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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

LACE flight dynamics experiment

The Low Power Atmospheric Compensation Experiment (LACE) is scheduled for launch in late 1989 into a 556 km altitude circular orbit of 43 deg inclination. The LACE flight dynamics experiment is an experiment secondary to the primary LACE mission. The purpose of the experiment is to provide on-orbit systems identification of the LACE spacecraft. The structure of the LACE spacecraft is of special interest to the CSI community. It incorporates 3 deployable/retractable booms of maximum length 45.72 m (150 ft) mounted on a rectangular parallelepiped bus of mass 1,200 kg. The zenith directed gravity gradient boom is mounted on the top of the bus; the retroreflector boom is mounted forward and deployed along the velocity vector, the balance boom is mounted and pointed aft. Attitude stabilization is accomplished by means of gravity gradient torques and by a momentum wheel. The LACE flight dynamics experiment is designed to measure modal frequencies, damping ratios, and oscillation amplitudes of the LACE spacecraft, as well as the vibration intensity generated by boom deployments and retractions. It is anticipated that this experiment will provide an opportunity for improvements in the accuracy of computer simulations of flexible structures and multibody dynamics.

Fisher, Shalom↗
NASA NTRS1990

A solar power system for an early Mars expedition

As NASA looks at missions that will expand human presence in the solar system, the power requirements for such missions need to be defined, developed and analyzed. One mission under consideration consists of a 40 day manned Mars surface expedition to perform science experiments. The mission time was centered around an aerocentric longitude (Ls) of 90 deg to lessen the probability of an occurrence of a local or planetary dust storm. The mission site was arbitrarily located at the Martian equator. The power requirements were assumed to be 40 kWe for life support and experiment power during the Martian day and 20 kWe for life support during the Martian night. A solar energy system consisting of roll-out amorphous silicon arrays and a hydrogen-oxygen regenerative fuel cell energy storage system was chosen for the study. The power available from a roll-out array, when plotted against time, approaches a cosine-like curve and depends on both array area and the amount of solar irradiance impinging on its horizontal surface. The array is sized to provide at least 20 KWe when the sun is 12.5 deg above the horizon and ramp up to 140 kWe peak power at Martian noon. In this configuration, the array is capable of supplying 40 KWe continuously to the user for the majority of the Martian day while supplying the excess energy to the electrolyzer portion of the energy storage system. A roll-out, pumped loop radiator system is used to dissipate the waste heat produced by the fuel cell. The power management and distribution system inverts the power from the individual solar array sub-modules and the fuel cell stacks and connects them to a 440 VAC single phase 20 kHz main bus. The total power system is comprised of 80 individual solar array modules with an integral bus and three energy storage modules consisting of fuel cell and electrolyzer stacks, reactant storage tanks, and a roll-out radiator. Power system mass, stowed volume, and deployed area were determined. Day/night power splits of 40/10 kWe, 40/30 kWe, and 40/40 kWe were also considered to determine the impact of a range of nighttime power requirements on the baseline system.

Mckissock, Barbara I.↗
NASA NTRS1989

Hybrid interconnection structures for real-time parallel processing

The use of hybrid interconnection structures that combine link connections and bus connections for real-time parallel processing is discussed. Idealistic parallel computation models for two real-time computing applications are described with attention given to a tightly coupled network model for object tracking and a network model for image processing. Consideration is given to the following different interconnection structures: the crossbar, the hypercube, the circular linked array, and the bus array.

Kim, K. H.↗
NASA NTRS1989

COLD-SAT - An orbital cryogenic hydrogen technology experiment

The COLD-SAT spacecraft will perform subcritical liquid hydrogen storage and transfer experiments under low-gravity conditions to provide engineering data for future space transportation missions. Consisting of an experiment module mated to a spacecraft bus, COLD-SAT will be placed in an initial 460 km circular orbit by an Atlas I commercial launch vehicle. After deployment, the three-axis-controlled spacecraft bus will provide electric power, experiment control and data management, communications, and attitude control along with propulsive acceleration levels ranging from 10 (-6) to 10(-4) g. These accelerations are an important aspect of some of the experiments, as it is desired to know the effects that low gravity levels might have on the heat and mass transfer processes involved. The experiment module will contain the three liquid hydrogen tanks, valves, pressurization equipment, and instrumentation. At launch all the hydrogen will be in the largest tank, which has helium-purged MLI and is loaded and topped off by the hydrogen tanking system used for the Centaur upper stage of the Atlas. The two smaller tanks will be utilized in orbit for performing some of the experiments. The experiments are grouped into two classes on the basis of their priority, and include six regarded as enabling technology and nine regarded as enhancing technology.

