Showing papers on "Propulsion published in 1993"

History of electric vehicles in General Motors

Abstract: The propulsion systems being used by General Motors in different electric vehicle projects are described, and the performances achieved are presented. The past projects discussed are electrovan, an electric truck for military application, STIR-LEC I (a Stirling electric hybrid car), the GM512 series car. The AT&T van, and the Electrovette. Current projects such as IMPACT and the electric shuttle bus are also discussed. The IMPACT was developed because of a concern for air quality. The technology of impact is based on advanced propulsion system technology and is suitable for mass production at affordable costs. >

Hybrid motor vehicle having an electric motor and utilizing an internal combustion engine for fast charge during cruise mode off condition

Abstract: A hybrid motor vehicle utilizing electric motor propulsion prior to cruise mode detection condition and internal combustion engine propulsion during cruise mode

Ship propulsion arrangement

Abstract: A main propulsion arrangement for a high power ship or the like comprises an underwater drive unit connected to and turnable by means of a substantially vertical tubular shaft journalled in the ship. The drive unit and the tubular shaft define a hollow casing enclosing an electrical propulsion motor connected to a propeller shaft, which is connected to a driving propeller external of the casing. The casing is, at its inside, supported by several mainly vertical web plates, which are arranged to act, in combination, as elements structurally stiffening and supporting the casing, as elements securing the propulsion motor in place relative to the casing, as elements transmitting to the casing reaction forces to the torque developed by the propulsion motor, and as wall elements of ducts for incoming and outgoing gaseous coolant for the propulsion motor.

Control system for an electrically propelled traction vehicle

Abstract: A control system for an electrical propulsion system for a large wheeled vehicle adapted to haul a payload, the vehicle having an internal combustion engine and an electric generating means driven by the engine. The control system measures selected parameters and controls the engine and generating means to maximize output, and records historical operating data relating to the vehicle and its systems, and has a 2 digit display that provides information useful in troubleshooting problems. The control system also enhances fuel consumption by conserving fuel use, particularly on flat terrain and when the vehicle is approaching the overspeed point. Depression of the foot pedal is no longer input directly to the engine controller. Based on the amount of depression of the foot pedal, a fuel enhancement means determines the horsepower request from the operator of the foot pedal, but generates an engine rpm signal which will run the engine at only the rpm necessary to provide the power. The fuel enhancement means is further adapted to conserve fuel usage during periods of vehicle coast and electric brake by requiring minimum engine rpm to maintain sufficient cooling of vehicle equipment.

Microwave-powered aircraft

Abstract: An unmanned, remotely controlled microwave-powered aircraft for use as a stationary communications platform. The aircraft is generally a flying wing with a large, flat inner wing having a rectenna on the underside. Rectennas may also be provided on the underside of the wings, the combined output from the rectenna being used to provide power to two electric motors housed within torpedo-shaped nacelles which drive two rear propellers. The rectenna converts a microwave signal at 35 GHz generated by a ground power station utilizing dual gyrotrons and a 34-meter diameter antenna dish. The aircraft has a preferred airfoil cross section throughout and is constructed of lightweight but strong materials in order to provide an enhanced flying time of several months. A power management and distribution system manages the DC power produced by the rectenna to supply power to the flight controls, propulsion system and payload.

Advanced Pogo stability analysis for liquid rockets

Abstract: An advanced modeling method for determining engine-coupled Pogo oscillation modes, with general applicability to any liquid rocket vehicle, is presented. The modes result from interaction of structural vibrations with pressure and flow oscillations in the liquid propulsion system. A time-invariant linearized mathematical model of the system is developed for a selected flight time. Perturbations of the propulsion system are modeled using finite element representations for its physical elements (such as flow duct, pump, accumulator, and thrust chamber), each of which undergoes structural motion described in terms of the vibration modes of the overall vehicle. The structural modes, developed in a separate analysis, are determined with the fluids frozen in place in the feedlines and engines and involve motions of the propulsion elements. The system equations are written in a homogeneous second-order matrix form in the Laplace domain, yielding coefficient matrices that are all complex, unsymmetric, and singular. The major advances are 1) rigorous treatment of arbitrary translational motions of the vessels through which the fluids flow, including all forces (pressure area, inertial, and momentum) that react on the structural system, and 2) a powerful numerical eigensolver that yields eigenvalues and eigenvectors directly, without requiring elimination of dependent fluid state variables (pressure and flows).

