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Chang'e 5 test vehicle "Xiaofei" lands successfully

cirr

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Chang'e 5 test vehicle "Xiaofei" lands successfully

Posted by Emily Lakdawalla

31-10-2014 18:23 CDT

Xinhua news reported today the successful landing of the Chang'e 5 test vehicle. It landed in Inner Mongolia, in the same region used for landing by the Shenzhou capsules of China's human spaceflight program. The capsule was located within minutes of touchdown.


Xinhua news

Chang'e 5 test vehicle "Xiaofei" safely on the ground

The Chang'e 5 test vehicle launched October 23, 2014 and successfully returned a test sample return capsule eight days later, on October 31.

This is an important step for China's methodical lunar exploration program. The program was laid out in three phases. The first phase, orbital reconnaissance of the Moon, was completed successfully by the Chang'e 1 and 2 orbiters in 2007 and 2010, respectively. The Chang'e 3 lander and rover represent the second phase, demonstrating a successful soft landing on the lunar surface in 2013. The Chang'e 3 backup spacecraft may be launched to another lunar landing as Chang'e 4 next year to a different location, possibly even the lunar south pole.

But the next step will be a doozy. Chang'e 5, to be launched in 2017, will be a stack of four spacecraft with a complicated mission. It must launch, traverse the distance to the Moon, enter lunar orbit, separate into a service module and lander, land, collect samples, place them into a capsule, launch it into lunar orbit, rendezvous with an orbiting service module, transfer back to Earth, and protect the precious cargo as it enters Earth's atmosphere and lands -- in the right spot! -- on the surface.

The Chang'e 5 test vehicle, which (according to Xinhua) has been nicknamed "Xiaofei" ("little flyer") on Chinese social media, was designed to test just a couple of these steps: transfer from Moon to Earth and Earth reentry. It did not have the full four-component stack, only an orbiter based on the Chang'e 1 and 2 design and a sample return capsule that appears to most observers to be a scaled-down version of the Shenzhou capsule.

It launched on October 23 at 18:00 UTC onto a free-return trajectory, looping once around the lunar farside and returning to Earth. Its reentry trajectory skipped in and out of the atmosphere once to bleed off energy without overheating the spacecraft before entering a second time, deploying parachutes, and landing today at 22:42 UTC.

The successful landing of the Chang'e 5 test vehicle is a piece of bright news in a sad week for space enthusiasts, coming on the heels of the Antares launch accident and the SpaceShipTwo tragedy.

The Chang'e 5 test vehicle success makes the Chang'e 5 mission slightly less scary. I would assume that the spacecraft to be launched as Chang'e 4 will test some of the sample handling technology they will need to make Chang'e 5 a success, but that's just my own speculation.

I congratulate China on today's success, and hope that the future holds similar success for the Chang'e 5 mission itself. The samples that Chang'e 5 may return would be the first since the Apollo and Luna samples revolutionized our understanding of the origins of Earth and the Moon. Hopefully some of the Chang'e 5 samples will be shared with the rest of the world, so we can add to the scientific edifice that continues to be built with ongoing examination of Apollo and Luna material.

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Congratulations :nana::yay::dance3::lock:
Welcome Home Baby Xiaofei :china::victory::chilli::bounce:

嫦娥5号试验器 - “跳跃”的返回者

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2014年10月24日凌晨2时 嫦娥五号试验器在西昌卫星发射中心发射成功,这是中国首次实施从月球轨道返回地球的返回飞行试验器。试验器将对嫦娥五号关键技术进行相关验证,以确保后续的探月计划顺利进行。

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在嫦娥三号任务成功后,中国探月工程全面进入“绕、落、回”的第三期——“回”,即“从月球采样返回”。通俗地讲,就是发射探测器在月球上挖一勺土,然后带回地球。

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要实现这个目的,我国目前面临着四大技术难题:首先是如何在月球上挖土取样;接下来登陆器怎么从月球表面起飞返回月球轨道;然后如何在月球轨道实现交会对接;最后探测器还要以接近第二宇宙速度的极高速度返回地球大气层着陆。

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第一难题在玉兔号成功登月之后,已有相关经验可供参考;由于月球引力较小,因此第二个难题在技术上可行性也很高;第三个难题,在我国已成功实现了天宫一号与神舟飞船成功对接的条件下,也是有章可循;唯独第四个难题是从来没有遇到过的,也没有经验可供参考,因此,试验器如何顺利返回地球是本次试验的重中之重。

