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Are We Shaking Too Much? An Inquiry into Environmental Random Vibration Testing Margins

Problem Statement: The conventional, MIL-STD-810 approach to vibration environment derivation is perhaps too conservative, leading to unnecessary failures during acceptance & qualification vibration testing of Armstrong’s one-off flight equipment. Objective: This presentation explores some alternative understandings of the distributions of vibration severity in nonstationary environments. Proposed methods of sorting and adding appropriate margin are explored.

Scott L. Stebbins↗
NASA NTRS2022

Feedback-Directed Random Sequence Generation for Verifying Spacecraft Flight Rule Violations

The Psyche: Journey to a Metal World mission will be launched in 2022 to study the largest metal asteroid in the main asteroid belt, (16) Psyche. The spacecraft will perform a Mars Flyby in 2023 and enter (16) Psyche’s orbit in 2026. Throughout the mission, safely operating the spacecraft will require abiding by a set of flight rules that can be defined at any point in the mission lifecycle. These flight rules ensure that the spacecraft is operating within allowed regimes and a discrete event simulation tool, SEQGEN, will be used to model all command sequences prior to uplink. One of SEQGEN’s responsibilities is to determine if a command sequence violates any flight rules. For each flight rule, the necessary logic to determine if a violation has occurred is implemented in the SEQGEN adaptation, which is maintained by the mission. This adaptation must be tested thoroughly to ensure that the flight rule logic was interpreted and implemented correctly. This work describes a tool, RandSEQ, that autogenerates a suite of flight rule violating test sequences for each flight rule implemented in SEQGEN, and can be used by any mission using SEQGEN. The Psyche SEQGEN adaptation is still being developed, but so far, RandSEQ has been used to generate 532 test cases, that can be reviewed by various stakeholders, for 40 flight rules. The ability to autogenerate these test cases has significantly reduced the amount of time required to implement and test each flight rule.

Su, Laura↗