Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

System for controlling the propulsion on motor vehicles

Abstract: A system for controlling the propulsion on motor vehicles which not only enables the output torque of the drive unit of the vehicle to be utilized in an optimum manner in critical driving situations, especially under extreme road conditions, but also endows the vehicle with good stability and enhanced driving safety. A comparator is provided, in a propulsion control system which is triggered by at least one presettable or permanently preset threshold value of the speed of the vehicle, and generating an output signal causing the drive torque to be reduced, as soon as this threshold value is exceeded and a signal is present, which indicates that an individual wheel brake is being activated and/or that one of the driven wheels is tending to spin. The threshold value of the speed of the vehicle, which value governs the control process, is preferably regulated in accordance with the transverse acceleration which acts on the vehicle whenever it follows a curved path.

A Micro-Fabricated Linear Array of Electrospray Emitters for Thruster Applications

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

Thin silicon solar cells for large flexible arrays.

Abstract: THE past year has witnessed increasing interest in solar-powered, electrical propulsion systems for spacecraft in both the United States and the United Kingdom. In the United States the main interest is in the use of electrical propulsion for missions to Mars and Jupiter, where there is a marked payload advantage over chemically powered spacecraft which are limited by their energy rather than by their power. The incentive for the United Kingdom to initiate development in this field was provided by Burt1 who theoretically showed that it was possible to change independently all the elements of a spacecraft's orbit by means of small continuous thrusts from an electrical propulsion unit. In particular, he showed that the ability of the unit to change the inclination of an orbit made it possible for a communications satellite launched from a non-equatorial site to attain a geostationary orbit.

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).

Micropropulsion for Space — A Survey of MEMS-based Micro Thrusters and their Solid Propellant Technology

Abstract: In the last two decades, advances in microsystems technology have made micro mechanics mature enough to envisage miniaturization in the space industry. The motivation behind this development is the reductions in mass, satellite costs and launch costs in parallel with an increase in the reliability and flexibility of satellites. A cluster of many small satellites, commanded from a mothership, or totally independent, will, without any doubt, reduce the risk of mission failure and increase mission flexibility. This revolution in the space industry will rely on propulsion system development to ensure the maneuvering and fine positioning of micro and nano satellites (defined as satellites with mass between 20—100 kg and under 20 kg, respectively). This paper is provides a state-of-the-art review of micro thruster technologies for space applications. the intention is to overview the different technical solutions under investigation in the micropropulsion field, to assess their merits and disadvantages and to try to identify the promising ones in relation to future missions needs. First, the principles of propulsion and basic concepts and equations useful in describing and comparing propulsion systems are described. Then, a review micropropulsion needs for space is made and the options and technologies available for propulsion are presented. An outline is given of the technological efforts made in miniaturizing propulsion systems through examples from current research programs and the different micropropulsion technologies are compared. After illustrating the assets of microsystem technology in the micropropulsion field by the detailed presentation of one particular micropropulsion option investigated at LAAS-CNRS, namely solid propellant micro thruster arrays, a short discussion is given of the capability of microsystem technology to serve micropropulsion needs.