1、Public Lessons Learned Entry: 4618 Lesson Info: Lesson Number: 4618 Lesson Date: 2010-09-20 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Cryogenic Line Sizing Abstract: A major problem in designing a cryogenic system in a spacecraft or launch vehicle is avoiding back-pressure bui
2、ldup, which will affect the ability to service and deservice the vehicle with cryogenic reactants. Servicing lines should be sized adequately for an existing baseline system; then the baseline tubing should be oversized to accommodate increased fluid flow rates that can result from new equipment or
3、changes in requirements. If these accommodations are not part of the initial design, servicing or venting paths may need to be added later. Description of Driving Event: Several years into the Shuttle Program, Extended Duration Operations (EDO) pallets were added in the Orbiter mid-body for some mis
4、sions. These pallets included up to four additional tanks of liquid hydrogen and liquid oxygen to support the onboard fuel cells, which generate power on orbit. This added capacity made it possible to run fuel cells for missions lasting up to 28 days. (The original Shuttle design was for a maximum o
5、f 14 days on orbit.) On several occasions (and in all instances of pallet loading), full loading of the pallet was not achieved. The consensus at the time was that the vent tubing for the EDO pallets and Tank 3 was not sized to accommodate the increased flow from additional tanks during loading. The
6、 EDO pallets were not part of the original Shuttle design. Therefore, original fill and vent tubes were not sized to accommodate the added requirements. However, if the lines had been sized with excess capacity, this modification might have been better supported. Lesson(s) Learned: Oversizing cryoge
7、nic (or other) commodity lines in a spacecraft to accommodate higher flow rates is an advantage, but the future need for more capacity must be likely in order to justify the additional cost and weight. Recommendation(s): During initial design, engineers should consider the cost and weight of oversiz
8、ing servicing and vent lines against the likelihood of increased flow rate requirements. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directorate(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Explor
9、ation Systems Space Operations Aeronautics Research Additional Key Phrase(s): 1.Systems analysis - cost analysis 1.Mission and systems trade studies 1.Long term sustainability and maintenance planning 1.Level II/III requirements definition 1.Engineering design and project processes and standards 0.C
10、rew operations and support concepts 1.Pressure Vessels 1.Spacecraft 0.Acquisition / procurement strategy and planning 1.Orbiting Vehicles 1.Cryogenic Systems 1.Launch Vehicle 0.Crew Operations Additional Info: Project: Space Shuttle Program Approval Info: Approval Date: 2011-09-28 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
