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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

A transceiver module of the Mu radar

The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.

Kato, S.↗
NASA NTRS1984

Earth Observing System, Conclusions and Recommendations

The following Earth Observing Systems (E.O.S.) recommendations were suggested: (1) a program must be initiated to ensure that present time series of Earth science data are maintained and continued. (2) A data system that provides easy, integrated, and complete access to past, present, and future data must be developed as soon as possible. (3) A long term research effort must be sustained to study and understand these time series of Earth observations. (4) The E.O.S. should be established as an information system to carry out those aspects of the above recommendations which go beyond existing and currently planned activities. (5) The scientific direction of the E.O.S. should be established and continued through an international scientific steering committee.

Source record↗
NASA NTRS1984

Solar-terrestrial data access distribution and archiving

It is recommended that a central data catalog and data access network (CDC/DAN) for solar-terrestrial research be established, initially as a NASA pilot program. The system is envisioned to be flexible and to evolve as funds permit, starting from a catalog to an access network for high-resolution data. The report describes the various functional requirements for the CDC/DAN, but does not specify the hardware and software architectures as these are constantly evolving. The importance of a steering committee, working with the CDC/DAN organization, to provide scientific guidelines for the data catalog and for data storage, access, and distribution is also stressed.

Source record↗
NASA NTRS1983

Generation and evoluation of near-optimum vertical flight profiles

The overall objectives of this research effort have been to develop and evaluate algorithms and flight management concepts for minimization of fuel or direct operating costs. These concepts are to be used for flight planning or for on-board computation and steering of turbojet transport aircraft in the vertical path. Within this research context, a computer program, called OPTIM, has been developed to use these algorithms to generate near-optimum vertical reference profiles. OPTIM contains control options to examine effects of various flight constraints on cost performance. A companion program, called TRAGEN, was developed to simulate an aircraft flying along a given vertical reference profile. TRAGEN is used to verify OPTIM's output , to examine the effects of parameter value uncertainty (such as prevailing wind), and to compare cost performance of profiles generated by different techniques. This paper describes OPTIM and TRAGEN and presents examples of the programs utility.

Sorensen, J. A.↗
NASA NTRS1982

Electronically Steerable Spherical Array capabilities and interfaces

The development of the Electronically Steerable Spherical Array (ESSA) was started in 1975. ESSA provides the inertialess antenna needed by user satellites for communication over their large coverage angles towards the Tracking Data Relay Satellite System (TDRSS). The performance of ESSA over large coverage angles is better than the performance provided by phased arrays. The primary difference between the two antenna types is the method of beam forming. The ESSA steers a beam by illuminating a set of elements which point in the desired direction. This set of elements is illuminated by a simple multipole switch called a switching power divider (SPD). Attention is given to details regarding the difference in performance between ESSA and phased arrays, the ESSA block diagram, the performance improvement achieved by phase compensation, power requirements, the four operating modes, multibeam operation, and the data interface.

Taylor, T. H., Jr.↗
NASA NTRS1984

Space station technology

In an evaluation of the current technological basis for a space station, the Space Station Technology Steering Committee (SSTSC) came to the conclusion that a space station could certainly be made with existing technology. It was, however, found that state-of-the-art technology would not provide for the evolutionary growth aspects of a long life system. In the process of its reviews, the SSTSC identified 10 specific disciplines to categorize the technology which was found to be relevant or potentially applicable to a future space station design. Attention is given to the objectives for the advanced development program, systems and operations, data management, crew and life support, power, thermal management, human capability, auxiliary propulsion, fluid management systems, attitude control and stabilization, structures and mechanisms, and communications.

Tumulty, W. T.↗
NASA NTRS1984

Centaur D-1A guidance/software system

The main body of this paper describes the evolution of the Centaur D-1A Guidance and Software System. Specifically, the performance of the explicit guidance equations, using a linear tangent steering law. Inherent flexibility exists in the equations in that they have multimission capability. They can accommodate both earth-orbital and earth-escape missions with either one or two Centaur burns. They can also guide for multi-burn orbital missions. The Centaur performance is indicated in terms of optimality (propellant usage), accuracy, flexibility and computer requirements. In the course of the Centaur Guidance development substantial changes and improvements have been made and more improvements are on the way for the Shuttle/Centaur Guidance. It is the intent of this paper to describe, provide insight into, and identify certain unique aspects of the individual Centaur flight profiles. Mission profile(s) are described narratively with some numerical data given in cases where it may be useful.

