Biosignatures from Earth-like planets around M dwarfs

Coupled one-dimensional photochemical-climate calculations have been performed for hypothetical Earth-like planets around M dwarfs. Visible/near-infrared and thermal-infrared synthetic spectra of these planets were generated to determine which biosignature gases might be observed by a future, space-based telescope. Our star sample included two observed active M dwarfs-AD Leo and GJ 643-and three quiescent model stars. The spectral distribution of these stars in the ultraviolet generates a different photochemistry on these planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially longer lifetimes and higher mixing ratios than on Earth, making them potentially observable by space-based telescopes. On the active M-star planets, an ozone layer similar to Earth's was developed that resulted in a spectroscopic signature comparable to the terrestrial one. The simultaneous detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been suggested as strong evidence for life. Planets circling M stars may be good locations to search for such evidence.     

Proposal for a new radiation dose control system for future manned space flights

Radiation risk on a future long-duration manned space mission appears to be one of the basic factors in planning and designing the mission. Since 1988 different active dosimetric investigations has been performed on board the MIR space station by the Bulgarian-Russian dosimeter-radiometer LIULIN and French tissue-equivalent proportional counters CIRCE and NAUSICAA. A joint French-Bulgarian-Russian dosimetry experiment and the dosimetry-radiometry system RADIUS-MD have been developed for the future MARS-96 mission. On the base of the results and experience of these investigations a conception for a new radiation dose control system for the future orbital stations, lunar bases and interplanetary space ships is proposed. The proposed system which consists of different instruments will allow personal radiation control for crew members, radiation monitoring inside and outside each habitat, analysis and forecasting of the situation and will suggest procedures to minimize the radiation risk.     

微型无人直升机飞控系统的设计及其半实物仿真

介绍一种以DSP和CPLD作为硬件核心的微型无人直升机飞行控制系统,包括系统传感器数据采集电路、串口扩展电路、舵机控制电路、电源电路等硬件功能模块的设计和实现。在此基础上辅以传感器信息融合、姿态解算、飞行控制算法等系统软件。最后构建一个半实物仿真系统,仿真结果表明该飞控系统的可行性。     

液体火箭发动机喷管流动特性及高度补偿研究进展

喷管作为液体火箭发动机产生推力的重要组件之一,其内部存在的复杂流动现象对发动机性能具有重要影响,本文综述了该领域的相关研究进展。传统喷管在过膨胀状态下会产生自由激波和受限激波两种分离模式,其非定常、非对称性给发动机带来严重的侧向载荷,也造成流动预测较为困难。采用凹坑或涡轮废气主动射流等方式能够避免受限激波分离的出现,抑制侧向载荷,但却无法对喷管损失的性能进行有效补偿。通过对传统喷管的创新设计,高度补偿喷管不仅能够有效控制管内流动,还能在不同程度上提升发动机性能。然而,高度补偿喷管形式众多、各有所长,工程应用应谨慎决策。此外,各种形式的高度补偿喷管内仍旧存在激波/边界层干扰、分离、回流等不利的流动现象,亟待对其开展深入研究。     

双组元姿控发动机液膜冷却对性能的影响分析

本文通过分析液膜/辐射冷却的双组元姿控发动机的工作特点,根据两边区流管的卷吸模型,按混合比近似地将燃烧室流场分为一个中心区和两个边区,计算了液膜/辐射冷却的低推力液体火箭发动机液膜冷却对性能损失的影响。并分析了考虑性能分析的结果,及综合传热模型对发动机的设计参数的选择。本文的方法可为同类发动机设计中的性能计算及参数优化提供参考。     

美国研究用中继卫星支持靶场安全

靶场安全是发射场提供的维持发射系统(飞行器和地面设备)完整、避免威胁人身安全的业务,是所有靶场(发射场)都要进行的一项工作。当前美国各靶场采用的指令炸毁和遥测方法要求地基天线系统与飞行器之间维持一条特高频(UHF)射频链路。由于某些发射场中靶场安全系统的作用范围已扩展到入轨段,因此要在很大的范围内布设多套下靶场停飞系统(FTS)。 尽管美国各靶场现有的安全系统具有出色的安全记录,但其大量支持设施的操作和维护费用极高,因此限制了发射周转时间、发射场的灵活性以及覆盖区域。为克服这些缺陷,NASA哥达德航天中心(GS-FC)正在研究将NASA天基网(SN)/跟踪与数据中继卫星(TDRSS)用做天基平台支持一次性运载器(ELV)和重复使用运载器(RLV)的靶场安全通信,提供一种灵活的、高效费比解决方案。该计划的重点是     

通过自主数据传输操作降低航天任务费用

航天任务的当前趋势不再是进行几项昂贵的大型任务,而是向着许多小型低成本任务的方向发展。如果总预算不增加,这种趋势必定意味着每项任务的费用要降低。一部分必要的费用降低可靠标准化和自动化来得到。操作的自动化以及通信协议和操作方法的标准化可使基础设施和软件的开发、维护、甚至操作费用能被多项任务分摊,可以大大降低任务的开发和操作费用。