Showing papers on "Propulsion published in 1974"

An oscillating-boundary-layer theory for ciliary propulsion

Abstract: This paper analyses the locomotion of a finite body propelling itself through a viscous fluid by means of travelling harmonic motions of its surface. The methods are developed with application to the propulsion of ciliated micro-organisms in mind. Provided that the metachronal wavelength (of the surface motions) is much smaller than the overall dimensions of the body, the flow can be divided into an oscillating-boundary-layer flow to which is matched an external complementary Stokes flow. The present paper employs the envelope model of fluid/cilia interaction to construct equations of motion for the oscillating boundary layer. The final solution for the propulsive velocity is obtained by application of the condition of zero total force on the self-propelling body; alternatively, if the organism is held at rest, the thrust it generates can be computed. Various optimum propulsive velocities for self-propelling bodies and optimum thrusts for restrained bodies are analysed in some simple examples. The results are compared with the relatively sparse observations for a number of micro-organisms.

Hydrostatic propulsion system

Abstract: A closed recirculating hydrostatic transmission system suitable for driving a traction vehicle. The system includes a pair of hydrostatic engine driven variable displacement pumps either of different displacements or engine driven at different speed ratios and each pump being operative to drive hydrostatic motors at the various wheels and in separate closed loop drive circuits such that accurate flow division as between the circuits is effected for driving the vehicle in four-wheel drive or, at the operator's selection, for driving the motors in the one closed loop circuit at a higher speed in two-wheel drive by means of the pump of larger discharge volume. An operator's control operates both pumps together within the limits of the smaller discharge pump in four-wheel drive, and operates the larger discharge pump within the limits thereof while rendering ineffective the smaller discharge pump in two-wheel drive. Valve means enables smooth transition and shifting between two and four-wheel drive at any time. Flow divider-combiner means in each closed loop circuit adjusts fluid flow to each motor as a function of steering angle to assure positive traction at each driven wheel in either forward or reverse drive under all surface conditions, and to differentiate as required wheel speeds during vehicle steering operations. Braking may be effected by reversing pump flow at selected conditions of either decreasing, constant or increasing engine speed.

Mixed mode propulsion aerospace vehicles

Abstract: An aerospace vehicle incorporates within the same stage two different main propulsion systems that are operated in sequence. The first system involves the use of high density-impulse propellants, and the second system involves the use of lower density-impulse propellants to achieve higher final velocities than would otherwise be the case if the total available volume were used for either set of propellants separately. In one arrangement, one stage of a propulsion aerospace vehicle incorporates provisions for carrying and burning three different propellants, --two fuels and a common oxidizer or two oxidizers and a common fuel. Certain of the wing and/or body structures are designed to serve as tankage volume for low pressure storage of at least one of the propellants, which is one that does not require special pressurized tanks. The use of common oxidizer or fuel, and common wing/body/tankage structure, simplifies and lightens the vehicle, thus enhancing its ability to realize the benefits of what is referred to as the mixed-mode propulsion principle. When one of the fuels is utilized in airbreathing engines, additional flexibility is provided for vehicle operation in the atmosphere as well as in space.

Scramjet nozzle design and analysis as applied to a highly integrated hypersonic research airplane

Abstract: The configuration and performance of the propulsion system for the hypersonic research vehicle are discussed. A study of the interactions between propulsion and aerodynamics of the highly integrated vehicle was conducted. The hypersonic research vehicle is configured to test the technology of structural and thermal protection systems concepts and the operation of the propulsion system under true flight conditions for most of the hypersonic flight regime. The subjects considered are: (1) research vehicle and scramjet engine configurations to determine fundamental engine sizing constraints, (2) analytical methods for computing airframe and propulsion system components, and (3) characteristics of a candidate nozzle to investigate vehicle stability and acceleration performance.

Aircraft with combination stored energy and engine compressor power source for augmentation of lift, stability, control and propulsion

Abstract: Vertical and short take-off and landing (V/STOL) aircraft has at least one structural element which is an inflatable gas storage compartment rechargeable with compressed air from the engine compressors. This air when used in combination with suction air and compressed air from the engine compressors under control of the pilot produces in the case of vertical take-off and landing (VTOL) air flotation beneath the aircraft initiating vertical lift-off and completing a short hover just prior to the instant of touchdown during landing and during the remaining part of the take-off and landing maneuver augments lift and stability and control by such as enhancing the boundary layer and moving compressed air over the control surfaces. This air when used for short take-off and landing (STOL) flight when speed is below power-on stall can augment lift and stability and control by such as enhancing the boundary layer and moving compressed air over the control surfaces.

