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At least 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Virtual interface environment

A head-mounted, wide-angle, stereoscopic display system controlled by operator position, voice and gesture has been developed for use as a multipurpose interface environment. The system provides a multisensory, interactive display environment in which a user can virtually explore a 360-degree synthesized or remotely sensed environment and can viscerally interact with its components. Primary applications of the system are in telerobotics, management of large-scale integrated information systems, and human factors research. System configuration, application scenarios, and research directions are described.

Fisher, Scott S.↗
NASA NTRS1987

Explosive evaporation in solar flares

This paper develops a simple analytical model for the phenomenon of 'explosive evaporation' driven by nonthermal electron heating in solar flares. The model relates the electron energy flux and spectrum, plus details of the preflare atmosphere, to the time scale for explosive evaporation to occur, the maximum pressure and temperature to be reached, rough estimates for the UV pulse emission flux and duration, and the evolution of the blueshifted component of the soft X-ray lines. An expression is given for the time scale for buildup to maximum pressures and the onset of rapid motion of the explosively evaporating plasma. This evaporation can excite a rapid response of UV line and continuum emission. The emission lines formed in the plasma approach a given emissivity-weighted blueshift speed.

Fisher, George H.↗
NASA NTRS1986

Laminar flow integration: Flight tests status and plans

Under the Aircraft Energy Efficiency - Laminar Flow Control Program, there are currently three flight test programs under way to address critical issues concerning laminar flow technology application to commercial transports. The Leading-Edge Flight Test (LEFT) with a JetStar aircraft is a cooperative effort with the Ames/Dryden Flight Research Facility to provide operational experience with candidate leading-edge systems representative of those that might be used on a future transport. In the Variable Sweep Transition Flight Experiment (VSTFE), also a cooperative effort between Langley and Ames/Dryden, basic transition data on an F-14 wing with variable sweep will be obtained to provide a data base for laminar flow wing design. Finally, under contract to the Boeing Company, the acoustic environment on the wing of a 757 aircraft will be measured and the influence of engine noise on laminar flow determined with a natural laminar flow glove on the wing. The status and plans for these programs are reported.

Wagner, R. D.↗
NASA NTRS1988

Surface flow visualization of separated flows on the forebody of an F-18 aircraft and wind-tunnel model

A method of in-flight surface flow visualization similar to wind-tunnel-model oil flows is described for cases where photo-chase planes or onboard photography are not practical. This method, used on an F-18 aircraft in flight at high angles of attack, clearly showed surface flow streamlines in the fuselage forebody. Vortex separation and reattachment lines were identified with this method and documented using postflight photography. Surface flow angles measured at the 90 and 270 degrees meridians show excellent agreement with the wind tunnel data for a pointed tangent ogive with an aspect ratio of 3.5. The separation and reattachment line locations were qualitatively similar to the F-18 wind-tunnel-model oil flows but neither the laminar separation bubble nor the boundary-layer transition on the wind tunnel model were evident in the flight surface flows. The separation and reattachment line locations were in fair agreement with the wind tunnel data for the 3.5 ogive. The elliptical forebody shape of the F-18 caused the primary separation lines to move toward the leeward meridian. Little effect of angle of attack on the separation locations was noted for the range reported.

Fisher, David F.↗
NASA NTRS1988

Virtual interface environment

A head-mounted, wide-angle, stereoscopic display system controlled by operator position, voice and gesture is under development for use as a multipurpose interface environment. Initial applications of the system are in telerobotics, data-management and human factors research. System configuration and research directions are described.

Fisher, Scott S.↗
NASA NTRS1988

A plan for time-phased incorporation of automation and robotics on the US space station

A plan for the incorporation of Automation and Robotics technology on the Space Station is presented. The time phased introduction of twenty two selected candidates is set forth in accordance with a technology development forecast. Twenty candidates were chosed primarily for their potential to relieve the crew of mundane or dangerous operations and maintenance burdens, thus freeing crew time for mission duties and enhancing safety. Two candidates were chosen based on a potential for increasing the productivity of laboratory experiments and thus directly enhancing the scientific value of the Space Station. A technology assessment for each candidate investigates present state of the art, development timelines including space qualification considerations, and potential for technology transfer to earth applications. Each candidate is evaluated using a crew workload model driven by crew size, number of pressurized U.S. modules and external payloads, which makes it possible to assess the impact of automation during a growth scenario. Costs for each increment of implementation are estimated and accumulated.

