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In this first part of our paper, it is suggested to use solutions to boundary value problems in the optimization problems (in impulse formulation) for spacecraft trajectories in order to obtain the initial approximation, when boundary value problems of the maximum principle are solved numerically by the shooting method. The technique suggested is applied to the problems of optimal control over motion of the center of mass of a spacecraft controlled by the thrust vector of jet engine with limited thrust in an arbitrary gravitational field in a vacuum. The method is based on a modified (in comparison to the classic scheme) shooting method computation together with the method of continuation along a parameter (maximum reactive acceleration, initial thrust-to-weight ratio, or any other parameter equivalent to them). This technique allows one to obtain the initial approximation with a high precision, and it is applicable to a wide range of optimal control problems solved using the maximum principle, if the impulse formulation makes sense for these problems. 相似文献
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The problem of optimization of a spacecraft transfer to the Apophis asteroid is investigated. The scheme of transfer under analysis includes a geocentric stage of boosting the spacecraft with high thrust, a heliocentric stage of control by a low thrust engine, and a stage of deceleration with injection to an orbit of the asteroid’s satellite. In doing this, the problem of optimal control is solved for cases of ideal and piecewise-constant low thrust, and the optimal magnitude and direction of spacecraft’s hyperbolic velocity “at infinity” during departure from the Earth are determined. The spacecraft trajectories are found based on a specially developed comprehensive method of optimization. This method combines the method of dynamic programming at the first stage of analysis and the Pontryagin maximum principle at the concluding stage, together with the parameter continuation method. The estimates are obtained for the spacecraft’s final mass and for the payload mass that can be delivered to the asteroid using the Soyuz-Fregat carrier launcher. 相似文献
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Trajectories of spacecraft with electro-jet low-thrust engines are studied for missions planning to deliver samples of matter from small bodies of the Solar System: asteroids Vesta and Fortuna, and Martian moon Phobos. Flight trajectories are analyzed for the mission to Phobos, the limits of optimization of payload spacecraft mass delivered to it are determined, and an estimate is given to losses in the payload mass when a low-thrust engine with constant outflow velocity is used. The model of an engine with ideally regulated low thrust is demonstrated to be convenient for calculations and analysis of flight trajectories of a low-thrust spacecraft. 相似文献
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提高轨控发动机的真空比冲可以有效减少卫星变轨推进剂的消耗量,从而延长卫星的在轨工作寿命或增加有效载荷质量。介绍了我国在研的卫星用第三代铼/铱材料490 N发动机设计方案、技术攻关和试验情况,对工程化应用存在的问题进行了分析,并提出了改进和优化方案。在第二代490 N发动机的设计基础上,第三代490 N发动机成功攻克了可靠传热稳定工作喷注器、高性能喷注器与燃烧室匹配以及新型高温抗氧化材料制备等关键技术,真空比冲提高了10 s,达到325 s。两台发动机均通过了25 000 s鉴定级高空模拟热试车寿命考核,性能指标达到国际先进水平。但是针对试车子样数较少和铼/铱燃烧室制备工艺困难的问题,仍需进一步开展铼基体和铱涂层的高温性能研究,并继续优化发动机设计。 相似文献
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The problem of optimal control over many-revolution spacecraft orbit transfers between circular coplanar orbits of satellites is considered. The spacecraft flight is controlled by a thrust vector of a jet engine with restricted thrust (JERT). The mass expenditure is minimized at a limited time of flight. The optimal control problem is solved based on the maximum principle. The boundary value problem of the maximum principle is solved numerically using the shooting method. A modified computation scheme of the shooting method is suggested (multi-point shooting), as well as a method (correlated with the scheme) of choosing the initial approximation with the use of a solution to the optimization problem in the impulse formulation. The scheme and method allow one to construct many-revolution spacecraft orbit transfers. 相似文献
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《Acta Astronautica》2008,62(11-12):1019-1028
