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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Electric propulsion - Now

The state of the art of electric propulsion technology is discussed with a review of the many difficult engineering problems which must be resolved before the incorporation of electric propulsion in space missions. Interferences with the spacecraft and its scientific instrumentation, conducted and radiated electromagnetic interferences during the switching and processing of large electrical loads, and mercury and other eroded materials deposition on the spacecraft are indicated among the engineering and design challenges to be overcome and resolved.

Gerpheide, J. H.↗
NASA NTRS1983

Communications and tracking - Light and IR will help carry high traffic

The space station currently under consideration by NASA must simultaneously track and communicate with the many vehicles and objects surrounding it in orbit. While the Space Shuttle has 23 antennas, more than 50 will be required by the space station. In addition to Shuttle-compatible equipment at P, L, C, S, and Ku bands, the station system will probably incorporate Ka, W, IR and optical frequency equipment for tracking and communications. A major design challenge is foreseen in the placement of separate antennas, lenses and reflectors over the station's external geometry in order to give both the overlapping fields of view required for spherical coverage and the radiation of unambiguous navigation guide beams and markers. Adaptive distributed element arrays are under consideration. Another approach to spherical coverage involves the use of omnidirectional antennas which both transmit and receive RF energy over a wide range of angles.

Dickinson, R. M.↗
NASA NTRS1983

Advanced propfan engine characteristics and technology needs

A comparative study is presented for two of the advanced gas turbine engine designs developed in the course of a proprietary research effort for the NASA Advanced Propfan Engine Technology research program. In these engines, a cycle pressure ratio of 32.5:1 and a 2500 F maximum turbine temperature provide fuel efficient operation in the 32,000-ft altitude, Mach 0.72 cruise speed regime stipulated. Both of the engine configurations incorporate three spools, of which the compressors are dual-spool and the power turbines are free. A major design challenge for axial compressors in the 10,000-shp class was the maintenance of adequate blade heights in the later stages.

Anderson, R. D.↗
NASA NTRS1987

GPS antenna designs

Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

Laube, Samuel J. P.↗
NASA NTRS1987

WHAMII - An enumeration and insertion procedure with binomial bounds for the stochastic time-constrained traveling salesman problem

This paper presents an algorithm (WHAMII) designed to solve the Artificial Intelligence Design Challenge at the 1987 AIAA Guidance, Navigation and Control Conference. The problem under consideration is a stochastic generalization of the traveling salesman problem in which travel costs can incur a penalty with a given probability. The variability in travel costs leads to a probability constraint with respect to violating the budget allocation. Given the small size of the problem (eleven cities), an approach is considered that combines partial tour enumeration with a heuristic city insertion procedure. For computational efficiency during both the enumeration and insertion procedures, precalculated binomial probabilities are used to determine an upper bound on the actual probability of violating the budget constraint for each tour. The actual probability is calculated for the final best tour, and additional insertions are attempted until the actual probability exceeds the bound.

Dahl, Roy W.↗
NASA NTRS1991

A two-time-scale autopilot for high-performance aircraft

A two-time-scale autopilot is proposed for the Aircraft Controls Design Challenge problem. This control law uses a nonlinear aircraft model constructed from the given vehicle simulation. The vehicle model is partitioned into slow translational dynamics and fast rotational dynamics. Feedback linearization is then employed to synthesize control laws for these two-time scales. Due to the nature of the synthesis, the control law is suitable for automatic trajectory following, and also for pilot control.

Menon, P. K. A.↗
NASA NTRS1992

Programmable digital modem

Information on programmable digital modems (PDM) is given in viewgraph form. Topics covered include data rate range and operational modes, test and demonstration equipment, program goals, modulation formats, and PDM design challenges.

Kappes, M.↗
NASA NTRS1984

Spacecraft Control Laboratory Experiment: Status report

The Spacecraft Control Laboratory Experiment (SCOLE) will allow direct experimental comparison of competing control schemes for large flexible spacecraft structures. The experiment was designed to emulate the essential characteristics of a mathematical model design challenge which represents a Space Shuttle with a flexible mast and antenna attached. This experiment represents the third in a series of three flexible structure control experiments used by the Flight Dynamics and Control Division at LaRC. The key problem addressed by the facility is that flexible motion of the mast and antenna must be considered in the slewing and pointing control problems.

Williams, J. P.↗
NASA NTRS1992

A program to study antiprotons in the cosmic rays: Arizona collaboration

The Cherenkov detector designed and built for the LEAP (Low Energy AntiProton) experiment utilized a novel design to achieve appreciable sensitive area (02. sq m) with a refractive index of 1.25 in a magnetic fringe field region (500-1000 Gauss). The weight was held to only 64 kg by using 16 unshielded Hamamatsu R2490-01 photomultiplier tubes, each aligned with its local magnetic field. A filling and reservoir system for the highly volatile FC-72 liquid Cherenkov radiator also presented many design challenges. Relativistic particles yielded about 72 photoelectrons, total.

