Abstract:
A number of incidents, some of them documented in other lessons learned, are listed to support the thesis that ESD remains an insidious threat to the integrity of flight hardware despite extensive NASA and industry experience with controlling ESD and its effects. The lesson references a number of NASA Reliability Preferred Practices that should be implemented on flight projects.
Description of Driving Event:
Electrostatic discharge (ESD) remains an insidious threat to the integrity of flight hardware despite extensive NASA and industry experience with controlling ESD and its effects. ESD-induced damage during the latter stages of spacecraft development (e.g., system integration and test or launch vehicle integration) may be difficult to detect/analyze and expensive to repair. While the following NASA lessons learned do not define the total magnitude of the industry wide problem, they illustrate a sample of ESD-related issues: - On two occasions during integration and test of Mars Exploration Rover (MER), a braided ground strap being dragged across the floor contacted a facility power outlet, causing visible sparks and partial melting of the ground straps and power connectors. [LLIS # 1372]
- Nitrogen tetroxide flowing through a flex line during Galileo spacecraft propellant loading caused an electrostatic discharge that perforated the flex line. The resultant leak of this highly toxic and corrosive substance posed significant risk to launch personnel and flight hardware. [LLIS # 0217]
- The fire and destruction of a Pershing II stage I missile motor was attributed to unreliable tests that indicated that the solid propellant was not sensitive to ESD. [LLIS #0328]
- Discrepancies reported with shipment of Robotic Work Stations pointed out the need for formal handling, packaging, and shipping processes to preclude improper ESD packaging. [LLIS #1211]
- Electrostatic discharge from an ungrounded radiation "spot" shield may have caused an anomaly during the Voyager I Jupiter encounter. This prompted a recommendation that metal spot shields and other metal masses on circuit boards should be grounded even if they are inside equipment housings. [LLIS #0384]
- After an integrated circuit was damaged during installation of a discrete capacitor, it was determined that capacitors can accumulate a residual charge through normal handling and storage that is sufficient to destroy an integrated circuit. [LLIS #0297]
- The continually decreasing feature size within integrated circuits makes modern electronic devices increasingly susceptible to ESD induced damage during handling and use. In addition, the effectiveness of ESD protection circuits tends to decrease with decreasing device dimensions. [LLIS # 1315]
- During receiving activities, a spark was observed upon the attachment of a facility ground strap to the Mars Exploration Rover (MER) Rover Electronics Module (REM). This re-emphasized that ESD is an issue cutting across JPL hardware activities (Reference 1). [LLIS # 1371]
- Some modern materials (e.g. certain composites) thought to be conductive have instead been found to be susceptible to surface charging. Use of such materials can allow ESD energy to be transmitted internally from exterior spacecraft surfaces and damage flight electronics. [LLIS # 1330]
References: (1) Jet Propulsion Laboratory Corrective Action Notice No. Z77277, August 27, 2002. Additional Key Words: ESD Control Plan, ESD requirements, ESD sensitive devices, ESD sensitivity, personnel safety, system safety
Lesson(s) Learned:
Designers of ESD-sensitive devices and handlers of ESD-sensitive equipment cannot assume that routine ESD engineering principles and practices will continue to be adequate to prevent damage to flight equipment.
Recommendation(s):
Plan implementation of the ESD-related practices documented in NASA Technical Memorandum 4322A, NASA Reliability Preferred Practices for Design and Test, including: - "Assessment and Control of Electrical Charges," LLIS #0654.
- "Design Checklists for Microcircuits," Guideline LLIS #0680.
- "Electrostatic Discharge Control in GSE," LLIS #0685.
- "Spacecraft Thermal Control Coatings Design and Application," Practice No. PD-ED-1239.
- "Electrostatic Discharge (ESD) Control In Flight Hardware," LLIS #0732.
- "Design Practice to Control Interference from Electrostatic Discharge (ESD)," LLIS #0773.
- "Electrostatic Discharge (ESD) Test Practices," LLIS #0777.
- "Surface Charging / Electrostatic Discharge Analysis," LLIS #0788.
- "Analysis of Radiated EMI From ESD Events Caused by Space Charging," LLIS #0797.
- "Thick Dielectric Charging / Internal Electrostatic Discharge (IESD)," LLIS #0800.
Evidence of Recurrence Control Effectiveness:
Corrective Action Notice No. Z77277 was closed by JPL on September 5, 2003. The measures taken to implement Laboratory-wide corrective action on the above recommendations were (1) creating a procedure JPL QAP 61.12, “Packing and Unpacking ESD Sensitive Hardware” (JPL DocID 61692) which is referenced by D-1348, “Electrostatic Discharge Control”, (JPL DocID 34906), (2) releasing a JPL-wide safety alert regarding the use of non-static-dissipative shipping containers, (3) Attaching ESD warning labels to all shipping containers, (4) releasing the JPL Electrostatic Discharge Control Document (JPL D-1348) Rev. F, and the Packing and Unpacking ESD Sensitive Hardware (JPL QAP 61.12), Rev. 0, (5) populating the JPL JIT Critical Environments catalog with “approved” ESD/Contamination control items, and adding warning statements to the catalog, and (6) adding a depiction of problem shipping containers to ESD Certification training courseware to augment current discussion of packing and unpacking procedures. Also, JPL is working on a course focused on the packing and unpacking of hardware that will be introduced to the QA engineers as part of their ESD Auditor's certification, and JPL ESD Control Engineering is working with JPL Procurement to implement a controlled process for replacing all containers that are not static-dissipative.
Documents Related to Lesson:
N/A
Mission Directorate(s):
- Exploration Systems
- Science
- Space Operations
- Aeronautics Research
Additional Key Phrase(s):
- Energy
- Facilities
- Flight Equipment
- Flight Operations
- Ground Equipment
- Ground Operations
- Hardware
- Industrial Operations
- Launch Process
- Occupational Health
- Packaging Handling Storage
- Parts Materials & Processes
- Payloads
- Personal Protective Equipment
- Safety & Mission Assurance
- Spacecraft
- Test Facility
Additional Info:
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