Marine power transmission system

Abstract: A power transmission having an input shaft for connection to a single main propulsion engine, a pair of parallel output shafts and a pair of fluid actuated friction clutches disposed on each output shaft for selectively engaging gear sets to drive the output shafts in the same or opposite directions of rotation independently or simultaneously. A hydraulic control circuit including a manually operated control unit is used in connection with the transmission in a boat having two parallel propeller shafts whereby the clutches can be engaged and disengaged to provide forward and rearward propulsion of the boat as well as steering ofo the boat when underway.

Marine propulsion reversing transmission with hydraulic assist

Abstract: Disclosed herein is a marine propulsion device comprising a reversing transmission located in a propulsion unit and connecting a drive shaft to a propeller shaft and shiftable between neutral, forward drive, and rearward drive condition, together with a mechanical linkage extending in the propulsion unit and connected to the reversing transmission for operating the reversing transmission in response to movement of the mechanical linkage, and a hydramilic arrangement actuated in response to initial movement of the mechanical linkage for assisting in moving the mechanical linkage to operate the reversing transmission. The mechanical linkage includes a shift actuator carried by the propeller shaft for common rotary movement with the propeller shaft and for axial movement relative to the propeller shaft and connected to a clutch dog for common movement therewith, together with a rod movable transversely of the shift actuator, and a coupling connecting the rod and the shift actuator for effecting shift actuator movement in one direction axially of the propeller shaft in response to rod movement in one direction transversely of the propeller shaft and for effecting shift actuator movement in the other direction in response to rod movement in the other direction and for simultaneously permitting rotary shift actuator movement relative to the rod.

Detonation Propulsion for High Pressure Environments

Abstract: One limitation encountered by chemical rocket propulsion in high-pressure planetary atmospheres is illustrated by the conflict between the dependence of specific impulse on the ratio of chamber pressure to ambient pressure and the dependence of the motor structural design on the difference between the pressures. This work proposes to resolve the difficulty by employing detonating propellant in which the high pressures necessary for efficient propulsion are developed over a short time and need not be contained statically. Experimental results are presented to substantiate this claim of relatively high performance, together with an analytical development that approximately describes the flow dynamics. Nomenclature A = nozzle cross-sectional area ca — speed of sound in ambient gas CD = flow coefficient ea = specific energy released in explosion, EJme Ea — energy released in explosion Ea' = energy released per solid angle, Ejai /i/2 = functions of y, Eq. (15) /3 = function, Eq. (19) F = axial thrust g = acceleration of gravity gc = conversion constant G = integral, Eq. (16) H = integral, Eq. (16) Ht = total enthalpy A/I = height / = specific impulse L = axial length of nozzle m = mass of gas ma = mass of ambient gas contained in nozzle me = mass of explosive material ra = mass flow rate M = mass of equipment Mw = molecular weight P = static pressure Pa = ambient pressure Po = plateau pressure Ap = pressure difference, Pt — Pa r — radial distance from apex of cone re = effective radial length of nozzle, Table 4 R = gas constant Ru = universal gas constant Ri = characteristic radial length, Eq. (17) t — time T = temperature u = velocity V = volume z = elevation a = function of y, Table 3 y = specific heat ratio

Linear reluctance motor for the propulsion of rail transportation means

Abstract: A linear reluctance motor for the drive of rail transportation means which includes a primary part whose coils are fed with a.c. power while its secondary part is constructed rail-like, is arranged parallel to the track and is fixedly installed on the ground; the secondary part is thereby in the form of a toothed rack of ferromagnetic material whereby the primary part produces a magnetic field traveling cyclically in a direction opposite the drive direction and cooperating with the toothed rack.

Drive arrangement for a track-bound electric self-propelled vehicle

Abstract: A drive arrangement for a track-bound self-propelled vehicle includes a separate, high-speed electric propulsion motor for each driving wheel. The pinion of the propulsion motor forms the sun gear of a planetary drive. A stationary axle is provided for the driving wheel which also serves as the planet carrier for the planet gears which drive the ring gear. The ring gear in turn drives the hub of the driving wheel.

