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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Development of ADOCS controllers and control laws. Volume 1: Executive summary

The Advanced Cockpit Controls/Advanced Flight Control System (ACC/AFCS) study was conducted by the Boeing Vertol Company as part of the Army's Advanced Digital/Optical Control System (ADOCS) program. Specifically, the ACC/AFCS investigation was aimed at developing the flight control laws for the ADOCS demonstrator aircraft that will provide satisfactory handling qualities for an attack helicopter mission. The three major elements of design considered during the study are as follows: Pilot's integrated Side-Stick Controller (SSC) -- Number of axes controlled; force/displacement characteristics; ergonomic design. Stability and Control Augmentation System (SCAS)--Digital flight control laws for the various mission phases; SCAS mode switching logic. Pilot's Displays--For night/adverse weather conditions, the dynamics of the superimposed symbology presented to the pilot in a format similar to the Advanced Attack Helicopter (AAH) Pilot Night Vision System (PNVS) for each mission phase as a function of SCAS characteristics; display mode switching logic. Volume 1 is an Executive Summary of the study. Conclusions drawn from analysis of pilot rating data and commentary were used to formulate recommendations for the ADOCS demonstrator flight control system design. The ACC/AFCS simulation data also provide an extensive data base to aid the development of advanced flight control system design for future V/STOL aircraft.

Landis, Kenneth H.↗
NASA NTRS1994

Dual-Antenna Microwave Reception Without Switching

Receiver remains connected to both antennas, transmitter switched to connect it to one or other. Combination of hybrid junction, circulators, and filter provides simultaneous reception paths from both antennas without significantly altering radiation patterns of antennas. Communication system considered for use in spacecraft and in which mechanical switch permitted on downlink but not on uplink. Applicable to terrestrial microwave communication stations subject to dual-antenna requirements.

Hartop, Robert W.↗
NASA NTRS2012

Control Algorithms Charge Batteries Faster

On March 29, 2011, NASA s Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft beamed a milestone image to Earth: the first photo of Mercury taken from orbit around the solar system s innermost planet. (MESSENGER is also the first spacecraft to orbit Mercury.) Like most of NASA s deep space probes, MESSENGER is enabled by a complex power system that allows its science instruments and communications to function continuously as it travels millions of miles from Earth. "Typically, there isn't one particular power source that can support the entire mission," says Linda Taylor, electrical engineer in Glenn Research Center s Power Systems Analysis Branch. "If you have solar arrays and you are in orbit, at some point you re going to be in eclipse." Because of this, Taylor explains, spacecraft like MESSENGER feature hybrid power systems. MESSENGER is powered by a two-panel solar array coupled with a nickel hydrogen battery. The solar arrays provide energy to the probe and charge the battery; when the spacecraft s orbit carries it behind Mercury and out of the Sun s light, the spacecraft switches to battery power to continue operations. Typically, hybrid systems with multiple power inputs and a battery acting alternately as storage and a power source require multiple converters to handle the power flow between the devices, Taylor says. (Power converters change the qualities of electrical energy, such as from alternating current to direct current, or between different levels of voltage or frequency.) This contributes to a pair of major concerns for spacecraft design. "Weight and size are big drivers for any space application," Taylor says, noting that every pound added to a space vehicle incurs significant costs. For an innovative solution to managing power flows in a lightweight, cost-effective manner, NASA turned to a private industry partner.

Source record↗
NASA NTRS1985

Development of ADOCS controllers and control laws. Volume 2: Literature review and preliminary analysis

The Advanced Cockpit Controls/Advanced Flight Control System (ACC/AFCS) study was conducted by the Boeing Vertol Company as part of the Army's Advanced Digital/Optical Control System (ADOCS) program. Specifically, the ACC/AFCS investigation was aimed at developing the flight control laws for the ADOCS demonstrator aircraft which will provide satisfactory handling qualities for an attack helicopter mission. The three major elements of design considered are as follows: Pilot's integrated Side-Stick Controller (SSC) -- Number of axes controlled; force/displacement characteristics; ergonomic design. Stability and Control Augmentation System (SCAS)--Digital flight control laws for the various mission phases; SCAS mode switching logic. Pilot's Displays--For night/adverse weather conditions, the dynamics of the superimposed symbology presented to the pilot in a format similar to the Advanced Attack Helicopter (AAH) Pilot Night Vision System (PNVS) for each mission phase as a function of ACAS characteristics; display mode switching logic. Findings from the literature review and the analysis and synthesis of desired control laws are reported in Volume 2. Conclusions drawn from pilot rating data and commentary were used to formulate recommendations for the ADOCS demonstrator flight control system design. The ACC/AFCS simulation data also provide an extensive data base to aid the development of advanced flight control system design for future V/STOL aircraft.