Principles of Communications Satellites

Abstract: Introduction to Link Budgets Orbits for Communications Satellites Radio Frequencies Modulation, Multiplexing, and Multiple Access Antennas Power, EIRP, and Illumination Transmission Losses and Power Flux Density Receivers and Noise Temperatures System Performance Telemetry, Tracking, and Command Electric Power Spacecraft Attitude Propulsion Structure Thermal Control Spacecraft Testing Reliability Index.

Optimal impulsive intercept with low-thrust rendezvous return

Abstract: Primer vector theory is used to investigate a specific class of minimum-fuel spacecraft trajectory problems in which high- and low-thrust propulsion systems are utilized sequentially. The problem considered assumes a spacecraft initially on-station in an established orbit about the Earth. It is desired to intercept a predetermined position in space in a timely manner for collision avoidance or platform surveillance, using an optimal high-thrust program. The spacecraft then returns to the original orbit station using optimal low-thrust propulsion. Fixed-time minimum-fuel solutions are obtained using the Clohessy-Wiltshire linearized dynamic model. In the time-open case, the optimal final time is unbounded. For this case a composite performance index involving both fuel consumption and the final time is minimized to obtain optimal finite-time solutions.

Nuclear Thermal Rocket/vehicle design options for future NASA missions to the Moon and Mars

Abstract: The nuclear thermal rocket (NTR) provides a unique propulsion capability to planners/designers of future human exploration missions to the Moon and Mars. In addition to its high specific impulse (approximately 850-1000 s) and engine thrust-to-weight ratio (approximately 3-10), the NTR can also be configured as a 'dual mode' system capable of generating electrical power for spacecraft environmental systems, communications, and enhanced stage operations (e.g., refrigeration for long-term liquid hydrogen storage). At present the Nuclear Propulsion Office (NPO) is examining a variety of mission applications for the NTR ranging from an expendable, single-burn, trans-lunar injection (TLI) stage for NASA's First Lunar Outpost (FLO) mission to all propulsive, multiburn, NTR-powered spacecraft supporting a 'split cargo-piloted sprint' Mars mission architecture. Each application results in a particular set of requirements in areas such as the number of engines and their respective thrust levels, restart capability, fuel operating temperature and lifetime, cryofluid storage, and stage size. Two solid core NTR concepts are examined -- one based on NERVA (Nuclear Engine for Rocket Vehicle Application) derivative reactor (NDR) technology, and a second concept which utilizes a ternary carbide 'twisted ribbon' fuel form developed by the Commonwealth of Independent States (CIS). The NDR and CIS concepts have an established technology database involving significant nuclear testing at or near representative operating conditions. Integrated systems and mission studies indicate that clusters of two to four 15 to 25 klbf NDR or CIS engines are sufficient for most of the lunar and Mars mission scenarios currently under consideration. This paper provides descriptions and performance characteristics for the NDR and CIS concepts, summarizes NASA's First Lunar Outpost and Mars mission scenarios, and describes characteristics for representative cargo and piloted vehicles compatible with a reference 240 t-class heavy lift launch vehicle (HLLV) and smaller 120 t HLLV option. Attractive performance characteristics and high-leverage technologies associated with both the engine and stage are identified, and supporting parametric sensitivity data is provided. The potential for commonality of engine and stage components to satisfy a broad range of lunar and Mars missions is also discussed.

SP-100 nuclear electric propulsion for Mars cargo missions

Abstract: This paper summarizes an evaluation of mission performance (in terms of vehicle mass and trip time) of the use of the near-term SP-100 reactor technology for nuclear electric propulsion for Mars cargo missions, and of the technology requirements for the propulsion and dynamic power conversion systems of the vehicle. The reactor power system uses dynamic power conversion (Rankine), and the propulsion system uses lithium-propellant magnetoplasmadynamic (MPD) thrusters. Three reactor power modules are used to give a total 'bus' power of 1.7 MWe. The total power, power conditioning, and propulsion systems specific mass is 24.8 kg/kWe; the propellant tankage factor is 2.8 percent. The power conditioning system has an efficiency of 90.2 percent and the MPD thrusters an efficiency (electric-to-jet) of 60 percent at a nominal specific impulse of 5000 lb(f)-s/lb(m). Rankine, Brayton, and Stirling dynamic power conversion systems were compared, and the Rankine was found to give the best performance in terms of smallest specific mass and volume; however, it has the longest development time requirement.

