1、Public Lessons Learned Entry: 2736 Lesson Info: Lesson Number: 2736 Lesson Date: 2010-04-22 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Ground Cooling Reliability and Operating Stability Design Enhancement Abstract: The Space Shuttle Orbiter rejects heat from onboard electrical
2、equipment, crew members, and other sources to an independent ground refrigerant loop through an onboard heat exchanger. Ground-provided umbilicals that separate from the spacecraft at launch provide primary loop single-phase coolant to the onboard heat exchanger from the circulation unit located at
3、the base of the launch pad. The collected heat is in turn rejected from this primary coolant loop to a secondary two-phase refrigerant system. This method of heat rejection proved to be unreliable and difficult to control for the ground cooling system operator because the spacecraft heat loads varie
4、d. A much more stable, reliable system was put in place when a third intermediate loop was implemented into the ground cooling system with a heating element that allowed the refrigerant loop to operate at a constant set point. Description of Driving Event: The ground cooling unit was experiencing re
5、gular failures, and was consuming many engineering hours identifying and resolving problems. Also, constant vigilance was required because it was difficult for the operator to control to the desired cooling set points. Lesson(s) Learned: To reject varying spacecraft heat loads prior to launch, circu
6、late a primary loop single-phase refrigerant through the spacecraft-to-ground heat exchanger while maintaining a constant heat load via a heater on a secondary ground loop to a tertiary two-phase refrigeration loop because that makes a more stable and reliable system for ground-cooling equipment tha
7、n the previously used variable-load system. The heaters eliminate mechanical load control devices such as hot gas bypass, cylinder unloaders, and desuperheat, and allow the refrigeration loop to operate at one known set point, providing the ability to quickly identify and correct problems. Recommend
8、ation(s): For ground cooling equipment at the launch pad used to reject varying spacecraft heat loads prior to launch, circulate a primary loop single-phase refrigerant through the spacecraft-to-ground heat exchanger while maintaining a constant heat load via a heater on a secondary ground loop that
9、 rejects heat to a tertiary two-phase refrigeration loop operating at a single set point. Evidence of Recurrence Control Effectiveness: Not Applicable Documents Related to Lesson: Click here to download Ground Coolant Design Presentation 1990 Click here to download Ground Coolant System Presentation
10、 1991 Click here to download Ground Coolant Presentation 1993 Click here to download Ground Coolant System Reliability Improvement Study Mission Directorate(s): Space Operations Exploration Systems Additional Key Phrase(s): 1.Launch support systems 1.Orbiting Vehicles Provided by IHSNot for ResaleNo
11、 reproduction or networking permitted without license from IHS-,-,- 1.Launch Systems Additional Info: Project: Space Shuttle Orbiter Approval Info: Approval Date: 2010-06-23 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
