Abstract: A simple way to generate propulsion at low Reynolds number is to periodically oscillate a passive flexible filament. Here we present a macroscopic experimental investigation of such a propulsive mechanism. A robotic swimmer is constructed and both tail shape and propulsive force are measured. Filament characteristics and actuation are varied, and the resulting data are quantitatively compared with existing linear and nonlinear theories.

Abstract: A vehicle propulsion system includes an internal combustion engine having an engine output, an electro-mechanical transmission and a control system. The engine output is coupled to the transmission output at a speed ratio which is established by one of a plurality of electrically variable or fixed operating modes. Selection and control among the various operating modes is managed by a control in accordance with preferred optimum operating costs.

Abstract: A tool developed for the preliminary design of low-thrust trajectories is described. The trajectory is discretized into segments and a nonlinear programming method is used for optimization. The tool is easy to use, has robust convergence, and can handle many intermediate encounters. In addition, the tool has a wide variety of features, including several options for objective function and different low-thrust propulsion models (e.g., solar electric propulsion, nuclear electric propulsion, and solar sail). High-thrust, impulsive trajectories can also be optimized.

Abstract: The availability of electric engines as primary sources of propulsion has opened the doors to new scenarios for future interplanetary missions, but has increased the complexity of trajectory design. This paper proposes a novel approach to the preliminary design of interplanetary trajectories characterized by a combination of low-thrust propulsion and multiple gravity-assist maneuvers. Low-thrust arcs are obtained by shaping the trajectory through a set of parameterized pseudoequinoctial elements. The characterization of the solution space for a particular set of planetary encounters and a range of launch dates is then performed through a global optimization method, blending a particular evolutionary algorithm with a deterministic domain decomposition technique. The effectiveness of the proposed approach is demonstrated through a number of examples of the design of low-thrust, gravity-assist interplanetary trajectories.

Abstract: The Silent Aircraft Initiative is a research project funded by the Cambridge-MIT Institute aimed at reducing aircraft noise to the point where it is imperceptible in the urban environments around airports. The propulsion system being developed for this project has a thermodynamic cycle based on an ultrahigh bypass ratio turbofan combined with a variable area exhaust nozzle and an embedded installation. This cycle has been matched to the flight mission and thrust requirements of an all-lifting body airframe, and through precise scheduling of the variable exhaust nozzle, the engine operating conditions have been optimized for maximum thrust at top-of-climb, minimum fuel consumption during cruise, and minimum jet noise at low altitude. This paper proposes engine mechanical arrangements that can meet the cycle requirements and, when installed in an appropriate airframe, will be quiet relative to current turbofans. To reduce the engine weight, a system with a gearbox, or some other form of shaft speed reduction device, is proposed. This is combined with a low-speed fan and a turbine with high gap-chord spacing to further reduce turbomachinery source noise. An engine configuration with three fans driven by a single core is also presented, and this is expected to have further weight, fuel burn, and noise benefits.

Abstract: A system and method for maintaining a vehicle at a predetermined velocity on a graded surface is provided, which includes a propulsion system to supply motive torque to a vehicle wheel, a vehicle stability sensor, and a control system adapted to receive signal input from the vehicle stability sensor. The control system controls magnitude of the motive torque supplied to the wheel. The propulsion system may include an electric wheel motor powered by an electrical energy storage system, a hybrid powertrain system, and an internal combustion engine and transmission. The vehicle stability sensor determines orientation of the vehicle relative to a horizontal plane, including a longitudinal acceleration sensor and a virtual longitudinal acceleration sensor. The control system receives inputs from a wheel speed sensor, an accelerator pedal sensor, and a brake pedal sensor to control motive torque. Motive torque is controlled to maintain wheel speed sensor at a null output.

