NASA-LLIS-0184

Lessons Learned - LO2/LH2 Vent and Relief Position Indicator Switch

contributor author	NASA - National Aeronautics and Space Administration (NASA)
date accessioned	2017-09-04T17:54:00Z
date available	2017-09-04T17:54:00Z
date copyright	33905
date issued	1992
identifier other	FFZCQCAAAAAAAAAA.pdf
identifier uri	http://yse.yabesh.ir/std/handle/yse/177136
description abstract	Description of Driving Event: The LO2 and LH2 vent and relief valve position indicator switch tolerance allows the valve to indicate "closed" when it may be open up to 0.30 inch. This condition could allow undetected ullage gas leakage prior to launch. Hot GO2 may auto-ignite the ET thermal protection system (TPS) after SSME ignition. GH2 in flight can cause fire and loss of TPS which could result in a catastrophic situation. The vent/relief valve uses a position indicator switch that is highly accurate. However, no matter how accurate, no position indicator can accurately assure closure because leakage rates for qualification and acceptance are roughly 5E-6 lb/sec. Therefore, a redesign to eliminate the hazard has proven to be virtually impossible.
language	English
title	NASA-LLIS-0184	num
title	Lessons Learned - LO2/LH2 Vent and Relief Position Indicator Switch	en
type	standard
page	2
status	Active
tree	NASA - National Aeronautics and Space Administration (NASA):;1992
contenttype	fulltext
subject keywords	Flight Equipment
subject keywords	Ground Operations
subject keywords	Hazardous/Toxic Waste/Materials