SEARCH · Search NASA

Results for “end of performance”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30

All sources NASA NTRS DOE OSTI

NASA NTRS1996

Characterization testing of MEASAT GaAs/Ge solar cell assemblies

The first commercial communications satellite with gallium-arsenide on germanium (GaAs/Ge) solar arrays is scheduled for launch in December 1995. The spacecraft, named MEASAT, was built by Hughes Space and Communications Company. The solar cell assemblies consisted of large area GaAs/Ge cells supplied by Spectrolab Inc. with infrared reflecting (IRR) coverglass supplied by Pilkington Space Technology. A comprehensive characterization program was performed on the GaAs/Ge solar cell assemblies used on the MEASAT array. This program served two functions; first to establish the database needed to accurately predict on-orbit performance under a variety of conditions; and second, to demonstrate the ability of the solar cell assemblies to withstand all mission environments while still providing the required power at end-of-life. Characterization testing included measurement of electrical performance parameters as a function of radiation exposure, temperature, and angle of incident light; reverse bias stability; optical and thermal properties; mechanical strength tests, panel fabrication, humidity and thermal cycling environmental tests. The results provided a complete database enabling the design of the MEASAT solar array, and demonstrated that the GaAs/Ge cells meet the spacecraft requirements at end-of-life.

Brown, Mike R.↗

NASA NTRS1994

Telecommunications End-to-End Systems Monitoring on TOPEX/POSEIDON: Tools and Techniques

The TOPEX/Poseidon Project Satellite Performance Analysis Team's (SPAT) roles and responsibilities have grown to include functions that are typically performed by other teams on JPL flight projects. In particular, SPAT Telecommunication's role has expanded beyond the nominal function of monitoring, assessing, characterizing, and trending the spacecraft RF/telecom subsystem to one of End-to-End Information Systems (EEIS) monitoring. This has been accomplished by taking advantage of the spacecraft and ground data system structures and protocols.

telecom↗

NASA NTRS1988

Finite area combustor theoretical rocket performance

Previous to this report, the computer program of NASA SP-273 and NASA TM-86885 was capable of calculating theoretical rocket performance based only on the assumption of an infinite area combustion chamber (IAC). An option was added to this program which now also permits the calculation of rocket performance based on the assumption of a finite area combustion chamber (FAC). In the FAC model, the combustion process in the cylindrical chamber is assumed to be adiabatic, but nonisentropic. This results in a stagnation pressure drop from the injector face to the end of the chamber and a lower calculated performance for the FAC model than the IAC model.

Gordon, Sanford↗

NASA NTRS2005

Hubble Space Telescope Magnetometer and Two-Gyro Control Law Design, Implementation, and On-Orbit Performance

For f i h years, the science mission of the Hubble Space Telescope (HST) required using at least three of six rate gyros for attitude control. In the past, HST has mitigated gyro hardware failures by replacement of the failed units through Space Shuttle Servicing Missions. Following the tragic loss of Space Shuttle Columbia on STS-107, the desire to have a safe haven for astronauts during missions has resulted in the cancellation of all planned maxu14 missions to HST. While a robotic servicing mission is being currently being planned, controlling with alternate sensors to replace failed gyros can extend the HST Science mission until the robotic mission can be performed and extend science at HST s end of life. A two-gym control law has been designed and implemented using magnetometers (Magnetic Sensing System - MSS), fixed head star trackers (FHSTs), and Fine Guidance Sensors (FGSs) to control vehicle rate about the missing gyro axis. The three aforementioned sensors are used in succession to reduce HST boresight jitter to less than 7 milli-arcseconds rms and attitude error to less than 10 milli-arcseconds prior to science imaging. The MSS and 2-Gyro (M2G) control law is used for large angle maneuvers and attitude control during earth occultation of FHSTs and FGSs. The Tracker and 2-Gyro (T2G) control law dampens M2G rates and corrects the majority of attitude error in preparation for guide star acquisition with the FGSs. The Fine Guidance Sensor and 2-Gyro (F2G) control law d a m p T2G rates and controls HST attitude during science imaging. This paper describes the M2G control law. Details of M2G algorithms are presented, including computation of the HST 3-axis attitude error estimate, design of the M2G control law, SISO hear stability analyses, and restrictions on operations to maintain the h d t h and safety requirement of a 10degree maximum attitude error. Results of simulations performed in HSTSIM, a high-fidelity non-linear time domain simulation, are presented to predict HST on-orbit performance in attitude hold and maneuver modes. Simulation results are compared to on-orbit data from M2G flight tests performed in November and December 2004 and February 2005. Flight telemetry, using a currently available third gyro, shows that HST attitude error with the new M2G control law is maintained below the 10-degree requirement, and attitude errors are under 2 degrees for 95% of the time.

