In-situ Lunar Penetrating Radar Experiments on the Moon of CE-3 and CE-4 Missions

来源 :中国航天(英文版) | 被引量 : 0次 | 上传用户:bokui0913
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
China\'s Chang\'e 3 (CE-3) and Chang\'e 4 (CE-3) missions made historic progress by sending rovers equipped with scientific instruments to the new sites on the nearside and farside of the moon, respectively. The same lunar penetrating radar (LPR) that uses pulses of electromagnetic energy to reveal the underground structure and prop-erties of the lunar soil “regolith” covering most of the lunar surface was carried by the rovers. It provided for the first time the opportunity for in situ LPR measurements of the subsurface substrate in two geologically different places on the moon. At present, the Yutu rover of CE-3 mission traveled along a path of total length of about 114 m while the Yutu 2 rover of CE-4 has traversed over 1000 m and keeps going. This paper summarizes the fruitful results so far obtained by LPRs, including the physical properties and layered structure of the lunar regolith and shallow crust beneath the two landing sites. The regolith layer thickness at the CE-3 site is thinner than that at the CE-4 site due to its relatively young age. The penetration depth below CE-4 site is about 2.85 times (in terms of the forward and return path delay) deep-er than CE-3 as indicated by their different loss tangent values (0.0039 ± 0.0002 vs. 0.013), which is probably due to the differences in abundance of ilmenite and rocks in the regolith. Other physical parameters including dielectric per-mittivity vs. depth profile, bulk density and electrical conductivity have been estimated using various methods. Thanks to the low signal loss, CE-4 LPR is able to present clear cross section views of two buried craters and the paleo-surface (ancient surface) of the landing site. The multiple stratums observed by the low frequency channel of LPRs indicate sev-eral episodes of lava eruptions occurred in the late stage of the formation of the nearside Imbrium Basin and the farside Von Kármán crater despite the asymmetric volcanisms distributed on two sides. The discoveries revealed by LPRs advance our knowledges on the formation process and properties of lunar rego-lith, thickness of ejecta deposits caused by lunar impact events, the evolution of the nearside and farside volcanisms, etc. They also demonstrate the feasibility of applying ground penetrating radar for non-terrestrial explorations such as China\'s first Martian mission, Tianwen 1 mission.
其他文献
论述了大连湾海底隧道干坞在临时围堰的渗漏位置采用压密注浆封堵止水的设计方案与施工方法,压密注浆工艺的实施达到了良好的止水效果,满足干坞施工期作业要求.施工中积累的数据及经验可为类似工况条件的工程提供参考.
以大连湾海底隧道建设工程干坞子项工程为依托,通过分析机制砂与河砂的特性,对机制砂塑性混凝土配合比的相关性能进行试验研究及实际应用效果分析,验证机制砂塑性混凝土各项性能指标满足该工程设计要求,并成功应用于本工程坞壁的止水咬合桩施工中,为类似工程提供借鉴.
浮坞门沉箱作为干坞坞室的口门结构,采用原位现浇工艺施工成型,技术难度大.文中详细介绍了浮坞门沉箱现浇施工方法、预留顶升廊道形式、Ω形止水带埋件安装方法、沉箱顶升方法、沉箱回落方式、止水施工应用效果等.原位现浇浮坞门施工工艺已成功应用于大连湾海底隧道干坞预制场,积累了施工经验和参数,可为类似原位现浇沉箱结构工程提供参考.
大连湾海底隧道建设工程干坞子项工程分为东、西两个坞室,用于沉管预制施工,坞口区止水主要采用了帷幕灌浆+现浇沉箱+钢闸门的施工工艺.文章论述了坞口止水结构的施工工艺及关键技术,干坞投入使用后,坞口止水效果良好,可为类似工程提供参考.
大连湾海底隧道建设工程属于大型综合性集群工程,具有涉及的工程专业多、结构复杂、施工作业面广、交叉作业多、工期任务紧、资源投入密集等特点.安全管理主要难点在通航环境复杂,施工干扰大;冬施项目多,保障难度高;地质条件复杂,工艺保障难;施工船舶多,管控难度大;临海深基坑,安全风险高.针对本工程,文中提出了安全管理的新思路和方法.
In the recovery process of the reusable rocket with vertical take-off and landing, it has to go through the active control process, such as power drop, hover and vertical landing. The key technology lies in the development of high-precision vertical recov
通过对大连湾海底隧道建设工程干坞子项工程-防波堤工程高低基础沉箱间隔安装施工,明确了各工序施工所采取的相应技术质量控制措施及合理的施工顺序.结果 表明:通过采取相应的技术质量控制措施及合理安排各工序的施工顺序,西防波堤高低基础沉箱一次性安装成功.
大连湾海底隧道建设工程中预制及现浇沉管、沉箱、胸墙等结构形式复杂多样,并且结构断面尺寸大、模板需用量多.传统桁架结构钢模板结构设计繁琐、改制成本大、耗时长,而且存在周转通用性差、不易存放和保养等问题.现提出并使用一种适应不同结构施工的大型组合式钢模板,在实际施工应用中验证了其方便安装及拆分组合,可满足在各类预制及现浇混凝土结构间的周转使用.
Noise characteristic is one of the important factors to be considered during the design of a launch vehicle system. In this paper, the acceptance conditions for the external noise environment of the instrument cabin are given based on multi-source data, i
全回转钻机适用于复杂地质情况钻孔施工,相对于传统旋挖钻及冲击钻,具有桩身垂直度控制较好、施工灵活等优点.通过在大连湾海底隧道沉管预制场咬合桩止水施工应用可知,全回转钻机可驱动套管做360°回转,压入套管和挖掘同时进行,无需依赖缓凝剂控制混凝土强度,并且不会出现由于单桩成桩时间过长,Ⅰ序桩混凝土强度过高导致无法进行Ⅱ序桩咬合施工的弊病,施工工效及质量均满足相关要求.