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Results for “requirements verification”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Preliminary criteria for the fracture control of space shuttle structures

The complex and multidisciplinary factors are presented which relate to the prevention of structural failure due to the initiation or propagation of cracks or crack-like defects. The fracture control criteria are applicable to space shuttle components which are: (1) susceptible to cracking or fracture on the basis of anticipated loads and environment, and (2) critical to either crew safety or system performance. The criteria define the design, fabrication, environmental control, inspection, maintenance, repair, and verification procedures required for adequate fracture control.

Source record↗
NASA NTRS1973

The theory of charged particle temperatures in the upper atmosphere.

The thermal structure of the earth's upper atmosphere is examined in detail, with emphasis on the physical processes that govern the behavior of charged-particle temperatures. The characteristic features of and competition between the heating, cooling, and thermal conduction processes that govern electron and ion temperatures in the mid-latitude and auroral ionospheric regions are theoretically analyzed, and appropriate comparisons are made with experimental data. The proposed elaborate theory is considered qualitatively successful in accounting for the thermal structure of the ionosphere, and points requiring quantitative verification are delineated.

Schunk, R. W.↗
NASA NTRS1974

In flight ground control of high drag satellites utilizing on-board accelerometer data and rapid orbit prediction techniques

High drag satellites frequently require precise verification of orbital maneuvers and the accurate prediction of perigee height. An in-flight ground support system designed to monitor and compute orbital state and maneuvers is described. The use of on-board three-axis accelerometer data in a flight support software system to perform on-line maneuver analysis and atmospheric model updating is discussed. In addition, automated analytic techniques to rapidly and accurately predict perigee height following a maneuver are described, as well as semianalytic averaging techniques designed to predict a decaying orbital state for mission control.

Fuchs, A. J.↗
NASA NTRS1975

Strainrange Partitioning - A tool for characterizing high-temperature low-cycle fatigue

The basic concepts of Strainrange Partitioning are reviewed, with particular reference to the areas requiring expanded verification. A cooperative program is proposed for achieving this broader verification through the additional experience provided by the participants in this program. The suggested program includes verification of the four basic life relationships (for PP, CC, PC, and CP type inelastic strainranges) for a variety of materials chosen by the participating organizations. The four relationships are then used in conjunction with the Interaction Damage Rule to predict the cyclic lives of tests involving various combinations of the basic strainrange components. The testing program also includes evaluation of the degree of insensitivity of these relationships to temperature as well as their utility in representing bounds on life.

Hirschberg, M. H.↗
NASA NTRS1978

Satellite power systems (SPS) concept definition study. Volume 7: SPS program plan and economic analysis, appendixes

Three appendixes in support of Volume 7 are contained in this document. The three appendixes are: (1) Satellite Power System Work Breakdown Structure Dictionary; (2) SPS cost Estimating Relationships; and (3) Financial and Operational Concept. Other volumes of the final report that provide additional detail are: Executive Summary; SPS Systems Requirements; SPS Concept Evolution; SPS Point Design Definition; Transportation and Operations Analysis; and SPS Technology Requirements and Verification.

Hanley, G.↗
NASA NTRS1979

Hg ion thruster component testing

Electron bombardment thrusters, under development to provide both auxiliary and primary propulsion functions for a large variety of space missions are tested. Thruster design verification which requires life tests of durations of the order of the time anticipated in space applications, are discussed. The life time and reliability of an electron bombardment thruster is dependent upon the performance of several critical components including cathodes, vaporizers, and isolators. The performances of the cathode, vaporizer, and propellant isolaters during fatigue analyses are examined.

Mantenieks, M. A.↗
NASA NTRS1980

An effective combined environment test facility

A critical missile component required operational verification while subjected to combined environments within and beyond flight parameters. The testing schedule necessitated the design and fabrication of a test facility in order to provide the specified temperatures combined with humidity, altitude and vibration.