Gordan, A. L.↗
NASA NTRS1986

Compact Hybrid Automotive Propulsion System

Power train proposed for experimental vehicle powered by internal combustion engine and electric motor. Intended for front-wheel drive automobile, power train mass produced using existing technology. System includes internal-combustion engine, electric motor, continuously variable transmission, torque converter, differential, and control and adjustment systems for electric motor and transmission. Continuously variable transmission integrated into hydraulic system that also handles power steering and power brakes. Batteries for electric motor mounted elsewhere in vehicle.

Lupo, G.↗
NASA NTRS1984

Laser balancing system for high material removal rates

A laser technique to remove material in excess of 10 mg/sec from a spinning rotor is described. This material removal rate is 20 times greater than previously reported for a surface speed of 30 m/sec. Material removal enhancement was achieved by steering a focused laser beam with moving optics to increase the time of laser energy interaction with a particular location on the circumferential surface of a spinning rotor. A neodymium:yttrium aluminum garnet (Nd:YAG) pulse laser was used in this work to evaluate material removal for carbon steel, 347 stainless steel, Inconal 718, and titanium 6-4. This technique is applicable to dynamic laser balancing.

Jones, M. G.↗
NASA NTRS1984

Numerical Modeling of the Atmosphere

Numerical models and numerical analyses of observations were used to improve the understanding of the physical processes important in global weather and climate. Results from a study of the effect of baroclinic waves on mid-latitude vertical temperature structure show that the waves' vertical eddy heat flux tend to eliminate the potential vorticity gradient near the steering level by causing the static stability to decrease rapidly with height in the lower troposphere above the boundary layer. An empirical study of the relationship between eddy heat fluxes and the meridional temperature gradient has been completed. The results indicate that the feedback in the flux-gradient system is comparable to dissipation on all time scales between the synoptic and the seasonal. The definition of the Eliassen-Palm flux and the Eliassen-Palm and non-acceleration theorems has been generalized to include eddy forcing of condensation. Calculations based on the generalized diagnostics showed that the annual mean eddy forcing of the zonal mean zonal wind is two and one half times stronger when the condensation effects are included.

Stone, P. H.↗
NASA NTRS1985

The Solid Rocket Booster Auxiliary Power Unit: Meeting the Challenge

The thrust vector control systems of the solid rocket boosters are turbine-powered, electrically controlled hydraulic systems which function through hydraulic actuators to gimbal the nozzles of the solid rocket boosters and provide vehicle steering for the Space Shuttle. Turbine power for the thrust vector control systems is provided through hydrazine fueled auxiliary power units which drive the hydraulic pumps. The solid rocket booster auxiliary power unit resulted from trade studies which indicated significant advantages would result if an existing engine could be found to meet the program goal of 20 missions reusability and adapted to meet the seawater environments associated with ocean landings. During its maturation, the auxiliary power unit underwent many design iterations and provided its flight worthiness through full qualification programs both as a component and as part of the thrust vector control system. More significant, the auxiliary power unit has successfully completed six Shuttle missions.

Hughes, R. W.↗
NASA NTRS1985

Adaptive antenna arrays for weak interfering signals

The interference protection provided by adaptive antenna arrays to an Earth station or satellite receive antenna system is studied. The case where the interference is caused by the transmission from adjacent satellites or Earth stations whose signals inadverently enter the receiving system and interfere with the communication link is considered. Thus, the interfering signals are very weak. To increase the interference suppression, one can either decrease the thermal noise in the feedback loops or increase the gain of the auxiliary antennas in the interfering signal direction. Both methods are examined. It is shown that one may have to reduce the noise correlation to impractically low values and if directive auxiliary antennas are used, the auxiliary antenna size may have to be too large. One can, however, combine the two methods to achieve the specified interference suppression with reasonable requirements of noise decorrelation and auxiliary antenna size. Effects of the errors in the steering vector on the adaptive array performance are studied.

