REG NASA-LLIS-0394-1995 Lessons Learned - Voyager Scan Platform Problems.pdf

1、Lessons Learned Entry: 0394Lesson Info:a71 Lesson Number: 0394a71 Lesson Date: 1995-05-30a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: Voyager Scan Platform Problems Abstract: Near the end of the Voyager 2 Saturn encounter, the scan platform azimuth actuator seized, causing

2、a scan platform pointing error that resulted in a loss of some data. Recommendations involved the need for life cycle testing of critical rotating mechanical equipment, and attention to factors that could cause increased drive torque requirements for rotating elements used in a space environment.Des

3、cription of Driving Event: The Voyager 2 scan platform, on which are mounted the spacecraft cameras and several science instruments, is rotated in elevation and azimuth by actuators. Near the end of the Voyager 2 Saturn encounter, the scan platform azimuth actuator exhibited an anomaly. This anomaly

4、 was evidenced by the azimuth actuator seizing, causing a scan platform pointing error that resulted in a loss of some data. Through a series of ground commands, the problem was alleviated to the extent that the scan platform could perform its function. A prototype scan platform actuator was life-te

5、sted in a laboratory and it failed after approximately the same total number of slewed degrees as the flight unit. Upon disassembly of the test actuator, the problem was determined to be a design flaw in the actuator shaft bearing and gear lubrication system. In addition, dissimilar metal electro-ch

6、emical reactions produced corrosion. There was also debris build-up due to a lack of relief ports resulting in the deposition of this debris on the drive gear bearing assembly. For details, refer to “Voyager Engineering Improvements for Uranus Encounter“ by Howard P. Marderness.Lesson(s) Learned: Li

7、fe cycle testing of rotating mechanical equipment used in a space environment can aid in design verification, and can enable analysis of in-flight faults.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): 1. On mission critical rotati

8、ng mechanical equipment, life cycle testing should be performed under realistic conditions to obtain a reasonably accurate life-time forecast prior to final design acceptance and flight qualification.2. For design of rotating elements used in a space environment, care should be taken on those facets

9、 of the design which could contribute to increased drive torque requirements with continuing use. a. For precision mechanisms containing moving parts which are susceptible to binding in the presence of particulate matter or fluid contaminants, the use of bonding agents for locking devices should be

10、tightly controlled. This particular application used nylon, Solithane and Stycast for the purposes of screw locking and wire harness bonding. Post assembly cleaning and inspection for contaminants are critical elements in the fabrication process. Properly applied, nylon, Stycast and Solithane are st

11、able compounds. All of these materials however, are highly productive of particulate contamination when abraded or disturbed. Rework, such as breaking free a screw head which is bonded in place, or cutting a Stycast spot bond away, tends to produce large quantities of very small particles which must

12、 be subsequently located and removed.3. A set of spare spacecraft hardware should be maintained in the flight configuration and within specification to enable detailed analysis of suspected causes of in-flight faults and validation of proposed corrective actions or workarounds.Evidence of Recurrence

13、 Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Parts Materials & Processesa71 Spacecrafta71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1996-03-14a71 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-,-,-