Bowen, Theodore↗
NASA NTRS1994

Implementation of heaters on thermally actuated spacecraft mechanisms

This paper presents general insight into the design and implementation of heaters as used in actuating mechanisms for spacecraft. Problems and considerations that were encountered during development of the Deep Space Probe and Science Experiment (DSPSE) solar array release mechanism are discussed. Obstacles included large expected fluctuations in ambient temperature, variations in voltage supply levels outgassing concerns, heater circuit design, materials selection, and power control options. Successful resolution of these issues helped to establish a methodology which can be applied to many of the heater design challenges found in thermally actuated mechanisms.

Busch, John D.↗
NASA NTRS1994

Combustor technology for future small gas turbine aircraft

To enhance fuel efficiency, future advanced small gas turbine engines will utilize engine cycles calling for overall engine pressure ratios, leading to higher combustor inlet pressures and temperatures. Further, the temperature rise through the combustor and the corresponding exit temperature are also expected to increase. This report describes future combustor technology needs for small gas turbine engines. New fuel injectors with large turndown ratios which produce uniform circumferential and radial temperature patterns will be required. Uniform burning will be of greater importance because hot gas temperatures will approach turbine material limits. The higher combustion temperatures and increased radiation at high pressures will put a greater heat load on the combustor liners. At the same time, less cooling air will be available as more of the air will be used for combustion. Thus, improved cooling concepts and/or materials requiring little or no direct cooling will be required. Although presently there are no requirements for emissions levels from small gas turbine engines, regulation is anticipated in the near future. This will require the development of low emission combustors. In particular, nitrogen oxides will increase substantially if new technologies limiting their formation are not evolved and implemented. For example, staged combustion employing lean, premixed/prevaporized, lean direct injection, or rich burn-quick quench-lean burn concepts could replace conventional single stage combustors. Due to combustor size considerations, staged combustion is more easily accommodated in large engines. The inclusion of staged combustion in small engines will pose greater combustor design challenges.

Lyons, Valerie J.↗
NASA NTRS1996

The future of very large subsonic transports

The Very Large Subsonic Transport (VLST) is a multi-use commercial passenger, commercial cargo, and military airlifter roughly 50% larger than the current Lockheed C-5 and Boeing 747. Due to the large size and cost of the VLST, it is unlikely that the commercial market can support more than one aircraft production line, while declining defense budgets will not support a dedicated military VLST. A successful VLST must therefore meet airline requirements for more passenger and cargo capacity on congested routes into slot-limited airports and also provide a cost effective heavy airlift capacity to support the overseas deployment of US military forces. A successful VLST must satisfy three key missions: commercial passenger service with nominal seating capacity at a minimum of 650 passengers with a range capability of 7,000 to 10,000 miles; commercial air cargo service for containerized cargo to support global manufacturing of high value added products, 'just-in-time' parts delivery, and the general globalization of trade; and military airlift with adequate capacity to load current weapon systems, with minimal break-down, over global ranges (7,000 to 10,000 miles) required to reach the operational theater without need of overseas bases and midair refueling. The development of the VLST poses some technical issues specific to large aircraft, but also key technologies applicable to a wide range of subsonic transport aircraft. Key issues and technologies unique to the VLST include: large composite structures; dynamic control of a large, flexible structure; aircraft noise requirements for aircraft over 850,000 pounds; and increased aircraft separation due to increased wake vortex generation. Other issues, while not unique to the VLST, will critically impact the ability to build an efficient and affordable aircraft include: active control systems: Fly-By-Light/Power-By-Wire (FBL/PBW); high lift systems; flight deck associate systems; laminar flow; emergency egress; and modular design. The VLST will encounter severe restrictions on weight, ground flotation, span, length, and door height to operate at current airports/bases, gates, and cargo loading systems. One option under consideration is for a sea-based VLST, either a conventional seaplane or Wing-In-Ground effect (WIG) vehicle, which would allow greater operational flexibility, while introducing other design challenges such as water impact loads and salt-water corrosion. Lockheed Martin is currently developing a floatplane version of the C-130 Hercules which will provide experience with a modern sea-based aircraft. In addition to its own ongoing research activities, Lockheed Martin is also participating in the NASA Advanced Subsonic Technology, High Speed Research (HSR), and other programs which address some of the technologies needed for the VLST. The VLST will require NASA and US aerospace companies to work together to develop new capabilities and technologies for make the VLST a viable part of transportation beyond 2000.

Justice, R. Steven↗
NASA NTRS1996

Status of Electrical Actuator Applications

An ever increasing number of actuation functions historically performed by hydraulics or pneumatics are being accomplished by electric actuation. If 'end to end' systems are considered, electric actuators (EA's) are potentially lighter and more efficient. In general, system redundancies may be more easily implemented and operationally monitored. Typically, electrical components exhibit longer mean times to failure and projected lifetime costs of EA's are potentially much lower than those of other options. EA's have certain characteristics which must be considered in their application. The actual mechanical loadings must be established, for the more easily controlled EA may be operated much closer to its full capabilities. At higher rates of motion, EA's are operating as constant power devices. Therefore, it may be possible to start a movement that can not be stopped. The incorporation of high power electronics into remote locations introduces new concerns of EMI and thermal control. It is the management of these and other characteristics that forms the engineering design challenges. Work is currently in progress on EA's for aircraft and expendable launch vehicles. These applications span from ten to 40+ horsepower. The systematics and status of these actuators will be reported along with current technical trends in this area.

