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Flight-Seal Redesign and GH2 Leakage History Overview for STS-116 and STS-122

This document provides an in-depth analysis of the redesign of the flight-side seal configuration for STS-116 and STS-122 missions, specifically focusing on the new ground umbilical disconnect flight seal design. It highlights the transition from a one-piece seal to a flexible two-piece seal to mitigate misalignment issues during installation. Additionally, it reviews the historical leakage issues associated with previous designs and discusses the performance of the new seal in various loading phases, including fill and replenishment stages, under varying pressure conditions.

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Flight-Seal Redesign and GH2 Leakage History Overview for STS-116 and STS-122

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  1. Interface Seal GroundSide FlightSide Design Overview GH2 Vent Disconnect

  2. STS-116 GUCA Performance Body Seals Pre STS-116 and STS-122 and subs Body Seals STS-116

  3. Background – Design / Leakage History(Pre-STS-116) • STS-116 / ET-123 was first use of new ground umbilical disconnect flight seal design • One-piece seal replaced with flexible two-piece seal to accommodate misalignment during installation • History of leakage with previous disconnect ground side / flight seal design

  4. Historical Changes • Seal Graphic: Flight-Side Seal Configuration(Pre-STS-108 and Post STS-120) STS-116 Flight-Side Seal Redesign

  5. GH2 vent valveremains open in Replenish LH2 IFA STS-116-T-001, Unexpected GH2 Leakage • Background – Loading Phases GH2 unavailable GH2 vent valveclosed GH2 vent valveopen Ground/ETInterface GH2 vent valve GH2 press.line GH2vent line GHe GH2diffuser LH2 LH2 GH2 LH2 • Fast Fill • Tank volume partially filled with LH2 • Ullage gas consists of mixture of GHe / GH2 – GH2 concentration increases as tank is filled • Vent valve opening / closing • Tank pressure: 32.9 – 43.2 psia • Transition to Topping(leakage detected on STS-116) • Valve opens and vents high concentration of GH2 and someLH2 into the vent line • Vent line/umbilical interface exposed to rapid cryo cool-down/press. pulse • Replenish • Steady-state thermal conditions present • No delta pressure at umbilical / tank interface • Less volume / lower concentration of GH2 than during topping phase • Terminal Count • Vent valve closed – GH2 unavailable Critical Environments For Excessive Leakage Not Present During Majority Of Loading Operations

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