Abstract: This paper presents the comparison of four linear switched reluctance machines (LSRMs) as possible candidates for application in vertical elevators. Linear induction and linear synchronous machines have been presented and experimentally tested in vertical elevators. In this paper, four longitudinal LSRM configurations are presented and designed to operate as propulsion actuators in a vertical elevator prototype. Two of the four configurations have been presented earlier in horizontal propulsion experiments, and a third one has been proposed for application in vertical elevators. All four LSRMs are designed for similar static force profiles to allow for their comparison. The designed LSRM configurations are compared by using finite-element analysis and dynamic control simulations. The stator, translator, and copper winding weight and dimensions, footprint area, active material weight, normal forces and payload capabilities for all four configurations are contrasted. The configuration with the highest payload capability is chosen for implementation in an experimental prototype. The prototype vertical elevator is 1.27 m tall with a 1-ft-tall elevator vehicle with no counterweights and uses two LSRM setups on each side. The experimental correlation of propulsion force and inductance is presented to validate the theoretical design method used in this research.

Abstract: To provide an aircraft propulsion system which can secure the optimum thrust and thrust vector for flight conditions, as well as the optimum sectional area for the engine, and which is highly compatible with the environment. An electrical generator is coupled to a turbofan engine, the electrical generator is driven by output power of the turbofan engine to output electric power, and an electromagnetic driving fan is driven by the electric power. On the other hand, after bringing each of coils in the electromagnetic driving fan to a superconductive state, liquid hydrogen is introduced to a heat exchanger, collects the energy of exhaust as heat, is then vaporized, and thereafter supplied to a combustor and to a fuel cell. Further, the electromagnetic driving fan is changed in its rotational phase by a rotating mechanism portion, is made movable in a width direction of a wing and a wing chord direction by a slide mechanism portion, and can be stored inside or outside the wing by a storage mechanism portion.

Abstract: The present invention is directed to a control strategy for operating a plurality of prime power sources during propulsion, idling and braking and is applicable to large systems such as trucks, ships, cranes and locomotives utilizing diesel engines, gas turbine engines, other types of internal combustion engines, fuel cells or combinations of these that require substantial power and low emissions utilizing multiple power plant combinations. The present invention is directed at a general control strategy for multi power plant systems where the power systems need not be of the same type or power rating and may even use different fuels. The invention is based on a common DC bus electrical architecture so that prime power sources need not be synchronized.

Abstract: This paper reports the design, fabrication, and experimental characterization of an internally fed linear array of electrospray emitters intended for space propulsion applications. The engine uses doped formamide as propellant and operates in the single-Taylor-cone droplet emission regime. The engine implements the concept of hydraulic and electrodynamic flow rate matching to achieve electrical control. The engine uses a set of meso-scaled silicon deflection springs to assemble the hydraulics to the electrodes, allowing to decouple the corresponding process flows. The micro-fabrication of the engine is described and novel technologies that were developed are reported. Experimental results that demonstrate cumulative uniform and steady operation are provided. Current-flowrate characteristics of the engine are in agreement with a reduced-order model. Experimental data demonstrating the low divergence of electrospray emitter arrays operated in the single Taylor Cone is in qualitative agreement with a reduced-order mode that assumes the absence of a thermalized tail in the plume

Abstract: The F-35 Joint Strike Fighter (JSF) prognostics and health management (PHM) program is redefining the baseline for aircraft PHM. The objective is a management system that enables the F-35 aircraft to identify and report its own maintenance requirements, maximising aircraft use and minimising logistical overhead. JSF PHM offers aircraft operational cost and safety benefits above and beyond any air-vehicle strategy currently employed. For the propulsion system, the required input to F-35 PHM is achieved through monitoring a range of engine subsystems, using both mature and new technologies, and combining the information to form the engine health status and prognosis. The propulsion system PHM sensor suite incorporates several emerging technologies, including gas path debris monitoring. This paper provides a top-level description of the debris monitoring technology, its implementation and integration for F-35 and the development route planned to achieve the maturity level required for initial service release.