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承担此次发射任务的是长征三号丙改二型火箭,这也是该型火箭的首飞。与长三丙基本型相比,增强型有多项改进、创新。首次在长三丙火箭上使用双惯组加复合制导。从外形上看比长三丙基本型长高了1米多。运载能力由原来的3.8吨提高到3.9吨。

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到2017年左右发射嫦娥五号时,将使用我国新一代的长征五号运载火箭,采用“一级半”或“二级半”结构,运载能力将达到近地轨道25吨,地球同步转移轨道14吨,其运载能力将比中国长征二号、长征三号系列火箭提升约一倍。

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飞行试验器由返回器和服务舱两部分组成。服务舱与嫦娥2号的外形很像,返回器则与神舟飞船神似,但体积只有神舟飞船的1/8。试验飞行器的轨道采用“8”字形的地月自由返回轨道,这种特殊设计巧妙地利用地球和月球引力,让探测器飞抵月球附近后绕半圈自动向地球飞来。



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为何这次试验器返回时的速度成为探月路上“拦路虎”?普通卫星只是围绕地球旋转,速度达到第一宇宙速度(约为每秒7.9公里)即可。而这次试验飞行器还包括了从月球返回地球轨道的过程,速度越来越快,再入返回大气层时的速度已接近第二宇宙速度(每秒11.2公里)。

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返回器从100多公里高度进入大气层时,会产生一系列特殊气体效应,由摩擦产生的热量也会大很多,因此现有的载人飞船和返回式卫星的着陆模式都无法满足需求,试验器采用了“半弹道跳跃式飞行”的方式来减速并进入大气层。

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返回器进入大气层后,通过飞行控制提升高度,在太空中滑行一段距离后再次进入大气层,然后在内蒙古中部地区着陆。“半弹道跳跃式飞行”增加了在大气层的“一出一入”,消耗掉返回器的部分能量,减小着陆速度,拉长航程,有利于选择降落区。

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即便采用“半弹道跳跃式飞行”的特殊降落轨迹,返回器“回家之路”仍有很多未知难题,再入返回试验的基础是大量的地面设计、研究和试验工作。但是地面模拟条件没有那么充分:比如地面要想模拟每秒11公里左右的飞行速度非常难;要模拟高层大气的真空度和化学反应也很难。

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由于返回器返回地球时速度会越来越快,不但进入大气层时的姿态需要精确调整,而且对再入角控制的精度要求也非常高。如果角度小了,返回器就落不到原先指定的降落区,如果角度大了,就直接落入大气层飞不起来。

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返回器降落时的速度非常快,不可能依靠地面遥控指挥,为此返回器配备了制导、导航与控制系统(GNC)技术,让其能自主控制。返回器在降落过程中的微小变动都可能带来影响。例如第一次进入大气层时,返回器会因高温烧蚀使其外形和重量发生改变,因此第二次进入大气层时,就必须考虑到这些因素进行自动调整。

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返回器的防热设计也是这次试验的重要科目,返回器的特殊需求也为热防护技术带来难题。例如在太空时,返回器内部的电子设备工作会产生大量废热,需要被及时排出;而再入大气层时正好相反,返回器外壁与空气摩擦产生的上千度高温需要隔绝。

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苏联和美国探月时也曾利用过类似原理返回地球,但他们的航天器航程没我国长,而着陆场比我们大。由于当今中国的人口密度大,适合充当降落区的地方有限,在克服高温、高速等诸多困难的基础上,对返回器的降落精度也提出更高要求。
 
2017 shall be the big test we are waiting for, It must launch, traverse the distance to the Moon, enter lunar orbit, separate into a service module and lander, land, collect samples, place them into a capsule, launch it into lunar orbit, rendezvous with an orbiting service module, transfer back to Earth, and protect the precious cargo as it enters Earth's atmosphere. This is one hell of a challenge
 
China's unmanned lunar orbiter returns home View attachment 139839

中国探月工程三期再入返回飞行试验获圆满成功
中国国防科技工业局1日宣布,北京时间11月1日6时42分,再入返回飞行试验返回器在内蒙古四子王旗预定区域顺利着陆,中国探月工程三期再入返回飞行试验获得圆满成功。[查看全文]2014-11-01 10:05XinhuaWeb Editor: Qian RuishaView attachment 139842

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Researchers retrieve the return capsule of China's unmanned lunar orbiter in the central region of north China's Inner Mongolia Autonomous Region, Nov. 1, 2014. Return capsule of China's test lunar orbiter landed successfully early Saturday morning in north China's Inner Mongolia Autonomous Region, according to the Beijing Aerospace Control Center. (Xinhua/Ren Junchuan)

China succeeded Saturday in the world's first mission to the Moon and back in some 40 years, becoming the third nation to do so after the former Soviet Union and the United States.

