Propulsion

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

Electrodynamic Tether Applications and Constraints

Abstract: Propulsion and power generation by bare electrodynamic tethers are revisited in a unified way and issues and constraints are addressed. In comparing electrodynamic tethers, which do not use propellant, with other propellantconsuming systems, mission duration is a discriminator that defines crossover points for systems with equal initial masses. Bare tethers operating in low Earth orbit can be more competitive than optimum ion thrusters in missions exceeding two-three days for orbital deboost and three weeks for boosting operations. If the tether produces useful onboard power during deboost, the crossover point reaches to about 10 days. Power generation by means of a bare electrodynamic tether in combination with chemical propulsion to maintain orbital altitude of the system is more efficient than use of the same chemicals (liquid hydrogen and liquid oxygen) in a fuel cell to produce power for missions longer than one week. Issues associated with tether temperature, bowing, deployment, and arcing are also discussed. Heating/cooling rates reach about 4 K/s for a 0.05-mm-thick tape and a fraction of Kelvin/second for the ProSEDS (0.6-mm-radius) wire; under dominant ohmic effects, temperatures areover200K (night) and 380 K (day) for the tape and 320 and 415 K for that wire. Tether applications other than propulsion and power are briefly discussed.

Reconfigurable spacecraft attitude takeover control in post-capture of target by space manipulators

Abstract: Most current research on reconfigurable control system puts emphasis on reconfiguration for adapting to actuator failures. However, the reconfigurable control system is necessitated for spacecraft attitude takeover control in the application of capturing target spacecraft whose fuel is exhausted to extend its operational lifetime by supplying them propulsion, navigation and guidance services. In this scenario, the capture of target spacecraft by space manipulators will cause a large shift in the dynamics of the service spacecraft. Not only do the mass properties change, but also does the thruster configuration. The changes in the mass, center of mass and inertia of the combined spacecraft will cause changes in the equivalent force exerted by each thruster. In this paper, considering the changes of thruster configuration and the control reallocation, a reconfigurable control system is designed for spacecraft attitude takeover control in post-capture of target by space manipulators in order to adapt to changes in the mass properties. The unknown inertia properties of target spacecraft in the system constitute a formidable technical challenge for controller design. Therefore, a modified adaptive dynamic inverse controller is proposed to provide global asymptotic stability in the presence of model uncertainties and nonlinearities. Moreover, by the null-space intersections control reallocation method, the thrust forces of service spacecraft can be redistributed and satisfy some constraints. Numerical simulations validate the feasibility of reconfigurable spacecraft attitude takeover control with large center of mass shifts and unknown inertia properties.

Modeling for Control of a Generic Airbreathing Hypersonic Vehicle

Abstract: The unique airframe-engine configuration of airbreathing hypersonic flight vehicles (AHFV) pose a significant challenge for design of controllers for these vehicles. The Airframe-engine configuration, the wide range of speed and the extreme flight conditions result in significant coupling among various dynamics and modeling uncertainties. There is almost a complete absence of models that adequately include and quantify the unique attributes for this class of vehicles. This paper describes a high-fidelity CFD-based model of a full scale generic airbreathing hypersonic flight vehicle under development at the Multidisciplinary Flight Dynamics and Control Laboratory (MFDCLab, www.calstatela.edu/centers/mfdclab) at California State University, Los Angeles (CSULA). The vehicle (CSULA-GHV), which has an integrated airframe-propulsion system configuration, resembles an actual test vehicle. The vehicle is specifically designed to study the challenges associated with modeling and control of airbreathing hypersonic vehicles and to investigate and quantify the couplings between the aerodynamics, the propulsion system, the structural dynamics, and the control system. The configuration of the vehicle and its dimensions are developed based on 2-D compressible flow theory, and a set of mission requirements broadly accepted for a hypersonic cruise vehicle intended for both space access and military applications. Analytical aerodynamic calculations are conducted assuming a cruising condition of Mach 10 at an altitude of 30 km. The 2-D oblique shock theory is used to predict the shock wave angles, the pressure on the frontal surface, and the Mach number at the engine inlet. The scramjet engine is simply modeled by a 1-D compressible flow with heating. The exit flow is modeled using 2-D expansion wave theory to predict the pressure on the rear surface. The unique aspect of this study is the use of coupled simulations using multi-physic software in conjunction with theory enabling quantification of the couplings which are broadly ignored in models used for control system design. Simulation results developed to date are presented.

Aircraft System Study of Boundary Layer Ingesting Propulsion

Abstract: A trade-factor-based system study has been carried out to identify fuel burn benefits associated with boundary layer ingestion (BLI) for generation-after-next (N+2) aircraft and propulsion system concepts. The analysis includes detailed propulsion system engine cycle modeling for a next-generation, Ultra-High-Bypass (UHB) propulsion system with BLI using the Numerical Propulsion System Simulation (NPSS) computational model. Cycle modeling was supplemented with one-dimensional theory to identify limiting theoretical BLI benefits associated with the blended wing body reference vehicle used in the study. The system study employed low-order models of engine extractions associated with inlet flow control; nacelle weight and drag; fan performance; and inlet pressure losses. Aircraft trade factors were used to estimate block fuel burn reduction for a long-range commercial transport mission. Results of the study showed that a 3-5% BLI fuel burn benefit can be achieved for N+2 aircraft relative to a baseline high-performance, pylon-mounted, UHB propulsion system. High-performance, distortion-tolerant turbomachinery, and low-loss, low-drag inlet systems, were identified as key enabling technologies. Larger benefits were estimated for N+3 configurations for which larger fractions of aircraft boundary layer can be ingested.

Preliminary Sizing Method for Hybrid-Electric Distributed-Propulsion Aircraft

Abstract: The use of hybrid-electric propulsion (HEP) entails several potential benefits such as the distribution of power along the airframe, which enables synergistic configurations with improved aerodynamic and propulsive efficiency. This paper presents a comprehensive preliminary sizing method suitable for the conceptual design process of hybridelectric aircraft, taking into account the powertrain architecture and associated propulsion–airframe integration effects. To this end, the flight-performance equations are modified to account for aeropropulsive interaction. A series of component-oriented constraint diagrams are used to provide a visual representation of the design space. A HEPcompatible mission analysis and weight estimation are then carried out to compute the wing area, powerplant size, and takeoff weight. The resulting method is applicable to a wide range of electric and hybrid-electric aircraft configurations and can be used to estimate the optimal power-control profiles. For demonstration purposes, the method is applied to a regional HEP aircraft featuring leading-edge distributed propulsion (DP). Three powertrain architectures are compared, showing how the aeropropulsive effects are included in the model. Results indicate that DP significantly increases wing loading and improves the cruise lift-to-drag ratio by 6%, although the growth in aircraft weight leads to an energy consumption increase of 3% for the considered mission.