Purpose

The purpose of this standard is to establish NASA structural strength design and test factors, as well as service life factors to be used for spaceflight hardware development and verification. It is intended to reduce space project costs and schedules by enhancing the commonalty of use of hardware designs among NASA flight projects, Centers, and their contractors. While it is true that structural designs are sometimes governed by criteria other than strength, the criteria in this document are to be considered as minimum acceptable values unless adequate engineering risk assessment is provided which justifies the use of lower values.

Applicability

This standard recommends engineering practices for NASA programs and projects. It may be cited in contract, program, and other Agency documents as a technical requirement. Requirements are numbered and indicated by the word "shall." Explanatory text or guidance is indicated in italics beginning in section 4.

Tailoring of this standard for application to a specific program or project shall be formally documented as part of program/project requirements and approved by the assigned Technical Authority.

Determining the suitability of this standard and its provisions is the responsibility of program/project management and the performing organization. Project-specific tailoring may generate other project-specific requirements that are derivatives of this standard.

NASA programs and projects that do not meet the provisions of this document shall be assessed by the NASA Program Manager for the associated risk to the success of the planned NASA mission and approved by the assigned Technical Authority.

This document shall not supersede applicable laws and regulations unless a specific exemption has been obtained by the Office of the NASA Chief Engineer.

The criteria in this standard are applicable to payloads and launch vehicle structures (including propellant tanks and solid rocket motor (SRM) cases). These criteria apply to flight hardware that is utilized for NASA missions. The standard presents acceptable minimum factors of safety for use in analytical assessment and test verification of structural adequacy of the flight hardware. Designs must generally be verified by both structural strength analyses and tests.

The factors shall be multiplied by the limit stresses (including additive thermal stresses), and the products shall be verified not to exceed material allowable stresses (yield and ultimate) under the expected temperatures and other operating conditions.

Criteria are specified for design and test of flight articles when the actual flight hardware is tested (protoflight), and when qualification tests are conducted on a separate (prototype) article. In general, no distinction is made between "manned" and "unmanned" missions. Structures of manned flight systems may be subjected to additional verification and/or safety requirements (e.g., fracture control) that are consistent with the established risk levels for mission success and flight crew safety.

The requirements specifically excluded from this standard are design loads determination, fracture control, engines, rotating hardware, solid propellant, insulation, ground support equipment, and facilities. Also excluded are specific configuration factors, such as fitting factors, buckling knockdown factors, and load uncertainty factors.