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NASA’s Role in Certifying COTS Parts for Space


by Knowles Precision Devices

After decades of viewing MIL-SPECs as the gold standard for qualifying and screening parts for viability in space, NASA has recently changed course and is adopting commercial-off-the-shelf (COTS) parts as an option for various space applications. Burgeoning changes in industry trends, a drive to remain competitive, and the desire to guide budget-constrained missions pushed the organization to commission a NASA Engineering and Safety Center (NESC) study to evaluate the reliability of COTS parts. Upon completion of the study, NASA aims to create a consistent set of requirements at the agency level to minimize the risk and impact of part selection/usage on the performance of NASA spaceflight technology.

NASA Determines Characteristics of a COTS Part

To begin, it is crucial to understand NASA’s definition of what constitutes a COTS component. As defined by NASA Chief Safety and Mission Assurance Engineer Jesse Leitner, COTS parts are “parts where the manufacturer establishes and controls the specifications for performance, configuration and reliability.” This means that the manufacturer is the sole party involved in selecting the design, material, processes, and testing used to assess the viability of a part. After completing manufacturer-designed testing and meeting safety criteria, COTS parts are then usually sold through commercial distributors.

It is crucial to keep in mind that the term “COTS” alone does not mean that the part is unqualified, unscreened, or untested; instead, the only actual difference between a COTS part and a part verified by MIL-SPECs is that a COTS part has been qualified by an entity other than the government or typical third party. Therefore, the critical insight revealed in the NESC study is that COTS parts can be equally reliable when it comes to usage in space applications, even though in the past, organizations may have assumed otherwise.

Potential Problems with Traditional Screening Methods

When NASA viewed MIL-SPECs as the only trustworthy method of assuring complete reliability in mission-critical and space application parts, NASA then had to meet quality specifications that catered to the most extreme range of conditions. Although MIL-SPECs were deemed reliable due to reliance on U.S. government-produced drawings and requirements, the NESC study suggests that this methodology may arbitrarily link certain parts with reliability. Since MIL-SPEC testing is conducted using generic specifications that might not pertain to actual part usage (or might only cater to extreme uses), parts tested through MIL-SPEC screening practices might be over-tested and become less reliable.

NASA COTS Parts Qualification Criteria

By design, NASA-screened COTS parts undergo a different testing version than MIL-SPEC-screened parts. This testing aims to establish consistent criteria for the selection, screening, qualification, and derating of the electrical, electronic, and electromechanical parts.

Although not required, many times MIL-SPEC tests are also performed to test for reliability. However, it is essential to be aware of the danger of over-testing due to implementing this method since this specific type of testing is not curated based on specifications in the part’s datasheet. According to the NESC study, this option can potentially yield the most significant uncertainty for reliability, especially if the COTS part being tested is a low-volume part.