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At least 127 records · Page 7

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NASA NTRS1981

Verification of the Space Shuttle entry GN&C system

The certification procedures for the initial Shuttle flight are discussed. Particular attention is paid to the entry guidance, navigation, and control (GNC) verification, comprising tests, analysis, demonstration, inspection, and simulation. Flow diagrams for the verification and operational flight sequences are provided, along with a block diagram of the GNC circuitry interfaces. The development of the test matrix software for the GNC is outlined, noting the constant interplay between software verification and spacecraft reconfiguration to meet simulated performance requirements. Comparison of GNC performance predictions with actual entry flight data showed a good match in all performance areas except for sideslip excursions, bank overshoots, an area of transonic buffet, and an increased lift/drag ratio in the preflare to landing flight phase.

Van Hoften, J. D. A.↗

NASA NTRS1982

An integrated user-oriented laboratory for verification of digital flight control systems: Features and capabilities

A Digital Flight Control Systems Verification Laboratory (DFCSVL) has been established at NASA Ames Research Center. This report describes the major elements of the laboratory, the research activities that can be supported in the area of verification and validation of digital flight control systems (DFCS), and the operating scenarios within which these activities can be carried out. The DFCSVL consists of a palletized dual-dual flight-control system linked to a dedicated PDP-11/60 processor. Major software support programs are hosted in a remotely located UNIVAC 1100 accessible from the PDP-11/60 through a modem link. Important features of the DFCSVL include extensive hardware and software fault insertion capabilities, a real-time closed loop environment to exercise the DFCS, an integrated set of software verification tools, and a user-oriented interface to all the resources and capabilities.

Defeo, P.↗

NASA NTRS1982

A digital flight control system verification laboratory

A NASA/FAA program has been established for the verification and validation of digital flight control systems (DFCS), with the primary objective being the development and analysis of automated verification tools. In order to enhance the capabilities, effectiveness, and ease of using the test environment, software verification tools can be applied. Tool design includes a static analyzer, an assertion generator, a symbolic executor, a dynamic analysis instrument, and an automated documentation generator. Static and dynamic tools are integrated with error detection capabilities, resulting in a facility which analyzes a representative testbed of DFCS software. Future investigations will ensue particularly in the areas of increase in the number of software test tools, and a cost effectiveness assessment.

De Feo, P.↗

NASA NTRS1982

NASA payload interface verification requirements - Process and implementation

The separate and combinatorial roles played by NASA and STS payload contractors in the processes of interfacing cargo with the Shuttle are described. NASA personnel aid payload interface verification beginning at the hardware development level and perform independent interface verification once the payload is delivered to the payload processing facility. The cargo is first checked for operational and flight readiness, including inspection of installed devices to specification for the interface connections. Checklists furnished to the user are returned to NASA prior to integration simulation unless formal statements of compliance or waivers are exchanged. The continuance of strict adherence to predelivery interface verification testing is emphasized as necessary for meeting the turnaround times projected for the Orbiter fleet.

Huffstetler, W. J.↗

NASA NTRS1984

Assessment of Galileo modal test results for mathematical model verification

The modal test program for the Galileo Spacecraft was completed at the Jet Propulsion Laboratory in the summer of 1983. The multiple sine dwell method was used for the baseline test. The Galileo Spacecraft is a rather complex 2433 kg structure made of a central core on which seven major appendages representing 30 percent of the total mass are attached, resulting in a high modal density structure. The test revealed a strong nonlinearity in several major modes. This nonlinearity discovered in the course of the test necessitated running additional tests at the unusually high response levels of up to about 21 g. The high levels of response were required to obtain a model verification valid at the level of loads for which the spacecraft was designed. Because of the high modal density and the nonlinearity, correlation between the dynamic mathematical model and the test results becomes a difficult task. Significant changes in the pre-test analytical model are necessary to establish confidence in the upgraded analytical model used for the final load verification. This verification, using a test verified model, is required by NASA to fly the Galileo Spacecraft on the Shuttle/Centaur launch vehicle in 1986.

Trubert, M.↗

NASA NTRS1984

Definition of ground test for Large Space Structure (LSS) control verification

An overview for the definition of a ground test for the verification of Large Space Structure (LSS) control is given. The definition contains information on the description of the LSS ground verification experiment, the project management scheme, the design, development, fabrication and checkout of the subsystems, the systems engineering and integration, the hardware subsystems, the software, and a summary which includes future LSS ground test plans. Upon completion of these items, NASA/Marshall Space Flight Center will have an LSS ground test facility which will provide sufficient data on dynamics and control verification of LSS so that LSS flight system operations can be reasonably ensured.