Deitch, A.↗
NASA NTRS1982

Results of the mission profile life test

Seven J series 30-cm diameter thrusters have been tested in segments of up to 5,070 hr, for 14,541 hr in the Mission Profile Life Test facility. Test results have indicated the basic thruster design to be consistent with the lifetime goal of 15,000 hr at 2-A beam. The only areas of concern identified which appear to require additional verification testing involve contamination of mercury propellant isolators, which may be due to facility constituents, and the ability of specially covered surfaces to contain sputtered material and prevent flake formation. The ability of the SCR, series resonant inverter power processor to operate the J series thruster and autonomous computer control of the thruster/processor system were demonstrated.

Bechtel, R. T.↗
NASA NTRS1988

Constrained structural dynamic model verification using free vehicle suspension testing methods

Verification of the validity of a spacecraft's structural dynamic math model used in computing ascent (or in the case of the STS, ascent and landing) loads is mandatory. This verification process requires that tests be carried out on both the payload and the math model such that the ensuing correlation may validate the flight loads calculations. To properly achieve this goal, the tests should be performed with the payload in the launch constraint (i.e., held fixed at only the payload-booster interface DOFs). The practical achievement of this set of boundary conditions is quite difficult, especially with larger payloads, such as the 12-ton Hubble Space Telescope. The development of equations in the paper will show that by exciting the payload at its booster interface while it is suspended in the 'free-free' state, a set of transfer functions can be produced that will have minima that are directly related to the fundamental modes of the payload when it is constrained in its launch configuration.

Blair, Mark A.↗
NASA NTRS1989

Experience with advanced instrumentation in a hot section cascade

The Lewis Research Center gas turbine Hot Section Test Facility was developed to provide a real engine environment with known boundary conditions for the aerothermal performance evaluation and verification of computer design codes. This verification process requires experimental measurements in a hostile environment. The research instruments used in this facility are presented, and their characteristics and how they perform in this environment are discussed. The research instrumentation consisted of conventional pressure and temperature sensors, as well as thin-film thermocouples and heat flux gages. The hot gas temperature was measured by an aspirated temperature probe and by a dual-element, fast-response temperature probe. The data acquisition mode was both steady state and time dependent. These experiments were conducted over a wide range of gas Reynolds numbers, exit gas Mach numbers, and heat flux levels. This facility was capable of testing at temperatures up to 1600 K, and at pressures up to 18 atm. These corresponded to an airfoil exit Reynolds number range of 0.5 x 10(6) to 2.5 x 10(6) based on the airfoil chord of 5.55 cm. The results characterize the performance capability and the durability of the instrumentation. The challenge of making measurements in hostile environments is also discussed. The instruments exhibited more than adequate durability to achieve the measurement profile. About 70 percent of the thin-film thermocouples and the dual-element temperature probe survived several hundred thermal cycles and more than 35 hr at gas temperatures up to 1600 K. Within the experimental uncertainty, the steady-state and transient heat flux measurements were comparable and consistent over the range of Reynolds numbers tested.

Yeh, Frederick C.↗
NASA NTRS1989

Frame synchronization methods based on channel symbol measurements

The current DSN frame synchronization procedure is based on monitoring the decoded bit stream for the appearance of a sync marker sequence that is transmitted once every data frame. The possibility of obtaining frame synchronization by processing the raw received channel symbols rather than the decoded bits is explored. Performance results are derived for three channel symbol sync methods, and these are compared with results for decoded bit sync methods reported elsewhere. It is shown that each class of methods has advantages or disadvantages under different assumptions on the frame length, the global acquisition strategy, and the desired measure of acquisition timeliness. It is shown that the sync statistics based on decoded bits are superior to the statistics based on channel symbols, if the desired operating region utilizes a probability of miss many orders of magnitude higher than the probability of false alarm. This operating point is applicable for very large frame lengths and minimal frame-to-frame verification strategy. On the other hand, the statistics based on channel symbols are superior if the desired operating point has a miss probability only a few orders of magnitude greater than the false alarm probability. This happens for small frames or when frame-to-frame verifications are required.

