scope:

Purpose

This NASA Technical Standard provides an Agency-wide basis from which test programs and procedures are developed for NASA vehicles, subsystems and their components, and payloads. This Standard defines a set of space flight hardware leak test requirements that provide the necessary verification of pressure integrity for NASA vehicles, subsystems and their components, and payloads (both pressurized and sealed). Compliance of qualification and acceptance test programs and procedures with this Standard will provide consistency across the Agency and its contractors, facilitating the sharing of hardware between Centers and programs.

This Standard has been developed for vehicles, subsystems and their components, and payloads that will operate in space environment (Earth's orbit and beyond) but may be tailored to include other operating environments. The leak test methods included are generally regarded as the most critical and the ones having the highest cost and schedule impact. This Standard specifies test levels, factors, margins, durations, and other parameters. In some cases, these specifics are expressed statistically or are referenced in other NASA standards.

Applicability

This Standard is approved for use by all NASA space flight programs, including vehicles, subsystems and their components, and payloads developed in-house or under contract. This Standard defines baseline leak test methodologies that are applicable to all NASA vehicles, subsystems and their components, and payloads regardless of mission risk classification as defined in particular for the payloads in NASA Procedural Requirements (NPR) 8705.4, Risk Classification for NASA Payloads. However, these test methodologies may be tailored (see section 1.3 of this Standard) based on risk classification following the Center's defined risk philosophy and with approval from the delegated NASA Technical Authority. The levels of assembly for which this Standard applies are vehicles, subsystems and their components, and payloads. Small instruments may be treated as components.

This Standard is developed for the typical NASA space flight hardware or payload wherein one qualification unit or article is built and serves to qualify the design, while other units undergo acceptance testing for workmanship screening purposes and are subsequently used for flight. If a protoflight approach is used, the qualification unit or article is also used for flight. Consistent and effective leak testing is a critical aspect of functional verification for all of these types of hardware and payload items.

The major objective of leak testing is to verify proper assembly and workmanship during qualification and acceptance testing and to reveal possible design deficiencies relative to pressure integrity during hardware qualification. The principal goal of the leak test method is to reliably verify the maximum allowable leakage rate (MALR) requirement (see section 3.2 in this Standard for Leakage Rate Verification definition). Tailoring the leak test method, with supplemental analysis, is appropriate in some cases (see section 1.3 in this Standard).

This Standard is approved for use by NASA Headquarters and NASA Centers and Facilities, and applicable technical requirements may be cited in contract, program, and other Agency documents. This language applies to the Jet Propulsion Laboratory (a Federally Funded Research and Development Center), other contractors, recipients of grants, cooperative agreements, or other agreements only to the extent specified or referenced in the applicable contracts, grants, or agreements.

References to "this Standard" refer to NASA-STD-7012A; references to other documents state the specific document information.

Verifiable requirement statements are designated by the acronym "LTR" (Leak Test Requirement), numbered, and indicated by the word "shall." This Standard contains 39 requirements. To facilitate requirements selection by NASA programs and projects, a Requirements Identification Matrix is provided in Appendix A.

Explanatory or guidance text is indicated in italics beginning in section 4. The terms "may" or "can" denote discretionary privilege or permission, "should" denotes a good practice and is recommended but not required, "will" denotes expected outcome, and "is/are" denotes descriptive material or a statement of fact.

Tailoring

Tailoring of the requirements in this Standard for application to a specific program or project is acceptable when formally approved by the delegated NASA Technical Authority in accordance with NPR 7120.10, Technical Standards for NASA Programs and Projects, and NPR 7120.5, NASA Space Flight Program and Project Management Requirements, and documented in program or project requirements.