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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The broadening of calcium II H and K lines by helium

Laboratory measurements of widths and shifts of the Ca II H and K lines have been made under conditions simulating those in the atmospheres of metallic-line white dwarfs, namely, densities of 10 to the 21st power helium atoms per cu cm and temperatures of 4500 to 6000 K. There are significant differences in the shifts and damping constants of the two fine-structure components. The impact theory is evidently applicable to the Ca II/He system under these conditions, and the observed damping constants are fortuitously close to the predictions of conventional Lindholm-Foley/van der Waals theory. The widths and shifts have also been analyzed in terms of Lennard-Jones potential theory.

Hammond, G. L.↗
NASA NTRS1978

Preliminary power train design for a state-of-the-art electric vehicle

The state-of-the-art (SOTA) of electric vehicles built since 1965 was reviewed to establish a base for the preliminary design of a power train for a SOTA electric vehicle. The performance of existing electric vehicles were evaluated to establish preliminary specifications for a power train design using state-of-the-art technology and commercially available components. Power train components were evaluated and selected using a computer simulation of the SAE J227a Schedule D driving cycle. Predicted range was determined for a number of motor and controller combinations in conjunction with the mechanical elements of power trains and a battery pack of sixteen lead-acid batteries - 471.7 kg at 0.093 MJ/Kg (1040 lbs. at 11.7 Whr/lb). On the basis of maximum range and overall system efficiency using the Schedule D cycle, an induction motor and 3 phase inverter/controller was selected as the optimum combination when used with a two-speed transaxle and steel belted radial tires. The predicted Schedule D range is 90.4 km (56.2 mi). Four near term improvements to the SOTA were identified, evaluated, and predicted to increase range approximately 7%.

Ross, J. A.↗
NASA NTRS1985

Spacecraft heat transfer by two-phase flow method

A refrigerator/freezer has been designed with an oil-free compressor to provide an economical two-phase flow system for heat transfer. A computer simulation has been done for the condenser and evaporator to determine the design parameters, such as length, diameter, and flow regimes, for different refrigerants and load requirements. A large Reynolds number was considered to ensure annular flow (in order to maximize heat transfer coefficients) and large Froude number. The simulation was correlated with the test data of a vapor compression refrigerator/freezer flown on STS-4 (which provided information on vapor compression in a zero-gravity environment). The two-phase system will be used for the Spacelab mission SLS-1 and can be used in future spacecraft and high-speed aircraft, where weight, volume, and power requirements are critical.

Hye, A.↗
NASA NTRS1995

Variable speed generator application on the MOD-5A 7.3 mW wind turbine generator

This paper describes the application of a Scherbiustat type variable speed subsystem in the MOD-5A Wind Turbine Generator. As designed by General Electric Company, Advanced Energy Programs Department, under contract DEN3-153 with NASA Lewis Research Center and DOE, the MOD-5A utilizes the subsystem for both starting assistance in a motoring mode and generation in a controlled airgap torque mode. Reactive power control is also provided. The Scherbiustat type arrangement of a wound rotor machine with a cycloconverter in the rotor circuit was selected after an evaluation of variable speed technologies that followed a system evaluation of drivetrain cost and risk. The paper describes the evaluation factors considered, the results of the evaluations and summarizes operating strategy and performance simulations.

Barton, Robert S.↗
NASA NTRS1995

Ultrasonic frequency selection for aqueous fine cleaning

A study was conducted to evaluate ultrasonic cleaning systems for precision cleaning effectiveness for oxygen service hardware. This evaluation was specific for Rocketdyne Division of Rockwell Aerospace alloys and machining soils. Machining lubricants and hydraulic fluid were applied as soils to standardized complex test specimens designed to simulate typical hardware. The study consisted of tests which included 20, 25, 30, 40, 50, and 65 kHz ultrasonic cleaning systems. Two size categories of cleaning systems were evaluated, 3- to 10-gal laboratory size tanks and 35- to 320-gal industrial size tanks. The system properties of cavitation, frequency vs. cleaning effectiveness, the two types of transducers, and the power level of the system vs. size of the cleaning tank were investigated. The data obtained from this study was used to select the ultrasonic tanks for the aqueous fine clean facility installed at Rocketdyne.

