Showing papers on "Propulsion published in 2007"

Vehicle Propulsion Systems: Introduction to Modeling and Optimization

Abstract: Introduction.- Vehicle Energy and Fuel Consumption - Basic Concepts.- IC-Engine-Based Propulsion Systems.- Models of Fuel-Cell Propulsion Systems.- Supervisory Control Algorithms.- Appendix I - Case Studies.- Appendix II - Optimal Control Theory.

Nonlinear Longitudinal Dynamical Model of an Air-Breathing Hypersonic Vehicle

Abstract: A nonlinear, physics-based model of the longitudinal dynamics for an air-breathing hypersonic vehicle is developed. The model is derived from first principles and captures a number of complex interactions between the propulsion system, aerodynamics, and structural dynamics. Unlike conventional aircraft, air-breathing hypersonic vehicles require that the propulsion system be highly integrated into the airframe. Furthermore, full-scale hypersonic aircraft tend to have very lightweight, flexible structures that have low natural frequencies. Therefore, the first bending mode of the fuselage is important, as its deflection affects the amount of airflow entering the engine, thus influencing the performance of the propulsion system. The equations of motion for the flexible aircraft are derivedusingLagrange’sequations.Theequationsof motioncaptureinertial couplingeffectsbetween thepitch and normal accelerations of the aircraft and the structural dynamics. The linearized aircraft dynamics are found to be unstableand,inmostcases,exhibitnonminimumphasebehavior.Thelinearizedmodelalsoindicatesthatthereisan aeroelastic mode that has a natural frequency more than twice the frequency of the fuselage bending mode, and the short-period mode is very strongly coupled with the bending mode of the fuselage.

Fault-Tolerant Interior-Permanent-Magnet Machines for Hybrid Electric Vehicle Applications

Abstract: Multiphase interior permanent magnet (IPM) motors are very good candidates for hybrid electric vehicle applications. High torque pulsation is the major disadvantage of most IPM motor configurations. A five-phase IPM motor with low torque pulsation is discussed. The mathematical model of the five-phase motor is given. A control strategy that provides fault tolerance to five-phase permanent-magnet motors is introduced. In this scheme, the five-phase system continues operating safely under loss of up to two phases without any additional hardware connections. This feature is very important in traction and propulsion applications where high reliability is of major importance. The system that is introduced in this paper will guarantee high efficiency, high performance, and high reliability, which are required for automotive applications A prototype four-pole IPM motor with 15 stator slots has been built and is used for experimental verification.

User's Guide for the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS)

Abstract: This report is a Users Guide for the NASA-developed Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) software, which is a transient simulation of a large commercial turbofan engine (up to 90,000-lb thrust) with a realistic engine control system. The software supports easy access to health, control, and engine parameters through a graphical user interface (GUI). C-MAPSS provides the user with a graphical turbofan engine simulation environment in which advanced algorithms can be implemented and tested. C-MAPSS can run user-specified transient simulations, and it can generate state-space linear models of the nonlinear engine model at an operating point. The code has a number of GUI screens that allow point-and-click operation, and have editable fields for user-specified input. The software includes an atmospheric model which allows simulation of engine operation at altitudes from sea level to 40,000 ft, Mach numbers from 0 to 0.90, and ambient temperatures from -60 to 103 F. The package also includes a power-management system that allows the engine to be operated over a wide range of thrust levels throughout the full range of flight conditions.

Simulation study of solar wind push on a charged wire: basis of solar wind electric sail propulsion

Abstract: . One possibility for propellantless propulsion in space is to use the momentum flux of the solar wind. A way to set up a solar wind sail is to have a set of thin long wires which are kept at high positive potential by an onboard electron gun so that the wires repel and deflect incident solar wind protons. The efficiency of this so-called electric sail depends on how large force a given solar wind exerts on a wire segment and how large electron current the wire segment draws from the solar wind plasma when kept at a given potential. We use 1-D and 2-D electrostatic plasma simulations to calculate the force and present a semitheoretical formula which captures the simulation results. We find that under average solar wind conditions at 1 AU the force per unit length is (5±1×10−8 N/m for 15 kV potential and that the electron current is accurately given by the well-known orbital motion limited (OML) theory cylindrical Langmuir probe formula. Although the force may appear small, an analysis shows that because of the very low weight of a thin wire per unit length, quite high final speeds (over 50 km/s) could be achieved by an electric sailing spacecraft using today's flight-proved components. It is possible that artificial electron heating of the plasma in the interaction region could increase the propulsive effect even further.

Development and testing of the mentor flapping-wing micro air vehicle

Abstract: In 1997 the Defense Advanced Research Projects Agency initiated a program to explore the possibility of micro air vehicles for the purpose of individually portable surveillance systems for close-range operations. The various contractors approached the problem in several ways, such as developing tiny fixed-wing airplanes, rotary-wing aircraft, and ornithopters mimicking animal flight This paper describes one such flapping-wing aircraft, which drew upon the clap-fling phenomenon that is exploited by many flying animals and insects for lift generation. Essentially this aircraft was a mechanical simulation of hummingbird flight, though with two sets of wings to eliminate the unbalanced side-to-side flapping forces. Two flying demonstration models were built, one with an internal-combustion engine and another with an electric motor. In both cases, these incorporated a drive train to reduce the high rpm rotary shaft motion to lower-frequency oscillation for flapping. Also required was a programmable logic board for stabilization. Successful hovering flight was achieved with both models, and initial studies of transition to horizontal flight were also explored.

HTS machines as enabling technology for all-electric airborne vehicles

Abstract: Environmental protection has now become paramount as evidence mounts to support the thesis of human activity-driven global warming. A global reduction of the emissions of pollutants into the atmosphere is therefore needed and new technologies have to be considered. A large part of the emissions come from transportation vehicles, including cars, trucks and airplanes, due to the nature of their combustion-based propulsion systems. Our team has been working for several years on the development of high power density superconducting motors for aircraft propulsion and fuel cell based power systems for aircraft. This paper investigates the feasibility of all-electric aircraft based on currently available technology. Electric propulsion would require the development of high power density electric propulsion motors, generators, power management and distribution systems. The requirements in terms of weight and volume of these components cannot be achieved with conventional technologies; however, the use of superconductors associated with hydrogen-based power plants makes possible the design of a reasonably light power system and would therefore enable the development of all-electric aero-vehicles. A system sizing has been performed both for actuators and for primary propulsion. Many advantages would come from electrical propulsion such as better controllability of the propulsion, higher efficiency, higher availability and less maintenance needs. Superconducting machines may very well be the enabling technology for all-electric aircraft development.

Experimental and theoretical studies of cylindrical Hall thrusters

Abstract: The Hall thruster is a mature electric propulsion device that holds considerable promise in terms of the propellant saving potential. The annular design of the conventional Hall thruster, however, does not naturally scale to low power. The efficiency tends to be lower and the lifetime issues are more aggravated. Cylindrical geometry Hall thrusters have lower surface-to-volume ratio than conventional thrusters and, thus, seem to be more promising for scaling down. The cylindrical Hall thruster (CHT) is fundamentally different from the conventional design in the way the electrons are confined and the ion space charge is neutralized. The performances of both the large (9-cm channel diameter, 600–1000W) and miniaturized (2.6-cm channel diameter, 50–300W) CHTs are comparable with those of the state-of-the-art conventional (annular) design Hall thrusters of similar sizes. A comprehensive experimental and theoretical study of the CHT physics has been conducted, addressing the questions of electron cross-field tr...

Propulsion Method for Swimming Microrobots

Abstract: This paper presents a novel swimming method mediated by traveling waves in elastic tails. The propulsion method is potentially appropriate for maneuvering microrobots inside the human body. The swimming action relies on the creation of a traveling wave along a piezoelectric layered beam divided into several segments. This requires that a voltage with the same frequency, but different phases and amplitudes, be applied to each segment. The swimming pattern was analyzed theoretically by solving the coupled electric-elastic-fluidic problem, and was optimized to attain reasonable thrust. It was found that despite extreme size limitations, a tail manufactured by current microelectromechanical-devices technology, using piezoelectric material, is able to swim in water at a speed of several centimeters per second. The swimming theory was verified experimentally using an upscaled model that produced propulsion of 0.04 mN, which matches closely the theoretically predicted propulsion

Flagella-like Propulsion for Microrobots Using a Nanocoil and a Rotating Electromagnetic Field

Abstract: A propulsion system similar in size and motion to the helical bacterial flagella motor is presented. The system consists of a magnetic nanocoil as a propeller (27 nm thick ribbon, 3 mun in diameter, 30-40 mum long) driven by an arrangement of macro coils. The macro coils generate a rotating field that induces rotational motion in the nanocoil. Viscous forces during rotation result in a net axial propulsion force on the nanocoil. Modeling of fluid mechanics and magnetics was used to estimate the requirements for such a system. The fabrication of the magnetic nanocoils and the system setup are explained. Experimental results from electromagnetic actuation of nanocoils as well as from their propulsion in both paraffin oil and water are presented. This is the first time a propulsion system of this size and motion-type has been fabricated and experimentally verified.

Hybrid energy off highway vehicle propulsion circuit

Abstract: A system and method for retrofitting a propulsion circuit of an existing Off Highway Vehicle to enable the propulsion circuit to operate as a hybrid energy Off Highway Vehicle propulsion circuit. The hybrid propulsion circuit includes a primary power source, and a traction motor for propelling an Off Highway Vehicle in response to the primary electric power. The traction motor has a motoring mode of operation and a power dissipation mode of operation. The traction motor generates dynamic braking electrical power in the power dissipation mode of operation. An electrical energy storage system includes a chopper circuit coupled to an energy storage device. The storage device is responsive to the chopper circuit to selectively store electrical energy generated in the power dissipation mode. The storage system selectively provides secondary electric power from the storage device to traction motor to assist in propelling the Off Highway Vehicle during the motoring mode.

Spacecraft formation flying using Lorentz forces

Abstract: The Lorentz Augmented Orbit (LAO) concept is an electromagnetic propulsion system without a tether that uses the interaction between an electrostatically charged spacecraft and the Earth's magnetic field to provide a useful thrust. In Low Earth Orbit (LEO), the Lorentz force acting on a charged spacecraft flying relative to Earth's magnetic field causes acceleration in a direction perpendicular to both its velocity and the magnetic field. In this paper, the concept of spacecraft propulsion using Lorentz force is investigated for LEO formation flying. A triangular spacecraft formation configuration is used to simulate and validate the advantages and disadvantages of the proposed concept. It is illustrated that simple formation manoeuvres can be performed solely using the Lorentz force.

Modeling and Near-Space Stationkeeping Control of a Large High-Altitude Airship

Abstract: 3andissolarelectricpowered,with the entire upper surface covered by solar cells. Electric motors and propellers provide propulsion, and batteries are used for power storage. In this paper, the vehicle’s surge and directional dynamics are characterized, the wind environmentismodeled,andsimplecontrolandguidancealgorithmsaredevelopedandevaluated.Inparticular,the maneuvering power required is statistically determined, using a covariance analysis. It is shown that the vehicle is dynamically stable and sluggish, and that significant thrust and control power may be required to stationkeep in turbulence. This additional maneuvering power required may be a significant design driver.

Evaluation of Solar Electric Propulsion Technologies for Discovery Class Missions

Abstract: A detailed study examines the potential benefits that advanced electric propulsion technologies offer to costcapped missions in NASA’s Discovery program. The study looks at potential cost and performance benefits provided by three electric propulsion technologies that are currently in development: NASA’s evolutionary xenon thruster, an enhanced NSTAR system, and a low-power Hall effect thruster. These systems are analyzed on three potential Discovery-class missions and their performance is compared with a state-of-the-art system using the NSTAR ion thruster. An electric propulsion subsystem cost model is used to conduct a cost–benefit analysis for each option. The results show that each proposed technology offers a different degree of performance and/or cost benefit for Discovery-class missions. However, lower subsystem costs (particularly, power processing and digital control interface unit costs) are needed for ion thruster systems, to make them more competitive for cost-capped missions. It is observed that the best mass performance generally comes from electric propulsion systems that best use available solar array power during the mission. Finally, first-flight qualification costs are identified as a significant barrier to the implementation of new electric propulsion technologies on costcapped missions.

Design of HTS Axial Flux Motor for Aircraft Propulsion

Abstract: Development of all-electric aircraft would enable more efficient, quieter and environmentally friendly vehicles and would contribute to the global reduction of greenhouse gas emissions. However, conventional electric motors do not achieve a power density high enough to be considered in airborne applications. Bulk high temperature superconducting (HTS) materials, such as YBCO pellets, have the capacity of trapping magnetic flux thus behaving as permanent magnets. Experimental data show that one single domain YBCO pellets could trap up to 17 T at 29 K, which enables the design of very high power density motors that could be used in aircraft propulsion. We designed a superconducting motor based on an axial flux configuration and composed of six YBCO plates magnetized by a superconducting coil wound on the outside of the motor. The six-pole homopolar machine uses a conventional air-gap resistive armature. Axial-flux configuration allows several rotors and stators to be stacked together and therefore enables the use of one or several conventional permanent magnet rotors to generate minimum safety torque in case of loss of superconductivity. All-electric aircraft are expected to be powered by fuel cells or turbo-generators fed with pure hydrogen cryogenically stored that would provide the motor with a convenient cooling system at 20 K. This paper presents the design and simulated performance of the motor for an application in aircraft propulsion.