Abstract: A “silent † aircraft” is defined to be an aircraft that, in a typical urban area, is inaudible outside of the airport boundary. This paper describes the creation, implementation, and use of an integrated design tool to predict and optimize the performance and costs associated with producing a novel, commercial aircraft design with a step change in noise reduction. The silent aircraft uses a highly integrated configuration where a quiet propulsion system is embedded in a Blended-Wing-Body type airframe. This allows the shielding of forward radiated engine noise and the extensive use of acoustic liners. Multidisciplinary aircraft design models, which use a combination of simple physics and empirical relations, are adapted for the silent aircraft configuration. These models are used in conjunction with a multidisciplinary planform optimization capability. The resulting silent aircraft design is assessed in terms of performance and acoustic signature. Significant component noise reductions can be achieved with a design that has a fuel burn competitive with next-generation commercial aircraft. Barriers to achieving the aggressive noise goal of the Silent Aircraft Initiative and the associated required technology developments are described.

Abstract: The present invention relates to a propulsion system of a vertical takeoff and landing aircraft or vehicle moving in any fluid or vacuum and more particularly to a vector control system of the vehicle propulsion thrust allowing an independent displacement with six degrees of freedom, three degrees of translation in relation to its centre of mass and three degrees of rotation in relation to its centre of mass. The aircraft displacement ability using the propulsion system of the present invention depends on two main thrusters or propellers and which can be tilted around pitch is (I) by means of tilting mechanisms and, used to perform a forward or backward movement, can be tilted around roll axis (X) by means of tilting mechanisms and, used to perform lateral movements to the right or to the left and to perform upward or downward movements (Z), the main thrusters being further used to perform rotations around the vehicle yaw axis (Z) and around the roll is (X). The locomotion function also uses one or two auxiliary thrusters or propellers and mainly used to control the rotation around the pitch axis, these thrusters or propellers and being fixed at or near the longitudinal is of the vehicle, with there thrust perpendicular or nearly perpendicular to the roll and pitch axis of the vehicle.

Abstract: U.S. share of the world launch market fell to 20% by 2002. During that period, only two new booster engines have been developed and flight certified in this country. Only limited progress has been made in reducing engine costs or increasing performance although these factors are not necessarily directly related. Upper-stage and in-space propulsion in the United States have not fared much better in the world market. On the other hand, space-faring nations in Europe, the Middle East, Asia, and the former Soviet Union are believed to have developed 40–50 new, high-performance engines over the same period. This trend will have to be reversed to enable future exploration missions. The intent of this paper is to summarize past propulsion-system development, assess the current status of U.S. space propulsion, survey future options, evaluate potential impact of ultra low-cost, small launch-vehicle programs, and discuss some future propulsion needs for space exploration.

Abstract: A propulsion system for a vehicle, comprising of an internal combustion engine, a thermoelectric device in thermal communication with the engine, and a control system for controlling the engine and the thermoelectric device during a first mode, supply electrical energy to the thermoelectric device to cause the thermoelectric device to produce at least some heat, and during a second mode, operate the engine to produce at least some heat, where the thermoelectric device is operated to convert a temperature gradient at the thermoelectric device to electrical energy.

Abstract: High temperature sensors and electronics are necessary for a number of aerospace propulsion applications. The Sensors and Electronics Branch at NASA Glenn Research Center (NASA GRC) has been involved in the design, fabrication, and application of a range of sensors and electronics that have use in high temperature, harsh environment propulsion environments. The emphasis is on developing advanced capabilities for measurement and control of aeropropulsion systems as well as monitoring the safety of those systems using Micro/Nano technologies. Specific areas of work include SiC based electronic devices and sensors; thin film thermocouples, strain gauges, and heat flux gauges; chemical sensors; as well as integrated and multifunctional sensor systems. Each sensor type has its own technical challenges related to integration and reliability in a given application. These activities have a common goal of improving the awareness of the state of the propulsion system and moving towards the realization of intelligent engines. This paper will give an overview of the broad range of sensor-related development activities on-going in the NASA GRC Sensors and Electronics Branch as well as their current and potential use in propulsion systems.

Abstract: Hub motors have always been considered as propulsion for electric vehicles, but not widely used due to various negative aspects. One of these is the uncertainty of the effect the added wheel mass has on the stability, safety and comfort of the vehicle. In this paper, frequency analysis as well as simulations of the system is done using a simple model that represents the vehicle suspension system and wheels. The results of the hub driven vehicle are compared to that of a standard vehicle. It is shown that the added wheel mass has no effect on the stability of the vehicle and that the frequency response is within the accepted comfort range.