Waites, H. B.↗

NASA NTRS1985

Software verification and testing

General procedures for software verification and validation are provided as a guide for managers, programmers, and analysts involved in software development. The verification and validation procedures described are based primarily on testing techniques. Testing refers to the execution of all or part of a software system for the purpose of detecting errors. Planning, execution, and analysis of tests are outlined in this document. Code reading and static analysis techniques for software verification are also described.

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NASA NTRS1984

Component testing for dynamic model verification

Dynamic model verification is the process whereby an analytical model of a dynamic system is compared with experimental data, adjusted if necessary to bring it into agreement with the data, and then qualified for future use in predicting system response in a different dynamic environment. These are various ways to conduct model verification. The approach taken here employs Bayesian statistical parameter estimation. Unlike curve fitting, whose objective is to minimize the difference between some analytical function and a given quantity of test data (or curve), Bayesian estimation attempts also to minimize the difference between the parameter values of that funciton (the model) and their initial estimates, in a least squares sense. The objectives of dynamic model verification, therefore, are to produce a model which: (1) is in agreement with test data; (2) will assist in the interpretation of test data; (3) can be used to help verify a design; (4) will reliably predict performance; and (5) in the case of space structures, will facilitate dynamic control.

Hasselman, T. K.↗

NASA NTRS1987

A computer program for model verification of dynamic systems

Dynamic model verification is the process whereby an analytical model of a dynamic system is compared with experimental data, and then qualified for future use in predicting system response in a different dynamic environment. There are various ways to conduct model verification. The approach adopted in MOVER II employs Bayesian statistical parameter estimation. Unlike curve fitting whose objective is to minimize the difference between some analytical function and a given quantity of test data (or curve), Bayesian estimation attempts also to minimize the difference between the parameter values of that function (the model) and their initial estimates, in a least squares sense. The objectives of dynamic model verification, therefore, are to produce a model which: (1) is in agreement with test data, (2) will assist in the interpretation of test data, (3) can be used to help verify a design, (4) will reliably predict performance, and (5) in the case of space structures, facilitate dynamic control.

Chrostowski, J. D.↗

NASA NTRS1987

Verification of large beam-type space structures

The verification approach of large beam type space structures is verified. The proposed verification approach consists of two parts. The first part is to remove the gravity effect on the tested substructure and to identify the on-orbit dynamic characteristics of the substructure by using the measurements of the ground test. A scaling law is also established to define the critical length of the structure which can be tested in 1-g field without incurring a buckling problem. The second part is to develop an adequate scaling law to extrapolate the dynamic characteristics of the prototype structure by using results from the substructure. The verification approaches are demonstrated on two typical structural configurations, the feed support structure of a wrap-rip antenna and a candidate shuttle flight experiment. The results indicate that it is practical to verify the on-orbit dynamic characteristics of these structures by using the proposed approach.

Shih, Choon-Foo↗

NASA NTRS1987

Space station data management system - A common GSE test interface for systems testing and verification

This paper examines the fundamental problems and goals associated with test, verification, and flight-certification of man-rated distributed data systems. First, a summary of the characteristics of modern computer systems that affect the testing process is provided. Then, verification requirements are expressed in terms of an overall test philosophy for distributed computer systems. This test philosophy stems from previous experience that was gained with centralized systems (Apollo and the Space Shuttle), and deals directly with the new problems that verification of distributed systems may present. Finally, a description of potential hardware and software tools to help solve these problems is provided.

Martinez, Pedro A.↗

NASA NTRS1987

Digital-flight-control-system software written in automated-engineering-design language: A user's guide of verification and validation tools

The user guide of verification and validation (V&V) tools for the Automated Engineering Design (AED) language is specifically written to update the information found in several documents pertaining to the automated verification of flight software tools. The intent is to provide, in one document, all the information necessary to adequately prepare a run to use the AED V&V tools. No attempt is made to discuss the FORTRAN V&V tools since they were not updated and are not currently active. Additionally, the current descriptions of the AED V&V tools are contained and provides information to augment the NASA TM 84276. The AED V&V tools are accessed from the digital flight control systems verification laboratory (DFCSVL) via a PDP-11/60 digital computer. The AED V&V tool interface handlers on the PDP-11/60 generate a Univac run stream which is transmitted to the Univac via a Remote Job Entry (RJE) link. Job execution takes place on the Univac 1100 and the job output is transmitted back to the DFCSVL and stored as a PDP-11/60 printfile.

