan was to fly the experiment on a precursor
  flight of the Space Shuttle and then fly again on
  the ISS for 3 operational years
• AMS successfully flew on the precursor flight
  (STS-91) in June, 1998
• The first flight was very successful, and the
  experiment team decided to upgrade the magnet
  from a permanent magnet to a cryogenic super
  conducting magnet. They also decided to add
  several new detectors. (In addition to the
  magnet, AMS has a total of 7 different Physics
  detectors)
• AMS will be carried to ISS on UF-4, currently
  scheduled for September, 2003
• For more information on AMS, go to
  http//ams.cern.ch/AMS/ams_homepage.html

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Certification Plan for AMS-02 Vacuum Seals

• Double o-ring design for large (gt95 Ø) o-rings
• 3 o-ring design not possible
• Not adequate space
• Can not get proper compression
• Double o-ring design for small ports (lt6 Ø)
  wherever possible
• Small o-ring interfaces have high reliability
  because
• Easy to replace
• Minimal mechanical stressing/loading
• Easy to produce
• Easy to inspect
• Easy to properly compress
• Not adequate space for 3rd o-ring

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Certification Plan for AMS-02 Vacuum Seals, Cont.

• Bolted Interfaces
• Bolt spacing of lt2o for large (gt95 Ø) o-rings
• Currently 192 ¼ inch bolts around circumference
  for each of the large o-ring interfaces
• Bolt spacing of at least 45 deg. for small (lt6
  Ø) o-rings
• Currently 8 - 10 bolts around circumference
• Welded Interfaces
• Must meet requirements in JSC-28792 (AMS-02
  Structural Verification Plan), Section 12
  (Materials and Welds)
• Include complete NDE
• LMSO and NASA/EM currently developing weld and
  NDE procedures for large circumferential weld of
  Inner Cylinder to Conical Flange
• Development will include multiple sample test
  welds, full scale test weld, full scale STA weld
  destructive testing, NDE procedure development

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Certification Plan for AMS-02 Vacuum Seals, Cont.

• STA Vacuum Case
• Proof Pressure Test upon delivery to NASA and
  prior to Cold Mass Replica (CMR) installation
• Vacuum Leak Check upon delivery to NASA and prior
  to CMR installation
• Proof Pressure Test after installation of CMR
• Vacuum Leak Check after installation of CMR
• High level sine-sweep test (used to develop FEM
  of non-linear strap support system)
• Random Vibration test to excite the o-ring sealed
  interfaces to flight levels
• Vacuum Leak Checks during sine-sweep and random
  vibration testing
• Modal test and Static test of entire payload with
  vacuum on STA VC
• Vacuum Leak Checks during Modal and Static tests

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Certification Plan for AMS-02 Vacuum Seals, Cont.

• Flight Vacuum Case
• Proof Pressure Test upon delivery to NASA and
  prior to Cryomagnet/Cryosystem installation
• Vacuum Leak Check upon delivery to NASA and prior
  to Cryomagnet/Cryosystem installation
• Proof Pressure Test after installation of
  Cryomagnet/Cryosystem
• Vacuum Leak Check after installation of
  Cryomagnet/Cryosystem
• Long duration (12-18 Months) vacuum quality
  measurements during magnet development
• Includes several long duration truck and airplane
  transports

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Certification Plan for AMS-02 Pressure System
Mechanical Fittings

• To ensure integrity of all mechanical fittings
  used in pressure systems on AMS-02, the following
  requirements will be added to the SVP (JSC-28792)
• Qual. Vibration Test of Fitting Design to MWL
  (Table 6, JSC-28792). Subsequent Leak Check.
• Qual. Thermal Cycle Test of Fitting Design.
  Subsequent Leak Check.
• Qual. Pressure Cycle Test of Fitting Design to
  predict operational surge pressure cycle.
  Subsequent Leak Check.
• Acceptance Pressure Cycle Test of Flight Fitting.
  Subsequent Leak Check.
• Ultimate Factor of Safety will meet Appendix A,
  Lines and Fittings of JSC-28792.
• Integrity of hazardous fluid system shall be
  verified as specified in NASA-STD-5003.

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Certification Plan for AMS-02 Pressure System
Mechanical Fittings, Cont.

• To ensure integrity of all mechanical fittings
  used in pressure systems on AMS-02, the following
  requirements will be added to the SVP, Cont.
• Engagement and operational disengagement cycle
  life test data to qualify fitting for predicted
  processing cycle life is required (includes mate
  and demate to 4 x expected processing cycle life,
  and performed in combination with additional
  environmental tests when appropriate.)
• Compatibility data for metallic and nonmetallic
  materials for appropriate fluid and environmental
  exposure conditions and durations will be
  provided. Must ensure continuous exposure does
  not cause property changes of materials which
  would result in leakage, inadequate safety
  factor, or loss of capability to meet subsequent
  operations or environments.