In this paper, the concept of Orbit Transfer Vehicle for Deep Space Exploration (Deep Space OTV) is proposed, and its effectiveness and feasibility are discussed. Basic concept is the separation of two functions required for the deep space exploration, the transportation to the destination, and the exploration at the destination. Deep Space OTV is a spacecraft specialized for the transportation to the deep space destination. It is an expendable spacecraft propelled by solar electric propulsion. The payload of Deep Space OTV is Explorer, which is a spacecraft specialized for the exploration at the deep space destination. The effectiveness of the concept is discussed qualitatively, focused on the merits of the separations of two functions. The feasibility of Deep Space OTV is discussed based on the conceptual design of the spacecraft and its applicability to deep space missions. Several deep space missions are modeled and the payload capacity of Deep Space OTV is estimated. The missions include Asteroid rendezvous, Mars orbiter, Lunar lander, and so on. 相似文献
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In this paper, the concept of Orbit Transfer Vehicle for Deep Space Exploration (Deep Space OTV) is proposed, and its effectiveness and feasibility are discussed. Basic concept is the separation of two functions required for the deep space exploration, the transportation to the destination, and the exploration at the destination. Deep Space OTV is a spacecraft specialized for the transportation to the deep space destination. It is an expendable spacecraft propelled by solar electric propulsion. The payload of Deep Space OTV is Explorer, which is a spacecraft specialized for the exploration at the deep space destination. The effectiveness of the concept is discussed qualitatively, focused on the merits of the separations of two functions. The feasibility of Deep Space OTV is discussed based on the conceptual design of the spacecraft and its applicability to deep space missions. Several deep space missions are modeled and the payload capacity of Deep Space OTV is estimated. The missions include Asteroid rendezvous, Mars orbiter, Lunar lander, and so on. 相似文献
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A new and innovative type of gridded ion thruster, the “Dual-Stage 4-Grid” or DS4G concept, has been proposed and its predicted high performance validated under an ESA research, development and test programme. The DS4G concept is able to operate at very high specific impulse and thrust density values well in excess of conventional 3-grid ion thrusters at the expense of a higher power-to-thrust ratio. This makes it a possible candidate for ambitious missions requiring very high delta-V capability and high power. Such missions include 100 kW-level multi-ton probes based on nuclear and solar electric propulsion (SEP) to distant Kuiper Belt Object and inner Oort cloud objects, and to the Local Interstellar medium. In this paper, the DS4G concept is introduced and its application to this mission class is investigated. Benefits of using the DS4G over conventional thrusters include reduced transfer time and increased payload mass, if suitably advanced lightweight power system technologies are developed.A mission-level optimisation is performed (launch, spacecraft system design and low-thrust trajectory combined) in order to find design solutions with minimum transfer time, maximum scientific payload mass, and to explore the influence of power system specific mass. It is found that the DS4G enables an 8-ton spacecraft with a payload mass of 400 kg, equipped with a 65 kW nuclear reactor with specific mass 25 kg/kW (e.g. Topaz-type with Brayton cycle conversion) to reach 200 AU in 23 years after an Earth escape launch by Ariane 5. In this scenario, the optimum specific impulse for the mission is over 10,000 s, which is well within the capabilities of a single 65 kW DS4G thruster. It is also found that an interstellar probe mission to 200 AU could be accomplished in 25 years using a “medium-term” SEP system with a lightweight 155 kW solar array (2 kg/kW specific mass) and thruster PPU (3.7 kg/kW) and an Earth escape launch on Ariane 5. In this case, the optimum specific impulse is lower at 3500 s which is well within conventional gridded ion thruster capability. 相似文献
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航天器力学环境分析与条件设计研究进展 总被引:9,自引:0,他引:9
航天器力学环境条件是航天器及其部组件设计和地面试验验证的主要依据,直接影响着航天器的总体设计水平。随着我国航天事业的飞速发展,对航天器及其有效载荷的设计提出了越来越高的要求,而力学环境分析与条件设计技术已经成为制约我国航天器荷载比提高的瓶颈技术。本文重点针对航天器力学环境分析与条件设计技术所涉及的航天器力学环境预示理论方法,高精度有限元建模与模型修正技术以及航天器力学环境条件设计技术三个方面国内外研究进展进行了回顾,特别是对近五年来我国航天工业部门在航天器力学环境分析与条件设计领域取得的成就进行了综合评述。在此基础上,结合我国航天工程的实际需求,分析指出了今后在航天器力学环境分析与条件设计领域的主要研究方向。 相似文献
