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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 379 records · Page 21

All sources NASA NTRS DOE OSTI

NASA NTRS1986

Switching System for Redundant Power Supplies

Load-transfer unit connects airborne computer to standby power supply in case primary supply fails. Concept adaptable to systems in which power interruptions cannot be tolerated; for example, computers with volatile memories, safety equipment, and precise timers. Load-transfer unit monitors voltages and load current. Microprocessor controls transistor switches that connect load to whichever power supply has highest priority and correct voltage.

Bradford, M.↗

NASA NTRS1987

Gain-Compensating Circuit For NDE and Ultrasonics

High-frequency gain-compensating circuit designed for general use in nondestructive evaluation and ultrasonic measurements. Controls gain of ultrasonic receiver as function of time to aid in measuring attenuation of samples with high losses; for example, human skin and graphite/epoxy composites. Features high signal-to-noise ratio, large signal bandwidth and large dynamic range. Control bandwidth of 5 MHz ensures accuracy of control signal. Currently being used for retrieval of more information from ultrasonic signals sent through composite materials that have high losses, and to measure skin-burn depth in humans.

Kushnick, Peter W.↗

NASA NTRS1988

Fundamental principles of hollow-cathode-discharge operations in space and the design of a rocket-borne demonstration

The issue of hollow-cathode operations in space is treated from the point of view of fundamental principles of plasma interactions and their control over currents involving the device, the spaceborne vehicle, and the ambient space plasma. Particular attention is given to collective plasma processes, the effects of the ambient magnetic field, and the high probability of plasma turbulence triggered by hallow cathode operations. The paper presents a rocket payload and experiment scenario designed for accommodation on a Black Brant booster, launched from a midlatitude site to an apogee in excess of 400 km.

Szuszczewicz, Edward P.↗

NASA NTRS1989

Impact of tether cutting on onboard navigation during the Tethered Satellite Mission-1

The first Tethered Satellite System mission (TSS-1) is manifested for Shuttle Flight STS-44 in January of 1991. The TSS mission presents a new challenge to engineers, requiring advanced guidance, navigation and control concepts. Current NASA flight rules require that the navigational state of the Orbiter at deorbit burn be known to an accuracy of 20 nautical miles. Response of the Shuttle crew to this contingency may involve cutting the tether prior to a complete retrieval. The degradation of the navigational state accuracy as modelled by Shuttle navigation system is examined. Responses to the loss of communication scenario are proposed for two cases. The first case examines navigational performance during a nominal attitude profile. The second case is identical to the first, with the inclusion of modelled tether electrodynamical forces. Comparisons of trajectories propagated from the onboard navigational state vector and a reference ephemeris state vector were performed, with the tether cut simulated at various points during the mission. Additionally, updates to the onboard navigational state via ground uplinks were provided prior to the assumed loss of communication. Through these comparisons, the onboard navigation state error was determined. Alternative responses result from efforts to minimize this error during the various phases of TSS-1 deployment. These results demonstrated existing NASA flight rules could be violated by cutting the tether, and suggests reponses to a loss of communications contingency to maintain a more accurate navigational state.

Pirker, Dana M.↗

NASA NTRS1989

Thermoplastic coating of carbon fibers

A process is being developed which evenly coats individual carbon fibers with thermoplastic polymers. In this novel, continuous coating process, the fiber tow bundle is first spread cover a series of convex rollers and then evenly coated with a fine powder of thermoplastic matrix polymer. Next, the fiber is heated internally by passing direct current through the powder coated fiber. The direct current is controlled to allow the carbon fiber temperature to slightly exceed the flow temperature of the matrix polymer. Analysis of the thermoplastic coated carbon fiber tows produced using this continuous process indicates that 30 to 70 vol pct fiber prepregs can be obtained.

Edie, D. D.↗

NASA NTRS1990

Space Station Freedom altitude strategy

The Space Station Freedom (SSF) altitude strategy provides guidelines and assumptions to determine an altitude profile for Freedom. The process for determining an altitude profile incorporates several factors such as where the Space Shuttle will rendezvous with the SSF, when reboosts must occur, and what atmospheric conditions exist causing decay. The altitude strategy has an influence on all areas of SSF development and mission planning. The altitude strategy directly affects the micro-gravity environment for experiments, propulsion and control system sizing, and Space Shuttle delivery manifests. Indirectly the altitude strategy influences almost every system and operation within the Space Station Program. Evolution of the SSF altitude strategy has been a very dynamic process over the past few years. Each altitude strategy in turn has emphasized a different consideration. Examples include a constant Space Shuttle rendezvous altitude for mission planning simplicity, or constant micro-gravity levels with its inherent emphasis on payloads, or lifetime altitudes to provide a safety buffer to loss of control conditions. Currently a new altitude strategy is in development. This altitude strategy will emphasize Space Shuttle delivery optimization. Since propellant is counted against Space Shuttle payload-to-orbit capacity, lowering the rendezvous altitude will not always increase the net payload-to-orbit, since more propellant would be required for reboost. This altitude strategy will also consider altitude biases to account for Space Shuttle launch slips and an unexpected worsening of atmospheric conditions. Safety concerns will define a lower operational altitude limit, while radiation levels will define upper altitude constraints. The evolution of past and current SSF altitude strategies and the development of a new altitude strategy which focuses on operational issues as opposed to design are discussed.

