1、Lessons Learned Entry: 0642Lesson Info:a71 Lesson Number: 0642a71 Lesson Date: 2000-01-13a71 Submitting Organization: JPLa71 Submitted by: P. Narvaez/D. OberhettingerSubject: “Non-Magnetic“ Materials May Become Magnetized Abstract: Although stainless steel material is generally assumed to be non-mag
2、netic, it is possible for a stainless steel propellant tank to become residually magnetized, either from “working” the material into its shape or from an external magnetic field. The associated dipole moment imparted roll torque to a commercial communications satellite, resulting in mission failure.
3、Do not rely solely on the known magnetic properties of constituent material(s), and take steps to control residual magnetization of flight hardware. Description of Driving Event: An unanticipated roll torque was imparted to a commercial communications satellite launched in 1989. This torque mandated
4、 excessive thruster corrections by the attitude control system until the propellant was prematurely exhausted, resulting in mission failure.Subsequent magnetic characterization tests performed on an engineering model of the large stainless steel propellant tanks revealed that the tanks could be easi
5、ly magnetized during or after fabrication. The dipole moment of a magnetized tank would interact with the earths magnetic field. This force would attempt to align the spacecraft with magnetic north, like a compass needle, producing the observed roll torque and requiring excessive attitude correction
6、s by the thrusters. Testing showed that once magnetized, the tank would be capable of retaining a residual field that produces a dipole moment much greater than the 580 A-m2 required to produce the observed torque.The satellites two stainless steel propellant tanks had been substituted for titanium
7、tanks due to schedule deadlines. Since stainless steel material is generally assumed to be non-magnetic, no magnetic testing was performed. However, it is possible for the stainless steel sheet metal to become Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
8、IHS-,-,-residually magnetized, with an associated moment, either by working it into the tanks hemispheric shape or by exposure to an external magnetic field. As a corrective measure, this moment can be reduced significantly (to approximately 5 A-m2) after manufacturing by subjecting the tanks to a 4
9、0 Gauss alternating field and by monitoring subsequent exposure.Additional Keyword(s): Helmholtz coil, demagnetization, magnetic compatibility, attitude control, mission operationsReference(s):1. Magnetic Test Results of Engineering Model Propellant Tank, P. Narvaez, Jet Propulsion Laboratory IOM 52
10、19-89-341, October 17, 1989.2. Roll Torque Anomaly Review Committee Findings, K. P. Bhat, August 21, 1989.Lesson(s) Learned: 1. A spacecraft component may possess a significant magnetic moment despite the non-magnetic characteristics of the constituent materials. In this case, the stainless steel ta
11、nks were magnetized either during fabrication or by subsequent magnetic exposure.2. 3. Magnetic contamination is a mission critical risk on spacecraft with magnetic sensitive instrumentation or subjected to magnetic environments during flight.Recommendation(s): 1. When determining the magnetic prope
12、rties of an end product by analysis, do not rely solely on the known magnetic properties of the constituent material(s). Consider factors that may have changed the original magnetic characteristics, including the fabrication method and the shape, length, and mass of the end item. Also, consider expo
13、sure to external fields that may magnetize materials during fabrication and handling.2. 3. Steps to control residual magnetization of flight hardware may include: a) imposition of a limit on residual dipole moments (e.g., degauss to less than 5 A-m2), b) performance of magnetic testing on end items,
14、 c) implementation of controls to maintain a magnetically clean ambient ground environment, and d) monitoring of spacecraft field exposure with magnetic sensors attached to the spacecraft during handling and ground transportation.Evidence of Recurrence Control Effectiveness: N/AProvided by IHSNot fo
15、r ResaleNo reproduction or networking permitted without license from IHS-,-,-Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Parts Materials & Processesa71 Spacecrafta71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 2000-02-07a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
