1、Lessons Learned Entry: 1125Lesson Info:a71 Lesson Number: 1125a71 Lesson Date: 1999-02-01a71 Submitting Organization: HQa71 Submitted by: David M. LengyelSubject: Computer Hardware-Software/Space Shuttle/I-Loads Description of Driving Event: Lack of Dependency Matrix for I-Load RecalculationLesson(s
2、) Learned: There is no formal requirement that dependent Space Shuttle I-loads be recalculated or checked when an I-load patch is to be uplinked.Recommendation(s): NASA should create a dependency matrix of all I-loads. Furthermore, it should assess its Space Shuttle and ISS procedures and ensure tha
3、t they are all fully documented.Evidence of Recurrence Control Effectiveness: NASA believes that we already meet the intent of the recommendation. Flight Operations processes and documentation ensures proper I-load change implementation for all flight design I-loads, including uplinkable I-loads. Th
4、ese procedures include positive verification that the selected or uplinked values do not violate sub-system, element, or integrated vehicle certification and that the update meets mission requirements. I-load dependencies are verified as part of the certification assessment. Procedures for verifying
5、 I-loads to be uplinked vary. In some instances uplinked I-loads change vehicle response in a way that impacts several of the remaining I-loads; i.e., Day-of-Launch I-load Update (DOLILU). Those verification assessments include an analysis, which uses a high fidelity computer model to simulate integ
6、rated vehicle response to the new I-loads. These simulations include models of the onboard flight software of sufficient detail to verify that all applicable I-load interactions are assessed. In other cases, specific I-load dependencies are evaluated. Provided by IHSNot for ResaleNo reproduction or
7、networking permitted without license from IHS-,-,-A number of flight design uplinks involve an uplink of values that are generated and verified days or sometimes months before launch. These I-loads include vehicle navigation, targeting, and abort parameters. Verification procedures for these I-loads
8、 are identical to that used during the normal flight design template.For all cases, procedures clearly specifying verification requirements including specific I-load dependency evaluations, as applicable, are in place and under configuration control.Documents Related to Lesson: N/AMission Directorat
9、e(s): a71 Exploration Systemsa71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Aerospace Safety Advisory Panela71 Computersa71 Launch Processa71 Risk Management/Assessmenta71 Softwarea71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2002-02-12a71 Approval Name: Bill Loewya71 Approval Organization: HQa71 Approval Phone Number: 202-358-0528Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