Schuster, J. R.↗
NASA NTRS1989

20 kHz main inverter unit

A proof-of-concept main inverter unit has demonstrated the operation of a pulse-width-modulated parallel resonant power stage topology as a 20-kHz ac power source driver, showing simple output regulation, parallel operation, power sharing and short-circuit operation. The use of a two-stage dc input filter controls the electromagnetic compatibility (EMC) characteristics of the dc power bus, and the use of an ac harmonic trap controls the EMC characteristics of the 20-kHz ac power bus.

Hussey, S.↗
NASA NTRS1990

High heat flux single phase heat exchanger

This paper presents the results obtained to date in a program to develop a high heat flux, single-phase heat exchanger for spacecraft thermal management. The intended application is a net generation interface heat exchanger to couple the crew module water thermal bus to the two-phase ammonia main thermal bus in the Space Station Freedom. The large size of the interface heat exchanger is dictated by the relatively poor water-side heat transfer characteristics. The objective of this program is to develop a single-phase heat transfer approach which can achieve heat fluxes and heat transfer coefficients comparable to those of the evaporation ammonia side. A new heat exchanger concept has been developed to meet these objecties. The main feature of this heat exchanger is that it can achieve very high heat fluxes with a pressure drop one to two orders of magnitude lower than those of previous microchannel or jet impingement high heat flux heat exchangers. This paper describes proof-of-concept experiments performed in air and water and presents analytical model of the heat exchanger.

Valenzuela, Javier A.↗
NASA NTRS1990

A model-based approach to the symbolic control of space subsystems

A multilayered approach to the symbolic control of complex electromechanical assemblies, such as spaceborne thermal, power, and life subsystems, is discussed. An example of this approach is given in some recent tests of the Thermal Expert System (TEXSYS) in control of the Boeing Aerospace Thermal Bus System (BATBS), a prototype two-phase Space Station Freedom thermal bus. The BATBS hardware requires read-update-act cycles of under a minute, and it is subject to dynamic reconfiguration while operating. These performance requirements are addressed by layering model-based expert system software on a conventional numerical data acquisition and control system. TEXSYS test results demonstrate both nominal control and fault recovery actions with the BATBS. Dynamic modification of the symbolic model used in this approach is compared to that of a classical numerical adaptive controller.

Glass, B. J.↗
NASA NTRS1990

Low-temperature thermal control for a lunar base

The generic problem of rejecting low- to moderate-temperature heat from space facilities located in a hot thermal sink environment is studied, and the example of a lunar base located near the equator is described. The effective thermal sink temperature is often above or near nominal room temperature. A three heat pump assisted thermal bus concept appears to be the most viable as they are the least sensitive to environmental conditions. Weight estimates are also developed for each of the five thermal control concepts studied: (1) 149kg/kW for a central thermal loop with unitary heat pumps; (2) 133 kg/kW for a conventional bus connected to large, central heat pumps at the radiator; (3) 134 kg/kW for a central, dual loop heat pump concept; (4) 95 kg/kW for the selective field-of-view radiator; and (5) 126 kg/kW for the regolith concept.

Swanson, Theodore D.↗
NASA NTRS1991

Final Report

The discussion of simulators and simulation, data aquisition and transmission and evaluation of Ada compilers and programming environments is presented. The following subject areas are covered: Bus 1553B software development; simulator development; and Ada programs to interface with C-software which drives PC-based interface cards for 1553B bus.