Wirzburger, John H.↗

NASA NTRS2010

Summary of Test Results From a 1 kW(sub e)-Class Free-Piston Stirling Power Convertor Integrated With a Pumped NaK Loop

As a step towards development of Stirling power conversion for potential use in Fission Surface Power (FSP) systems, a pair of commercially available 1 kW class free-piston Stirling convertors was modified to operate with a NaK liquid metal pumped loop for thermal energy input. This was the first-ever attempt at powering a free-piston Stirling engine with a pumped liquid metal heat source and is a major FSP project milestone towards demonstrating technical feasibility. The tests included performance mapping the convertors over various hot and cold-end temperatures, piston amplitudes and NaK flow rates; and transient test conditions to simulate various start-up and fault scenarios. Performance maps of the convertors generated using the pumped NaK loop for thermal input show increases in power output over those measured during baseline testing using electric heating. Transient testing showed that the Stirling convertors can be successfully started in a variety of different scenarios and that the convertors can recover from a variety of fault scenarios.

Briggs, Maxwell H.↗

NASA NTRS2010

Summary of Test Results From a 1 kWe-Class Free-Piston Stirling Power Convertor Integrated With a Pumped NaK Loop

Briggs, Maxwell H.↗

NASA NTRS1982

RCA SATCOM in-orbit experience: An update

The SATCOM in-orbit battery performance was evaluated. The capacitance and constant current charge rates for each of the three batteries were monitored. A typical eclipse discharge profile was generated and attendant reconditioning recharge conditions were considered. Battery temperatures, pressures, and average battery voltages are presented in tabular form. In-orbit data from monitoring the end of discharge voltage during eclipses, a key performance parameter, are also given.

Stewart, D.↗

NASA NTRS1998

High End Computer Network Testbedding at NASA Goddard Space Flight Center

The Earth & Space Data Computing (ESDC) Division, at the Goddard Space Flight Center, is involved in development and demonstrating various high end computer networking capabilities. The ESDC has several high end super computers. These are used to run: (1) computer simulation of the climate systems; (2) to support the Earth and Space Sciences (ESS) project; (3) to support the Grand Challenge (GC) Science, which is aimed at understanding the turbulent convection and dynamos in stars. GC research occurs in many sites throughout the country, and this research is enabled by, in part, the multiple high performance network interconnections. The application drivers for High End Computer Networking use distributed supercomputing to support virtual reality applications, such as TerraVision, (i.e., three dimensional browser of remotely accessed data), and Cave Automatic Virtual Environments (CAVE). Workstations can access and display data from multiple CAVE's with video servers, which allows for group/project collaborations using a combination of video, data, voice and shared white boarding. The ESDC is also developing and demonstrating the high degree of interoperability between satellite and terrestrial-based networks. To this end, the ESDC is conducting research and evaluations of new computer networking protocols and related technologies which improve the interoperability of satellite and terrestrial networks. The ESDC is also involved in the Security Proof of Concept Keystone (SPOCK) program sponsored by National Security Agency (NSA). The SPOCK activity provides a forum for government users and security technology providers to share information on security requirements, emerging technologies and new product developments. Also, the ESDC is involved in the Trans-Pacific Digital Library Experiment, which aims to demonstrate and evaluate the use of high performance satellite communications and advanced data communications protocols to enable interactive digital library data access between the U. S. Library of Congress, the National Library of Japan and other digital library sites at 155 MegaBytes Per Second. The ESDC participation in this program is the Trans-Pacific access to GLOBE visualizations in real time. ESDC is participating in the Department of Defense's ATDNet with Multiwavelength Optical Network (MONET) a fully switched Wavelength Division Networking testbed. This presentation is in viewgraph format.

