Abstract: For a liquid rocket engine including the SSME the gaseous heat exchanger that is in the liquid oxygen turbopump exit flow path that serves to gasify the liquid oxygen for pressurizing the liquid oxygen tank and the POGO is modified by changing the flow circuit to replace the liquid oxygen with high pressure hydrogen tapped off of the low pressure fuel turbopump so that hydrogen/hydrogen at a favorable pressure differential is in indirect heat relation for providing a safe environment and avoiding what may result in a catastrophic failure in the event the heat exchanger fails. An external heat exchanger in communication with the heat exchanger in the liquid oxygen turbopump is provided to gasify the liquid oxygen for the pressurizing purposes.