Partitioning of centralized integrated flight/propulsion control design for decentralized implementation

Abstract: The notion of partitioning a centralized controller into a decentralized, hierarchical structure suitable for integrated flight/propulsion control (IFPC) implementation is discussed. A systematic procedure is developed for determining partitioned airframe and engine subsystem controllers (subcontrollers), with the desired interconnection structure, that approximate the closed-loop performance and robustness characteristics of a given centralized controller. The procedure is demonstrated by application to IFPC design for a short take-off and vertical landing (STOVL) aircraft in the landing-approach-to-hover-transition flight phase. >

Hybrid-drive vehicle drive control method

Abstract: A method of controlling a hybrid-drive vehicle i.e. a vehicle equipped with a main IC engine (6) and a battery powered electric machine and including separate clutch couplings (3, 5) employs an electrical auxiliary (4) which can be engaged to power the transmission shaft (1) and output gearbox (2) when independently supplied from an accumulator (7) or to operate as a recharging generator. In this latter mode the IC engine (6) provides both vehicle propulsion and generator drive or on a downward incline regenerative braking may temporarily replace the engine (6) for accumulator (7) re-charging.The electric drive is employed for environmentally restricted low speed/low energy running e.g. in town centres followed by main engine running/recharging elsewhere.

Recent developments of electric vehicles and their propulsion systems

Abstract: Major recent electric vehicle (EV) programs in North America, Europe, and Japan are reviewed. The developments discussed include electric vehicles for fleet operation and electric passenger cars for urban transit. All major auto makers have had their own concept electric vehicle programs, targeted at commercial production in the late 1990s. It Is noted that, with different objectives for various electric vehicles, considerations such as cost, reliability, efficiency, maintenance, durability, weight, size, and noise level should be compromised for the propulsion system design. Consequently, DC motor drives, induction motor drives, and permanent magnet brushless DC motor drives will continually be used for EV propulsion systems in the future, with DC drives being gradually replaced by AC drives. The rapid advances in power semiconductor devices and microprocessors have made it possible to build reliable and cost-effective AC drive systems. >

Water jet propulsion unit

Abstract: A water jet propulsion unit in which water is drawn off of the jet propulsion unit through a tap for other purposes, such as pumping the bilge with a jet pump or delivering coolant to the engine. A filter element which can be easily serviced is positioned in the conduit for precluding small particles which could clog the conduit from entering the conduit.

Role of hydrogen/air chemistry in nozzle performance for a hypersonic propulsion system

Abstract: A computer model for describing quasi-one-dimensional flow of a gas mixture with area change and finiterate chemical reactions was used to study the role of hydrogen/air chemistry in nozzle performance for a hypersonic propulsion system. The important results obtained for a typical nozzle at a Mach 18 flight condition are as follows: 1) finite-rate chemistry should not be neglected in nozzle performance simulations because beneficial chemical processes persist throughout the entire nozzle length; 2) termolecular recombination reactions represent the principal chemical contribution to nozzle performance; 3) intermediate HNO species have little effect on hydrogen radical recombination; and 4) nitrogen oxides are not involved directly in the hydrogen radical recombination process but rather they provide a source of oxygen for recombination. In addition, the study shows that any major reduction in the detailed reaction mechanism used here may lead to incorrect simulations of nozzle performance.

Power console development for NASA's electric propulsion outreach program

Abstract: NASA LeRC is developing a 30 cm diameter xenon ion thruster for auxiliary and primary propulsion applications. To maximize expectations for user-acceptance of ion propulsion technology, NASA LeRC, through their Electric Propulsion Outreach Program, is providing sectors of industry with portable power consoles for operation of 5 KW-class xenon ion thrusters. This power console provides all necessary functions to permit thruster operations over a 0.5-5 KW envelope under both manual and automated control. These functions include the following: discharge, cathode heater, neutralizer keeper, and neutralizer heater currents, screen and accelerator voltages, and a gas feed system to regulate and control propellant flow to the thruster. An electronic circuit monitors screen and accelerator currents and controls arcing events. The power console was successfully integrated with the NASA 30 cm thruster.

