Optimum design of power-limited propulsion systems with application to fast Earth-to-Mars transfer
- 作者：Nicolas Bé ; rend nicolas.berend@onera.fr
- 关键词：FPI ; Fixed-Point Iteration ; IMLEO ; Initial Mass in Low-Earth Orbit ; LEO ; Low-Earth Orbit ; VASIMR® ; VAriable Specific Impulse Magnetoplasma Rocket
- 刊名：Acta Astronautica
- 出版年：2012
- 期刊代码：1_00945765
- 类别：et
- 出版时间：October-November, 2012
- 卷：79
- 期：Complete
- 页码：107-117
- 文件大小：432 K
摘要
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鈥檚 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 fraction. 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 鈥渢rajectory characteristic鈥?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鈥檚 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.