Gary, James Patrick↗

NASA NTRS1962

Paraglider Recovery Systems

In 1945 it occurred to the writer that if we could discover how to make flexible wings that could be packaged and deployed somewhat like a parachute, such wings would have many new applications as well as replacing some parachutes and rigid wings. Previous uses of flexible materials in aerodynamic surfaces - parachutes, kites, boat sails, and wind mills - were reviewed, and some crude experiments were performed with gliders and kites. Before the end of 1948, the device now generally called a paraglider was evolved and developed sufficiently to merit a patent application. The study was continued privately as time permitted, and in 1954 a short paper on the subject was presented to an audience of about 50 Reserve Air Force officers. This paper was given rather wide distribution, although it suffers from lack of the many kite and glider demonstrations of the original presentation. Little serious interest was shown by the aeronautical community, however, until about a year after Sputnik I. In December 1958 the flexible-wing concept was presented to the Langley Committee on General Aerodynamics with the aid of the hurriedly prepared charts shown in figure 1, faithfully reproduced here for historical purposes.

Flexible wing↗

NASA NTRS1977

Task and work performance on Skylab missions 2, 3, and 4: Time and motion study: Experiment M151

Human task performance was evaluated under weightlessness conditions during long duration space flight in order to study the characteristics of the adaptation function. Results show that despite pronounced variability in training schedules and in initial reaction to the Skylab environment, in-flight task performance was relatively equivalent among Skylab crews, and behavioral performance continued to improve from beginning to end of all missions.

Kubis, J. F.↗

NASA NTRS1979

Elastomer mounted rotors - An alternative for smoother running turbomachinery

This paper describes the design of elastomeric bearing supports for a rotor built to simulate the power turbine of an advanced gas turbine engine which traverses two bending critical speeds. The elastomer dampers were constructed so as to minimize rotor dynamic response at the critical speeds. Results are presented of unbalance response tests performed with two different elastomer materials. These results showed that the resonances on the elastomer-mounted rotor were well damped for both elastomer materials and showed linear response to the unbalance weights used for response testing. Additional tests were performed using solid steel supports at either end (hand-mounted), which resulted in drastically increased sensitivity and nonlinear response, and with steel supports in one end of the rotor and the elastomer at the other, which yielded results which were between the soft- and hard-mounted cases. It is concluded that elastomeric supports are a viable alternative to other methods of mounting flexible rotors, that damping was well in excess of predictions and that elastomeric supports are tolerant of small rotor misalignments.

Tecza, J. A.↗

NASA NTRS1981

DSN frequency and timing system Mark 3-81

The DSN frequency and timing system configuration and functions are described. The text is historical in nature, ending with the current system design and performance.

Curtright, J. B.↗

NASA NTRS1982

Chemical mixing model studies of lunar orbital geochemical data - Apollo 16 and 17 highlands compositions

Chemical mixing model studies of lunar geochemical data for the central and Taurus-Littrow lunar highlands were performed utilizing pristine highland rock types as end member compositions. The central highlands show considerable diversity in composition; anorthosite is the principal rock type in the Apollo 16/Descartes region, while norite predominates in the highlands west of the landing site. This change in crustal composition is coincident with a major color boundary seen in earth-based multispectral data and probably represents the presence of distinct geochemical provinces within the central highlands. The Taurus-Littrow highlands are dominated by norite; anorthosite is far less abundant than in the central highlands. This suggests that the impact target for the Serenitatis basin was different than that of the Nectaris basin and further strengthens the hypothesis that the lunar highlands are petrologically heterogeneous on a regional basis. It is suggested that the lunar highlands should be viewed in terms of geochemical provinces that have undergone distinct and complex igneous and impact histories.

Spudis, P. D.↗

NASA NTRS1983

Space station propulsion system trade study

This study evaluates alternative space station propulsion system options for a range of space station configurational and operational architectures. Space station propulsion requirements ranging from those representative of the first generation space station to those of an advanced space station with a space based OTV are considered. A methodology for comparing the candidate propulsion technologies is developed which considers design/development/qualification and operational costs, system mass, performance, reliability, and other relevant parameters. Advanced propulsion systems are shown to reduce space station costs by providing higher performance but to require a larger front end investment for development and qualification. This study indicates that if the full potential of such systems is to be realized, then low cost implementations of this technology must be developed.