Deacetis, Louis A.↗
NASA NTRS1989

Transportable telemetry workstation

The goal was to complete the design of a prototype for a Transportable Telemetry Workstation (TTW). The Macintosh 2 is used to provide a low-cost system which can house real-time cards mounted on the NuBus inside the Macintosh 2 plus provide a standardized user interface on the Macintosh 2 console. Prior to a telemetry run, the user will be able to configure his real-time telemetry processing functions from the Macintosh 2 console. During a telemetry run, the real-time cards will store the telemetry data directly on a hard disk while permitting viewing of the data cards on the Macintosh 2 console on various selectable formats. The user will view the cards in terms of the functions they perform and the selectable paths through the cards, it is not required to become involved directly in hardware issue except in terms of the functional configuration of the system components. The TTW will accept telemetry data from an RS422 serial input data bus, pass it through a frame synchronizer card and on to a real time controller card via a telemetry backplane bus. The controller card will then route the data to a hard disk through a SCSI interface, and/or to a user interface on the Macintosh 2 console by way of the Macintosh 2 NuBus. The three major components to be designed, therefore, are the TTW Controller Card, the TTW Synchronizer Card, and the NuBus/Macintosh 2 User Interface. Design and prototyping of this state-of-the-art, transportable, low-cost, easy-to-use multiprocessor telemetry system is continuing. Other functions are planned for the future.

Collins, Aaron S.↗
NASA NTRS1989

The transient performance of a two-phase fluid reservoir

Thermal control of future large, high power spacecraft will require a two-phase fluid central bus. The two-phase fluid reservoir is a critical component in the two-phase fluid bus. It both controls the saturation temperature and provides a space for volumetric changes. A dynamic reservoir simulation model does not currently exist, but it is needed to expedite efforts and reduce risk. During 1989 an effort was made to develop a simulation model of the transient performance of a two-phase fluid reservoir. As a beginning, a preliminary model was developed. It is based upon component mathematical models in lumped parametric form and build upon five component mathematical models for calculating dynamic responses of two-phase fluid reservoirs, primary feedback elements, controller commands, heater actuators, and reservoir heaters. As much as possible, the model took advantage of the available SINDA'85/FLUINT thermal/fluid integrator. Additional calculation logic and computer subroutines were developed to complete implementation of the model. The model is capable of simulating dynamic response of an equilibrium two-phase fluid reservoir. Modification of the model to include the liquid/vapor nonequilibrium is required for applications of the model to simulate performance of reservoir in which the liquid and vapor phases of the reservoir fluid are not in equilibrium. In addition, the model in its present form, needs to be refined in several respects. More empirical data are needed to guide the model development. The model may then be used to conduct a full parametric study of two-phase fluid reservoirs. More complexities in two-phaes flow regions in laboratory and flight conditions may have to be considered eventually if empirical data cannot be simulated satisfactorily. System with other components arrangement also need to be simulated if optimization is ever to be attained. The present model does, however, preliminarily demonstrates that such analyses are quite possible and offers a far less expensive method to understand the transient of a two-phase fluid reservoir system than a totally headware approach.

Chi, Joseph↗
NASA NTRS1991

A universal computer control system for motors

A control system for a multi-motor system such as a space telerobot, having a remote computational node and a local computational node interconnected with one another by a high speed data link is described. A Universal Computer Control System (UCCS) for the telerobot is located at each node. Each node is provided with a multibus computer system which is characterized by a plurality of processors with all processors being connected to a common bus, and including at least one command processor. The command processor communicates over the bus with a plurality of joint controller cards. A plurality of direct current torque motors, of the type used in telerobot joints and telerobot hand-held controllers, are connected to the controller cards and responds to digital control signals from the command processor. Essential motor operating parameters are sensed by analog sensing circuits and the sensed analog signals are converted to digital signals for storage at the controller cards where such signals can be read during an address read/write cycle of the command processing processor.

Szakaly, Zoltan F.↗
NASA NTRS1990

Performance results of Grumman prototype Space Station Space Erectable Radiator System ground test articles

The paper addresses individual-radiator performance results of the prototype Space Erectable Radiator System (SERS) in both ambient and thermal vacuum environments. The radiator design utilizing a two-phase fluid loop is outlined, along with SERS design requirements, radiator panel hardware, and whiffletree clamp hardware providing a dry-contact interface of the SERS panel with the heat exchanger of the thermal bus. It is observed that throughout integrated thermal-bus tests, SERS panels managed the load demands whether interfacing with twin condensers, in parallel-flow configuration, or with shear-flow condensers, in a cross-flow configuration. It is found that the insulation losses in the integrated and stand-alone test points are approximately 2 to 6 pct. The motorized whiffletree clamp is seen as performing satisfactorily during remote operations as well as maintaining 28,800-lb force throughout the test duration without requiring further adjustments.