Saito, Jim↗

NASA NTRS1988

Verification and validation of rulebased systems for Hubble Space Telescope ground support

As rulebase systems become more widely used in operational environments, the focus is on the problems and concerns of maintaining expert systems. In the conventional software model, the verification and validation of a system have two separate and distinct meanings. To validate a system means to demonstrate that the system does what is advertised. The verification process refers to investigating the actual code to identify inconsistencies and redundancies within the logic path. In current literature regarding maintaining rulebased systems, little distinction is made between these two terms. In fact, often the two terms are used interchangeably. Verification and validation of rulebased systems are discussed as separate but equally important aspects of the maintenance phase. Also described are some of the tools and methods that were developed at the Space Telescope Science Institute to aid in the maintenance of the rulebased system.

Vick, Shon↗

NASA NTRS1987

Correction, improvement and model verification of CARE 3, version 3

An independent verification of the CARE 3 mathematical model and computer code was conducted and reported in NASA Contractor Report 166096, Review and Verification of CARE 3 Mathematical Model and Code: Interim Report. The study uncovered some implementation errors that were corrected and are reported in this document. The corrected CARE 3 program is called version 4. Thus the document, correction. improvement, and model verification of CARE 3, version 3 was written in April 1984. It is being published now as it has been determined to contain a more accurate representation of CARE 3 than the preceding document of April 1983. This edition supercedes NASA-CR-166122 entitled, 'Correction and Improvement of CARE 3,' version 3, April 1983.

Rose, D. M.↗

NASA NTRS1989

SSME Alternate Turbopump Development Program: Design verification specification for high-pressure fuel turbopump

The design and verification requirements are defined which are appropriate to hardware at the detail, subassembly, component, and engine levels and to correlate these requirements to the development demonstrations which provides verification that design objectives are achieved. The high pressure fuel turbopump requirements verification matrix provides correlation between design requirements and the tests required to verify that the requirement have been met.

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NASA NTRS1990

Software verification plan for GCS

This verification plan is written as part of an experiment designed to study the fundamental characteristics of the software failure process. The experiment will be conducted using several implementations of software that were produced according to industry-standard guidelines, namely the Radio Technical Commission for Aeronautics RTCA/DO-178A guidelines, Software Consideration in Airborne Systems and Equipment Certification, for the development of flight software. This plan fulfills the DO-178A requirements for providing instructions on the testing of each implementation of software. The plan details the verification activities to be performed at each phase in the development process, contains a step by step description of the testing procedures, and discusses all of the tools used throughout the verification process.

Dent, Leslie A.↗

NASA NTRS1990

METCAN verification status

The status of the verification (comparisons of predictions with experimental data) of the METCAN (METal-matrix Composite ANalyzer) code at high temperature is summarized. Verification includes select available room temperature of W/Cu composites for different fiber volume ratios. It also includes high temperature properties for thermal expansion, moduli, strength and stress/strain behavior for SiC/Ti composites. Furthermore it includes limited cases for thermal fatigue strength degradation. The verification results summarized herein indicate that METCAN simulates complex high temperature metal matrix composite bahavior with reasonable accuracy and that it can be used with confidence to identify in-situ nonlinear behavior that influences composite properties.

Chamis, Christos C.↗

NASA NTRS1990

Verifying an interactive consistency circuit: A case study in the reuse of a verification technology

The work done at ORA for NASA-LRC in the design and formal verification of a hardware implementation of a scheme for attaining interactive consistency (byzantine agreement) among four microprocessors is presented in view graph form. The microprocessors used in the design are an updated version of a formally verified 32-bit, instruction-pipelined, RISC processor, MiniCayuga. The 4-processor system, which is designed under the assumption that the clocks of all the processors are synchronized, provides software control over the interactive consistency operation. Interactive consistency computation is supported as an explicit instruction on each of the microprocessors. An identical user program executing on each of the processors decides when and on what data interactive consistency must be performed. This exercise also served as a case study to investigate the effectiveness of reusing the technology which was developed during the MiniCayuga effort for verifying synchronous hardware designs. MiniCayuga was verified using the verification system Clio which was also developed at ORA. To assist in reusing this technology, a computer-aided specification and verification tool was developed. This tool specializes Clio to synchronous hardware designs and significantly reduces the tedium involved in verifying such designs. The tool is presented and how it was used to specify and verify the interactive consistency circuit is described.

Bickford, Mark↗