Becker, Joann F.↗
NASA NTRS1990

Embedded CLIPS for SDI BM/C3 simulation and analysis

Nichols Research Corporation is developing the BM/C3 Requirements Analysis Tool (BRAT) for the U.S. Army Strategic Defense Command. BRAT uses embedded CLIPS/Ada to model the decision making processes used by the human commander of a defense system. Embedding CLlPS/Ada in BRAT allows the user to explore the role of the human in Command and Control (C2) and the use of expert systems for automated C2. BRAT models assert facts about the current state of the system, the simulated scenario, and threat information into CLIPS/Ada. A user-defined rule set describes the decision criteria for the commander. We have extended CLIPS/Ada with user-defined functions that allow the firing of a rule to invoke a system action such as weapons release or a change in strategy. The use of embedded CLIPS/Ada will provide a powerful modeling tool for our customer at minimal cost.

Gossage, Brett↗
NASA NTRS1994

Ultrasonic frequency selection for aqueous fine cleaning

A study was conducted to evaluate ultrasonic cleaning systems for precision cleaning effectiveness for oxygen service hardware. This evaluation was specific for Rocketdyne Div. of Rockwell Aerospace alloys and machining soils. Machining lubricants and hydraulic fluid were applied as soils to standardized complex test specimens designed to simulate typical hardware. The study consisted of tests which included 20, 25, 30, 40, 50, and 65 kHz ultrasonic cleaning systems. Two size categories of cleaning systems were evaluated, 3- to 10-gal laboratory size tanks and 35- to 320-gal industrial size tanks. The system properties of cavitation; frequency vs. cleaning effectiveness; the two types of transducers; and the power level of the system vs. size of the cleaning tank were investigated. The data obtained from this study was used to select the ultrasonic tanks for the aqueous fine clean facility installed at Rocketdyne.

Becker, Joann F.↗
NASA NTRS2000

Background Simulation of the MSFC GSPC Balloon Payload

Numerical simulations are used to predict the cosmic-ray induced background in a passively shielded gas scintillation proportional counter to be used as the focal plane instrument of a balloon-borne hard x-ray telescope system. The predicted background in the 20-75 keV operating range of the detector shows a spectral shape characteristic of a power law photoelectrically absorbed by the stainless steel pressure vessel walls. It is found that the dominant background radiation component is simply cosmic diffuse and atmospheric gamma-ray leakage though there is a contribution from nuclear interactions of energetic particles in the walls and nearby payload structures. The correlation between shielding properties and background flux is examined parametrically using one-dimensional slab models, within material and weight constraints, in order to optimize predicted sensitivity. The addition of a few mm thick Sn passive shielding reduces the primary photon contribution by up to 50% at the spectral peak, E 150 keV, and adds only negligibly to the flux due to photon production within the high-Z shields at lower energies.

Swartz, D. A.↗
NASA NTRS2003

Simulating the ARES Aircraft in the Mars Environment

NASA Langley proposed the Aerial Regional-scale Environmental Survey (ARES) of Mars science mission in response to the NASA Office of Space Science 2002 Mars Scout Opportunity. The science-driven mission proposal began with trade studies and determined that a rocket powered aircraft was the best suited platform to complete the ARES science objectives. A high fidelity six degree of freedom flight simulation was required to provide credible evidence that the aircraft design fulfilled mission objectives and to support the aircraft design process by providing performance evaluations. The aircraft was initially modeled using the aero, propulsion, and flight control system components of other aircraft models. As the proposed aircraft design evolved, the borrowed components were replaced with new models. This allowed performance evaluations to be performed as the design was maturing. Basic autopilot features were also developed for the ARES aircraft model. Altitude hold and track hold modes allowed different mission scenarios to be evaluated for both science merit and aircraft performance. Platform stability and data rate requirements were identified for each of the instruments and the aircraft performance was evaluated against those requirements. The results of the simulation evaluations indicate that the ARES design and mission profiles are sound and meet the science objectives.