Landis, Kenneth H.↗
NASA NTRS1990

Space station common module network topology and hardware development

Conceptual space station common module power management and distribution (SSM/PMAD) network layouts and detailed network evaluations were developed. Individual pieces of hardware to be developed for the SSM/PMAD test bed were identified. A technology assessment was developed to identify pieces of equipment requiring development effort. Equipment lists were developed from the previously selected network schematics. Additionally, functional requirements for the network equipment as well as other requirements which affected the suitability of specific items for use on the Space Station Program were identified. Assembly requirements were derived based on the SSM/PMAD developed requirements and on the selected SSM/PMAD network concepts. Basic requirements and simplified design block diagrams are included. DC remote power controllers were successfully integrated into the DC Marshall Space Flight Center breadboard. Two DC remote power controller (RPC) boards experienced mechanical failure of UES 706 stud-mounted diodes during mechanical installation of the boards into the system. These broken diodes caused input to output shorting of the RPC's. The UES 706 diodes were replaced on these RPC's which eliminated the problem. The DC RPC's as existing in the present breadboard configuration do not provide ground fault protection because the RPC was designed to only switch the hot side current. If ground fault protection were to be implemented, it would be necessary to design the system so the RPC switched both the hot and the return sides of power.

Anderson, P.↗
NASA NTRS1990

Neutron and gamma irradiation effects on power semiconductor switches

The performance characteristics of high power semiconductor switches subjected to high levels of neutron fluence and gamma dose must be known by the designer of the power conditioning, control and transmission subsystem of space nuclear power systems. Location and the allowable shielding mass budget will determine the level of radiation tolerance required by the switches to meet performance and reliability requirements. Neutron and gamma ray interactions with semiconductor materials and how these interactions affect the electrical and switching characteristics of solid state power switches is discussed. The experimental measurement system and radiation facilities are described. Experimental data showing the effects of neutron and gamma irradiation on the performance characteristics are given for power-type NPN Bipolar Junction Transistors (BJTs), and Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). BJTs show a rapid decrease in gain, blocking voltage, and storage time for neutron irradiation, and MOSFETs show a rapid decrease in the gate threshold voltage for gamma irradiation.

Schwarze, G. E.↗
NASA NTRS1990

Neutron and gamma irradiation effects on power semiconductor switches

The performance characteristics of high-power semiconductor switches subjected to high levels of neutron fluence and gamma dose must be known by the designer of the power conditioning, control and transmission subsystem of space nuclear power systems. Location and the allowable shielding mass budget will determine the level of radiation tolerance required by the switches to meet performance and reliability requirements. Neutron and gamma ray interactions with semiconductor materials and how these interactions affect the electrical and switching characteristics of solid state power switches is discussed. The experimental measurement system and radiation facilities are described. Experimental data showing the effects of neutron and gamma irradiation on the performance characteristics are given for power-type NPN Bipolar Junction Transistors (BJTs), and Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). BJTs show a rapid decrease in gain, blocking voltage, and storage time for neutron irradiation, and MOSFETs show a rapid decrease in the gate threshold voltage for gamma irradiation.

Schwarze, G. E.↗
NASA NTRS1986

ACTS Experiments Program

An overview of the ACTS Experiments Program is presented. ACTS is being developed and will flight test the advanced technologies associated with: a Ka-band multibeam antenna, onboard signal processing and switching as well as laser communications. A nominal 3 yr experiments program is planned. Through the experiments program, the capabilities of the ACTS system will be made available to U.S. industry, university and government experimenters to test, prove the feasibility and evaluate the key ACTS system technologies. Communication modes of operation using the baseband processor and microwave switch matrix are presented, along with the antenna coverage pattern. Potential experiment categories are also presented and briefly discussed. An overall schedule of activities associated with the experiments program is outlined. Results of the ACTS Experiments Program will provide information vital to successful industry implementation of ACTS technology in a future operational system.