Roth, Mary Ellen↗
NASA NTRS1997

Ultra-Capacitor Energy Storage in a Large Hybrid Electric Bus

The power requirements for inner city transit buses are characterized by power peaks about an order of magnitude larger than the average power usage of the vehicle. For these vehicles, hybrid power trains can offer significantly improved fuel economy and exhaust emissions. A critical design challenge, however, has been developing the energy storage and power management system to respond to these rapid power variations. Most hybrid vehicles today use chemical energy storage batteries to supplement the power from the fuel burning generator unit. Chemical storage batteries however, present several difficulties in power management and control. These difficulties include (1) inadequate life, (2) limited current delivery as well as absorption during regenerative braking, (3) inaccurate measurement of state of charge, and (4) stored energy safety issues. Recent advances in ultra-capacitor technology create an opportunity to address these concerns. The NASA Lewis Research Center, in cooperation with industry and academia, has developed an advanced hybrid electric transit bus using ultra-capacitors as the primary energy storage system. At over 15,000-kg gross weight, this is the largest vehicle of its kind ever built using this advanced energy storage technology. Results of analyses show that the vehicle will match the performance of an equivalent conventionally powered vehicle over typical inner city drive cycles. This paper describes the overall power system architecture, the evolution of the control strategy, and analysis of power flow and vehicle performance.

Viterna, L. A.↗
NASA NTRS1999

Wave-Rotor-Enhanced Gas Turbine Engine Demonstrator

The U.S. Army Research Laboratory, NASA Glenn Research Center, and Rolls-Royce Allison are working collaboratively to demonstrate the benefits and viability of a wave-rotor-topped gas turbine engine. The self-cooled wave rotor is predicted to increase the engine overall pressure ratio and peak temperature by 300% and 25 to 30%. respectively, providing substantial improvements in engine efficiency and specific power. Such performance improvements would significantly reduce engine emissions and the fuel logistics trails of armed forces. Progress towards a planned demonstration of a wave-rotor-topped Rolls-Royce Allison model 250 engine has included completion of the preliminary design and layout of the engine, the aerodynamic design of the wave rotor component and prediction of its aerodynamic performance characteristics in on- and off-design operation and during transients, and the aerodynamic design of transition ducts between the wave rotor and the high pressure turbine. The topping cycle increases the burner entry temperature and poses a design challenge to be met in the development of the demonstrator engine.

Welch, Gerard E.↗
NASA NTRS2000

Development of a High Output Fluorescent Light Module for the Commercial Plant Biotechnology Facility

To maximize the use of available resources provided onboard the International Space Station, the development of an efficient lighting 1 system is critical to the overall performance of the CPBF. Not only is it important to efficiently generate photon energy, but thermal loads on the CPBF Temperature and Humidity Control System must be minimized. By utilizing optical coatings designed to produce highly diffuse reflectance in the visible wavelengths while minimizing reflectance in the infrared region, the design of the fluorescent light module for the CPBF is optimized for maximum photon flux, spatial uniformity and energy efficiency. Since the Fluorescent Light Module must be fully enclosed to meet (ISS) requirements for containment of particulates and toxic materials, heat removal from the lights presented some unique design challenges. By using the Express Rack moderate C, temperature-cooling loop, heat is rejected by means of a liquid/air coolant manifold. Heat transfer to the manifold is performed by conduction using copper fins, by forced air convection using miniature fans, and by radiation using optically selective coatings that absorb in the infrared wavelengths. Using this combination of heat transfer mechanisms builds in redundancy to prevent thermal build up and premature bulb failure.

Turner, Mark↗
NASA NTRS2000

Non-Volatile Memory Technology Symposium 2000: Proceedings

This publication contains the proceedings for the Non-Volatile Memory Technology Symposium 2000 that was held on November 15-16, 2000 in Arlington, Virginia. The proceedings contains a wide range of papers that cover the presentations of myriad advances in the nonvolatile memory technology during the recent past including memory cell design, simulations, radiation environment, and emerging memory technologies. The papers presented in the proceedings address the design challenges and applications and deals with newer, emerging memory technologies as well as related issues of radiation environment and die packaging.

Aranki, Nazeeh↗
NASA NTRS2001

Mars Rovers: Past, Present, and Future

This viewgraph presentation provides information on the exploration of Mars through the use of rover vehicles. Mars is considered an interesting planet because it is the most like Earth of all known planets, and it may have or have had water on or below its surface. There are many different engineering design challenges for roving vehicles intended for Mars. These include: communications time delay, narrow communications bandwidth, extreme temperatures, rough and rocky terrain, the lack of a global positioning system, and dust. The Sojourner Rover specifications are provided including wheel diameter and instruments. There are prototypes being tested at NASA's Ames Research Center of the next generation Mars rovers.

Bualat, Maria↗