Kenney, P. Sean↗
NASA NTRS2018

Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) Users' Workshop Presentations

NASA Glenn Research Center hosted a Users' Workshop on the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) on August 21, 2017. The objective of this workshop was to update the user community on the latest features of T-MATS, and to provide a forum to present work performed using T-MATS. Presentations highlighted creative applications and the development of new features and libraries, and emphasized the flexibility and simulation power of T-MATS.

and Control↗
NASA NTRS2004

Hydrogen-Oxygen PEM Regenerative Fuel Cell at NASA Glenn Research Center

The NASA Glenn Research Center has constructed a closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) to explore its potential use as an energy storage device for a high altitude solar electric aircraft. Built up over the last 2 years from specialized hardware and off the shelf components the Glenn RFC is a complete "brassboard" energy storage system which includes all the equipment required to (1) absorb electrical power from an outside source and store it as pressurized hydrogen and oxygen and (2) make electrical power from the stored gases, saving the product water for re-use during the next cycle. It consists of a dedicated hydrogen-oxygen fuel cell stack and an electrolyzer stack, the interconnecting plumbing and valves, cooling pumps, water transfer pumps, gas recirculation pumps, phase separators, storage tanks for oxygen (O2) and hydrogen (H2), heat exchangers, isolation valves, pressure regulators, nitrogen purge provisions, instrumentation, and other components. It specific developmental functions include: (1) Test fuel cells and fuel cell components under repeated closed-cycle operation (nothing escapes; everything is used over and over again). (2) Simulate diurnal charge-discharge cycles (3) Observe long-term system performance and identify degradation and loss mechanisms. (4) Develop safe and convenient operation and control strategies leading to the successful development of mission-capable, flight-weight RFC's.

Bents, David J.↗
NASA NTRS2005

Low-order aberration sensitivity of eighth-order coronagraph masks

In a recent paper, Kuchner, Crepp, and Ge describe new image-plane coronagraph mask designs that reject to eighth order the leakage of starlight caused by image motion at the mask, resulting in a substantial relaxation of image centroiding requirements compared to previous fourth-order and second-order masks. They also suggest that the new masks are effective at rejecting leakage caused by low-order aberrations (e.g., focus, coma, and astigmatism). In this paper, we derive the sensitivity of eighth-order masks to aberrations of any order and provide simulations of coronagraph behavior in the presence of optical aberrations.We find that the masks leak light as the fourth power of focus, astigmatism, coma, and trefoil. This has tremendous performance advantages for the Terrestrial Planet Finder Coronagraph.

planetary systems↗
NASA NTRS1986

Development of an Emulation-simulation Thermal Control Model for Space Station Application

Analysis techniques to evaluate the effects of changing thermal loads and the methods utilized to control temperature distributions in the orbital space station are essential. Analysis techniques including a user-friendly computer program, were developed which should prove useful in thermal design and system analysis of the the space station. The program uses a data base and user input to compute costs, sizes, and power requirements for individual components and complete systems. User input consists of selecting mission parameters, selecting thermal acquisition configurations, transport systems and distances, and thermal rejection configurations.

Colwell, G. T.↗
NASA NTRS1994

Magnetotail dynamics under isobaric constraints

Using linear theory and nonlinear MHD simulations, we investigate the resistive and ideal MHD stability of two-dimensional plasma configurations under the isobaric constraint dP/dt = 0, which in ideal MHD is equivalent to conserving the pressure function P = P(A), where A denotes the magnetic flux. This constraint is satisfied for incompressible modes, such as Alfven waves, and for systems undergoing energy losses. The linear stability analysis leads to a Schroedinger equation, which can be investigated by standard quantum mechanics procedures. We present an application to a typical stretched magnetotail configuration. For a one-dimensional sheet equilibrium characteristic properties of tearing instability are rediscovered. However, the maximum growth rate scales with the 1/7 power of the resistivity, which implies much faster growth than for the standard tearing mode (assuming that the resistivity is small). The same basic eigen-mode is found also for weakly two-dimensional equilibria, even in the ideal MHD limit. In this case the growth rate scales with the 1/4 power of the normal magnetic field. The results of the linear stability analysis are confirmed qualitatively by nonlinear dynamic MHD simulations. These results suggest the interesting possibility that substorm onset, or the thinning in the late growth phase, is caused by the release of a thermodynamic constraint without the (immediate) necessity of releasing the ideal MHD constraint. In the nonlinear regime the resistive and ideal developments differ in that the ideal mode does not lead to neutral line formation without the further release of the ideal MHD constraint; instead a thin current sheet forms. The isobaric constraint is critically discussed. Under perhaps more realistic adiabatic conditions the ideal mode appears to be stable but could be driven by external perturbations and thus generate the thin current sheet in the late growth phase, before a nonideal instability sets in.

