3.2Definitions

Additive Manufacturing: Any process for making a three-dimensional object from a 3-D model or other electronic data source primarily through processes in which successive layers of material are deposited under computer control.

Catastrophic Hazard: Presence of a risk situation that could directly result in a catastrophic event, which is defined as loss of life, disabling injury, or loss of a major national asset.

Corrosive Environment: Solid, liquid, or gaseous environment that deteriorates the materials by reaction with the environment. Clean rooms and vacuum are normally considered noncorrosive.

NOTE: Per section 4.1.6: The use of M&P that do not comply with the requirements of this NASA Technical Standard may be acceptable in the actual hardware applications. MUAs are required for all M&P that are technically acceptable but do not meet the requirements of this NASA Technical Standard, as implemented by the approved Materials and Processes Selection, Control, and Implementation Plan.

NASA-STD-6016B

NOTE: Per section 4.1.6: The use of M&P that do not comply with the requirements of this NASA Technical Standard may be acceptable in the actual hardware applications. MUAs are required for all M&P that are technically acceptable but do not meet the requirements of this NASA Technical Standard, as implemented by the approved Materials and Processes Selection, Control, and Implementation Plan.

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Critical Hazard: Hazard that can result in the potential for severe injury, severe occupational illness, or major property/equipment damage.

Design Value: The design value is a statistically determined minimum value of a property, most commonly strength properties of materials, design features/elements, or components/parts used in the design of a structure. For A-basis strength properties, at least 99% of the population of strength values is expected to equal or exceed this lower bound with 95% confidence. For B-basis, 90% of the population of strength values is expected to equal or exceed this lower bound with 95% confidence. For metallic materials S-basis design values, the statistics defined by MMPDS are the same as for A-basis, but the test requirements are less comprehensive. Numbers of lots and test specimens required to develop design values are defined in applicable standards. The terms “material allowables,” “design allowables,” and “design values” are commonly used to address the design values used in structural analysis.

Fretting Corrosion: Occurs when two contacting surfaces under mechanical load are subjected to repeated relative surface motion. Mechanical wear and material transfer at the surfaces can lead to corrosion, metallic debris, and increased contact resistance due to the electrical insulating properties of corrosion products that may build up at the contact interfaces.

Mission Critical Hardware: Hardware, the failure of which may result in the inability to retain operational capability for mission continuation if a corrective action is not successfully performed.

Nondestructive Evaluation (NDE)/Nondestructive Testing (NDT): Inspection techniques which do not cause physical, mechanical, or chemical changes to the part being inspected or otherwise impair its adequacy for operational service. These inspection techniques are applied to materials and structures to verify required integrity and to detect flaws.

Refractory Alloys: Alloys with a melting point above 2000 °C (3632 °F), plus osmium and iridium.

Safety-Critical: Term describing any condition, event, operation, process, equipment, or system that could cause or lead to severe injury, major damage, or mission failure if performed or built improperly, or allowed to remain uncorrected.

Structural: Pertaining to structure.

Structural Adhesive Bond: Structural joint using adhesive bonds for the purpose of transferring structural load between structures.

NOTE: Per section 4.1.6: The use of M&P that do not comply with the requirements of this NASA Technical Standard may be acceptable in the actual hardware applications. MUAs are required for all M&P that are technically acceptable but do not meet the requirements of this NASA Technical Standard, as implemented by the approved Materials and Processes Selection, Control, and Implementation Plan.

NASA-STD-6016B

Structure: All components and assemblies designed to sustain loads or pressures, provide stiffness and stability, or provide support or containment.

Structure, Primary: That part of a flight vehicle or element that sustains the significant applied loads and provides main load paths for distributing reactions to applied loads. Also, the main structure that is required to sustain the significant applied loads, including pressure and thermal loads, and that, if it fails, creates a catastrophic hazard. If a component is small enough and in an environment where no serious threat is imposed if it breaks, then it is not primary structure.

Subcontractor: A hardware contractor that reports to a higher level contractor.

Technical Authority: Provides technical checks and balances by assuring that safety and mission success, relevant technical standards, engineering work, and safety and reliability analysis products are being conducted properly in accordance with established, high-reliability processes independent of nontechnical program/project constraints.

Tin Pest: The allotropic transformation of tin that may occur at or below 13.2 °C, where tin transforms from β-phase into its α-phase, a grey, brittle semiconductor that occupies about 27 percent greater volume than the β-phase.

Useful Life: Total life span, including storage life, installed life in a nonoperating mode, and operational service life.

Wet Installed: Fasteners covered with primer or sealant during installation to prevent moisture from penetrating the fastener joint and causing corrosion.

Whisker (Metal): A spontaneous growth that may form on surfaces of metals, primarily tin, zinc, and cadmium. Metal whiskers may also detach from the surfaces on which they form, producing conductive FOD.