The test lunar orbiter, nicknamed "Xiaofei" on Chinese social networks, landed in Siziwang Banner of China's Inner Mongolia Autonomous Region early Saturday morning.

Search teams have already recovered the orbiter at the designated landing area, about 500 kilometers away from Beijing.

The last documented mission of this kind was by the Soviet Union in the 1970s.

Launched Friday last week, the orbiter traversed 840,000 kilometers on its eight-day mission that saw it round the far side of the Moon and take some incredible pictures of Earth and Moon together.

The re-entry process began at around 6:13 a.m. Saturday morning, with the orbiter approaching Earth at a velocity of about 11.2 kilometers per second.

The high speed led to hefty friction between the orbiter and air and high temperatures on the craft's exterior, generating an ion sheath that cut off contact between ground command and the orbiter.

To help it slow down, the craft is designed to "bounce" off the edge of the atmosphere, before re-entering again. The process has been compared to a stone skipping across water, and can shorten the "braking distance" for the orbiter, according to Zhou Jianliang, chief engineer with the Beijing Aerospace Command and Control Center.

"Really, this is like braking a car," said Zhou, "The faster you drive, the longer the distance you need to bring the car to a complete stop."

The "bounce" was one of the biggest challenges of the mission, because the craft must enter the atmosphere at a very precise angle. An error of 0.2 degrees would have rendered the mission a failure.

Wu Yanhua, vice director of China's State Administration of Science, Technology and Industry for National Defense, said the successful test mission has gathered a lot of experimental data and laid a solid foundation for future missions.`

Paving way for new probe

The eight-day program is a test run for the final chapter of China's three-step--orbiting, landing and finally returning--lunar program.

"Xiaofei" is obtaining data and validating re-entry technology such as the heat shield and trajectory design for a future landing on the moon by Chang'e-5.

Earlier reports said Chang'e-5 will be launched around 2017. The goal is to collect samples from the Moon and return to Earth. If successful, China will become the third nation to do so.

Calling "Xiaofei" a pathfinder for Chang'e-5, Zhou Jianliang said the data acquired by the lunar orbiter will optimize technology for Chang'e-5.

Hao Xifan, deputy chief of China's third phase lunar exploration program, also said the mission validated ground support capacities, craft landing technology and recoverable spacecraft technology.

According to Wu Weiren, chief designer of China's lunar exploration program, Chang'e-5 is expected to collect a 2-kg sample from two meters under the Moon's surface and bring it home.

Aside from the high-speed re-entry, major technological challenges for the craft center on surface sampling, taking off from the Moon, and lunar orbit rendezvous, Wu said.

READY TO MAKE HISTORY, AGAIN

China launched a pair of orbiting lunar probes and last year landed a craft on the moon with a rover on board.

Saturday's success is another step forward for China's ambition that could eventually land a Chinese citizen there. Few countries can rival China's space program although China never intended to participate in any "space race".

In an earlier interview with Xinhua, Wu Weiren said lunar probe technology and software could be of great economic value if adapted for commercial use.

Commercial gains aside, the space program is already a marker of China's global stature and technical expertise. The Chang'e lunar probes - named after a goddess who took her pet Yutu, or jade rabbit, to the moon - are a symbol of great national pride.

The country sent its first astronaut into space in 2003, becoming the third nation after Russia and the U.S. to achieve manned space travel independently. In 2008, astronauts aboard the Shenzhou-7 made China's first space walk. There are plans for a permanent space station, expected to be set up around 2022.

The Chang'e-1 and Chang'e-2 missions in 2007 and 2010 respectively, capped the orbital phase of the three step project. Chang'e-1 crashed onto the Moon's surface at the end of its mission, and Chang'e-2 was sent into deep space to become China's first man-made asteroid.

The ongoing second phase saw Chang'e-3 soft land on the moon carrying moon rover Yutu in December 2013. Chang'e-4 was a backup for Chang'e-3 and has not been deployed.

In the meantime, Yutu has entered its 11th dormancy earlier October, although its functions have degraded considerably after it encountered control issues in January this year. Experts had feared that it might never function again, but Yutu has stubbornly managed to wake up from its sleep mode ever since.

None of those missions were intended to return to Earth and this has pushed the 2017 mission further into spotlight.