Gisondo, Francine↗
NASA NTRS1990

Control of multiple resonant power processors in a multi-source system

Analysis and test results show that phasor-regulated, Mapham-derived resonant inverters can be paralleled to provide standardizing interfaces for multiple sources on a utility-type, aerospace power distribution bus. The basic sources do not require matching in any way, and may have grossly different characteristics. Fully stable system architectures with multiple sources, parallel/redundant distribution buses, and a wide variety of loads can be easily constructed and controlled. The commands and parameters available for system control allow for tight tolerance bus voltage control, and absolute power-sharing control from the various sources over the full range of possible source and load variations. That level of control enables simplified load power processing hardware and the distribution of losses to optimally load the source thermal control system. Positive control of all system performance and allocation of losses are not required by all missions or vehicles, and overall vehicle considerations do not always require the loads on vehicle energy sources and thermal control systems to be balanced. In those cases, power system control can be simplified, and a hierarchical set of defaults can be substituted for computer-generated or supervisory input commands to allow for stable, fully autonomous system operation.

Mildice, James↗
NASA NTRS1990

Galileo spacecraft power management and distribution system

The Galileo PMAD (power management and distribution system) is described, and the design drivers that established the final as-built hardware are discussed. The spacecraft is powered by two general-purpose heat-source-radioisotope thermoelectric generators. Power bus regulation is provided by a shunt regulator. Galileo PMAD distributes a 570-W beginning of mission (BOM) power source to a user complement of some 137 load elements. Extensive use of pyrotechnics requires two pyro switching subassemblies. They initiate 148 squibs which operate the 47 pyro devices on the spacecraft. Detection and correction of faults in the Galileo PMAD is an autonomous feature dictated by requirements for long life and reliability in the absence of ground-based support. Volatile computer memories in the spacecraft command and data system and attitude control system require a continuous source of backup power during all anticipated power bus fault scenarios. Power for the Jupiter Probe is conditioned, isolated, and controlled by a Probe interface subassembly. Flight performance of the spacecraft and the PMAD has been successful to date, with no major anomalies.

Detwiler, R. C.↗
NASA NTRS1990

Modeling and simulation of the space platform power system

A comprehensive computer-aided modeling and simulation technique for the space platform power system is described. Large-signal and small-signal modeling is presented for the system components. The component models have been integrated to form the complete power system model. The system model is shown to be a powerful tool in simulating the behavior of the system with variation of illumination level and load. It can be used to study the bus regulation in each mode and to observe mode changes as the solar array is subjected to transitions from sunlight to eclipse and back to sunlight. System simulations show how the bus regulation is maintained by activating the shunt switching unit, the charger, or the discharger, depending on the available illumination level. The system model is suitable for verifying hardware results of for analyzing the performance of a proposed system where hardware testing is not feasible. The EASY5 dynamic analysis program is used as the host software for the modeling and simulation.

Patil, A. R.↗
NASA NTRS1991

TEXSYS - A large scale demonstration of model-based real-time control of a Space Station subsystem

A hybrid approach to qualitative and temporal reasoning, using a device-oriented model-based representation in conjunction with both consistency-based and classification diagnosis methods, can be effectively used to monitor and control a complex electromechanical system. An example of this approach is given in some recent tests of the Thermal Expert System (TEXSYS) in control of the Boeing Aerospace Thermal Bus System (BATBS), a prototype two-phase Space Station Freedom thermal bus. The constraints of realtime performance and changing target hardware led to significant changes in the initial approach, including a reduction in the use of deep structural reasoning and the addition of temporal reasoning capabilities. TEXSYS test results show the successful completion of both nominal control and fault recovery actions with the BATBS.

Glass, B. J.↗
NASA NTRS1992

Initializing Embedded Data Processors From A Single Source

Initial-computer-program-loading system provides startup information to all embedded data processors (EDP's) in general-purpose computer system. Remote processors given image of startup diskette so real local diskette and drive unneeded. System less complex and equipment costs less. Additional benefit, initial program loading tests bus. If boot-up program transmitted correctly, bus assumed to be operating properly.

Chavez, Edward A.↗