Schertler, R. J.↗
NASA NTRS1985

Development of ADOCS controllers and control laws. Volume 3: Simulation results and recommendations

The Advanced Cockpit Controls/Advanced Flight Control System (ACC/AFCS) study was conducted by the Boeing Vertol Company as part of the Army's Advanced Digital/Optical Control System (ADOCS) program. Specifically, the ACC/AFCS investigation was aimed at developing the flight control laws for the ADOCS demonstator aircraft which will provide satisfactory handling qualities for an attack helicopter mission. The three major elements of design considered are as follows: Pilot's integrated Side-Stick Controller (SSC) -- Number of axes controlled; force/displacement characteristics; ergonomic design. Stability and Control Augmentation System (SCAS)--Digital flight control laws for the various mission phases; SCAS mode switching logic. Pilot's Displays--For night/adverse weather conditions, the dynamics of the superimposed symbology presented to the pilot in a format similar to the Advanced Attack Helicopter (AAH) Pilot Night Vision System (PNVS) for each mission phase is a function of SCAS characteristics; display mode switching logic. Results of the five piloted simulations conducted at the Boeing Vertol and NASA-Ames simulation facilities are presented in Volume 3. Conclusions drawn from analysis of pilot rating data and commentary were used to formulate recommendations for the ADOCS demonstrator flight control system design. The ACC/AFCS simulation data also provide an extensive data base to aid the development of advanced flight control system design for future V/STOL aircraft.

Landis, Kenneth H.↗
NASA NTRS1988

Bistable direction switching in an off-axis pumped continuous wave ruby laser

A report is presented of the observation of hysteretic bistable direction switching in a single-mode CW ruby laser system. This effect is only observed when the pump beam which is focused into the ruby rod is misaligned with respect to the rod end faces. At low pump powers, the ruby lases in a mode nearly collinear with the pump axis. At a higher pump power the ruby switches to a mode that is collinear with the rod end faces and preserves the original polarization. The effect is large enough to switch the beam by an angle equal to twice the diffraction angle. The observations show that under steady-state pumping, a CW ruby laser can exhibit bistable operation in its output direction and power. A calculation using the heat equation with two concentric cylinders with one as a heat source (pump laser) and the outer wall of the other held at 77 K, gives an increase in core temperature of about 0.01 K. Therefore, the increase in temperature is not large enough to change the index of refraction to account for such large macroscopic effects.

Afzal, R. Sohrab↗
NASA NTRS1988

Hardware realization of a baseband processor for a SS-FDMA/TDMA/DAMA system

Hardware implementation of the NASA ACTS baseband processor is described which achieves the system message data handling performance required to perform satellite switching of high-rate baseband data. The hardware meets payload specifications for size, weight, and power. Hardware redundancy applied to critical paths in several functional areas insures that the reliability and life expectancy requirements are fulfilled. The remote reprogrammability of the processor message data handling and routing functions provides system flexibility for dynamic reconfiguration during rapidly changing traffic loads.

Moat, Richard L.↗
NASA NTRS1978

Design of a microprocessor based packet switch

The design of a packet switch incorporating a minicomputer to control and process data packets in a communications system has been reported. This paper proposes a design which uses a 6500 series microprocessor to realize the functions of a message switch in order to evaluate the viability of microprocessors in this application. The proposed design realizes the functions of header analysis, packet security, error control and line prioritization. The system hardware and software are presented together with a brief description of operation.

Carville, D. E.↗
NASA NTRS1979

Preliminary study, analysis and design for a power switch for digital engine actuators

Innovative control configurations using high temperature switches to operate actuator driving solenoids were studied. The impact on engine control system life cycle costs and reliability of electronic control and (ECU) heat dissipation due to power conditioning and interface drivers were addressed. Various power supply and actuation schemes were investigated, including optical signal transmission and electronics on the actuator, engine driven alternator, and inside the ECU. The use of a switching shunt power conditioner results in the most significant decrease in heat dissipation within the ECU. No overall control system reliability improvement is projected by the use of remote high temperature switches for solenoid drivers.

