SPACECRAFT PROPULSION - KTH

- 39 -4.2.5 General System Design ConsiderationsIn order to ensure safety of personnel during spacecraft groundoperations, in general the following pressure ratings ofpressurized systems have to be followed:- The burst pressure (causing rupture) of theintegrated system shall be not less than fourtimes the maximum system operating pressure.Only the tank burst pressure in general is twotimes the maximum propellant storage pressurefor the reason of low tank mass.- The proof pressure (checking safety) of theintegrated system shall be not less than 1.5 timesthe maximum system operating pressure. Thesystem has to pass successfully the proofpressure before operating it for the first time.This applies also for the case of system repairwhere faulty equipment has to be replaced. Afterrepair, again the system has to pass successfullya proof pressure cycle.In general, propellant feed systems are an all-welded design in orderto minimize mass and ensure leak-tightness. Screw mountedconnections are used only for the connection of thrusters. This allowseasy mounting and even later replacement of this equipment ifrequired.All components, which are in contact with the propellants aredesigned for and have demonstrated their long term compatibility.Therefore, high strength titanium alloy 6AL4V and pure titaniumA40 are normally used for tanks and all other components includingtubing lines.