Purves, R. B.↗
NASA NTRS1987

Weathering of sulfides on Mars

Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produce degradation products in the Martian regolith. By analogy and terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni, and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato-and hydroxo-complex ions and sols formed gossan above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite), and silica (opal). Underlying groundwater, now permafrost contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates, and phyllosilicates during dust storms on Mars.

Burns, Roger G.↗
NASA NTRS1986

A smoke-wire study of low Reynolds number flow over a NASA LRN(1) - 1007 airfoil section

Smoke-filament visualization photographs are presented for two-dimensional flow over a NASA LRN(1) - 1007 airfoil section designed specifically for high-efficiency operation at low chord Reynolds numbers. Results are included for chord Reynolds numbers of 60,000, 100,000, and 220,000 and for angles of attack ranging from 0 to 16 degrees. Two kinds of laminar separation bubble are found to develop in the flow over the airfoil. The sites and characteristics of formation of these bubbles are described, and their dimensional properties are estimated. The transition-to-turbulence Reynolds numbers, surface pressure coefficient distributions, and lift coefficients deduced from the measured coefficients are compared with those obtained by other authors.

Fisher, S. S.↗
NASA NTRS1987

Telepresence master glove controller for dexterous robotic end-effectors

This paper describes recent research in the Aerospace Human Factors Research Division at NASA's Ames Research Center to develop a glove-like, control and data-recording device (DataGlove) that records and transmits to a host computer in real time, and at appropriate resolution, a numeric data-record of a user's hand/finger shape and dynamics. System configuration and performance specifications are detailed, and current research is discussed investigating its applications in operator control of dexterous robotic end-effectors and for use as a human factors research tool in evaluation of operator hand function requirements and performance in other specialized task environments.

Fisher, Scott S.↗
NASA NTRS1987

Virtual workstation - A multimodal, stereoscopic display environment

A head-mounted, wide-angle, stereoscopic display system controlled by operator position, voice and gesture has been developed for use in a multipurpose interface environment. The system provides a multisensory, interactive display environment in which a user can virtually explore a 360-degree synthesized or remotely sensed environment and can viscerally interact with its components. Primary applications of the system are in telerobotics, management of large-scale integrated information systems, and human factors research. System configuration, application scenarios, and research directions are described.

Fisher, S. S.↗
NASA NTRS1988

The Atlas-Centaur 67 incident

The conditions leading to the breakup of the Atlas-Centaur 67 (AC-67) vehicle launched on March 26, 1987 during a typical winter-time storm are analyzed, and a most probable lightning strike scenario was developed based on inspection of the AC-67 debris, the AC-68 vehicle, and appropriate drawings, electrical diagrams, and photographs. It is shown that, during ascent, the vehicle encountered increasingly larger electric fields and flew through clouds that produced precipitation static on the vehicle, eventually triggering a cloud-to-ground lightning, comprised of at least four return strokes. The resulting lightning current coupled a signal into the wiring which goes to the AC-67 digital computer unit (DCU), effecting a single-word memory alteration and causing the DCU to issue a hardover engine gimbal command. This led to an excessive angle of attack, large dynamic loads, and the breakup of the AC-67.

Christian, H. J.↗
NASA NTRS1988

Cloud-to-ground strikes to the NASA F-106 airplane

Cloud-to-ground (CG) lightning strike data on the NASA F-106B research aircraft obtained during the 1984-86 storm seasons in the vicinity of Wallops Island, Virginia, are analyzed. The results suggest that CG strikes may represent a significant portion of the total number of lightning strikes encountered by the aircraft at altitudes below 6 km. It is unlikely that an aircraft encounters the first return stroke of the CG flash. The current values of the CG strikes are not different from currents in other types of strikes.