Beattie, E. C.↗
NASA NTRS2005

AC/DC Power Systems with Applications for future Lunar/Mars base and Crew Exploration Vehicle

ABSTRACT The Power Systems branch at JSC faces a number of complex issues as it readies itself for the President's initiative on future space exploration beyond low earth orbit. Some of these preliminary issues - those dealing with electric power generation and distribution on board Mars-bound vehicle and that on Lunar and Martian surface may be summarized as follows: Type of prime mover - Because solar power may not be readily available on parts of the Lunar/Mars surface and also during the long duration flight to Mars, the primary source of power will most likely be nuclear power (Uranium fuel rods) with a secondary source of fuel cell (Hydrogen supply). The electric power generation source - With nuclear power being the main prime mover, the electric power generation source will most likely be an ac generator at a yet to be determined frequency. Thus, a critical issue is whether the generator should generate at constant or variable frequency. This will decide what type of generator to use - whether it is a synchronous machine, an asynchronous induction machine or a switched reluctance machine. The type of power distribution system - the distribution frequency, number of wires (3- wire, 4-wire or higher), and ac/dc hybridization. Building redundancy and fault tolerance in the generation and distribution sub-systems so that the system is safe; provides 100% availability to critical loads; continues to operate even with faulted sub-systems; and requires minimal maintenance. This report descril_es results of a summer faculty fellowship spent in the Power Systems Branch with the specific aim of investigating some of the lessons learned in electric power generation and usage from the terrestrial power systems industry, the aerospace industry as well as NASA's on-going missions so as to recommend novel surface and vehicle-based power systems architectures in support of future space exploration initiatives. A hybrid ac/dc architecture with source side and load side redundancies and including emergency generators on both ac and dc sides is proposed. The generation frequency is 400 Hz mostly because of the technology maturity at this frequency in the aerospace industry. Power will be distributed to several ac load distribution buses through solid state variable speed, constant frequency converters on the ac side. A segmented dc ring bus supplied from ac/dc converters and with the capability of connecting/disconnecting the segments will supply power to multiple de load distribution buses. The system will have the capability of reverse flow from dc to ac side in the case of an extreme emergency on the main ac generation side.

Chowdhury, Badrul H.↗
NASA NTRS1993

Low-latency digital frequency synthesizer using the residue number system

A low-latency frequency synthesizer using the Direct Digital Synthesis (DDS) technique has been designed. Called the Residue Assisted Frequency Synthesizer (RAFS), it exhibits frequency switching times which are reduced by more than 50 percent below previously published designs. The switching speed advantage is made possible by the use of the Residue Number System, which allows the pipeline lengths in the Phase Accumulator and other circuitry to be reduced significantly.

Chren, William A., Jr.↗
NASA NTRS1990

General-Purpose Serial Interface For Remote Control

Computer controls remote television camera. General-purpose controller developed to serve as interface between host computer and pan/tilt/zoom/focus functions on series of automated video cameras. Interface port based on 8251 programmable communications-interface circuit configured for tristated outputs, and connects controller system to any host computer with RS-232 input/output (I/O) port. Accepts byte-coded data from host, compares them with prestored codes in read-only memory (ROM), and closes or opens appropriate switches. Six output ports control opening and closing of as many as 48 switches. Operator controls remote television camera by speaking commands, in system including general-purpose controller.

Busquets, Anthony M.↗
NASA NTRS1992

The Astromag superconducting magnet facility configured for a free-flying satellite

The magnet parameters of a free-flying version of Astromag and the parameters of the space cryogenic system for the magnet are presented. Consideration is given to the free-flyer version of the Astromag magnet. The diameter of the magnet, its cryostat, the satellite and the two instruments is limited by the 4.27-m shroud diameter of the Atlas IIa. The magnet coil must use a stable reliable superconductor which can carry the full magnet current at 4.2 K at a peak induction in the coil of 7.5 T. The magnet must operate in the persistent mode. The changes in the overall design and operating requirements for the free-flying-design Astromag suggest that the coils, the cryogenic system, and the charging system can be simplified without a loss of required magnet function. Attention is given to switches, trim coils, and plumbing in the low field region between the coils; the magnet charging system and the quench protection system; and cooled helium supply to the magnet gas-cooled electrical leads.

Green, M. A.↗