An Assessment of Space Shuttle Flight Software Development Processes (1993) / Chapter Skim
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Appendix C: Interim Report of the Committee for Review of Oversight Mechanisms for Space Shuttle Flight Software Process: Independent Verification and Validation for Space Shuttle Flight Software
Appendix C: Interim Report of the Committee for Review of Oversight Mechanisms for Space Shuttle Flight Software Process: Independent Verification and Validation for Space Shuttle Flight Software
Pages 107-130
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From page 107... ...
APPENDIX C Interim Report of the Committee for Review of Oversight Mechanisms for Space ShuHIe Flight Software Processes 107
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From page 109... ...
The source of much of this reaction was, In the Commi~e's view, a misinterpretation by IBM and others of He scope and intent of the statements involved. For example, IBM, Rockwell, and Be MarshaD Space Flight Center each expressed concern about the following statement from the Executive Summary of the Interim Report: Me Committee believes that the Space Shuttle software-development process is not adequate without IV&V arm that elimination of IV&V as currently practiced wig adversely Affect the overall!
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From page 110... ...
3. There was concern expressed by representatives of the development contractors regarding the following statement that appears in the Intenm Report: For example, the current flight-sofzware IV&V contractor has been particularly active in addressing issues that relate to the interface between the primary avionics software (d~eveloped by IBM)
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Independent Verification and Validation for Space Shuttle Flight Software Committee for Review of Oversight Mechanisms for Space Shuttle Flight Software Processes Aeronautics and Space Engineering Board Commission on Engineering and Technical Systems Nabonal Research Council July 1992
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This study was supported by Contract NASW4003 between the National Academy of Sciences and the National Aeronautics and Space Administration. Available in limited supply from The Aeronautics and Space Engineering Board 2101 Constitution Avenue, N.W.
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Clayton, Director, Aeronautics and Space Engineering Board Christina A Weiniand, Senior Project Assistant /
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Nay, Redred Vice President of Engineering, Piper Aircraft Corporation, Vero Beach, Florida Frank E Pickering, Vice President and Chief Engineer, Aircraft Engines, General Electric Company, Lynn, Massachusetts Anatol Roshko, Theodore van Karman Professor of Aeronautics, California Institute of Technology, Pasadena Maunc~e E
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APPEMOIX C: INTERIM REPORT Aeronautics and Space Engineering Board Staff JoAnn C Clayton, Director Marlin I
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One of the issues the Space Shuttle program of lice requested that the Committee specifically consider was the office's pending decision to eliminate the IV&V function currently performed ~ It should be noted that the Committee was specifically asked not to evaluate the performance of the current IV&V contractor, Intermetrics, or its subcontractor at the Marshall Space Flight Center, Smith Advanced Technologies, but rawer to concentrate on the need to continue the function they serve.
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From page 118... ...
In short, the Shuttle program of lice believes that the process is adequate without IV&V and ache money may be better spent in other ways. Because He IV&V function is currently scheduled to be elim~na~ by October 1992, the Office of Space Flight request Hat the Committee first address whether Here is a need to continue this function and later address ocher aspects of the flight software development process.
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From page 119... ...
In February 1990, the House Committee requested that He GAO determine NASA's progress In improving independent oversight of Shuttle software development. The GAO 3 Report of the Presidential Commission on the Space Shuttle Challenger Accident, by William P
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. ~ The software steering group consisted of officials from the Johnson Space Center, the Kennedy Space Center, the Marshall Space Flight Center, NASA Headquarters, the software development contractors, and the Space Transportation System Operations Contractor.
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From page 121... ...
It should be noted Hat He Committee was specifically asked not to evaluate the performance of the current IV&V contractor, Intermetrics, or its subcontractor at He Marshall Space Flight Center, Smith Advanced Technologies, but rawer to concentrate on the need to continue the function the contractors serve. This proved to be a difficult restriction because the argument for con cinued IV&V hinges pardy on He capabilities these two companies bring to He process.
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From page 122... ...
. Provides a broad pe~pectilve: As mentioned above, He embedded process relies heavily on the development contractors IBM, Rockwell, and Rocket~yne3 to perform their internal verification 9 National Aeronautics and Space Administration, Space Shuttle Flight Software Venfication and Validation Requirements, NSTS~8271 (Houston, Texas: Johnson Space Center, 19911.
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From page 123... ...
Independent oversight is a partial solution, but only if the group that performs the oversight also provides a significant level of experience and technical capability. Avoids bras and peer pressure: The emphasis on consensus that is evident in the embedded process is ad~rurable, but the Committee believes it brings wig it the possibility that individual assessments of important issues can be stifled through peer pressure, Trough He desire to |3 In discussions with Me Co~i~ee, IBM ~ estimated that it Ekes at least two yew for new employees to adequately understand the Shuttle flight software.
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From page 124... ...
Although the IV&V contractors are, by definition, independent, they interact with the software developers and other members of the flight software community throughout the process through their evaluation of Change Requests and Discrepancy Reports, through routine discussions wad the developers, and ultimately through participation in the Shuttle Avionics Software Control Board, which is He final arbiter of software changes. \4 Shuttle flight software erron are categorized by the seventy of their potential consequences without regard to the likelihood of their occurrence.
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From page 125... ...
is a factor In He pending decision to eliminate IV&V. On an era when NASA is experiencing little real growth in its overall budget, and given the internal pressure to reduce costs associated with the Shuttle program, it is understandable that He Shuttle program office would seek to unburden itself of the current $3.2 million annual cost for IV&V.
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From page 126... ...
These two factors make it increasingly difficult to change the software without introducing errors. Each new release of Be Shuttle flight software includes significant additions to increase functionality or to fix errors that have been identified.
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From page 128... ...
Proposals presented to Me Committee, such as the implementation of the new HAL/S compiler and the Enhanced Software Product Assurance program proposed by the Safety, Reliability, and Quality Assurance office at the Johnson Space Center, were judged to be less important. Thus, it is the opinion of the Committee that the current implementation of IV&V provides important, low-cost insurance to the Shuttle program that materially reduces the risk of a software failure and, thus, of a software-related accident.
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From page 129... ...
Furthermore, the Committee concludes that the Space Shuttle software development process is not adequate without current IV&V practices and |9 Metrics has acquired or develop numerous tools specifically for Shuttle software. These include tools tailored for the IV&V task that check cross-references and data dependencies, compare source code listings, and identify absolute addresses.
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From page 130... ...
Furler recommendations regarding He development process for Shuttle flight software, including an evaluation of He embedded V&V process and a comparison with other, similar processes, win be contained In the Committee's final report.
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