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At least 955 records · Page 53

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NASA NTRS1972

Reaction propagation test. Evaluation of the behavior of nonmetallic materials in hydrogen

Results of tests conducted to evaluate the behavior of nonmetallic materials in hydrogen are described. The reaction propagation test simulates the conditions resulting from the interaction of an electrical wire in an overload condition in contract with a material in the test medium. The test is designed to evaluate the behavior of a material subjected to an energy input (usually heat) sufficient to cause a reaction which propagates to consume larger quantities of the material. Ten nonmetallic materials were evaluated to establish baseline data on the behavior of nonmetallic materials in hydrogen and to characterize, on an initial basis, one mode of material failure considered to be a factor pertinent to the safe use of a material in hydrogen.

Smith, I. D.↗

NASA NTRS1972

Flash and fire test: Evaluation of the behavior of nonmetallic materials in hydrogen

Tests conducted to evaluate the behavior of nonmetallic materials in hydrogen are described. The results of the flash and fire test are presented. The flash and fire test is used to evaluate the tendency of heated materials to ignite in a hydrogen atmosphere when subjected to an ignition source. The test represents a hydrogen parallel to a hazard condition known to exist in oxygen systems. Ten nonmetallic materials were evaluated to establish baseline data on the behavior of the materials and to characterize one mode of material failure considered to be a factor pertinent to the safe use of a material in hydrogen.

Source record↗

NASA NTRS1972

Motivation in vigilance - Effects of self-evaluation and experimenter-controlled feedback.

Vigilance experiments have been performed to study the relative efficiency of feedback operations in enhancing vigilance performance. Two feedback operations were compared - i.e., experimenter-controlled feedback in the form of knowledge of results (KR) regarding response times to signal detections, and subject-controlled feedback in the form of self-evaluation (SE) of response times to signal detections. The subjects responded to the aperiodic offset of a visual signal during a 1-hr vigil. Both feedback operations were found to enhance performance efficiency: subjects in the KR and SE conditions had faster response times than controls receiving no evaluative feedback. Moreover, the data of the KR and SE groups did not differ significantly from each other. The results are discussed in terms of the hypothesis that self-evaluation is a critical factor underlying the incentive value of KR in vigilance tasks.

Warm, J. S.↗

NASA NTRS1972

A simulator evaluation of the use of spoilers on a light aircraft

A fixed-base flight simulator was used to evaluate wing spoilers for longitudinal flight path control on a modified Cessna Cardinal aircraft. Spoilers which generated the proper pitching moment to maintain aircraft trim C sub L constant could be used as an effective descent rate control. More than 100 simulated ILS approaches were flown by evaluation pilots using both conventional methods and spoiler descent rate control. Three spoiler control schemes were evaluated during the ILS approaches. Using the spoilers for control, instrument approaches could be flown smoothly and precisely with constant airspeed and pitch attitude. While the spoilers could adequately control ILS approaches, a spoiler system with greater authority would be desirable for use in visual approaches.

Brainerd, C. H.↗

NASA NTRS1972

Path selection system simulation and evaluation for a Martian roving vehicle

The simulation and evaluation of proposed path selection systems for an autonomous Martian roving vehicle was developed. The package incorporates a number of realistic features, such as the simulation of random effects due to vehicle bounce and sensor-reading uncertainty, to increase the reliability of the results. Qualitative and quantitative evaluation criteria were established. The performance of three different path selection systems was evaluated to determine the effectiveness of the simulation package, and to form some preliminary conclusions regarding the tradeoffs involved in a path selection system design.

Boheim, S. L.↗

NASA NTRS1972

The Short Haul Air Travel Market: Evaluation of New Forms of Service

Aspects of the demand for air travel and an approach for incorporating them in evaluations of new services are discussed. The approach as described here is being used to evaluate the market for STOL aircraft in the 1980's but it could just as well be used to evaluate the market effects of schedule changes, equipment changes, and new routes, if certain basic data relating these changes to demand are available. A most important change in the market which is likely to take place in the next fifteen years, and which is already underway, is the increasing availability of alternative airports in major cities.

Couts, D. A.↗

NASA NTRS1972

Development and evaluation of graphite and boron polyimide composites.

This paper covers the development and evaluation of the HT-S/710 graphite/polyimide system and initial evaluations of high modulus graphite and boron reinforced polyimide systems. Detail design properties of the HT-S/710 graphite/polyimide systems, test results of test sheet stringer components, and initial test evaluations of high modulus graphite and boron reinforced polyimide composites are presented. Preliminary design applications utilizing the basic processing and design data from this development program are presented as to their utilization in aircraft and space applications.

Scheck, W. G.↗

NASA NTRS1973

An evaluation of the relative fire hazards of jet A and jet B for commercial flight

The relative fire hazards of Jet A and Jet B aircraft fuels are evaluated. The evaluation is based on a consideration of the presence of and/or the generation of flammable mixtures in fuel systems, the ignition characteristics, and the flame propagation rates for the two fuel types. Three distinct aircraft operating regimes where fuel type may be a factor in fire hazards are considered. These are: (1) ground handling and refueling, (2) flight, and (3) crash. The evaluation indicates that the overall fire hazards for Jet A are less than for Jet B fuel.

Hibbard, R. R.↗

NASA NTRS1973

Investigation of solidification in zero-gravity environment; M553 sphere forming experiment. Phase C: Evaluation of Skylab specimens

Results on specimen evaluation and discussion of solidification behavior in each case are reported in the following order: (1) specimen SL-1.6, (2) specimen SL-2.8, (3) specimen SL-2.4, (4) specimen SL-1.10 and (5) specimen SL-1.11. Comparison is made with ground-processed specimens of similar composition, whenever pertinent and meaningful. Among the nondestructive evaluation methods the measurement of sphericity was conducted by micrometric and shadowgraphic techniques. The intricate shape of specimens in some cases appeared difficult to define. In measuring the density, liquid penetration inside cavities that outcrop on the surface was avoided by sealing off these cavities. Among the destructive evaluation methods the use of the Quantimet 720 required particular attention, because of the small difference in contrast between second phases and micropores. With regard to microporosity microvoids in the core of some specimens were so fine that X-ray microradiography had to be used.