High-speed rotor dynamics - An assessment of current technology for small turboshaft engines

Abstract: An extensive study was made to determine current needs for research in rotor dynamics to solve problems encountered in small high-speed turboshaft engines for helicopter and aircraft propulsion. The purpose of this paper is to report the state-of-the-art for this area as completely and concisely as possible. The present and past philosophy of rotor-bearing system design including the impact of the demand for front drives, is discussed. Methods for critical speed prediction and high-speed balancing are reviewed. The trend to higher speeds is seen to require consideration of new approaches to balancing through flexural modes. The major parameters available for control by the designer are shown to be the bearing support properties, and recommendations are made for improving the accuracy of prediction of these properties. Nonsynchronous excitation is categorized according to the mechanisms producing the forces, and a need is shown for better methods to identify the resulting whirling and vibration, since several of these motions are potentially unstable. Finally, reasons are given for the predominant use of rolling-element bearings in these engines, and the potential for special applications of oil-film and gas bearings is discussed.

Flat guidance schemes for magnetically levitated high‐speed guided ground transport

Abstract: A magnetically levitated high‐speed vehicle requires a noncontact guidance system. Guideway configurations are discussed, and the possibility of achieving guidance from a flat surface is investigated. A vehicle with electrodynamic suspension and linear synchronous motor propulsion carries superconducting magnets which may be used for guidance purposes. Eight possible ``flat'' guidance mechanisms are examined. It is shown that the interaction between vehicle‐borne magnets and levitation strips or linear synchronous motor (LSM) windings cannot provide adequate restoring forces. Additional conductors are therefore required for guidance. The use of either vertically mounted rectangular loops or horizontally mounted null‐flux (NF) loops under either the levitation magnets or propulsion magnets is therefore examined. The most promising system involves the interaction between propulsion magnets and horizontal NF loops, with the interaction between propulsion magnets and the edges of the levitation strips providing backup guidance. The guidance characteristics are analyzed and checked by model impedance measurements, and it is shown that, for this system a lateral stiffness of 106 N/m can be achieved.

Methods and apparatus for controlling the propulsion of aquatic vessels incorporating such apparatus

Abstract: For the purpose of controlling the position of an oil rig or other vessel, it is provided with a plurality of steerable thrusters, one pair being located at the bow and one pair at the stern. The two thrusters of each pair are arranged to exert thrust at an angle of 90° so that the net thrust vector may be "steered" merely by controlling the magnitude and direction of thrust of each thruster. By this means it is only necessary to change the directions of the thrust of the thrusters relatively infrequently.

Pulsed Plasma Propulsion Technology.

Abstract: : An engineering prototype pulsed plasma propulsion system delivering lmlb (4.45mN) of thrust at a specific impulse of 1794s and having a total impulse capability of 38,284 lb-s (166,OONs) has been designed and completely fabricated. The thrust efficiency is 31.5% and the overall system efficiency is 25.3%. The system, including structure, capacitors, breadboard power converter and propellant weighs 50.23lb (22.8kg).

Propulsion control system for electrically powered vehicles

Abstract: Propulsion control system for electrically powered vehicles, typically heavy duty off-road type work vehicles having electric motor driven wheels. In embodiment shown, power is supplied from direct current generator driven by internal combustion engine. Motor and generator field excitation is automatically varied responsive to selected machine operating conditions and improved means are provided to accomplish such variation. The provision and application of certain propulsion system parameters effects improved machine performance with minimum demand for operator skill and attention.

Propulsion system for watercraft and the like

Abstract: A propulsion and control system for watercraft, surface craft and the like wherein at least one thrust generator capable of continuously producing thrusts of variable magnitudes is pivotally mounted to the vehicle in a manner such that it is capable of simultaneous swing movement about at least two axes angularly oriented with respect to each other. The invention includes steering control apparatus operative during normal maneuvering of the watercraft to selectively position the thrust generator in a plurality of orientations with respect to the axes such that selective combinations of thrust magnitudes and directions facilitates selective propulsion and control of the vehicle. The steering control apparatus being positionable during normal maneuvering of the watercraft such that the thrust generator is positionable from forward to reverse and back again for facilitating selective propulsion and control of the craft between corresponding forward and reverse directions.