Gupta, I. J.↗
NASA NTRS1985

Report of the Artificial Gravity Panel

Tethers can be embodied into NASA's future space station development both as an experimental facility and as a technology for systems enhancement. Early action should be taken to ensure that the basic tether system be baselined into the initial space station architecture and that further concept studies be arranged to embody this basic capability. Space station tethered satellite operations would be continuous, subject to need and occasional association with local spacecraft operations in the proximity of the space station. The use of the tether principles would be further explored for attitude control and/or attitude stabilization damping, and proximity operations. For new tether uses, action should be taken to look at the tether for holding storage uses, proximity operations, and for extension of the capabilities of attached payloads systems. These applications should emphasize dynamic off-vertical tethers, rapid deployment, active-steered tethers, tether-boom combinations, and other concepts.

Butler, G.↗
NASA NTRS1982

Middle Atmosphere Program. Handbook for MAP, volume 4

Topics include winter in the Northern Hemisphere, temperature measurement, geopotential heights, wind measurement, atmospheric motions, photochemical reactions, solar spectral irradiance, trace constituents, tides, gravity waves, and turbulence. Highlights from the Map Steering Committee and a Map Open Meeting including organizational structure are also given.

Sechrist, C. F., Jr.↗
NASA NTRS1982

Middle Atmosphere Program. Handbook for MAP, volume 6

A directory of scientists associated with the Middle Atmosphere Program (MAP) is presented. The MAP steering committee, the standing committees, MAP study groups, and MAP projects are mentioned along with the MAP secretariat and regional consultative group.

Sechrist, C. F., Jr.↗
NASA NTRS1985

Maintenance of Time and Frequency in the DSN Using the Global Positioning System

The Deep Space Network must maintain time and frequency within specified limits in order to accurately track the spacecraft engaged in deep space exploration. The DSN has three tracking complexes, located approximately equidistantly around the Earth. Various methods are used to coordinate the clocks among the three complexes. These methods include Loran-C, TV Line 10, very long baseline interferometry (VLBI), and the Global Positioning System (GPS). The GPS is becoming increasingly important because of the accuracy, precision, and rapid availability of the data; GPS receivers have been installed at each of the DSN complexes and are used to obtain daily time offsets between the master clock at each site and UTC(USNO/NBS). Calculations are made to obtain frequency offsets and Allan variances. These data are analyzed and used to monitor the performance of the hydrogen masers that provide the reference frequencies for the DSN frequency and timing system (DFT). A brief history of the GPS timing receivers in the DSN, a description of the data and information flow, data on the performance of the DSN master clocks and GPS measurement system, and a description of hydrogen maser frequency steering using these data are presented.

Clements, P. A.↗
NASA NTRS1985

First results of GPS time transfer to Australia

A Global Positioning System time transfer unit built by NBS under contract to JPL was installed at Tidbinbilla Deep Space Communications Complex of the NASA Deep Space Network in June 1983. It has been used to estimate the relationship to UTC(USNO MC) of the Tidbinbilla frequency and time system TID(FTS) based on a hydrogen maser, and thence to estimate the performance of the Australian free-running time scale UTC(AUS). Data from the first three months has been analyzed three ways: by two-hop common view using JPL as intermediary; by long-arc interpolation of measurements against space vehicle clocks; and by long-arc interpolation of GPS-Time results. Residuals from a single quadratic fit through three months of UTC(USNO MC) - TID (FTS) results were white noise with standard error 15 ns, and a flying clock measurement gave 70 ns agreement. A straight line fit through results UTC(USNO MC) - UTC (AUS) gave 90 ns standard error and 120 bns agreement. It is proposed to use the GPS measurements to steer UTS(AUS) to UTC(BIH), and to rename the existing time scale TA(AUS).

Luck, J. M.↗
NASA NTRS1984

Maintenance of time and frequency in the Jet Propulsion Laboratory's Deep Space Network using the Global Positioning System

The Deep Space Network (DSN), managed by the Jet Propulsion Laboratory for NASA, must maintain time and frequency within specified limits in order to accurately track the spacecraft engaged in deep space exploration. Various methods are used to coordinate the clocks among the three tracking complexes. These methods include Loran-C, TV Line 10, Very Long Baseline Interferometry (VLBI), and the Global Positioning System (GPS). Calculations are made to obtain frequency offsets and Allan variances. These data are analyzed and used to monitor the performance of the hydrogen masers that provide the reference frequencies for the DSN Frequency and Timing System (DFT). Areas of discussion are: (1) a brief history of the GPS timing receivers in the DSN, (2) a description of the data and information flow, (3) data on the performance of the DSN master clocks and GPS measurement system, and (4) a description of hydrogen maser frequency steering using these data.

Clements, P. A.↗