Dolinar, S.↗
NASA NTRS1991

Experiments for locating damaged truss members in a truss structure

Locating damaged truss members in large space structures will involve a combination of sensing and diagnostic techniques. Methods developed for damage location require experimental verification prior to on-orbit applications. To this end, a series of experiments for locating damaged members using a generic, ten bay truss structure were conducted. A 'damaged' member is a member which has been removed entirely. Previously developed identification methods are used in conjunction with the experimental data to locate damage. Preliminary results to date are included, and indicate that mode selection and sensor location are important issues for location performance. A number of experimental data sets representing various damage configurations were compiled using the ten bay truss. The experimental data and the corresponding finite element analysis models are available to researchers for verification of various methods of structure identification and damage location.

Mcgowan, Paul E.↗
NASA NTRS1992

Solidification in immiscible systems: The influence of processing conditions on resulting microstructures

Research carried out over the past two decades in which attempts have been made to produce desirable microstructures in immiscible alloys is reviewed. Factors affecting the formation of desirable microstructures in immiscible alloys are addressed and some of the techniques that have been successful in controlling these factors in order to produce useful structures are discussed. Some of the intended applications of these alloys require a dispersion of one phase in the other, while other applications favor the use of aligned, fibrous microstructures with continuity of both phases. The microstructures obtained in immiscible alloys are often strongly influenced by processing conditions. Perhaps the most well known effect is gravity induced sedimentation of the denser immiscible phase during solidification. This difficulty with sedimentation led to low gravity processing in attempts to produce dispersed microstructures. However, experimentation under low gravity conditions soon revealed that many other factors, including wetting of the crucible walls and surface tension driven flows, often resulted in complete separation and coalescence of the two immiscible phases. The production of aligned fibrous microstructures in hypermonotectic alloys appears to be even more difficult than the formation of a dispersion. Here, in addition to sedimentation and crucible wetting, convective and interfacial instabilities must be considered as well. Calculation of the limits of stability during directional solidification were carried out but require experimental verification.

Andrews, J. Barry↗
NASA NTRS2001

Modal Testing of Seven Shuttle Cargo Elements for Space Station

From December 1996 to May 2001, the Modal and Control Dynamics Team at NASA's Marshall Space Flight Center (MSFC) conducted modal tests on seven large elements of the International Space Station. Each of these elements has been or will be launched as a Space Shuttle payload for transport to the International Space Station (ISS). Like other Shuttle payloads, modal testing of these elements was required for verification of the finite element models used in coupled loads analyses for launch and landing. The seven modal tests included three modules - Node, Laboratory, and Airlock, and four truss segments - P6, P3/P4, S1/P1, and P5. Each element was installed and tested in the Shuttle Payload Modal Test Bed at MSFC. This unique facility can accommodate any Shuttle cargo element for modal test qualification. Flexure assemblies were utilized at each Shuttle-to-payload interface to simulate a constrained boundary in the load carrying degrees of freedom. For each element, multiple-input, multiple-output burst random modal testing was the primary approach with controlled input sine sweeps for linearity assessments. The accelerometer channel counts ranged from 252 channels to 1251 channels. An overview of these tests, as well as some lessons learned, will be provided in this paper.

Kappus, Kathy O.↗
NASA NTRS2010

Seal Analysis for the Ares-I Upper Stage Fuel Tank Manhole Covers

Naflex seals have long history of use in launch vehicle components, including Saturn stages and Space Shuttle External Tank. Ares-I Upper Stage tank pressures are higher than ET pressures, requiring performance verification of heritage seal design in new manhole cover configurations. Heritage external tank analyses are reviewed for potential application to Upper Stage.

