具有反应流的固体冲压式火箭 发动机侧向进气道排放燃烧室的研究

固体冲压式火箭发动机是冲压发动机的一种变种。本研究使用一个带侧向空气道的排放燃烧室。考虑反应流,在燃气发生器中装填了50％高氯酸铵和50％聚酯的富燃推进剂。将κ—ε联立方程描述的湍流模型和一个简单、一步、快速反应的化学动力学总合成椭圆型偏微分方程来描述流场。为了适合所研究的问题,由改进的TEACH计算机程序来求解。基于此分析,更加深入地了解到混合和燃烧对固体冲压式火箭发动机全部性能的影响。将侧向空气进气道的位置移向燃料进气道,减少侧向空气进气道的角度,以及增加空气对燃料的比例,都能改善混合和燃烧特性,提高固体冲压式火箭发动机的比冲,这与Vanka的分析结果和Schadow的试验数据定性地一致。     

“飞马座”运载火箭

在“挑战者”号航天飞机失事之后,美国便竭力要为空军和民用用户提供一次性使用运载火箭.这些运载火箭包括“阿特拉斯”Ⅱ、“德尔它”Ⅱ、“大力神”Ⅳ,以及新研制的大推力先进运载火箭(ALV)和航天飞机C.与此同时,美国还正研制一种飞行轨迹全然不同的小型运载火箭——“飞马座”空中发射运载火箭.     

Blood volume regulating hormones response during two space related simulation protocols: four-week confinement and head-down bed-rest

The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P < 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.     

NASA再次选择轨道科学公司研制新的X—34

当１９９６年初轨道科学公司和洛克韦尔国际公司取消了与美航宇局（ＮＡＳＡ）之间的合作合同时，这两家公司就停止研制Ｘ－３４小型可重复使用的带翼运载器。但是美航宇局官员并不愿意放弃。美航宇局已于今年６月上旬从９个投标者中选择了轨道科学公司制造的一种尺寸更小...     

热流校准的不确定度——美国热流计的校准

AEDC(Arnold Engineering Derelopment Center)负责对热流传感器进行校准。本文介绍有关该校准不确定度的研究工作和研究结果。校准总的不确定度是综合AEDC和NBS(美国国家标准局)各自作的几组校准数据求得的。第一组数据是按块式卡计标准校准六个热流传感器得到的,块式卡计和六个热流传感器都是AEDC制造的。校验中采用九支(1kW/支)石英灯组成辐射热源。由这些校准数据计算六个传感器中每个传感器的精度。此六个传感器送到NBS Fire研究中心(华盛顿)进行标准复校。第二组校准数据取自这些复校试验。因此,可以说是按NBS热流标准进行了标准传递。NBS也采用辐射热源,也用AEDC类似的步骤进行校准。比较AEDC和NBS各自获得的数据,确定每一传感器的偏差值。综合此偏差和精度两个数据,计算每个传感器的总不确定度。六个传感器算出的平均不确定度是±3％。     

一种测量浇注弹性体材料导热系数的改性方法

最近,威尔金斯和阿什报导了一种用来测量浇注弹性体材料(如橡胶)导热系数的装置。从己进行的少量试验来看,数据的重现性很好(标准偏差为2.5%)但测得的导热系数比报导的标准值大约高出5%。他们指出,末端热损失是造成误差的原因。所以,为了确定末端损失修正系数,对试验装置作了改进。随后,用改进的装置进行了试验,测得了新的导热系数值,并把它和报导的标准值进行了比较。从本文报导的试验结果和介绍的装置,可以看出,本装置是测量橡胶绝热层或固体推进剂这类浇注弹性体材料导热系数的一种实用而经济的方法。     

使用连续流动法测量高氯酸铵表面积

1、引言为了予测复合固体推进剂的弹道性能,必须要知道推进剂中各组份的粒度或表面积。在塑料型推进剂的制造过程中固体粒子会发生机械破碎,尽管如此,仍发现高氯酸铵的初始表面积与推进剂的弹道性能有关。爆炸物研制公司(ERDE)测量高氯酸铵表面积的作法是采用以空气渗透法为基础的菲希尔(Fisher)筛分机。由于塑料型推进剂中使用的高氯酸铵的比表面积范围通常为1000～9000cm~2/cm~3(0.051～0.46m~2/g),因此,菲希尔法完全能满足这一要求。为了生产较高燃速的推进剂,爆炸物研制公司最近研究的推进剂配方中含有更细的高氯酸铵(9000～10000cm~2/cm~3)。在端羧基聚丁二烯和端羟基聚丁二烯两种橡胶型推进剂中,即     

Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested

The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5-50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5-10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms.