1、Best Practices Entry: Best Practice Info:a71 Committee Approval Date: 2000-04-06a71 Center Point of Contact: MSFCa71 Submitted by: Wilson HarkinsSubject: Systems Test Considerations for High Performance Liquid Propellant Rocket Engines Practice: To achieve high overall liquid rocket fueled propulsio
2、n system reliability, conduct a comprehensive test program that verifies and validates the liquid rocket engines operation as it interacts and interfaces with other elements of the propulsion system, (i.e., structures, propellant feed systems, propellant tankage, and control electronics).Programs th
3、at Certify Usage: This practice has been used on Space Shuttle Main Engine (SSME), and Main Propulsion Test Article (MPTA) testing at MSFC, Rocketdyne, and Stennis Space Center.Center to Contact for Information: MSFCImplementation Method: This Lesson Learned is based on Reliability Practice number P
4、T-TE-1439 from NASA Technical Memorandum 4322A, NASA Reliability Preferred Practices for Design and Test.Experience in systems testing of the Space Shuttle Main Engine has shown that integrated propulsion system testing, (1) provides the necessary test data for “model basing,“ thus enhancing the rel
5、iability of system analysis techniques; (2) integrates vehicle hardware, ground hardware, and procedures for propellant loading, safing, and firing operations; (3) provides a resource for determining stage/engine design margins, establishing redlines, developing procedures and time lines, and confir
6、ming extrapolated criteria used in engine development; (4) identifies potential risks for catastrophic flight failure, vehicle hardware damage, and launch complex damage; and (5) identifies potential risks of a Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
7、 IHS-,-,-delayed initial launch and subsequent launches.Implementation Method:I. Background:The Space Shuttle Main Propulsion Test Article (MPTA) program was conducted at NASAs Stennis Space Center test site in Mississippi. The program involved NASA and Space Shuttle element contractors. The tests i
8、ncluded an orbiter aft fuselage with three Space Shuttle Main Engines, an External Tank, and related ground and flight support equipment. Three non-firing tests and twelve combination development/verification firings met planned pretest objectives. The main propulsion test article was of a flight co
9、nfiguration with a few practical exceptions. External Tank insulation was of non-flight configuration. The auxiliary power unit was simulated by a ground powered hydraulic system. The Shuttle Avionics Test Set was used for propulsion system control rather than flight computers. A special load bearin
10、g structure was provided on the test stand to react against the engines thrust. Non-flight hardware was used for payload bay purge into the aft compartment, propellant loading, ground umbilical disconnects, and some Ground Support Equipment consoles.II. Propulsion System TestingTwenty hot-firing att
11、empts were required to meet the requirements of the 12 test series. Hot firing aborts were distributed throughout the 20 firing attempts, although the frequency of occurrence decreased after the sixth test series or after 50 percent of the test program was completed. Twenty-six terminal counts were
12、required. Fourteen of these were required during the first six firing attempts. Hydrogen leakage within the aft compartment occurred on 12 tests. Two tests experienced high leaks.The degree of severity of some of the test failures underscores both the risk involved in propulsion system development a
13、nd the absolute necessity of this type of testing in order to avoid and eliminate these types of failures during a flight mission. For example, fires occurred in nine firings. Eight of the nine fires resulted from engine discrepancies. Four of the fires at the vehicle base were typical of main fuel
14、valve leaks through the engine after shutdown. One aft compartment fire resulted in extensive hardware damage. Two external fires produced significant damage to the vehicle and facility, particularly to the instrumentation.III. Changes and Modifications Brought About by the Main Propulsion Test Arti
15、cle (MPTA) ProgramThe important issues that were addressed in the Space Shuttle Program to enhance the reliability, safety, and performance of the vehicle by MPTA testing were (1) unworkable designs and procedures were made workable by changes and then verified, (2) workable designs and procedures,
16、for which adjustments to achieve acceptance were initially anticipated, were tested and the adjustments were accomplished. Many action items resulted and were resolved in each test series. Table 1 is an example listing of some of the most important action items that resulted from the Provided by IHS
17、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-propellant loading test, an early test where there was not a hot firing. Thirty to forty similar actions from a hot firing test were not unusual.Table 1. Example Action Items From Engine System Testinga71 Review LH2hi
18、gh point feedline liquid level sensor operation during propellant load test and repair. Review the need for redundancy.a71 Determine the cause of tripped circuit breaker for LH2recirculation pump #2.a71 Determine requirements for a backup GHe injection system for the LOX antigeyser system operationa
19、71 Review the system requirements and reactivate MEC backup power.a71 Provide necessary engineering to connect the KSC hazardous gas detection system to the LH2vent system.a71 Perform special cryogenic test of LOX and LH2auxiliary dump valves using a solenoid actuated system as well as the existing
20、pressure control actuation system and recommend system changes required to improve valve performancea71 Review the need for changing the 1/8“ sample line on the bottom of the LH2tank to 1/4“ or larger line to facilitate tank sampling and verification of purge procedures.Testing identified oversights
21、 which could have resulted in serious consequences under differing circumstances later in the development program. For example, design and manufacturing methods were changed to prevent the release of large hydrogen quantities as a result of main fuel valve structural failure. Design changes were mad
22、e to prevent fuel preburner burn-through and associated engine software changes were made to facilitate automated prevalve closure under all failure conditions. Manual closure was delayed under some failure conditions until the prevalve benefits were seriously compromised. Changes to software correc
