Mechanical Systems Working Group


Charter Timeline Policies Links Contacts

Per NSTS 14046, a mechanical systems Technical Interchange Meeting (TIM) should be called prior to each phase safety review, with an agenda provided to the MSWG prior to each TIM. The MSWG chairperson or a designated representative will provide an assessment to the Engineering Directorate representative of the safety review panel prior to each phase safety review and a formal written recommendation prior to the signing of the hazard report. MSWG representatives will support the safety reviews and integration activities (such as the Cargo Integration Review) as required.

These are the required interactions.  Design organizations are encouraged to contact and interact with the MSWG as early as possible in the design process to ensure that there are no surprises and design effort is not wasted.  At the very least, organizations are encouraged to explore the MSWG web site and utilize the templates, examples, and other tools located there.

The following timeline details what documentation is requested by the MSWG prior to each phase safety review (early enough for a decent review and a discussion of issues prior to the safety review). In some cases the documented data requirements are somewhat inexact and scattered over mutiple documents, so this is what the MSWG has gathered and interpreted to be of the most help at the various phases. If you have any requests for exceptions to the following data requests or have any other questions at any phase of design or development, don’t hesitate to contact the MSWG (the earlier the better!)


Phase 0 Phase I Phase II Phase III


Phase 0

The current hazard report or RAESR for the system.
A draft version of the Mechanical Systems Verification Plan.  An MSVP Template is available here.  At this point, the MSVP only needs to contain the following:
A description of the system and each mechanism within it.
A fault-tolerance analysis for the safety-critical mechanisms outlining the hazard controls planned to meet fault-tolerance requirements (click here for a worksheet template.)  This can really help clarify mechanism operations and contingency scenarios.
If an MSVP cannot be provided in draft form, then at a minimum the contents above need to be supplied separately. At this stage an understanding of the mechanisms and the failure-tolerance approach is very important to avoid future setbacks.
Any requests for a "Simple Mechanism" designation. This designation must be granted PRIOR to the Phase I review per MA2-00-057.
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Phase I

Updated and additional hazard reports or RAESR for the system.
The fracture control plan for the system.
An updated MSVP according to the phase safety review stage. An MSVP Template is available here. At this stage, the MSVP should contain the following:
A description of the system and each mechanism within it, identifying the safety-critical mechanisms.
A fault-tolerance analysis for the safety-critical mechanisms explaining the hazard controls in place to meet fault-tolerance requirements. This is included in the MSVP template, but a separate template is available here.
A draft matrix detailing how each requirement in the MA2-00-057 Mechanical Systems Safety letter is or will be met for each mechanism relying upon a DFMR designation to meet requirements. Note that there are not 11 requirements, there are 78—one for each statement in the letter. A statement addressing each of the requirements is to be included and documented accordingly. This is included in the MSVP template, but a separate template is available here. At this stage the design and thus this matrix might not be complete, but it should be filled out to the maximum extent possible.
A preliminary discussion of the planned verification approach for each critical mechanism operation or feature, including operating or holding force or torque margin, qualification, acceptance, run-in, design life, and any other verification tests or analyses. The environment and the pass/fail criteria for each test should also be included. This data should also be summarized in a draft functional verification matrix. At this stage, special attention will be paid to verification plans for operating or holding force or torque margin verification. A separate functional verification matrix template is available here. Feel free to contact the MSWG if you have any questions.
An appendix that includes any documents referenced in the report, if these references are not supplied separately.
Any analysis pertaining to the mechanical operation that has been performed to date, if any. For example:
Tolerance Analysis (including thermal effects) per DFMR requirements. See our policy on tolerance analysis. Provide enough information that an independent review of the calculation can be conducted.
All force/torque margin calculations. Provide enough information that an independent review of the calculation can be conducted.
Any "Simple Mechanism" designations must have already been granted by the MSWG prior to this review!
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Phase II

Updated and additional hazard reports or RAESR for the system.
The fracture control status (including parts categorization).
A final version of the Mechanical Systems Verification Plan. At this stage, the MSVP should be complete and contain the following:
A description of the system and each mechanism within it, identifying the safety-critical mechanisms.
A fault-tolerance analysis for the safety-critical mechanisms explaining the independent success legs in place to meet fault-tolerance requirements. This is included in the MSVP template, but a separate template is available here.
A completed matrix detailing how each requirement in the MA2-00-057 Mechanical Systems Safety letter is or will be met for each mechanism relying upon a DFMR designation as a success leg. Note that there are not 11 requirements, there are 78—one for each shall statement in the letter. A statement addressing each of the requirements is to be included and documented accordingly. This is included in the MSVP template, but a separate template is available here.
A complete discussion of the verification approach for each critical mechanism operation or feature, including operating or holding force or torque margin, qualification, acceptance, run-in, design life, and any other verification tests or analyses. The environment and the pass/fail criteria for each test must also be included. This data should also be summarized in a functional verification matrix.
An appendix that includes any documents referenced in the report, if these references are not supplied separately.
Any analysis pertaining to the mechanical operation that has been performed to date. At this point, most of the analysis to be performed should be finished. Examples include:
A complete tolerance analysis (including thermal effects) for all features affecting safety-critical mechanisms per DFMR requirements. A comprehensive analysis must be supplied at this stage in order to receive final DFMR approval. See our policy on tolerance analysis. Provide enough information that an independent review of the calculation can be conducted.
All force/torque margin analyses. Provide enough information that an independent review of the calculation can be conducted.
A list of MIPs pertaining to safety-critical mechanisms, or access to all mechanism drawings.
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Phase III

Updated and additional hazard reports or RAESR for the as-built system.
A fracture control summary report.
An up-to-date copy of the MSVP.
A Mechanical Systems Verification Report. An MSVR Template is available here. The MSVR should contain the following:
A description of the as-built system and each mechanism within it, identifying the safety-critical mechanisms.
The results of all verification testing, analyses, and inspections.
A narrative explanation of how the testing, analysis and inspection performed and the results obtained satisfy the verification requirements.
A completed functional verification matrix detailing the testing that was performed on the system.
A record of all test failures, anomalies, and accidents involving qualification or potential flight hardware.
An appendix that includes any documents referenced in the report, if these references are not supplied separately.
Supplements to previously performed analysis of the system, including:
Any revisions to previously supplied tolerance analyses.
Any revisions to previously supplied force/torque margin analyses.
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Curator: Brandan Robertson
Responsible NASA Official: Deborah Graham
Last Update: 5/22/2017