GeoSail: an elegant solar sail demonstration mission

Abstract: In this paper a solar sail magnetotail mission concept was examined. The 43-m square solar sail is used to providethe required propulsion for continuous sun-synchronous apse-line precession. The main driver in this mission was found to be the reduction of launch mass and mission cost while enabling a nominal duration of 2 years within the framework of a demonstration mission. It was found that the mission concept provided an excellent solar sail technology demonstration option. The baseline science objectives and engineering goals were addressed, and mission analysis for solar sail, electric, and chemical propulsion performed. Detailed subsystems were defined for each propulsion system and it was found that the optimum propulsion system is solar sailing. A detailed tradeoff as to the effect of spacecraft and sail technology levels, and requirements, on sail size is presented for the first time. The effect of, for example, data acquisition rate and RF output power on sail size is presented, in which it is found that neither have a significant effect. The key sail technology requirements have been identified through a parametric analysis.

Power Electronics Technologies for Railway Vehicles

Abstract: This paper describes the current range of advanced IGBT propulsion inverters used in railways from light rail vehicles to high speed trains & locomotives. The second part of the paper describes future trends in IGBT railway propulsion drives. One such trend is the concept of power integration which leads to weight, volume and cost reduction . Finally, for systems with an AC input supply, a concept for reducing the weight of the main input transformer is also described. This uses a configuration of resonant converter and a medium frequency transformer , the so called e-transformer, and could be particularly targeted for 15 kV, 16.7 Hz supplied systems.

Challenges in the silent aircraft engine design

Abstract: The Silent Aircraft Initiative goal is to design an aircraft that is imperceptible above background noise outside the airport boundary. The aircraft that fulfils this objective must also be economically competitive with conventional aircraft of the future and therefore fuel consumption and mechanical reliability are key considerations for the design. To meet these ambitious targets, a multi-fan embedded turbofan engine with boundary layer ingestion has been proposed. This configuration includes several new technologies including a variable area nozzle, a complex high-power transmission system, a Low Pressure turbine designed for low-noise, an axial-radial HP compressor, advanced acoustic liners and a low-speed fan optimized for both cruise and off-design operation. These technologies, in combination, enable a low-noise and fuel efficient propulsion system but they also introduce significant challenges into the design. These challenges include difficulties in predicting the noise and performance of the new components but there are also challenges in reducing the design risks and proving that the new concepts are realizable. This paper presents the details of the engine configuration that has been developed for the Silent Aircraft application. It describes the design approach used for the critical components and discusses the benefits of the new technologies. The new technologies are expected to offer significant benefits in noise reduction without compromising fuel burn. However, more detailed design and further research are required to fully control the additional risks generated by the system complexity.

Rocket Grade Hydrogen Peroxide (RGHP) for use in Propulsion and Power Devices - Historical Discussion of Hazards

Abstract: Common historical anecdotal negative characteristics for propellant grade hydrogen peroxide are described and reviewed. Supporting evidence, analysis, historical technical data, recent test data, prior experience, current experience, modern and literature test data are provided to address the issues and perceived concerns and to provide referenced and established scientific data and evidence which can be used to make informed decisions.

Aircraft propulsion systems

Abstract: Disclosed are propulsion systems (30) providing reduced fuel burn, weight and cost. A single gas generator core (38) drives multiple bladed propulsion elements (36) with a power train (48). The core (38) has a forward compressor (56) and a rearward turbine (40) and rotates about a longitudinal core axis (62). The bladed propulsion elements (36) rotate about bladed propulsion element axes (78) that are not coaxial with the core axis (62). The bladed propulsion elements (36) discharge an ambient air stream (50) rearward as a bypass stream (52) portion and a core stream (54) portion. The core stream (54) portion is directed to the compressor (56). The propulsion systems (30) mount inside a fuselage (22) of an airframe (20) or they are suspended beneath a wing (24) via pylons (32).

Trajectory Design with Hybrid Low-Thrust Propulsion System

Abstract: propulsion thruster is coupled with an auxiliary system providing an inverse square radial thrust. In this way the spacecraft is virtually subjected to a reduced gravitational solar force. The primary purpose of this paper is to quantify the impact of the reduced solar force on the propellant consumption for an interplanetary mission. To this end the steering law that minimizes the propellant consumption for a circle-to-circle rendezvous problem is found using an indirect approach. The hybrid system is compared with a conventional solar electric thruster in terms of payload mass fraction deliverable for a given mission. A tradeoff between payload size and trip time is established.

