File:STS-134 High-Pressure Gas Tank (cover removed).jpg

English: High-Pressure Gas Tank with the cover removed.
High pressure oxygen onboard the space station provides support for EVAs and contingency metabolic support for the crew. This high pressure O2 is brought to the station by the High-Pressure Gas Tanks (HPGTs) and is replenished by the space shuttle by using the Oxygen Recharge Compressor Assembly (ORCA). There are several drivers that must be considered in managing the available high pressure oxygen on the station. The amount of oxygen the space shuttle can fly up is driven by manifest mass limitations, launch slips; and in-orbit shuttle power requirements. The amount of oxygen that is used from the station’s HPGTs is driven by the number of shuttle docked and undocked EVAs, the type of EVA prebreathe protocol that is used, contingency use of oxygen for metabolic support, and emergency oxygen. The HPGT will be transferred from ELC 3 to the Quest airlock. The HPGT measures 5 feet by 6.2 feet by 4.5 feet and weighs approximately 1,240 pounds of which 220 pounds is gaseous oxygen at 2,450 pounds per square inch of pressure. The HPGT was provided by Boeing.