The prediction of repair and maintenance measures, such as MTTR (Mean To Time Repair), MTBR/MTTS (Mean Time Between Repair/Mean Time To Service), MCMT (Mean Corrective Maintenance Time), and MPMT (Mean Preventive Maintenance Time), for performing a successful repair/refurbishment action. In other words, maintainability analyses measure the ease and speed with which maintenance tasks and/or repairs (i.e., a mission system can be restored to operational status after a downing-event occurs) can be performed, including diagnosis time, repair time, supply time, and any testing time as applicable.
Ease is estimated via process analysis (e.g. Process FEMCAs), testing, or simulations and can directly impact time estimates.
Time estimates for non-flight operations (e.g. ground systems, extraterrestrial systems/vehicles) that would be the time to return a system to service after a failure or shutdown or successful servicing and includes anomaly root cause determination, recovery planning, recovery execution, and/or re-supply planning/execution.
Time estimates for space-flight operations that would be the time to return a system to service after a failure or shutdown or safing event or successful servicing and includes anomaly root cause determination, recovery planning, recovery execution, and/or servicing mission planning/execution.
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- Preventative Mainatenance Analysis
- Corrective Maintentence Analysis
- Mean Time To Repair (MTTR) Analysis
- Life Analysis
- Spare Part Analysis
- TBD
Preventative Maintenance Analysis
Coming soon - Currently being formulated
Description
When Performed
Value
For Performance see R&M Guidance and Reference Data: Methods page
Corrective Maintenance Analysis
Coming soon - Currently being formulated
Description
When Performed
Value
For Performance see R&M Guidance and Reference Data: Methods page
Mean Time To Repair (MTTR) Analysis
Coming soon - Currently being formulated
Description
When Performed
Value
For Performance see R&M Guidance and Reference Data: Methods page
Life Analysis or Limited-Life Analysis (LLA)
The LLA identifies components that potentially have a finite or limited useful life inherent to the performance of their respective functions. It is intended to determine how much of the expected life is consumed by the stresses the component experiences during testing and operation, and to assess if this cumulative damage/use will limit mission success or if the item has an acceptable life ratio (Expected life/Required life) or life margin (Expected Life - Required Life).
Items are considered for their susceptibility to environmental or application factors such as atomic oxygen, solar radiation, shelf life, extreme temperatures, thermal cycling, wear, corrosion, fatigue, and vacuum. Typical items that will be identified include, but are not limited to:
- Items that deteriorate or degrade with time either during storage or during operational use (e.g., chemicals, lubricants, seals, O-rings, rubber seals, polymers, solar arrays, paints, adhesives, coatings)
- Items that exhibit characteristics of quality degradation or drift with age (e.g., sensors, equipment needing calibration, gases that decay or slowly leak)
- Items that are cycle/duty cycle sensitive (e.g., switches, relays, valves, Electrically Erasable Programmable Read Only Memory (EEPROM), connectors, batteries)
- Items that are subject to wear (e.g., moving mechanical parts, bearings, actuators, compressors, momentum wheels, gyros, scan mechanisms)
- Consumable hardware and supplies (e.g., filters, fluid)
Proper Limited-Life Analysis greatly reduces the risk of premature mission failures by ensuring life margin for wear out items. It also enables missions to be extended with some confidence that hardware will not wear out.
Value
Life/Limited-Life Analysis process and results can provide the following project benefits:
- Verification of mission-life requirement;
- Identification of candidates for Critical Items List;
- Loss of function risk identification;
- Optimized redundancy plans;
- Identification of items requiring maintenance or refurbishment;
- Input to sparing plans;
- Input to test plans and life testing plans.
When Performed
As early in the design cycle as possible and must be updated iteratively throughout the design cycle, testing/operations, and reviews. Since LLAs will help identify design and reliability issues the LLAs should completed to allow for changes/refurbishment to be implemented prior to implementation, testing, and operations.
