1、Lessons Learned Entry: 0415Lesson Info:a71 Lesson Number: 0415a71 Lesson Date: 1996-07-01a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: Radio Frequency (RF) Breakdown in Mariner Mars 71 Flight Radio Frequency Subsystem (RFS) Components and Circuits (1971) Abstract: During fin
2、al flight acceptance testing, an RF breakdown in an exciter revealed that its design was subject to RF breakdown at critical pressure. Costly design modifications late in the program were required to correct the design. All RF transmitter components and circuits should be analyzed and tested to dete
3、rmine their performance margin to any kind of RF breakdown. The lesson specifies the minimum margins.Description of Driving Event: (Relevant Historical Lesson(s) Learned)During the final flight acceptance testing of the second Mariner Mars 71 flight RFS, an RF breakdown occurred in one of the excite
4、rs at critical pressure. Investigation showed the exciter design had little or no margin to RF breakdown at critical pressure. Costly design modifications, late in the program, were required to correct the design.Also, during thermal-vacuum testing of the MM71 RFS Proof Test Model, the RF output was
5、 found to be a function of the vacuum chamber pressure. The problem was traced to the circulator switch used to select the traveling wave tube amplifier and antenna. Investigation showed that the switch had not been analyzed nor adequately tested by the subcontractor to determine its margin to RF br
6、eakdown. Costly design modifications late in the program, were required to achieve an acceptable RF breakdown margin.The MM71 Exciter RF breakdown investigation also determined that foam should not be used as an RF breakdown suppressant.Provided by IHSNot for ResaleNo reproduction or networking perm
7、itted without license from IHS-,-,-Reference(s): JPL Technical Memo 33-573 “MM71 RFS Subsystem“, R.S. HughesLesson(s) Learned: 1. All RF transmitter components and circuits should be analyzed and tested to determine their performance margin to any kind of RF breakdown.2. As a goal, all components an
8、d circuits should be designed to have a margin equal to a factor of four in power or a factor of two in voltage (6dB) against breakdown.Recommendation(s): 1. RF breakdown should be one component of the worst-case analysis normally required in the design, and it should be accomplished early in the de
9、velopment phase of the program. The breakdown margin must include all operating environments. Voltages, power levels, spacings should all be checked to determine the susceptibility to both multipaction and ionization (corona) discharge breakdown. The margin must be determined (tested) for each envir
10、onment expected.2. As a minimum, a margin of 3 dB (factor of two in power; factor of 1.4 in voltage), which has been verified by testing, is required. The breakdown margin of a passive component can usually be measured by applying up to 6 dB more input power than is expected during normal operation.
11、 However, measuring the breakdown margin of an active circuit, such as a transistor amplifier, is much more difficult and requires a well thought-out testing program.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s):
12、a71 Hardwarea71 Parts Materials & Processesa71 SpacecraftProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 1995-10-16a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