Kattamis, T. Z.↗

NASA NTRS1974

Apollo experience report: Data management for postflight engineering evaluation

The Apollo management of data for postflight engineering evaluation is described. The sources of Apollo telemetry data, the control of data processing by a single data team, the data techniques used to assist in evaluation of the large quantity of data, and the operation of the data team before the mission and during the evaluation phase are described. The techniques used to ensure the output of valid data and to determine areas in which data were of questionable quality are also included.

Foster, G. B., Jr.↗

NASA NTRS1974

Evaluation of three coding schemes designed for improved data communication

Three coding schemes designed for improved data communication are evaluated. Four block codes are evaluated relative to a quality function, which is a function of both the amount of data rejected and the error rate. The Viterbi maximum likelihood decoding algorithm as a decoding procedure is reviewed. This evaluation is obtained by simulating the system on a digital computer. Short constraint length rate 1/2 quick-look codes are studied, and their performance is compared to general nonsystematic codes.

Snelsire, R. W.↗

NASA NTRS1974

Path selection system development and evaluation for a Martian roving vehicle

A path selection system evaluation test procedure has been developed to enhance the analysis capability of an existing digital computer simulation package. The procedure investigates the obstacle avoidance ability of a path selection system on a sequence of test terrains with and without random effects. Using the standard test procedure a proposed mid-range sensor system has been evaluated and recommendations directed at improving the performance of the system have been made. In addition, the initial development and evaluation of a short range sensor system has been undertaken.

Campbell, R. S.↗

NASA NTRS1972

Evaluation of beryllium for space shuttle components

Application of beryllium to specific full-scale space shuttle structural components and assemblies was studied. Material evaluations were conducted to check the mechanical properties of as-received material to gain design information on characteristics needed for the material in the space shuttle environment, and to obtain data needed for evaluating component and panel tests. Four beryllium structural assemblies were analyzed and designed. Selected components of these assemblies, representing areas of critical loading or design/process uncertainty, were designed and tested, and two panel assemblies were fabricated. Trends in cost and weight factors were determined by progressive estimation at key points of preliminary design, final design, and fabrication to aid in a cost/weight evaluation of the use of beryllium.

Trapp, A. E.↗

NASA NTRS1973

Design, process development, manufacture, test and evaluation of boron-aluminum for space shuttle components

A multi phase boron-aluminum design and evaluation program for space shuttle components was conducted, culminating in the fabrication of a 1.22 m (48 inch) x 1.83 m (72 inch) boron-aluminum compression panel capable of distributing a point load of 1555 kN (350,000 lbs) into a uniform running load at a temperature of 589 K (600 F). This panel was of the skin-stringer construction with two intermediate frame supports; seven unidirectional stringers varied in thickness from 5 plies to 52 plies and the skin was contoured to thicknesses ranging from 10 plies to 62 plies. Both the stringers and the skin incorporated Ti-6Al-4V titanium interleaves to increase bearing and in-plane shear strength. The discrete program phases were materials evaluation, design studies, process technology development, fabrication and assembly, and test and evaluation.

Garrett, R. A.↗

NASA NTRS1974

Performance evaluation of a second-generation elastic loop mobility system

Tests were conducted to evaluate the mobility performance of a second-generation Elastic Loop Mobility System (ELMS II). Performance on level test lanes and slopes of lunar soil simulant (LSS) and obstacle-surmounting and crevasse-crossing capabilities were investigated. In addition, internal losses and contact pressure distributions were evaluated. To evaluate the soft-soil performance, two basic soil conditions were tested: loose (LSS1) and dense (LSS5). These conditions embrace the spectrum of soil strengths tested during recent studies for NASA related to the mobility performance of the LRV. Data indicated that for the tested range of the various performance parameters, performance was independent of unit load (contact pressure) and ELMS II drum angular velocity, but was influenced by soil strength and ELMS pitch mode. Power requirements were smaller at a given system output for dense soil than for loose soil. The total system output in terms of pull developed or slope-climbing capability was larger for the ELMS II operating in restrained-pitch mode than in free-pitch mode.

Melzer, K. J.↗

NASA NTRS1972

Special nondestructive techniques for evaluating space shuttle surface insulation

NDT techniques have been developed for performing in-process evaluations for material variability and for process control. Several of these techniques show considerable promise for evaluating the reusable surface insulation during the operational phase of the shuttle. Considered are radiographic dosimetry, sonic velocity and modulus sounding, infrared coating evaluation, and beta backscatter monitoring of coating thickness.

Stinebring, R. C.↗

NASA NTRS1974

Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application

A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs.

Laakso, J. H.↗

NASA NTRS1974

Remote sensing for evaluating post-disaster damage conditions: The Pierre, South Dakota tornado, 23 July 1973

Remote sensing data obtained from aerial reconnaissance of tornado damage to the city of Pierre, South Dakota on July 23, 1973 was evaluated to determine its value as a decision making and management tool in post-disaster restoration activities. The imaging techniques used are briefly discussed, and both aerial and closeup color photographs are provided which were used in the evaluation. The immediate advantages of the data are identified as a 'quick-look' assessment, and a list is given which outlines the additional advantages for which positive rescue and cleanup action may be initiated. Hail and flood damage evaluation, and remote sensing of crop damage due to insect of disease infestation is also briefly described.

Rusche, A. E.↗