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飞轮储能装置具有比能量高、寿命长、任务期内无衰减等优点,可替代航天器中传统的化学储能装置。为论证太阳电池阵-储能飞轮电源系统的可行性,本文从航天器总体设计的角度分析了其关键设计要素,论述了其对航天器机、电、热等方面的影响,并给出提高系统可行性的合理化建议,以及针对低轨卫星的太阳电池阵-储能飞轮电源系统的设计举例。通过与传统电源系统的技术指标对比分析,表明太阳电池阵-储能飞轮电源系统具有较高的比功率,并在降低航天器质量、节约发射成本方面具有很大优势,在未来航天器的应用中具有很大的潜力。 相似文献
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The X-33 program was initiated to develop a testbed for integrated RLV technologies that pave the way for a full scale development of a launch vehicle (Venture Star). Within the Nasa Future X Trailblazer program there is an Upgrade X-33 that focuses on materials and upgrades. The authors propose that the most significant gains can be realized by changing the propulsion cycle, not materials. The cycles examined are rocket cycles, with the combustion in the rocket motor. Specifically, these rocket cycles are: turbopump, topping, expander, air augmented, air augmented ram, LACE and deeply cooled. The vehicle size, volume, structural weight remain constant. The system and propellant tank weights vary with the propulsion system cycle. A reduction in dry weight, made possible by a reduced propellant tank volume, was converted into payload weight provided sufficient volume was made available by the propellant reduction. This analysis was extended to Venture Star for selected engine cycles. The results show that the X-33 test bed could carry a significant payload to LEO (10,000 Ib) and be a valuable test bed in developing a frequent flight to LEO capability. From X-33 published information the maximum speed is about 15,000 ft/sec. With a LACE rocket propulsion system Venture Star vehicle could be sized to a smaller vehicle with greater payload than the Venture Star baseline. Vehicle layout and characteristics were obtained from: http:// www.venturestar.com. 相似文献
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基于飞行轨迹及质量分析数学模型,对以RBCC为动力的巡航飞行器有效载荷的敏感性进行了分析,主要考虑了发动机比冲、发射马赫数、发射高度、模态转换点(转换马赫数)及惰性质量系数等对有效载荷质量的影响。分析结果表明,提高发射马赫数和发射高度、增加发动机比冲、降低模态转换马赫数及飞行器惰性质量系数有利于提高巡航飞行器的有效载荷质量。其中有效载荷质量对惰性质量系数最敏感,当惰性质量系数分别减小7.3%和增大7.3%时,有效载荷质量的增大量和减小量将分别达到58%和103.7%。 相似文献
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Power-limited systems with variable Isp, which have been studied theoretically since the beginning of astronautics, are getting closer to practical applications thanks to recent technological advances in the field of magnetosplasma rockets, such as Ad-Astra’s VASIMR concept. This type of propulsion system is considered for high-speed interplanetary transfers, such as Mars missions, with demanding payload fractions that would be compatible with manned missions. This paper explores the problem of the optimization of a power-limited propulsion system through simple performance models, and investigates the trade-off between the technological requirements, the transfer time and the payload fraction1. Following previous works existing in literature, we model the technological characteristics of the vehicle through a small number of parameters, the most important of which being the specific weight (or mass-to-power ratio) of the power generation system. Also, we use in our models the classical “trajectory characteristic” parameter (defined as the integral over time of the squared thrust acceleration) which represents – under certain hypotheses – the propulsion requirements for an orbital or interplanetary transfer with a given time and a given thrust strategy. In this paper, we first give a review of existing methods in literature, then we present the equations of a new class of optimal design which maximizes the payload fraction, for a given transfer time and given technological characteristics. This class of optimal design is described through very simple equations that make possible to study more straightforwardly than existing calculations the links between the main mission requirements (transfer time and payload fraction) and the main technological requirements (specific weight of the power generation and structure mass ratio of the whole vehicle, excluding the power generation system). One important result obtained from these equations is a simple expression which estimates the theoretical upper limit of the power source’s specific weight as a function of transfer time and the payload mass ratio. In the last part of this paper, we apply this simple performance model to discuss the feasibility of a fast Earth-to-Mars transfer using a power-limited system. 相似文献