Mcdonald, Brian M.↗

NASA NTRS1991

Advanced thermal control technology for commercial applications

A number of the technologies previously developed for the thermal control of spacecraft have found their way into commercial application. Specialized coatings and heat pipes are but two examples. The thermal control of current and future spacecraft is becoming increasingly more demanding, and a variety of new technologies are being developed to meet these needs. Closed two-phase loops are perceived to be the answer to many of the new requirements. All of these technologies are discussed, and their spacecraft and current terrestrial applications are summarized.

Swanson, Theodore D.↗

NASA NTRS1991

An intelligent control system for rocket engines - Need, vision, and issues

Several components of intelligence are defined. Within the context of these definitions an intelligent control system for rocket engines is described. The description includes a framework for development of an intelligent control system, including diagnostics, coordination, and direct control. Some current results and issues are presented.

Lorenzo, Carl F.↗

NASA NTRS1991

Range Scheduling Aid (RSA)

Range Scheduling Aid (RSA) is presented in the form of the viewgraphs. The following subject areas are covered: satellite control network; current and new approaches to range scheduling; MITRE tasking; RSA features; RSA display; constraint based analytic capability; RSA architecture; and RSA benefits.

Logan, J. R.↗

NASA NTRS1992

A new eddy current model for magnetic bearing control system design

This paper describes a new VLSI-based controller for the implementation of a Linear-Quadratic-Gaussian (LQG) theory-based control system. Use of the controller is demonstrated by design of a controller for a magnetic bearing and its performance is evaluated by computer simulation.

Feeley, Joseph J.↗

NASA NTRS1993

Representing operations procedures using temporal dependency networks

DSN Link Monitor & Control (LMC) operations consist primarily of executing procedures to configure, calibrate, test, and operate a communications link between an interplanetary spacecraft and its mission control center. Currently the LMC operators are responsible for integrating procedures into an end-to-end series of steps. The research presented in this paper is investigating new ways of specifying operations procedures that incorporate the insight of operations, engineering, and science personnel to improve mission operations. The paper describes the rationale for using Temporal Dependency Networks (TDN's) to represent the procedures, a description of how the data is acquired, and the knowledge engineering effort required to represent operations procedures. Results of operational tests of this concept, as implemented in the LMC Operator Assistant Prototype (LMCOA), are also presented.

Fayyad, Kristina E.↗

NASA NTRS1994

Carbon dioxide and water vapor production at rest and during exercise. A report on data collection for the Crew and Thermal Systems Division

The current environmental control device in the shuttle uses lithium hydroxide (LiOH) filter canisters to remove carbon dioxide (CO2) from the cabin air, requiring several bulky filter canisters that can only be used once and must be changed frequently. To alleviate a stowage problem and decrease launch weight, the Crew and Thermal Systems Division (CTSD) at the NASA Johnson Space Center has been researching a system to be used on future shuttle missions. This system uses two beds of solid amine material to absorb CO2 and water, later desorbing them to space vacuum. In this way the air scrubbing medium is regenerable and reusable. To identify the efficacy of this regenerable CO2 removal system (RCRS), CTSD began investigations in the shuttle mockup. The purpose of this investigation was to support the CTSD program by determining mean levels of carbon dioxide and water vapor production in normal, healthy males and females age-matched with the astronaut corps. Subjects' responses were measured at rest and during exercise at intensity levels equivalent to normal shuttle operation activities. The results were used to assess the adjustments made to RCRS and are reported as a reference for future investigations in shuttle environmental control.

Lee, Stuart M. C.↗

NASA NTRS1993

Converting the Minuteman missile into a small satellite launch system

Due to the Strategic Arms Reduction Talks (START) treaty between the United States and Ex-Soviet Union, 450 Minuteman 2 (MM 2) missiles were recently taken out of service. Minotaur Designs Incorporated (MDI) intends to convert the MM 2 ballistic missile from a nuclear warhead carrier into a small satellite launcher. MDI will perform this conversion by acquiring the Minuteman stages, purchasing currently available control wafers, and designing a new shroud and interfaces for the satellite. MDI is also responsible for properly integrating all systems.