23、ted this anomaly. Procedures for unloading oxygen from the ET/Orbiter were corrected to prevent serious pressure surges within the facility hardware. The tests identified the necessity to locate launch facility igniters to burn released raw hydrogen at engine start.The Space Shuttle MPTA testing, as
24、 well as testing of previous launch vehicle integrated propulsion systems, resulted in preferred practices that will ensure reliable performance if conscientiously applied. Preferred practices are summarized in Table 2.Table 2. Improved ProceduresProvided by IHSNot for ResaleNo reproduction or netwo
25、rking permitted without license from IHS-,-,-a71 Integrated testing is conducted to verify the performance of the feed system pressure drops, pressure surges, fluid-hammer responses, and resonances.a71 Mixing of incompatible and hazardous substances in fluid systems are precluded.a71 Contamination i
26、s excluded from contamination-sensitive systems.a71 Actual environments, conditions, and designs are simulated.a71 Margins are demonstrated during subsystem or system level tests.a71 Test plans and results are fully documented.a71 Stainless steel tubing and control lines are used for test facilities
27、.a71 Fuel and oxidizer prevalves are used in test facilities, and safe engine shutoff by prevalve closure is demonstrated in a subsystem test prior to propulsion system testing.a71 Thermal and environmental controls of propulsion systems components are provided to prevent freezing, loss of lubricati
28、on, and collection of hazardous gases.a71 An emergency source of ground power is provided to terminate the test in the event of a ground power loss.a71 Provisions for pressure relief, flow diversion and control during chill down, and protection against geysering during propellant loading are designe
29、d into the test facilities propellant feed system.a71 Reliable hazardous gas detection and measuring systems and rapid response leak detectors are used for integrated propulsion system firing programs and pre-flight operations.a71 Fire detection, fire protection capability, and internal protective n
30、eutralizing purges are used in static test programs, and are evaluated for launch site operations.a71 Heat flux at the vehicle base is measured to determine the relative contributions of convective and radiative heating.a71 Meticulous planning, training, and work control is employed in integrated pr
31、opulsion system ground tests.Recirculation of rocket engine plume low energy gases into the vehicle base may be a predominant heat source for clustered engine vehicles. Heat flux measurements from ground test programs to determine the relative contributions of convective and radiative heating and an
32、alytical methods developed to compensate for flight altitudes assist in establishing design requirements.Meticulous planning, training, and work control is employed in integrated propulsion system ground tests. Specific preplanned and measured personnel training and demonstration of qualifications i
33、s a prerequisite for reliable and repeatable success. Steps to assure effective shift change communications and the use of only experienced and qualified personnel is required. A process where both contractor and government safety personnel perform spot checks on all hazardous work control documenta
34、tion and operations is essential.IV. Other Related Development and Verification TestingProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-In addition to integrated systems ground tests such as those performed on the Space Shuttle MPTA, structural test a
35、rticles were built and tested, approach and landing tests were performed, an all-up hydraulic simulator Flight control Hydraulic Laboratory was developed and used, a Mated Vehicle Ground Vibration Test program was conducted, a Shuttle Avionics Integrated Laboratory was (and is) used, along with a Hy
36、draulic Simulation Laboratory, for software verification prior to launch, and full scale external tank terminal drain tests were conducted.Extensive development testing was performed at KSC with the flight vehicle prior to the first launch to improve propellant loading procedures and to resolve othe
37、r launch site/vehicle interface problems. Due to a thermal protection system failure on the External Tank and the desire to increase onboard propellant mass, several unplanned propellant loading tests were conducted both with the MPTA and with the flight vehicle at KSC.Technical Rationale:Several de
38、cades of integrated ground testing of launch vehicle propulsion systems, culminating in the MPTA Testing for the Space Shuttle Program, have proven that this type of testing is essential to perfect the interface between major hardware and software elements and to develop a reliable integrated launch
39、 vehicle propulsion system. The test programs themselves have shown that malfunctions, delays, and failures would be unacceptable in a flight situation. The successful performance of the Space Shuttle Main Propulsion System is attributable in great measure to the successful conduct of this series of
40、 ground tests and to the corrective actions that were taken to avoid failures.References1. “Advanced NSTS Propulsion System Verification Study,“ Space Transportation Systems Division, Huntsville Operations, Rockwell International, July 31, 1989.2. “History of MPT Test Program,“ Space Transportation
41、Systems Division, Huntsville Operations, Rockwell International, February 9, 1986.3. “Main Propulsion System Testing Tanking Test History,“ Space Transportation Systems Division, Huntsville Operations, Rockwell International, July 1983.4. Quick-Look Test Reports for: MPT-S1-001, MPT-S1-002, MPT-S2-0
42、01, MPT-S3-001, MPT-S4-001, MPT-5A, MPT-5, MPT-6-001, MPT-6-02, MPT-6-03, MPT-SF7-01, MPT-SF7-02, MPT-SF8, MPT-9-01, MPT-9-02, MPT-10-01, MPT-11-001, MPT-11-02, MPT-12; Transportation Systems Division, Huntsville Operations, Rockwell International, 1978 thru 1981.Impact of Non-Practice: Provided by
43、IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Failure to conduct integrated ground system tests of launch vehicle propulsion systems could result in the inability to locate and correct critical interface and launch preparation problems that could cause launch
44、delays, hazards to personnel, loss of the mission, and/or loss of the crew.Related Practices: N/AAdditional Info: Approval Info: a71 Approval Date: 2000-04-06a71 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-,-,-