Birn, Joachim↗
NASA NTRS1971

Performance of the Boeing LRV wheels in a lunar soil simulant. Report 2: Effects of speed, Wheel load, and soil

Two nearly identical Boeing-GM wire-mesh Lunar Roving Vehicle (LRV) wheels were laboratory tested in a lunar soil simulant to determine the influence of wheel speed and acceleration, wheel load, presence of a fender, travel direction, and soil strength on the wheel performance. Constant-slip and three types of programmed-slip tests were conducted with a single-wheel dynamometer system. Test results indicated that performance of single LRV wheels in terms of pull coefficient, power number, and efficiency were not influenced by wheel speed and acceleration, travel direction, the presence of a fender, or wheel load. Of these variables, only load influenced sinkage, which increased with increasing load. For a given slip, the pull coefficient and power number increased with increasing soil strength. However, for a given pull coefficient or slope, slip was less in firmer soil; thus, the power number decreased and efficiency increased with increasing soil strength.

Melzer, K.↗
NASA NTRS1975

Flight experience with time-of-arrival control for STOL aircraft in the terminal area

A research program on STOL operating systems is underway at the Ames Research Center. One investigation is concerned with design, analysis, and flight test of promising four-dimensional RNAV systems. One promising system generates a capture flight path from the present aircraft position to a waypoint on a selected fixed STOL approach route. It predicts arrival time at the runway and controls time and position along the path. The system was flight tested using a digital avionics system on a Convair 340 and on an experimental powered-lift STOL airplane. Flight tests in the flight director mode show that the pilot can choose and change the desired time of arrival, and meet this time within a few seconds, in spite of navigation errors and varying winds. Initial tests of the automatic mode using a flight simulator and the NASA Augmentor Wing Jet STOL Research Aircraft (AWJSRA) show that good time control was achieved at the cost of excess throttle activity. This fault was later corrected.

Neuman, F.↗
NASA NTRS1978

A safety margin and flight reference system and display for powered-lift aircraft

A study was conducted to explore the feasibility of a safety margin and flight reference system for those powered-lift aircraft which require a backside piloting technique. The main objective was to display multiple safety margin criteria as a single variable which could be tracked both manually and automatically and which could be monitored in order to derive safety margin status. The study involved a pilot-in-the-loop analysis of several system concepts and a simulator experiment to evaluate those concepts showing promise. A system was ultimately configured which yielded reasonable compromises in controllability, status information content, and the ability to regulate safety margins at some expense of the allowable low speed flight path envelope.

Heffley, R. K.↗
NASA NTRS1983

Pressure distributions on a 0.04-scale model of the Space Shuttle Orbiter's forward fuselage in the Langley unitary plan wind tunnel

Pressure distribution tests on a 0.04-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the Langley Unitary Plan Wind Tunnel (UPWT). The UPWT has two different test sections operating in the continuous mode. Each test section has its own Mach number range. The model was tested at angles of attack from -2.5 deg to 30 deg and angles of sideslip from -5 deg to 5 deg in both test sections. The test Reynolds number was 6.6 x 10 to the 6th power per meter. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS pressure orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations currently existing on the Space Shuttle Orbiter Columbia (OV-102). This DFI simulation has provided a means for comparisons between reentry flight pressure data and wind-tunnel data.

Bradley, P. F.↗