Garrison, P. W.↗

NASA NTRS1986

Analyzing Millimeter-Wave Mixers

Series of computer programs developed to serve as tool in understanding behavior and subsequent optimization of millimeter-wave mixers. Major program in collection is general mixer-analysis program that performs complete large- and small-signal analysis of mixer with known diode and mount characteristics. Primary objective behind programs to gain better understanding of factors that affect performance of room-temperature, single-ended Schottky-diode mixers operating above 100 GHz.

Siegel, P.↗

NASA NTRS1989

Lifetime predictions for the Solar Maximum Mission (SMM) and San Marco spacecraft

Lifetime prediction techniques developed by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) are described. These techniques were developed to predict the Solar Maximum Mission (SMM) spacecraft orbit, which is decaying due to atmospheric drag, with reentry predicted to occur before the end of 1989. Lifetime predictions were also performed for the Long Duration Exposure Facility (LDEF), which was deployed on the 1984 SMM repair mission and is scheduled for retrieval on another Space Transportation System (STS) mission later this year. Concepts used in the lifetime predictions were tested on the San Marco spacecraft, which reentered the Earth's atmosphere on December 6, 1988. Ephemerides predicting the orbit evolution of the San Marco spacecraft until reentry were generated over the final 90 days of the mission when the altitude was less than 380 kilometers. The errors in the predicted ephemerides are due to errors in the prediction of atmospheric density variations over the lifetime of the satellite. To model the time dependence of the atmospheric densities, predictions of the solar flux at the 10.7-centimeter wavelength were used in conjunction with Harris-Priester (HP) atmospheric density tables. Orbital state vectors, together with the spacecraft mass and area, are used as input to the Goddard Trajectory Determination System (GTDS). Propagations proceed in monthly segments, with the nominal atmospheric drag model scaled for each month according to the predicted monthly average value of F10.7. Calibration propagations are performed over a period of known orbital decay to obtain the effective ballistic coefficient. Progagations using plus or minus 2 sigma solar flux predictions are also generated to estimate the despersion in expected reentry dates. Definitive orbits are compared with these predictions as time expases. As updated vectors are received, these are also propagated to reentryto continually update the lifetime predictions.

Smith, E. A.↗

NASA NTRS1990

Navigation accuracies for GPS demonstration on Topex/Poseidon

When Topex/Poseidon, is launched in June 1992, the joint United States/French oceanographic satellite mission will carry a developmental Global Positioning System (GPS) receiver on board to support the planned GPS demonstration experiment. The navigation operations aspect of the demonstration will develop software and operational procedures for the GPS Data Processing Facility (GDPF) at NASA's Jet Propulsion Laboratory. This paper presents simulations and covariance analysis of operational scenarios in support of the GDPF. Multi-orbit filter techniques using GPS carrier phase and P-code pseudo-range are studied both to tune the filter parameters and to determine feasible arc lengths for use in operations. In addition, a baseline operational scenario is presented with performance results given in terms of end-to-end processing times and computational loading based on a prototype version of the operational software.

Williams, B. G.↗

NASA NTRS1991

Balancing antagonistic time and resource utilization constraints in over-subscribed scheduling problems

In this paper, we report work aimed at applying concepts of constraint-based problem structuring and multi-perspective scheduling to an over-subscribed scheduling problem. Previous research has demonstrated the utility of these concepts as a means for effectively balancing conflicting objectives in constraint-relaxable scheduling problems, and our goal here is to provide evidence of their similar potential in the context of HST observation scheduling. To this end, we define and experimentally assess the performance of two time-bounded heuristic scheduling strategies in balancing the tradeoff between resource setup time minimization and satisfaction of absolute time constraints. The first strategy considered is motivated by dispatch-based manufacturing scheduling research, and employs a problem decomposition that concentrates local search on minimizing resource idle time due to setup activities. The second is motivated by research in opportunistic scheduling and advocates a problem decomposition that focuses attention on the goal activities that have the tightest temporal constraints. Analysis of experimental results gives evidence of differential superiority on the part of each strategy in different problem solving circumstances. A composite strategy based on recognition of characteristics of the current problem solving state is then defined and tested to illustrate the potential benefits of constraint-based problem structuring and multi-perspective scheduling in over-subscribe scheduling problems.

Smith, Stephen F.↗