Alexander, Bill↗

NASA NTRS1997

Studies on Somatic Embryogenesis in Sweetpotato

The purpose of this study was to improve the somatic embryo (SE) system for plant production of sweetpotato Ipomoea batatas L.(Lam)l. Explants isolated from SE-derived sweet potato plants were compared with control (non SE-derived) plants for their competency for SE production. Leaf explants were cultured on Murashige-Skoog (MS) medium with 2,4-dichlorophenoxy acetic acid (0.2 mg/L) and 6-benzylaminopurine (2.5 mg/L) for 2 weeks in darkness and transferred to MS medium with abscisic acid (2.5 Explants isolated from those plants developed through somatic embryo-genesis produced new somatic embryos rapidly and in higher frequency than those isolated from control plants. They also appeared to grow faster in tissue culture than the control plants. Current studies in the laboratory are examining whether plants derived from a cyclical embryogenesis system (five cycles) would have any further positive impact on the rapidity and frequency of somatic embryo development. More detailed studies using electron microscopy are expected to show the point of origin of the embryos and to allow determination of their quality throughout the cyclical process. This study may facilitate improved plant micropropagation, gene transfer and germplasm conservation in sweet potato.

Bennett, J. Rasheed↗

NASA NTRS1997

Studies for Somatic Embryogenesis in Sweet Potato

The purpose of this study was to improve the somatic embryo (SE) system for plant production of sweet potato (Ipomoea batatas L(Lam)). Explants isolated from SE-derived sweet potato plants were compared with control (non SE-derived) plants for their competency for SE production. Leaf explants were cultured on Murashige-Skoog (MS) medium with 2,4-dichlorophenoxy acetic acid (0.2 mg/L) and 6-benzylaminopurine (2.5 mg/L) for 2 weeks in darkness and transferred to MS medium with abscisic acid (2.5 mg/L). Explants isolated from those plants developed through somatic embryogenesis produced new somatic embryos rapidly and in higher frequency than those isolated from control plants They also appeared to grow faster in tissue culture than the control plants. Current studies in the laboratory are examining whether plants derived from a cyclical embryogenesis system (five cycles) would have any further positive impact on the rapidity and frequency of somatic embryo development. More detailed studies using electron microscopy are expected to show the point of origin of the embryos and to allow determination of their quality throughout the cyclical process. This study may facilitate improved plant micropropagation, gene transfer and germplasm conservation in sweet potato.

Bennett, J. Rasheed↗

NASA NTRS1997

Development of Power Electronics for a 0.2kW-Class Ion Thruster

Applications that might benefit from low power ion propulsion systems include Earth-orbit magnetospheric mapping satellite constellations, low Earth-orbit satellites, geosynchronous Earth-orbit satellite north-south stationkeeping, and asteroid orbiters. These spacecraft are likely to have masses on the order of 50 to 500 kg with up to 0.5 kW of electrical power available. A power processing unit for a 0.2 kW-class ion thruster is currently under development for these applications. The first step in this effort is the development and testing of a 0.24 kW beam power supply. The design incorporates a 20 kHz full bridge topology with multiple secondaries connected in series to obtain outputs of up to 1200 V(sub DC). A current-mode control pulse width modulation circuit built using discrete components was selected for this application. An input voltage of 28 +/- 4 V(sub DC) was assumed, since the small spacecraft for which this system is targeted are anticipated to have unregulated low voltage busses. Efficiencies in excess of 91 percent were obtained at maximum output power. The total mass of the breadboard was less than 1.0 kg and the component mass was 0.53 kg. It is anticipated that a complete flight power processor could weigh about 2.0 kg.

Pinero, Luis R.↗

NASA NTRS2000

Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes

A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. Overall stability of a two-loop control system is addressed. An optimal control allocation algorithm is designed that allocates torque commands into end-effector deflection commands, which are executed by the actuators. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. This is a significant advancement in performance over that achieved with linear, gain scheduled control systems currently being used for launch vehicles.

Shtessel, Yuri↗

NASA NTRS1995

TRACON Aircraft Arrival Planning and Optimization Through Spatial Constraint Satisfaction

A new aircraft arrival planning and optimization algorithm has been incorporated into the Final Approach Spacing Tool (FAST) in the Center-TRACON Automation System (CTAS) developed at NASA-Ames Research Center. FAST simulations have been conducted over three years involving full-proficiency, level five air traffic controllers from around the United States. From these simulations an algorithm, called Spatial Constraint Satisfaction, has been designed, coded, undergone testing, and soon will begin field evaluation at the Dallas-Fort Worth and Denver International airport facilities. The purpose of this new design is an attempt to show that the generation of efficient and conflict free aircraft arrival plans at the runway does not guarantee an operationally acceptable arrival plan upstream from the runway -information encompassing the entire arrival airspace must be used in order to create an acceptable aircraft arrival plan. This new design includes functions available previously but additionally includes necessary representations of controller preferences and workload, operationally required amounts of extra separation, and integrates aircraft conflict resolution. As a result, the Spatial Constraint Satisfaction algorithm produces an optimized aircraft arrival plan that is more acceptable in terms of arrival procedures and air traffic controller workload. This paper discusses the current Air Traffic Control arrival planning procedures, previous work in this field, the design of the Spatial Constraint Satisfaction algorithm, and the results of recent evaluations of the algorithm.

Bergh, Christopher P.↗