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Auxiliary Power Unit Fuel Pump Redesign

Problem: APU fuel pump is subject to several failure modes:

  • Fuel pump housing cover o-ring "kinking" - may lead to loss of sealing redundancy.
  • Fuel pump housing corrosion - may lead to external leakage of hydrazine (Crit 1/1).
  • Start / bypass valve stiction - may lead to launch scrub and/or loss of APU for entry.
Solution: Solution for Issue #1: Modification to fuel pump housing eliminates inner O-ring deformation.

Solution for Issue #2: Splitline between fuel pump housing and cover will be sealed to prevent future corrosion.

Solution for Issue #3: SBPV piston and/or sleeve material change will solve stiction problem.

Initial Operation Date: Phase II Upgrade
Attrition; First flight after OMM, spares available sooner.
STS-103 (OV-102), STS-116 (OV-103), STS-97 (OV-104), STS-126 (OV-105)
Technology Goal: 1) Revise fuel pump housing machining process to secure inner O-ring and prevent deformation. Easy simple process change. Does not affect other existing components.

2) Seal splitline between fuel pump housing and cover. Proven technology (SRB HPU and aircraft sealant uses). Easy to implement.

3) SBPV Piston: material change is recommended. Materials being considered: Type 440C Martensitic stainless per AMS5630, MP-35N cobalt-nickel alloy steel per AMS5845, and Nitronic 60 stainless steel per AMS5848. Easy to implement.

Goals Supported: 1) Fly Safely


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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