Water injection propulsion device

Abstract: A jet propelled watercraft having a reverse thrust mechanism including a reverse thrust bucket. The hull is provided with a portion that underlies the discharge nozzle of the jet propulsion unit and which provides a continuous surface for the hull when the reverse thrust bucket is in the forward drive mode. However, when the reverse thrust bucket is moved to the reverse thrust position, a closure panel opens to provide an opening through which water may be discharged during reverse thrust operation.

High performance amphibious aircraft

Abstract: An amphibious aircraft, capable of high speed maneuverability on the surface of the water, utilizes a aerodynamic platform to generate lift and to define a tunnel with a pair of central sponsons extending inwardly of the wings of the aircraft longitudinally of the platform which supports the cockpit and propulsion system.

Rocket-powered single-stage vehicle configuration selection and design

Abstract: A reusable rocket-powered, single-stage launch vehicle has been designed as a part of NASA's Advanced Manned Launch System (AMLS) study to examine options for a next-generation manned space transportation system. The configuration selection process utilized a response surface methodology for multidisciplinary optimization. The methodology was utilized to determine the minimum dry weight entry vehicle to meet constraints on landing velocity and on subsonic, supersonic, and hypersonic trim and stability. Once the optimum configuration was determined, a multidisciplinary conceptual vehicle design was performed. This paper presents the results of the configuration selection methodology and summarizes the overall conceptual design process with special attention given to the individual disciplines of weights/ sizing, structures/materials, configuration, flight mechanics, aerodynamics, aeroheating, propulsion, and operations.

Propulsion arrangement for a marine vessel

Abstract: A propulsion arrangement for a marine vessel is described which comprises a propulsion unit (4) having: (i) a non-rotating housing in the form of a nozzle (10) extending along a principal axis (50); (ii) a propeller (22; 40) mounted for rotation within said nozzle (10); (iii) a support shaft (23) extending along the principal axis (50) of the nozzle (10) and to which shaft said propeller (22; 40) is affixed, and (iv) support shaft support means in the form of a plurality of arms (24) extending substantially radially from the inner surface (25) of the nozzle (10) to a bearing hub (26) for the support shaft (23). In order to provide a more efficient propulsion arrangement which also contributes to a reduction in the drag losses of the hull of the vessel to which it is fitted, the propulsion unit is coupled to the marine vessel (1) in such a manner that it can be trimmed to a desired angle to cause the nozzle (10) to generate a lift component at the stern of the vessel (1).

A retrospective on early cryogenic primary rocket subsystem designs as integrated into rocket-based combined-cycle (RBCC) engines

Abstract: A study (Escher and Flornes, 1966) of aerospace propulsion systems for a fully reusable earth-to-orbit space transport application that was performed in 1965-67 is reviewed. The present review provides a detailed, subject-focused technical retrospective on a key subsystem element of the rocket-based combined-cycle (RBCC) class of aerospace propulsion systems. The RBCC concept is considered to be a leading candidate propulsion approach for either SSTO or two-stage-to-orbit space transportaion applications.

Review of NASA's Hypersonic Research Engine Project

Abstract: The goals of the NASA Hypersonic Research Engine (HRE) Project, which began in 1964, were to design, develop, and construct a hypersonic research ramjet/scramjet engine for high performance and to flight-test the developed concept over the speed range from Mach 3 to 8. The project was planned to be accomplished in three phases: project definition, research engine development, and flight test using the X-15A-2 research aircraft, which was modified to carry hydrogen fuel for the research engine. The project goal of an engine flight test was eliminated when the X-15 program was canceled in 1968. Ground tests of engine models then became the focus of the project. Two axisymmetric full-scale engine models having 18-inch-diameter cowls were fabricated and tested: a structural model and a combustion/propulsion model. A brief historical review of the project with salient features, typical data results, and lessons learned is presented.