1、Lessons Learned Entry: 0915Lesson Info:a71 Lesson Number: 0915a71 Lesson Date: 2000-09-29a71 Submitting Organization: GRCa71 Submitted by: Richard J. KrawczykSubject: Propellant Management for Geosynchronous Satellite Description of Driving Event: Hydrazine fuel in pressurized tanks is used for sate
2、llite stationkeeping. Fuel consumption log indicated sufficient fuel to extend mission beyond date originally planned. During a north-south stationkeeping in July 1998, thruster firing was aborted due to satellite attitude instability caused by uneven thruster firing. This was determined to be cause
3、d by two-phase flow of liquid hydrazine and Helium pressurant gas to thrusters in the odd half-system. This only occurs when hydrazine in a tank is nearly depleted. The fuel log indicated that the tanks in both the odd and even half system should have had sufficient fuel for several more stationkeep
4、ing maneuvers, contrary to the observed performance. Lesson(s) Learned: The fuel log had been maintained by bookkeeping method where mission analysis software provides calculation of fuel used by each thruster, based on propulsion/maneuver parameters, to track incremental fuel consumption since laun
5、ch. Independent supplemental calculation of remaining fuel was done based on telemetry values for tank temperature and pressure relative to initial conditions. The uncertainty in the remaining mass of hydrazine increases with fuel depletion as calculated by both methods. This provided an overestimat
6、e of remaining fuel.Recommendation(s): Satellite builders and operators should plan for thermal capacitance testing as an additional method of fuel gauging. Since propellant tank system thermal response is defined by mass and heat capacity, the rate of temperature rise due to a known heat input is a
7、n indication of remaining fuel in the tank. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Careful location of heaters and temperature sensors can allow prelaunch calibraton and on-orbit thermal tests that can provide propellant gauging where the un
8、certainty decreases with depletion.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Configuration Managementa71 Energetic Materials - Explosive/Propellant/Pyrotechnica
9、71 Flight Operationsa71 Parts, Materials, & Processesa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2000-10-20a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