Mazur, Vladislav↗
NASA NTRS1988

Implications of a recent lightning strike to a NASA jet trainer

On February 24, 1987, a NASA T-38A airplane experienced a lightning strike while approaching the Los Alamitos Army Aviation Facility in California. The airplane was landed safely at Los Alamitos with no injury to the crew members. However, the airplane suffered extensive fire damage in the center fuselage section. The NASA investigation board concluded that the airplane was struck by lightning, which resulted in an inflight explosion with subsequent fire. This paper describes the most probable cause of the incident, and the implications of this mishap to aircraft lightning protection and to the avoidance of those conditions conducive to lightning strikes to aircraft.

Fisher, Bruce D.↗
NASA NTRS1987

User interface and operational issues with thermionic space power systems

Thermionic space power systems have unique features which facilitate predeployment operations, provide operational flexibility and simplify the interface with the user. These were studied in some detail during the SP-100 program from 1983 to 1985. Three examples are reviewed in this paper: (1) system readiness verification in the prelaunch phase; (2) startup, shutdown, and dormancy in the operations phase; (3) part-load operation in the operations phase.

Dahlberg, R. C.↗
NASA NTRS1987

In-flight environmental effects on airplane composite vertical fin caps

The NASA-Langley Storm Hazards Program has given attention to the effects of severe in-flight weather environments on composite structures, using an instrumented F-106B in storm penetration experiments. The vertical fin cap was chosen for the study of lightning strike attachments on composite structures of four different types: (1) glass/epoxy with flame-sprayed aluminum; (2) Kevlar/epoxy with aluminized glass cloth; (3) graphite-epoxy without lightning protection; and (4) unprotected graphite-epoxy with electrical isolation from the rest of the aircraft structure. Flight test results are evaluated.

Howell, William E.↗
NASA NTRS1987

Chromospheric downflow velocities as a diagnostic in solar flares

The dynamics of chromospheric condensations driven by evaporation during the impulsive phase of solar flares are explored. Specifically, it is found that the maximum chromospheric downflow speed is equal to 0.4(F/rho sub ch) exp 1/3, where F is that part of the flare energy flux driving chromospheric evaporation, and rho sub ch is the mass density in the preflare chromosphere just below the preflare transition region. This implies that chromospheric downflows as measured by H-alpha asymmetries may be a powerful probe of flare energetics.

Fisher, G. H.↗
NASA NTRS1988

Aircraft jolts from lightning bolts

The trend toward the use of composite materials and digital electronics has renewed the need to quantify the effects of lightning strikes to airplanes, since composite structures do not provide shielding equivalent to that of metal aircraft, and digital systems are potentially more susceptible to upset by electrical transients than are analog electronic systems. A research program, called the Storm Hazards Program, has been run by the National Aeronautics and Space Administration (NASA) for the past eight years and has provided the first statistically significant measurements of the electromagnetic interaction between lightning and aircraft. A NASA-owned F-106B airplane has been flown through thunderstorms about 1500 times at altitudes between 5,000 and 40,000 feet (1,500 to 12,000 meters). The airplane, lightning-hardened and outfitted with special instruments, was hit by lightning 714 times. The types of measurements made and the results are described.

Pitts, Felix L.↗
NASA NTRS1988

Implications of a recent lightning strike to a NASA jet trainer

On February 24, 1987, a NASA T-38A airplane experienced a lightning strike while approaching the Los Alamitos Army Aviation Facility in California. The airplane was landed safely at Los Alamitos with no injury to the crew members. However, the airplane suffered extensive fire damage in the center of the fuselage section. The NASA investigation board concluded that the airplane was struck by lightning, which resulted in an inflight explosion with subsequent fire. The implications of this mishap to aircraft lightning protection and the avoidance of those conditions conducive to lightning strikes to aircarft are discussed.

Fisher, Bruce D.↗