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Certification Plan for AMS-02 Pressure System
Mechanical Fittings, Cont.

• To ensure integrity of all mechanical fittings
  used in pressure systems on AMS-02, the following
  requirements will be added to the SVP, Cont.
• Fitting design to meet external leakage
  requirements will be certified to environmental
  compatibility as specified in paragraph 200.3 of
  NSTS 1700.7B, and for payload induced operational
  environments including the worst case mate
  configuration.
• Mated configuration will include a positive
  restraint to preclude loss of seal. (Back-off
  prevention)
• All test environments will meet or exceed those
  defined in the SVP.

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Puncture of Vacuum Case

• Puncture with Payload Bay Doors Open During
  On/Offline Ground Processing
• Puncture with Payload Bay Doors Closed
• Orbital Debris and Micro-Meteoroids

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Puncture with Payload Bay Doors Open During
On/Offline Ground Processing

• System incorporates burst disks so that the
  pressure systems will not exceed Maximum Design
  Pressure
• Emergency Vent Line will be plumbed away from
  personnel during ground operations
• Lines may have to be vented outside of some
  buildings to avoid Oxygen deprivation (TBD)
• These lines will be removed just prior to closing
  the Payload Bay Doors

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Puncture with Payload Bay Doors Closed

• Analysis has been performed to determine the
  effect of a sharp pointed object (ice pick)
  falling and hitting the bare vacuum case in the
  thinnest section
• AMS-02 Trunnions are currently located at
  Xo1163.4 inches, with the top of the Vacuum Case
  at Xo1145 inches
• The Shuttle Bulkhead is located at Xo581 inches,
  This gives a maximum distance of 564 inches
• To show a zero margin of safety, Analysis shows
  that the maximum weight object would be 0.23 lbs
  (from 564 inches)
• To show a zero margin of safety, Analysis shows
  that a 0.25 lbs sharp object would have to fall
  516 inches

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Puncture with Payload Bay Doors Closed, Cont.

• Analysis is Conservative because
• Does not include possible thermal blanket or
  debris shield on Vacuum Case
• Assumes object does not hit any other payload on
  the way down.
• Does not allow for plastic bending of the Vacuum
  Case
• Assumes object penetrates that thinnest section
  of the Vacuum Case

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Assumptions in Impact Analysis

• Impact force-displacement relationship is
  approximated by an elastic-linear work-hardening
  model
• f k ?e kp(? - ?e)
• ?e - elastic displacement limit beyond which
  plastic hardening begins
• kp - plastic hardening stiffness, kp 0.1k
  (based on material properties), k - elastic
  stiffness
• Diameter of impact area is assumed to be equal to
  shell thickness
• with which k and ?e are defined
• Energy conservation (no loss of energy) during
  impact
• mGh mG? k ?e2 kp(?2 - ?e2)/2
• from which ? is calculated and impact force f is
  determined.
• Failure impact load is determined based on
  ultimate strength of plate under concentrated
  load (Roarks Formula for Stress Strain)

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Mass of Falling Object vs. Margin of SafetyH
564 in (backward location) and under 3 gs
loading conditions
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Height of Falling Object vs. Margin of Safetym
0.25 lb and under 3 gs loading conditions
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Micro-Meteoroids and Orbital Debris Penetrations

• Analysis is ongoing by the Hypervelocity Impact
  Technology Facility (HTTF) of JSC (Eric
  Christiansen/NASA and Dana Lear/LMSO)
• Preliminary Analysis shows that for an 11 day
  Shuttle Mission, the Probability of a Vacuum Case
  Penetration is 1 in 2695 (0.037)
• Preliminary Analysis shows that for a 5 year ISS
  Mission, the Probability of a Vacuum Case
  Penetration is 1 in 231 (0.433) (Note The SFHe
  will run out in 2-3 years, and this is not a
  safety concern)
• Assumes minimal shielding, more shielding WILL be
  incorporated
• Can vent all Helium overboard prior to
  reinstallation into Shuttle

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Nominal Vent into Payload Bay

• Shuttle Integration has assessed the AMS-02
  nominal vent rate of 3.2 liters/min (without
  cryocoolers)
• Vent rate is acceptable
• Any vent direction is acceptable
• Will vent below the longeron
• Will vent in the Orbiter X or Y direction
• Vent will be zero thrust

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Conclusions

• With this certification plan in place, there is
  no risk of emergency venting into the payload bay
  with the doors closed
• AMS will consider this approach to be a design to
  minimum risk for the vacuum case and Cryomagnet
  pressure systems
• Shuttle Integration has already been assessed the
  AMS-02 nominal vent rate with the doors closed.
  Because the vent rate is very small, this is not
  a safety concern.