Propulsion Drive Models for Full Electric Marine Propulsion Systems

Abstract: Integrated full electric propulsion systems are being introduced across both civil and military marine sectors. Standard power systems analysis packages cover electrical and electromagnetic components, but have limited models of mechanical subsystems and their controllers. Hence electromechanical system interactions between the prime movers, power network and driven loads are poorly understood. This paper reviews available models of the propulsion drive system components: the power converter, motor, propeller and ship. Due to the wide range of time-constants in the system, reduced order models of the power converter are required. A new model using state-averaged models of the inverter and a hybrid model of the rectifier is developed to give an effective solution combining accuracy with speed of simulation and an appropriate interface to the electrical network model. Simulation results for a typical ship manoeuvre are presented.

Compression System for Internal Combustion Engine Including a Rotationally Uncoupled Exhaust Gas Turbine

Abstract: As one example, a vehicle propulsion system is provided. The system includes: an engine with an intake air compressor and an exhaust gas turbine. Further, a control is provided to operate the compressor at a different speed than the turbine, at least under an operating condition, and to adjust an amount of opening overlap between engine valves in response to a rotational speed of the compressor.

Surface tank-treading: propulsion of Purcell's toroidal swimmer

Abstract: In this work we address the "smoking ring" propulsion technique, originally proposed by E. M. Purcell. We first consider self-locomotion of a doughnut-shaped swimmer powered by surface tank-treading. Different modes of surface motion are assumed and propulsion velocity and swimming efficiency are determined. The swimmer is propelled against the direction of its outer surface motion, the inner surface having very little affect. The simplest swimming mode corresponding to constant angular velocity, can achieve propulsion speeds of up to 66% of the surface tank-treading velocity and swimming efficiency of up to 13%. Higher efficiency is possible for more complicated modes powered by twirling of extensible surface. A potential practical design of a swimmer motivated by Purcell's idea is proposed and demonstrated numerically. Lastly, the explicit solution is found for a two-dimensional swimmer composed of two counter-rotating disks, using complex variable techniques.

The MESSENGER Spacecraft

Abstract: The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was designed and constructed to withstand the harsh environments associated with achieving and operating in Mercury orbit. The system can be divided into eight subsystems: structures and mechanisms (e.g., the composite core structure, aluminum launch vehicle adapter, and deployables), propulsion (e.g., the state-of-the-art titanium fuel tanks, thruster modules, and associated plumbing), thermal (e.g., the ceramic-cloth sunshade, heaters, and radiators), power (e.g., solar arrays, battery, and controlling electronics), avionics (e.g., the processors, solid-state recorder, and data handling electronics), software (e.g., processor-supported code that performs commanding, data handling, and spacecraft control), guidance and control (e.g., attitude sensors including star cameras and Sun sensors integrated with controllers including reaction wheels), radio frequency telecommunications (e.g., the spacecraft antenna suites and supporting electronics), and payload (e.g., the science instruments and supporting processors). This system architecture went through an extensive (nearly four-year) development and testing effort that provided the team with confidence that all mission goals will be achieved.

An Electric Gearshift With Ultracapacitors for the Power Train of an Electric Vehicle With a Directly Driven Wheel Motor

Abstract: A novel electric gearshift with ultracapacitors is designed for the power train of a directly driven electric vehicle. The power train consists of two major subsystems: electric propulsion and energy source. The electric propulsion subsystem is composed of a dedicated wheel motor and its drive; the energy source subsystem is equipped with a stack of lead-acid batteries and ultracapacitor cells. This electric gearshift combines different parallel and serial connections of batteries, motor windings, and ultracapacitors to accommodate various driving patterns in the permissible range of speed and torque. A control core, which is realized by a field-programmable gate array, is employed to manage the energy source and direct optimal propulsion to extend the speed range of constant power, and thereby improve vehicle performance in terms of efficiency, acceleration, and driving range.

Small UAV Research and Evolution in Long Endurance Electric Powered Vehicles

Abstract: This paper describes recent research into the advancement of small, electric powered unmanned aerial vehicle (UAV) capabilities. Specifically, topics include the improvements made in battery technology, design methodologies, avionics architectures and algorithms, materials and structural concepts, propulsion system performance prediction, and others. The results of prototype vehicle designs and flight tests are discussed in the context of their usefulness in defining and validating progress in the various technology areas. Further areas of research need are also identified. These include the need for more robust operating regimes (wind, gust, etc.), and continued improvement in payload fraction vs. endurance.