重复使用航天运输系统设计与评估

Design and assessment of reusable space transportation system

航天运输技术是体现国家航天实力的重要标志,是实现进出空间的重要基础.经过几十年的发展,一次性运载火箭技术已经相对成熟,但仍面临着高可靠、高安全、低成本、快速发射、提升运载能力等挑战.重复使用航天运输系统是指能够实现往返于宇宙空间和地球之间,或在外层空间轨道之间飞行,执行任务后可返回地面,并可以多次使用的航天运输系统,如图1所示.重复使用航天运输系统技术的发展一直是航天运输领域研究的热点和难点.通过采用重复使用设计理念和简易发射方式,能够有效缩短发射周期、提高发射灵活性,同时基于多次重复使用、费用均摊的原则,可以大幅降低发射费用,最终实现低成本自由进出空间、高效利用空间、和平开发空间.

With decades of development,disposable launch vehicle technology has reached to a high maturity level.However,launch vehicles are still faced with problems of increasing reliability,decreasing launch preparation time and decreasing launch cost.Reusable launch vehicle transports between the ground and the orbit or between orbits for multiple times.It is one of the major directions for the development of space transportation system,and it is a cost efficient way for accessing to space.Therefore,design and assessment of reusable space transportation system must be studied.By analyzing the existing reusable space transportation systems worldwide,the development tendency can be concluded as follows.(1)Currently major countries and areas are mainly focusing on Two-Stage-To-Orbit(TSTO)system while still exploring the possibility of Single-Stage-To-Orbit(SSTO)system.(2)Rocket engine is the mainstream propulsion plan for TSTO system due to its maturity level.(3)Combined cycle engine will be at concept study phase for years since it is still seeking for technology breakthrough.(4)Vertical take-off and horizontal landing(VTHL)plan with lifting body configuration is widely applied.(5)Vertical take-off and vertical landing(VTVL)plan with axial-symmetrical configuration is mainly chosen by commercial corporations.According to the tendency and the current technical base,trading off between the technical feasibility and the economic affordability,the development strategy can be concluded.In short-term,it is suggested to achieve a reusable launch vehicle based on axial-symmetrical configuration,in order to solve the safety issue of launch vehicles.Meanwhile,it is also suggested to achieve a reusable launch vehicle based on lifting body configuration and rocket engine,in order to build the airplane-like reusable space transportation system.In long-term,it is suggested to achieve TTSO or STSO system using combined cycle engines.The design and assessment methodology of reusable space transportation system differs from traditional astronautical method,for it is reusable instead of disposable.It also differs from traditional aeronautical method,because of the harsh flight environment and the limited data size.Therefore,two major aspects,breaking through key technologies and innovating design philosophy,must be considered.On one hand,challenges such as aerodynamics and aerothermodynamics throughout the complex flight path,reusability of light-weight and heatproof structure,reusability of rocket engine must be solved.On the other hand,indicator system,design and assessment criteria specifically for reusable launch vehicles must be built.The design of reliability,maintenance,testability,supportability as well as prognostics and health management must be integrated into the R&D procedure.In conclusion,design and assessment of reusable space transportation system are of significance for solving problems occurred during the transition from disposable to reusable.Based on the reasonable development strategy and key technology breakthrough,the inherent capability of the launch vehicle can be guaranteed.Weighing the feasibility and the affordability based on advanced design philosophy,advantages of reusability can be insured.Furthermore,the study and application of the reusable space transportation system can not only be beneficial for future space transportation but can also be helpful for improving people’s livelihood as well.