Cogas--a new look for naval propulsion

Abstract: This paper discusses the combined gas and steam turbine system using second generation gas turbines with the purpose of analyzing the advantages of such a plant for U.S. Navy use. The discussion begins with the general criteria for Navy machinery development followed by target goals for design of a Navy propulsion plant. Results of a recent feasibility study of a compact COGAS plant for destroyer use, including plant description and performance analysis are presented. The impact of such a plant on the ship design of a typical destroyer is compared with the target goals discussed earlier. Finally, the reasons why such a plant should be considered for development by the Navy are summarized, showing how the COGAS plant fulfills Navy machinery development objectives. (Authors)

System for attenuating vertical oscillations of a suspended track bound propulsion vehicle

Abstract: In a suspended track bound propulsion vehicle driven by a synchronous linear motor comprising an exciter winding and a traveling field winding vertical oscillations are attenuated by supplying to the synchronous linear motor with an AC voltage variable in amplitude and phase with variations obtained through an adjustable controlled static converter responsive to a control signal developed in a damping control having an input from measuring means which output a variable which is proportional to the vertical oscillations of the propulsion vehicle.

Aerodynamics of jet flap and rotating cylinder flap STOL concepts

Abstract: The aerodynamic effectiveness of various propulsive lift concepts to provide for the low speed performance and control required for short takeoff and landing aircraft is discussed. The importance of the interrelationship between the propulsion system and aerodynamic components of the aircraft is stressed. The relative effectiveness of different lift concepts was evaluated through static and wind tunnel tests of various aerodynamic models and propulsion components, simulations of aircraft, and in some cases, flight testing of research aircraft incorporating the concepts under study. Results of large scale tests of lift augmentation devices are presented. The results of flight tests of STOL research aircraft with augmented jet flaps and rotating cylinder flaps are presented to show the steeper approach flight paths at low forward speeds.

Marine propulsion system

Abstract: A marine propulsion system includes a gas turbine, a generator, a motor and a fixed pitch propeller. Means are provided to operate the motor synchronously in the normal ahead and astern directions and to operate the motor asynchronously in the slow ahead and astern directions with the gas turbine operating at its idle setting. Means are also provided to brake the propeller before astern torque is applied when the power propulsion lever is rapidly moved from the normal ahead setting to the normal astern setting by operating the motor as a generator.

Steam-powered aircraft

Abstract: A steam generator on the aircraft selectively delivers high-pressure steam to atmospheric discharge jets on a lift rotor and/or to peripheral jets on a forwardly-directed propulsion propeller. The propeller is enclosed by a hollow shroud into which the steam jets discharge so that the shroud acts both as a propeller efficiency-enhancing device and a steam condenser to permit recycling of the condensate.

Postioning apparatus for tracked transport vehicles with linear motor propulsion

Abstract: This invention concerns a positioning device for a transport vehicle, constrained to travel along a track. These transport vehicles are propelled by linear motor propulsion. Along the track are positioning points typically located at stations for entering and exiting the vehicle. Associated with the means for linear motor propulsion, stationary in the track at the positioning points are two switches, means to detect the velocity of the vehicle and a logic control circuit, so that acceleration, deceleration and zero strength excitation signals can be applied to the linear motor in the vehicle so as to cause the vehicle to come to rest at the positioning point. The apparatus controls a vehicle travelling in either direction along the track.

On the velocity induced by a semi-infinite vortex cylinder: with extension to the short solenoid

Abstract: The mathematical analysis of the induced velocity components of a screw propeller has occupied the attention of fluid dynamicists for many years. Early approaches to the problem concentrated mainly on momentum and blade element theories, neither of which are capable of providing a detailed knowledge of the flow field, except at the propeller plane or the boundary of the fluid. The early vortex theories also suffered from equally significant, but less severe, limitations and such methods were found to be completely unsatisfactory for many applications. In particular, the development of the ducted propeller for the propulsion of supertankers and VTOL aircraft has demanded a highly detailed knowledge of the flow field, especially around the propeller tip.

