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91.
Meteoroids that dominate the Earth's extraterrestrial mass influx (50-300 microm size range) may have contributed a unique blend of exogenous organic molecules at the time of the origin of life. Such meteoroids are so large that most of their mass is ablated in the Earth's atmosphere. In the process, organic molecules are decomposed and chemically altered to molecules differently from those delivered to the Earth's surface by smaller (<50 microm) micrometeorites and larger (>10 cm) meteorites. The question addressed here is whether the organic matter in these meteoroids is fully decomposed into atoms or diatomic compounds during ablation. If not, then the ablation products made available for prebiotic organic chemistry, and perhaps early biology, might have retained some memory of their astrophysical nature. To test this hypothesis we searched for CN emission in meteor spectra in an airborne experiment during the 2001 Leonid meteor storm. We found that the meteor's light-emitting air plasma, which included products of meteor ablation, contained less than 1 CN molecule for every 30 meteoric iron atoms. This contrasts sharply with the nitrogen/iron ratio of 1:1.2 in the solid matter of comet 1P/Halley. Unless the nitrogen content or the abundance of complex organic matter in the Leonid parent body, comet 55P/Tempel-Tuttle, differs from that in comet 1P/Halley, it appears that very little of that organic nitrogen decomposes into CN molecules during meteor ablation in the rarefied flow conditions that characterize the atmospheric entry of meteoroids approximately 50 microm-10 cm in size. We propose that the organics of such meteoroids survive instead as larger compounds. 相似文献
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低轨对地观测卫星凝视成像仪探讨 总被引:1,自引:0,他引:1
文章介绍了典型空间信息获取方式及特点,阐述了低轨对地观测卫星凝视成像面临的问题及解决对策,对两种低轨对地观测卫星凝视成像仪及其应用进行了探讨。 相似文献
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本文介绍了惯性顶级(IUS)固体火箭发动机用的丁羟推进剂及推进剂/包复层/绝热层界而系统的研制情况及生产历程;介绍了根据发动机设计要求选择推进剂配方的情况和推进剂的主要性能;还介绍了研制期间对配方和工艺的某些小的修改及修改原因。本文亦讨论了推进剂/包复层/绝热层的界面系统,包括包复层化学的主要特性和控制迁移现象以提高粘结系统的完整性的方法。 相似文献
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本文介绍了乙烯基二茂铁与丁二烯的共聚物及其制备方法。当从偶氮—双—(2——甲基——5——羟基——戊腈),偶氮一双——(羟乙基——2——甲基丙酸酯)和偶氮——双——(2——甲基——3——羟基——丙腈)偶氮类引发剂中,选择一种引发剂引发进行聚合时,在有机溶剂中生成共聚物。该共聚物可用作固体推进剂配方的粘合剂,并用来提高固体推进剂的燃速。 相似文献
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Aldrin A Amara A Aris L Baierl N Beatty P Beaulieu C Behnke T Castegini R Chauhan A Cojanis P Dayawansa P Diop M Eito K Engle S Feretti S Gassama H Genova B Goulding C Janjua J Jansaeng T Jousset F Kopik A Laurin C Leggatt J Li H Mezzadri M Miura A Nolet S Ogami S Patry J Patten L Payerne C Peer G Prampolini M Rheaume C Saary J Spehar D Sufi A Sun B Thompson JB Thomson W Trautner R Tursunmuratov M Venet V Wilems E Wilson H Wittwer K Wokke F Wu Y Zhou S Zilioli I 《Acta Astronautica》2002,51(1-9):637-646
Issues about commercialization of space have been a growing concern in the past decade for the space community. This paper focuses on the work from a team of 51 students attending the Summer Session Program of the International Space University in Bremen, Germany. CASH 2021 (Commercial Access and Space Habitation) documents a plan that identifies commercial opportunities for space utilization that will extend human presence in space, and will chart the way forward for the next 20 years. The group selected four commercial sectors that show the most promise for the future: tourism, entertainment, space system service, assembly and debris removal, and research and development/production. The content of this document presents the results of their research. Historical activities in each of the commercial sectors are reviewed along with the current market situation. To provide a coherent background for future commercialization possibilities a scenario has been developed. This scenario includes a postulated upon ideal future and includes social, political and economic factors that may affect the space industry over the timeline of the study. The study also presents a roadmap, within the limited optimistic scenario developed, for the successful commercialization of space leading to future human presence in space. A broad range of commercially viable opportunities, not only within the current limits of the International Space Station, but also among the many new developments that are expected by 2021 are discussed. 相似文献
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<正>一些高等院校在研的创新性先进技术,将使航空维修业发生巨变,这其中包括先进的监控系统、复合材料的修理和先进检测技术等。未来10年,飞机的监控、修理以及检测方法有可能发生根本性变化,它涉及机载系统的可靠性重新定义、复合材料问题的解决方案以及金属加工技术等领域。 相似文献