"The Chang'e-5 mission will be yet another historic moment for China's lunar program," Wu said.
 
I want to know where the service module,which was separated from the return vehicle 5000km above earth,will go next。
 
I want to know where the service module,which was separated from the return vehicle 5000km above earth,will go next。

It depends where they were separated
Edit:
The separation was done at 5000 Km above Earth so the service module should be in Medium Earth Orbit. :-)
 
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Coming up next:the maiden flight of Yuanzheng-1(Expedition-1)space shuttle bus - the space ferry。:enjoy:

And 2015 will be an extremely busy year for the Beidou system。:tup:

It depends where they were separated
Edit:
The separation was done at 5000 Km above Earth so the service module should be in Medium Earth Orbit. :-)

The module is back on its way to the Moon for expanded tests:

许达哲:给再入返回飞行试验任务打满分

3rd paragraph。:tup::D
 
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Coming up next:the maiden flight of Yuanzheng-1(Expedition-1)space shuttle bus - the space ferry。:enjoy:

And 2015 will be an extremely busy year for the Beidou system。:tup:

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The module is back on its way to the Moon for expanded tests:

许达哲:给再入返回飞行试验任务打满分

3rd paragraph。:tup::D

:china::cheesy:

Unbelievable @cirr.

That was what I thought before the edit but I hesitated to make it as my firm conviction of where the service module should go next assuming all its fuel has been spent in ferrying the return capsule onto its homeward trajectory.

So all the marvels should be credited to our scientists who have done superbly precise calculations of
all the space paths and maneuvers for 2 crafts. No spacecraft is wasted. Very very well done :yahoo::dance3:

Let's see if there is any feedback from the service capsule soon :victory1:


ps if anyone still wonders of why we are not winning as many Nobel Prizes or where our Math Olympians go, here you are finding your answer :pop::china::yes4:
 
For those who are technically minded:

弹道升力进入飞行器一般最终需要通过伞回收,降落伞开启后就没有主控能力了,虽然可以通过气象部门预报风场补偿,但是总体来说主要的落点保证需要GN&C系统之前的导航制导和控制
其中制导能力很重要,所以主要考核整段再入飞行落点控制性能应该是针对GN&C系统的升力控制过程,因为即使风修正也需要GN&C系统来控制开伞点偏置来实现。

以下给出主要的弹道—升力式进入飞行器——这些飞行器一般采用钝头旋成体气动外形,升租比:神舟飞船:<0.3 Soyuz <0.3 Apollo 0.32 CEV/MPCV 0.35+,升租比越小表明可用升力越小,机动能力越小。

之前我说过,Zond6/7的近9000km航程30km精度了不起,当时的N1飞船升租比0。22以下,但是做类似工作的人知道,对于能量较高的进入任务来说:
1。面质比大的飞行器,弹道系数小的飞行器在长航程尤其是skip任务上往往难以获得大尺寸小面质比飞行器的性能和精度,虽然各方面的耦合很多,有利有弊,但是综合来说,对于low life entry vehicle而言,阻力更明显的往往需要付出更大的努力。——谁让你飞行过程阻力特性明显来着?
2。短航程尤其是double dips这种,是很讨巧的高能量再入飞行任务,一直在大气内控制和制导,少了跃出飞行段误差扩散以及导航制导耦合以及高空大气不确定性干扰,尤其是大气稠密段进行的FPA转向附近控制制导耦合问题,往往可以获得更高的精度。从我的研究来看,skip reentry性能好的制导律,完成短航程,精度可以有很明显提高。

对于使用skip reentry的飞行器来说,从这次来看,再入经历低纬度海面和中纬度地面两种不同环境,大气摄动更加呈现随机特征,尤其是据我所知,我国大气模型多以sa76为主,没有美国人用gram的福气。

所以,我佩服五院的同仁,尤其是听说到了那个数据后,目瞪口呆。不管是不是真正的人类弹道升力再入飞行器最高的开伞点精度,但是已经肯定是top几了。就因为:

1。 丫跳出大气了,着着实实。
2。 小尺寸,低升租比。
3。 国内相对弱的气动研究和试验能力,尤其是11km/s左右再入下高马赫气动参数十分不易获得精确数据。
4。要取得如此高的精度,制导导航系统势必有所革新。cev为了克服apollo不着调的skip reentry制导难题,提出全数字预测矫正——digital predictor corrector guidance law,但是只是测试,然而,看来这次,很可能,中国人干成了!

着着实实,在我心目中,No1!

:coffee::azn::tup:
 

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