Abstract: A combined analytic and CFD-based two-dimensional airbreathing generic hypersonic flight vehicle model has been developed for control design and flight simulation environment. The vehicle, CSULA-GHV, is inspired by a set of mission requirements broadly accepted for a hypersonic cruise vehicle intended as a reusable launch vehicle (RLV) for access to space or for military application. The GHV has a simple configuration consisting of a fore-body diffuser, a scramjet engine, and an aft-body expansion nozzle. Longitudinal control is affected by the thrust setting (hydrogen fuel rate) elevon deflection. Complete aerodynamic, coupled aero-propulsion and aeroelastic data for the vehicle are presented in graphic format, and polynomial form using FLUENT CFD simulations at various Mach numbers, angles of attack, fuel rate and elevon settings. The interaction between aerodynamics, propulsion system, and vehicle elasticity are calculated and quantified. For control design, a set of nonlinear longitudinal equations of motion for the vehicle are presented which include both an inverse square law, gravitational model and the centripetal acceleration. The combined analytic-CFD approach is used to generate the static aerodynamic and propulsion data in the form of polynomial expressions. The vehicle's structural dynamics are accounted for by assuming that elastic deformations in the first few modes amount to an effective change in angle of attack and elevon effectiveness. These changes in turn affect engine performance and control surface effectiveness. Structural modes are obtained from a finite element model using NASTRAN.

Abstract: Integrated propulsion systems and methods for blended wing aircraft are disclosed. In one embodiment, a propulsion system at least one engine operatively disposed within an engine flow duct having an engine inlet and an engine exhaust aperture, and at least one fan operatively disposed within a fan flow duct having a fan inlet and a fan exhaust aperture. The engine and fan rotational axes extending at least approximately along a lengthwise direction of the aircraft, the fan flow duct being separate from the engine flow duct. A transmission assembly is operatively coupled between the at least one engine and the at least one fan, the transmission assembly being configured to transmit a rotary output from the at least one engine to rotate the at least one fan.

Abstract: With turbine segments controlled electrically in a shaftless design, the turbine of the present invention creates high propulsion efficiencies over a broader range of operating conditions through the integration of gas turbine, electric and magnetic power systems, advanced materials and alternative petroleum-based combustion cycles.

Abstract: The application of pod propulsion in a number of vessel types has been increasing steadily over the last two decades. This increase is attributed to the great advantages being offered by pod propulsion systems such as high manoeuvring capability, low noise and vibration, low fuel consumption, etc. Despite these advantages, operators are cautious due to the encountered teething problems, especially in the very competitive passenger ship market, where reliability and the maintainability of the service are crucial. This paper presents a reliability assessment methodology and its application to a combined four-pod propulsion system on a vessel equipped with two fixed- and two rotating-pod units. The assessment methodology made use of Failure Mode and Effect Analysis, Fault Tree Analysis (FTA) and Markov Analysis complementarily. In the FTA, minimal cut set, reliability importance measure and availability analyses were also considered. From the quantitative reliability assessment, the calculated reliabilities of each fixed- and rotating-pod unit, their components' reliabilities as well as the reliability of the combined four-pod propulsion system showed good agreement with the acceptable reliability criteria suggested by the pod manufacturers/operators based on the service experience.

Abstract: The flow/acoustic environment around the jet exhaust of an engine when installed on an airplane, say, under the wing, is highly asymmetric due to the pylon, the wing and the high-lift devices. Recent scale model tests have shown that such Propulsion Airframe Aeroacoustic (PAA) interactions and the jet mixing noise can be reduced more than with conventional azimuthally uniform chevrons by uniquely tailoring the chevrons to produce enhanced mixing near the pylon. This paper describes the community noise results from a flight test on a large twin-engine airplane using this concept of azimuthally varying chevrons for engines installed under the wing. Results for two different nozzle configurations are described: azimuthally varying "PAA T-fan" chevrons on the fan nozzle with a baseline no-chevron core nozzle and a second with PAA T-fan chevrons with conventional azimuthally uniform chevrons on the core nozzle. We analyze these test results in comparison to the baseline no-chevron nozzle on both spectral and integrated power level bases. The study focuses on the peak jet noise reduction and the effects at high frequencies for typical take-off power settings. The noise reduction and the absolute noise levels are then compared to model scale results. The flight test results verify that the PAA T-fan nozzles in combination with standard core chevron nozzles can, indeed, give a reasonable amount of noise reduction at low frequencies without high-frequency lift during take-off conditions and hardly any impact on the cruise thrust coefficient.

