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The author:(作者)aaapublished in(发表于) 2013/12/16 0:35:14 Expert interpretation of Chang the third probe， fell during the month
Xinhua News Agency, Beijing, December 14 (reporters and Zhao Wei and and Tian Zhaoyun and and and)-Chang, third will be held on the night of 14th Lunar soft landing, the whole process is about 12 minutes.
"The moon landing was the most critical stages throughout the mission. "Wu Weiren, Chief Designer of China's lunar exploration engineering says," landed safely in just hundreds of seconds from 15 kilometers to the lunar surface preselected landing zone, this is the new and most important test. ”
This is bound to be soul-stirring 720 seconds: first until 12th attempt succeeded the former Soviet Union, United States also sampled the 3 failed sowing rear landing safely. Lunar soft landing in the end what are the risks? Experts believe that the goddess Moon faced at least five tests.
Falling Moon Rainbow Bay facing an unknown new world
With the United States, Soviet lunar exploration is concentrated near the Lunar equator in different Chinese Chang, third choice in Rainbow landings in the Bay area. To Rainbow Bay to explore Lunar research gaps will be filled, but Yu Change for the third, which was a new and unknown world filled with.
"Rainbow Cove on a macro level is relatively flat, but Chang finally landed third little environment, what kind of terrain, is still unknown. "Said Wu Weiren, Chief Designer of China's lunar exploration engineering, stones, ditches, slopes, and so is Chang, third facing a huge test.
For Chang, third "off" safe, smooth landing, Chang already for third, second "front": ending domain using a CCD stereo camera to Rainbow Bay, ultra high resolution stereoscopic imaging, obtained the image resolution is about 1 metre.
This is the first time China's spacecraft "comes" the extraterrestrial object. In order to ensure land security, technician or simulated lunar surface environment characteristics in the ground, made a lot of fire, obstacle avoidance, slow decline testing.
New technology and new products waiting for the lunar module test
The moon has no atmosphere, landing on Earth, completely different, traditional air friction and deceleration rocket engine and propulsion system is no longer working on the moon.
"To this end, we first use of our own design and manufacture of variable thrust engine. "Wu Weiren said large thrust engine with 1500 to 7,500 cattle, well adapted to the different flight phases on engine thrust requirements.
This is a variable thrust engine applied to the spacecraft for the first time. "Variable thrust engine has no backup and using for the first time, there are risks. "Chang ' e third detector systems Chief Scientist academician Ye Peijian said.
According to Ye Peijian introduction, Chang e, third over for newly developed technologies and products, equipment and higher risk than the relatively mature products of the product itself.
In order to reduce risks, technicians envisions hundreds of failures, and to develop an appropriate plan. "We think, walk, eat, think of one precludes a, still has to conduct experiments. "Ye Peijian said.
"Black 12 minutes" depends on autonomous control
Fell to 15 km altitude from the lunar surface, this soul-stirring 12 minutes were called "black 12 minutes" to become immortal, the third to rely entirely on autonomous control, complete the reduced height, distance, speed, the landing spots, freefall landing a series of maneuvers.
During this period, almost zero possibility of manual intervention. This is because every movement during the fall months are very short and once the sensor has been installed on the detector information, you need to respond very quickly to probe and earth-moon distance of 380,000 kilometers as well as signal delay, simply not enough to pass information back to the ground, and then uploaded by ground command.
Indeed, the probes around the world in the process of landing on the Moon or Mars, there is such a probe by independent control of the "black".
"The China leg," challenges of Lunar soft landing
Despite the use of sophisticated guidance navigation and control systems, landed in moments will still have an impact on surface. In order to avoid excessive shock loads to the device, sensors buffering system used on a landing, which Chang ' e third section 4 "legs". To become immortal, the third has become China's first "leg" of the spacecraft.
After landing in other countries there are three main types: a balloon bounce to meet Chang the third probe, weight requirements; the other is an aerial cable car, control, it's complicated, so Chang-third, choose a third, namely leg landed.
"Buffer institutions are mainly used for buffering the lander the landing impact energy, commonly known as the landing legs. "Probe Lander landing buffer system designer Yang Jianzhong, Director of the system features with 8 words sum up the landing legs: strong, light, soft, stable, more, new, all, is difficult.
In other words, the landing legs have strength to bear shocks and stresses, their lightweight, soft landing, posture and stability, can guarantee the safety equipment. In addition, landing return gathered, to spread and support functions, touch the moon also sent a signal. And as new landing legs with Chinese characteristics, in achieving technological leapfrogging and team-building both at the same time, also experienced a difficult development process.
Moment of impact test equipment reliability
"China's legs" enabled greatly reduces the impact of landing, but Chang, third on the device are still facing severe challenges.
"After testing, sensors on the device can withstand mechanical environment of landing examination, even if the impact force, electronic equipment is working correctly. "Wu Weiren said.
Chang, third is expanded in a solar flight, and before landing, the "wings" will withdraw until a smooth landing surface. "Landing solar panels may be broken," said Wu Weiren, "we designed the exhibition of repeatable for Chang, third collection of windsurfing, can guarantee the landing safer. ”
Moon dust for this moment poses more risks. On the surface there is a thin layer of dust, landed in time is likely to stir up moon dust, effects on the optical sensors and other equipment. Researchers screened dust control measures such as nets, to probe the "eyes" together with a layer of protective cover.