Apparatus for damping oscillations in the propulsion direction in a magnetically suspended propulsion vehicle driven by a synchronous linear motor

Abstract: A track bound propulsion vehicle such as a magnetically suspended vehicle and driven by a synchronous linear motor having a stator supplied from a fixed ac network with the stator installed along the track as a travelling field winding has a correcting element furnishing an ac output voltage at the network frequency and also connected to the travelling field winding to superimpose a voltage thereon with the phase of the ac output voltage of the correcting element adjustable by means of a control signal receiving an input from means measuring a quantity proportional to oscillations in the propulsion direction for damping such oscillations.

A method for determining optimum phasing of a multiphase propulsion system for a single-stage vehicle with linearized inert weight

Abstract: A general analytical treatment is presented of a single-stage vehicle with multiple propulsion phases. A closed-form solution for the cost and for the performance and a derivation of the optimal phasing of the propulsion are included. Linearized variations in the inert weight elements are included, and the function to be minimized can be selected. The derivation of optimal phasing results in a set of nonlinear algebraic equations for optimal fuel volumes, for which a solution method is outlined. Three specific example cases are analyzed: minimum gross lift-off weight, minimum inert weight, and a minimized general function for a two-phase vehicle. The results for the two-phase vehicle are applied to the dual-fuel rocket. Comparisons with single-fuel vehicles indicate that dual-fuel vehicles can have lower inert weight either by development of a dual-fuel engine or by parallel burning of separate engines from lift-off.

Ion Propulsion Flight Experience, Life Tests, and Reliability Estimates

Abstract: The application of low-thrust ion propulsion systems to space missions requires long duration (~ 5,000-20,000 hr) component operation Thus, components must be developed with wearout mean times to failure in excess of these required mission times Furthermore, chance failures which occur during the useful life of components must be minimized This paper makes an assessment of both early and wearout failure modes of ion propulsion systems by examining the results of existing developmental and long duration testing Estimates of chance failure rates of system components are also presented along with design concepts which maximize total propulsion system reliability I Introduction B ECAUSE of the long time operation required for most space applications, ion propulsion system reliability is a major concern For this reason, the long duration and space testing of critical components, subsystems, and systems associated with primary and auxiliary ion propulsion systems are of great importance It should be recognized, however, that although a large number of long duration tests have been conducted to date on ion propulsion systems, subsystems, and components, these tests have been part of a technology development phase and are not to be considered statistical reliability testing of fully developed systems Thus, even though space-qualified ion propulsion systems are becoming available, system reliability can only be inferred from the results of past and present developmental testing and estimated by analytical techniques

Design and Evaluation of a Highly Skewed Propeller for a Cargo Ship

Abstract: The design process and model evaluation of a highly-skewed propeller for a modern cargo ship are given. The design process is discussed in detail, including considerations of cavitation, mean and fatigue strength, and propeller-excited vibratory forces. Model experimental results are presented that tend to confirm the design process. Calculations, using unsteady lifting-surface theory, indicate that the highly skewed propeller will reduce blade-frequency thrust and torque by 90 percent, and will increase blade-frequency vertical bearing force by 2 percent, compared to the propeller currently installed on the ship.

Attitude Stability of a Flexible Solar Electric Spacecraft; A Parametric Study

Abstract: The influence of large area solar array flexibility on the attitude control of a solar electric spacecraft is analyzed. The spacecraft consists of a rigid central body, two flexible roll-out solar arrays, and a cluster of three electric propulsion engines. Each engine has gimballing or translational capacity, or both, for attitude control purposes. A parametric stability study of various spacecraft configurations was made, using hybrid coordinate techniques in an eigenvalue analysis. Parameters varied were solar array aspect ratio, solar array first natural frequency, solar array rotation angle about the yaw axis, and sensor gain factors. Only the first six modes of solar array vibration were included in the study. The attitude response characteristics of the various spacecraft configurations were obtained by means of a digital computer simulation program of the system's equations of motion. The feasibility of using the thrusters for attitude control of electric propulsion spacecraft is demonstrated. It is also shown that although the dynamics effects of large-area flexible solar arrays can be harmful, changes in the control system parameters can insure stable attitude control.

Special aircraft using a novel integrated lift, propulsion and steering system

Abstract: An aircraft having a body on which is mounted an integrated lift, propulsion and steeing system inclusive of cycloidal propellers having horizontal axes of rotation capable of developing net thrust forces at any given angle in a vertical plane Each propeller is externally driven and is formed with a circular array of blades at the periphery of a common rim and the blades can be turned to vary the angle of thrust by operation of a common control head