Abstract: The theory of optimal control is used to find the best trajectories for the capture maneuver of an interplanetary probe, which employs electric propulsion. The thrust magnitude and direction are optimized to exploit the spacecraft continuous steering capabilities and maximize the spacecraft final mass. Strategies, which involve propelled and coast arcs, are analyzed. The influence on the optimal trajectories of some parameters, such as the thrust, the specific impulse, and the initial velocity, is also discussed

Abstract: Lifting and propulsion system for aircraft with vertical take-off and landing that consists of applying to the aircraft certain propeller engines and rotating lifting systems around the transversal shafts and near the centre of gravity, presenting pairs of stabilizing propellers, turbines or fans in counter-rotation activated by electrical motors on the tips of the wings, nose and stabilizers on the tail of the aircraft, the electrical motors are powered by batteries, supercondensators, high powered electrical generators activated by the engines and by special auxiliary power units.

Abstract: A computational flow field and predicted jet noise source analysis is presented for asymmetrical fan chevrons on a modern separate flow nozzle at take off conditions. The propulsion airframe aeroacoustic asymmetric fan nozzle is designed with an azimuthally varying chevron pattern with longer chevrons close to the pylon. A baseline round nozzle without chevrons and a reference nozzle with azimuthally uniform chevrons are also studied. The intent of the asymmetric fan chevron nozzle was to improve the noise reduction potential by creating a favorable propulsion airframe aeroacoustic interaction effect between the pylon and chevron nozzle. This favorable interaction and improved noise reduction was observed in model scale tests and flight test data and has been reported in other studies. The goal of this study was to identify the fundamental flow and noise source mechanisms. The flow simulation uses the asymptotically steady, compressible Reynolds averaged Navier-Stokes equations on a structured grid. Flow computations are performed using the parallel, multi-block, structured grid code PAB3D. Local noise sources were mapped and integrated computationally using the Jet3D code based upon the Lighthill Acoustic Analogy with anisotropic Reynolds stress modeling. In this study, trends of noise reduction were correctly predicted. Jet3D was also utilized to produce noise source maps that were then correlated to local flow features. The flow studies show that asymmetry of the longer fan chevrons near the pylon work to reduce the strength of the secondary flow induced by the pylon itself, such that the asymmetric merging of the fan and core shear layers is significantly delayed. The effect is to reduce the peak turbulence kinetic energy and shift it downstream, reducing overall noise production. This combined flow and noise prediction approach has yielded considerable understanding of the physics of a fan chevron nozzle designed to include propulsion airframe aeroacoustic interaction effects.

Abstract: Microwave discharge ion engines "mu10" are dedicated to the main propulsion on the HAYABUSA asteroid explorer. In a development program, various tests and assessments were conducted on the ion engines and the spacecraft. They include endurance tests, an electromagnetic interference susceptibility test, an interference test between the plasma and communication microwave, a beam exhaust test on the spacecraft, assessments on the plasma interference with a solar array, and so on. The spacecraft was launched in deep space by the M-V rocket in May 2003. After vacuum exposure and several runs of baking for reduction of residual gas, the ion engine system established continuous acceleration of the spacecraft toward the asteroid ITOKAWA. The spacecraft passed through a perihelion of 0.86 astronomical unit (AU) in February 2004 and an aphelion of 1.7 AU in February 2005, becoming the first solar electric propulsion system to travel this far toward and away from the Sun. The HAYABUSA succeeded in rendezvousing with the target asteroid in September 2005