(Original title: expert translation: Moon Moon faces five major challenges in about 12 minutes)
新华社北京12月14日电(新华社记者赵薇、田兆运、白瑞雪) 嫦娥三号将于14日晚在月面实现软着陆，整个过程约12分钟。
“月球降落是整个任务最关键阶段。”中国探月工程总设计师吴伟仁说，“在短短几百秒内从15公里安全降落到月面预选着陆区，这是全新、也是最重要的考验。”
这注定是惊心动魄的720秒：前苏联直到第12次尝试才首获成功，美国也在品尝了3次失败苦果后方平安着陆。月面软着陆到底有何风险？专家认为，嫦娥落月至少面临五大考验。
落月虹湾面临未知新世界
与美国、苏联月球探测主要集中在月球赤道附近不同，中国的嫦娥三号选择在虹湾区着陆。对虹湾的探索将填补月球研究的空白，但对于嫦娥三号来说，这也是一个崭新的、充满未知的世界。
“尽管虹湾宏观上相对平坦，但是最后嫦娥三号降落的小环境到底是怎样的地形地貌，还是未知数。”中国探月工程总设计师吴伟仁说，石头、壕沟、斜坡等都是嫦娥三号面临的巨大考验。
为了能让嫦娥三号“落”得安全，嫦娥二号已经为三号的平稳着陆打了“前站”：它用CCD立体相机对虹湾进行了局域超高分辨率立体成像，获得了分辨率约为1米的图像。
这是中国航天器首次“降临”地外天体。为了保证着陆安全，技术人员还在地面模拟月面环境特性，进行了大量点火、避障、缓速下降的试验。
新技术新产品等待登月考验
月球上没有大气，着陆方式与在地球上完全不同，传统依靠空气摩擦减速的火箭发动机和推进系统在月球上不再奏效。
“为此，我们首次使用了我国自主设计制造的变推力发动机。”吴伟仁说，发动机具有1500牛到7500牛的大推力变化，能够很好地适应不同飞行阶段对发动机推力的需求。
这是我国首次将变推力发动机应用于航天器。“变推力发动机没有备份，又是首次使用，其中也存在风险。”嫦娥三号探测器系统首席科学家叶培建院士说。
据叶培建介绍，嫦娥三号80%以上的技术和产品为全新研制，设备和产品本身的风险比相对成熟的产品高。
为了降低风险，技术人员设想了上百个故障，并制定了相应的预案。“我们天天想，走路想、吃饭想，想到一种就排除一种，还要进行实验验证。”叶培建说。
“黑色12分钟”全凭自主控制
从15公里高度降至月球表面，这惊心动魄的12分钟被称为“黑色12分钟”，嫦娥三号要完全依靠自主控制，完成降低高度、测距、测速、选择着陆点、自由落体着陆等一系列动作。
这期间，人工干预的可能性几乎为零。这是因为落月过程中的每一个动作都非常短暂，安装在探测器上的传感器一旦获得信息，需要探测器作出极快的响应，而38万公里的地月距离以及信号延迟，根本不足以让信息传回地面、再由地面上传指令。
实际上，在世界各国探测器登陆月球或火星的过程中，都有这样一个由探测器自主控制的“黑色”时段。
“中国腿”挑战月面软着陆
尽管采用了先进的制导导航与控制系统，探测器着陆瞬间还是会对月面产生撞击。为了避免设备受到过大的冲击载荷，探测器上使用了一个着陆缓冲分系统，也就是嫦娥三号的4条“腿”。由此，嫦娥三号也成为我国首个有“腿”的航天器。
此前其他国家软着陆方式主要有三种：一种是气囊弹跳式，难以满足嫦娥三号探测器重量的要求；另一种是空中吊车式，控制起来很复杂；因此嫦娥三号选择了第三种，也就是腿式着陆。
“着陆缓冲机构主要用于缓冲着陆器的冲击能量，俗称着陆腿。”探测器系统着陆器着陆缓冲分系统主任设计师杨建中用8个字概括着陆腿的特点：强、轻、柔、稳、多、新、全、难。
也就是说，着陆腿要有强度承受冲击和压力，自身轻巧，着陆方式柔和、姿态稳定，能保证仪器设备安全。另外，着陆退还有收拢、展开、支撑的功能，触月时还能发来信号。而作为具有中国特色的新型着陆腿，在实现了技术跨越和团队建设的双丰收的同时，也经历了艰难的开发研制过程。
撞击瞬间考验设备可靠性
“中国腿”的启用极大降低了着陆时的冲击力，但嫦娥三号上的设备依旧面临严峻考验。
“经过试验，探测器上的设备能经受着陆时力学环境的考核，即便产生撞击力，电子设备也能正常工作。”吴伟仁说。
嫦娥三号的太阳能帆板在飞行中处于展开状态，而在着陆前，这对“翅膀”会收回，直到顺利着陆月面再展开。“着陆时太阳能帆板如果展开，可能会被折断，”吴伟仁说，“我们为嫦娥三号设计了可重复展收的帆板，可以保证着陆安全。”
月尘的存在为这一瞬间带来了更多风险。月面上有细细的一层尘埃，探测器着陆时很可能激起月尘，对光学敏感器等设备造成影响。科研人员们采取屏蔽网等防尘措施，给探测器的“眼睛”加上了一层保护罩。
(原标题：专家解读：嫦娥落月过程约12分钟 面临五大考验)
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