1、Lessons Learned Entry: 1878Lesson Info:a71 Lesson Number: 1878a71 Submitting Organization: JPLa71 Submitted by: David Oberhettingera71 POC Name: Eric Archera71 POC Email: Eric.D.Archerjpl.nasa.gova71 POC Phone: 818-354-7350Subject: Contamination from Flaked Silver Plating Off Waveguides and Microwav
2、e Components Abstract: Poorly plated RF waveguides pose a low to moderate risk of corona or arcing in NASA spacecraft that are presently in operation or under development. If use of plated waveguides cannot be avoided, NASA must maintain supplier oversight and verify that proper manufacturing proces
3、ses are followed.Description of Driving Event: A radio frequency (RF) waveguide transfer switch failed five months after the insertion of Mars Reconnaissance Orbiter (MRO) into Mars orbit. The likely cause was debris-induced RF breakdown that pyrolized a polyimide tape window in the switch, injectin
4、g additional debris that jammed the switch. The NASA/Caltech Jet Propulsion Laboratory (JPL) published a lesson learned (Reference (1) that describes this August 2006 incident and offers recommendations for materials design, mission design, and reconsidering exemptions to the JPL single-point failur
5、e policy. The source of the debris that triggered this chain of events is not known and was not central to the findings of this 2007 lesson learned. However, the most likely contamination source to have produced the conductive particle and resultant high voltage breakdown was flaked silver plating f
6、rom either the rigid or flex portion of the X-band RF waveguide. Previous NASA and Department of Defense missions have experienced silver plating anomalies on waveguides, and it may be a continuing problem. In late 2006 and early 2007, the Solar Dynamics Observer (SDO) spaceflight project had issues
7、 with a silver-plated rigid and flexible Ka-band waveguide obtained from the same vendor as the MRO waveguide. Incoming inspection at NASA revealed evidence of incorrect plating procedures (Figure 1) and varying levels of contamination or Provided by IHSNot for ResaleNo reproduction or networking pe
8、rmitted without license from IHS-,-,-corrosion (Figure 2). Figure 1 is a color close-up photo of a section of a waveguide. It looks like a length of rectangular metal tubing. The surface of the interior appears to be peeling, with a thin coating of plating peeling away from the interior surface.Figu
9、re 1. Peeled silver plating in the SDO waveguide S/N 004.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure 2 is a color photo of a light gold colored piece of metal that has parallel raised fins across its surface. On the side of the fins the su
10、rface shows evidence of dark splotches that appear to be discoloration.Figure 2. Evidence of surface contamination on the inside of a newly purchased MRO waveguide. Destructive Physical Analysis (DPA) performed by JPL in 2007 on the rigid and flex portions of flight spares obtained from the same sou
11、rce confirmed the presence of contamination, flaking, and corrosion (Reference (2). This included a Phoenix flight spare manufactured in 1999 that showed surface stains similar to Figure 2. Chemical analysis of a white powdery substance inside the rigid portion of a MRO waveguide purchased in 2007 s
12、howed the presence of silver carbonate and silver oxide, with traces of chlorine, titanium and hydrocarbon oil. Spectral analysis of corroded areas (Figure 3) within the above waveguide provided evidence of sodium, chlorine, calcium, magnesium, and silicon contamination, as well as peeling silver pl
13、ating (Figure 4). Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure 3 is a grayscale photo, apparently taken through a microscope, of a flat surface that is deeply eaten away in the area of interest, leaving a void in the surface. The surroundin
14、g surface is marred only by a few shallow scratches or striations.Figure 3. Corroded area in newly purchased MRO waveguide.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure 4 is a grayscale photo of a similar surface that is deeply furrowed inst
15、ead of flat. The bottoms of the furrows show significant peeling of the surface coating.Figure 4. Evidence of peeling silver plating in newly purchased MRO waveguide.The results of the 2007 study documented in Reference (2) suggest that poorly plated RF waveguides pose a low to moderate risk of coro
16、na or arcing in NASA spacecraft that are presently in operation or under development. References: 1. “MRO Waveguide Transfer Switch Anomaly,“ NASA Lesson Learned No. 1796, NASA Engineering Network, May 29, 2007.2. Eric Archer, “DPA Results on Waveguide,“ October 22, 2007.Lesson(s) Learned: Poorly si
17、lver-plated waveguides pose a residual risk for current and future missions. NASA spacecraft with high power transmitters, and with waveguides made using questionable manufacturing processes, (i.e., MRO) are likely to experience further peeling. Spacecraft that have low power transmitters (Phoenix),
18、 that used nickel-cobalt electroforming instead of plating (DAWN, Mars Science Laboratory, Juno), or that were silver plated using different processes (Phoenix, Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Kepler), present a lower risk.Recommendat
19、ion(s): 1. Use of plated waveguides is to be avoided in telecommunications system design. If plating is needed to reduce RF loss or to obtain thermal properties, maintain close scrutiny over the waveguide supplier (e.g., oversight of the dip brazing and plating processes). 2. For both plated and un-
20、plated waveguides, collect data and maintain rigorous verification of the dip braze salt removal process. 3. Perform DPA on samples of all waveguide lots, including verification of structural integrity.4. Engineering notes on waveguide design drawings should mandate:a71 Cleaning of the waveguide and
21、 performing conductivity tests to verify the absence of brazing salts on all waveguides in accordance with the customer-approved procedure.a71 Heat treating for 8 hours at 340- 360F per AMS 2772 with required T condition specified in accordance with structural requirements and analyses. Perform hard
22、ness measurements on all waveguides.a71 Application of a chemical conversion coat, plate, or paint in accordance with appropriate military specifications. Require coupons for verification of each process.5. Ensure that supplier quality assurance controls and inspections are adequate, and that qualit
23、y control standards are enforced over sub-tier suppliers (i.e., plating subcontractors).Evidence of Recurrence Control Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 7.3.3 (“Safety and Mission Assurance Practices: Quality Assurance“) i
24、n the Jet Propulsion Laboratory standard “Flight Project Practices, Rev. 6,“ JPL DocID 58032, March 6, 2006.Documents Related to Lesson: N/AMission Directorate(s): a71 Space Operationsa71 ScienceProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Exp
25、loration SystemsAdditional Key Phrase(s): a71 Program Management.Acquisition / procurement strategy and planninga71 Program Management.Business processesa71 Program Management.Contractor relationshipsa71 Program Management.Risk managementa71 Engineering Design (Phase C/D).Spacecraft and Spacecraft I
26、nstrumentsa71 Manufacturing and Assemblya71 Safety and Mission Assurance.Early requirements and standards definitiona71 Safety and Mission Assurance.Product Assurancea71 Safety and Mission Assurance.Qualitya71 Safety and Mission Assurance.Reliabilitya71 Additional Categories.Communication Systemsa71
27、 Additional Categories.Hardwarea71 Additional Categories.Industrial Operationsa71 Additional Categories.Parts, Materials, & Processesa71 Additional Categories.Payloadsa71 Additional Categories.Procurement, Small Business & Industrial Relationsa71 Additional Categories.Risk Management/Assessmenta71 A
28、dditional Categories.Safety & Mission Assurancea71 Additional Categories.SpacecraftAdditional Info: a71 Project: variousApproval Info: a71 Approval Date: 2008-09-12a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
