On the possibility of Earth-type habitable planets in the 55 Cancri system

We discuss the possibility of Earth-type planets in the planetary system of 55 Cancri, a nearby G8 V star, which is host to two, possibly three, giant planets. We argue that Earth-type planets around 55 Cancri are in principle possible. Several conditions are necessary. First, Earth-type planets must have formed despite the existence of the close-in giant planet(s). In addition, they must be orbitally stable in the region of habitability considering that the stellar habitable zone is relatively close to the star compared to the Sun because of 55 Cancri's low luminosity and may therefore be affected by the close-in giant planet(s). We estimate the likelihood of Earth-type planets around 55 Cancri based on the integrated system approach previously considered, which provides a way of assessing the long-term possibility of photosynthetic biomass production under geodynamic conditions.     

The challenges and opportunities of a commercial human spaceflight mission to the ISS

ESA astronauts' ISS flight opportunities are considered as a vital source to meet the utilisation, operation and political objectives that Europe has established for participating in the International Space Station programme. Recent internal ESA assessments have demonstrated that a rate of three flights per year for European Astronauts should be maintained as a minimum objective. The current flight rate is lower than this. In order to improve this situation, in the context of the activation of the ESA ISS Commercialisation programme, ESA is developing the conditions for the establishment of commercially based human spaceflights with the financial support of both ESA and the private sector or, in the future, only the latter. ESA is working in a Partnership with the space industry to facilitate the implementation of such projects and support customers with a range of end-to-end commercial services. The opportunities and challenges of a "commercial human spaceflight", involving a member of the European Astronaut Corps, or a privately employed flight participant, are discussed here.     

Subfreezing activity of microorganisms and the potential habitability of Mars' polar regions

The availability of water-ice at the surface in the Mars polar cap and within the top meter of the high-latitude regolith raises the question of whether liquid water can exist there under some circumstances and possibly support the existence of biota. We examine the minimum temperatures at which liquid water can exist at ice grain-dust grain and ice grain-ice grain contacts, the minimum subfreezing temperatures at which terrestrial organisms can grow or multiply, and the maximum temperatures that can occur in martian high-latitude and polar regions, to see if there is overlap. Liquid water can exist at grain contacts above about -20 degrees C. Measurements of growth in organisms isolated from Siberian permafrost indicate growth at -10 degrees C and metabolism at -20 degrees C. Mars polar and high-latitude temperatures rise above -20 degrees C at obliquities greater than ~40 degrees, and under some conditions rise above 0 degrees C. Thus, the environment in the Mars polar regions has overlapped habitable conditions within relatively recent epochs, and Mars appears to be on the edge of being habitable at present. The easy accessibility of the polar surface layer relative to the deep subsurface make these viable locations to search for evidence of life.     

Eye light flashes on the Mir space station

The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer.     

游标测距数据在导弹事后精度鉴定中的应用

Rockwell公司为奥基丹(Ogden)空军后勤中心对选定的民兵导弹试验飞行进行了精度鉴定。其中一部份工作是对“制导-雷达”斜距比对进行回归分析。一般有六或七部雷达跟踪装有C波段相干应答机的被动段飞行器(PBV)。这些雷达中有几部还能测得距离变化率数据。最近的民兵Ⅲ试验飞行中,Rockwell可以得到联邦电子公司录取的实验性距离游标器磁带。该磁带只记录了一个站的数据,在事后鉴定中与标准的雷达磁带联合使用。本报告以实例叙述了采用游标测距数据的作用。     

复合材料层板纯剪实验

本文提出一个测量复合材料层板面内剪切性质的方板纯剪试验法。首先对方法的可靠性进行试验检验,然后对两种复合材料层板的剪切行为进行试验。     

Growth and development of plants flown on the STS-3 Space Shuttle mission

Pre-germinated pine seedlings and germinating oat and mung bean seeds were flown on the STS-3 Space Shuttle mission. Overall, the seedlings grew and developed well in space. Some oat and mung bean roots, however, grew upward. Lignin content was slightly lower in flight tissues and protein content was higher.     

关于固体推进剂燃烧不稳定性研究

本文介绍了英国火箭推进研究院进行固体推进剂燃烧不稳定性研究的工作计划。 文中讨论了数据采集和处理的技术,并例举了实用发动机燃烧的不稳定性。还描述了研究不稳定性的发动机和测量在振荡压力和速度条件下固体推进剂试样的燃烧速率系统。给出一些实测结果的例子。     

孔、轮廓和表面(七)

第五章座标定位系统座标定位系统,是用座标镗床或座标磨床工作台的直线运动控制工件位置的一种手段。其中,工作台是由测量系统来控制的,这个系统是建立在第三章提到过的基准平面、垂直度和线值测量基础上的。这个系统与在图板上标定的工件尺寸系统是相同的。为了易于理解这一点,可举一例来说明这个系统本质上是何等的简单和适用。图纸上的尺寸一经注出,这些