Phillips, Dawn R.↗
NASA NTRS2010

Distributed Observer Network

The Distributed Observer network (DON) is a NASA-collaborative environment that leverages game technology to bring three-dimensional simulations to conventional desktop and laptop computers in order to allow teams of engineers working on design and operations, either individually or in groups, to view and collaborate on 3D representations of data generated by authoritative tools such as Delmia Envision, Pro/Engineer, or Maya. The DON takes models and telemetry from these sources and, using commercial game engine technology, displays the simulation results in a 3D visual environment. DON has been designed to enhance accessibility and user ability to observe and analyze visual simulations in real time. A variety of NASA mission segment simulations [Synergistic Engineering Environment (SEE) data, NASA Enterprise Visualization Analysis (NEVA) ground processing simulations, the DSS simulation for lunar operations, and the Johnson Space Center (JSC) TRICK tool for guidance, navigation, and control analysis] were experimented with. Desired functionalities, [i.e. Tivo-like functions, the capability to communicate textually or via Voice-over-Internet Protocol (VoIP) among team members, and the ability to write and save notes to be accessed later] were targeted. The resulting DON application was slated for early 2008 release to support simulation use for the Constellation Program and its teams. Those using the DON connect through a client that runs on their PC or Mac. This enables them to observe and analyze the simulation data as their schedule allows, and to review it as frequently as desired. DON team members can move freely within the virtual world. Preset camera points can be established, enabling team members to jump to specific views. This improves opportunities for shared analysis of options, design reviews, tests, operations, training, and evaluations, and improves prospects for verification of requirements, issues, and approaches among dispersed teams.

Conroy, Michael↗
NASA NTRS2009

Mending the Gap, An Effort to Aid the Transfer of Formal Methods Technology

Formal methods can be applied to many of the development and verification activities required for civil avionics software. RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, gives a brief description of using formal methods as an alternate method of compliance with the objectives of that standard. Despite this, the avionics industry at large has been hesitant to adopt formal methods, with few developers have actually used formal methods for certification credit. Why is this so, given the volume of evidence of the benefits of formal methods? This presentation will explore some of the challenges to using formal methods in a certification context and describe the effort by the Formal Methods Subgroup of RTCA SC-205/EUROCAE WG-71 to develop guidance to make the use of formal methods a recognized approach.

Hayhurst, Kelly↗
NASA NTRS2015

Internal NASA Study: NASAs Protoflight Research Initiative

The NASA Protoflight Research Initiative is an internal NASA study conducted within the Office of the Chief Engineer to better understand the use of Protoflight within NASA. Extensive literature reviews and interviews with key NASA members with experience in both robotic and human spaceflight missions has resulted in three main conclusions and two observations. The first conclusion is that NASA's Protoflight method is not considered to be "prescriptive." The current policies and guidance allows each Program/Project to tailor the Protoflight approach to better meet their needs, goals and objectives. Second, Risk Management plays a key role in implementation of the Protoflight approach. Any deviations from full qualification will be based on the level of acceptable risk with guidance found in NPR 8705.4. Finally, over the past decade (2004 - 2014) only 6% of NASA's Protoflight missions and 6% of NASA's Full qualification missions experienced a publicly disclosed mission failure. In other words, the data indicates that the Protoflight approach, in and of it itself, does not increase the mission risk of in-flight failure. The first observation is that it would be beneficial to document the decision making process on the implementation and use of Protoflight. The second observation is that If a Project/Program chooses to use the Protoflight approach with relevant heritage, it is extremely important that the Program/Project Manager ensures that the current project's requirements falls within the heritage design, component, instrument and/or subsystem's requirements for both the planned and operational use, and that the documentation of the relevant heritage is comprehensive, sufficient and the decision well documented. To further benefit/inform this study, a recommendation to perform a deep dive into 30 missions with accessible data on their testing/verification methodology and decision process to research the differences between Protoflight and Full Qualification missions' Design Requirements and Verification & Validation (V&V) (without any impact or special request directly to the project).

Protoflight↗