Chang'e 5: Ultimate Chinese challenge to get Moon rocks back to Earth

Sneak peek on something going to hit your spaceflight news headlines coming next week...pic.twitter.com/8WomXStq5G

...and it might have a milestone effect on human exploration of space, in many ways. Yet for most parts people involved absolutely don't like to talk about it (right now). More on this coming in the next days here.pic.twitter.com/GgNmBXS5HB

At T-1 week, w/ a decade of development & 3 additional years of wait for its ride to space behind, 23 intense days to the Moon and back ahead, this may be as much a watershed moment of beyond Earth human exploration as the Crew Dragon launch just now...pic.twitter.com/on8X2MXfdO

...but they are so shy that there has been literally close to no news of what any other places would proudly boast as one of their flagship spaceflight missions, one that might be only slightly easier than Mars Sample Return. Yes, the ultimate Chinese call to the Moon is here.pic.twitter.com/ZGTGHNcotp

So, um, before going through details of this, I have to report on the bad news that per someone's insider contacts (see below) we probably won't get much news of Chang'e 5, at least during launch phase. Yup, Chang'e 5 has an official identity crisis. https://twitter.com/Longmarch13/status/1326853162565730311/ …pic.twitter.com/J39QndMsOP

This doesn't retract from the fact that this mission has a lot that can go wrong, and yet being a fierce shot at the PRC's determination of beyond-Low-Earth-orbit robotic and human exploration at the same time. This rocket-rabbit logo (made by enthusiasts?) feels exactly that.pic.twitter.com/8oMlhgf8XV

Well they are rolling off a day earlier than reported! The Long March 5 rocket with Chang'e 5 is currently rolling out to its pad at Wenchang for launch on apparently November 23 evening UTC.pic.twitter.com/Wszi1L0E10

As usual, lots of flags and banners around here.pic.twitter.com/N6NYDl63qw

Meanwhile in China this is almost at the pad...pic.twitter.com/3XEfTzVlza

More flags and banners, with the spacecraft and rocket processing teams:pic.twitter.com/1PwQJPaXVT

Firstly, the ride to the Moon. While scoring successes w/ last Dec.'s RTF, the next-gen crew S/C (w/o 2nd stage) in May and sent TW-1 to Mars in July, the Long March 5 is still an inexperienced rocket. With every of its launches flagships, the pressure must be intense every time.pic.twitter.com/sX4LDc80C5

After separation the whole spacecraft will be on a direct trajectory towards the Moon. @coastal8049 made some calculations based on prior mission timelines and estimate the LOI will be around 4.5 days after launch, probably ~14:45 UTC on Nov. 28: http://satobs.org/seesat/Nov-2020/0156.html …pic.twitter.com/nPhw3bf9hh

What goes afterward is a bit hazy as I have never saw any detailed description of the mission timeline after this, but the spacecraft should stay in an unknown lunar orbit awaiting the sun to rise at the landing site, then separates from the orbiter and land.pic.twitter.com/VsMd4ORf5f

We still have no idea when it will land - I have seen Nov. 30 mentioned once but early Dec. is possible - but while the Chinese have 2 successful ones already, the 2 failed Moon landings still remind people that GNC is a harsh mistress.pic.twitter.com/KyOdQlpXpi

With the lander probably a bit different from the ones used on Chang'e 3/4, even this part will still be a challenge to nail down. All these parts will apparently be observed by a descent camera like the last 2 landings, though the only official source is from a Chinese paper.pic.twitter.com/4STjkSxoEr

The only mention of the PCAM is the paper excerpt below - I'm not even sure where they are located, perhaps it's the rotating platform in the picture on the descent stage. I can't find their technical parameters either... (https://meetingorganizer.copernicus.org/EGU2016/EGU2016-3858.pdf …)pic.twitter.com/xZz5YUUurV

And sorry for the interruption, but a certain insider has reported important timings of the mission! Launch time: 20:25 ~ 21:15 UTC on November 23 Landing time: Probably ~20:30 UTC on November 29 (base on MCC screen shots during final rehearsal) Source https://m.weibo.cn/u/5616492130 pic.twitter.com/f1SnOA8ZeD

Also it appears that after McGregor Texas, Wenchang is also a major habitat of Rocket Cows (TM):pic.twitter.com/GYTWHDV0fr

Like the Soviet LSR missions of the 1970s, the deep drilling will provide layered sub-surface samples of the lunar crust. Detailed description of drilling bit and sample sealing can be found at https://ieeexplore.ieee.org/abstract/document/8607979 …. I'm not sure how samples would be put into the ascent stage.pic.twitter.com/T2V1Reh5tf

The other method of sampling will be via a double scoop on the end of the robotic arm, assisted by twin cameras. IIRC some parts of it were designed by a team at Hong Kong Polytechnic University a few km from me, which has worked on Beagle 2 & Chang'e 3.pic.twitter.com/i8RbPPOChq

Getting the sampling working as planned may be more difficult than it seems (ask @NASAInSight's thermal probe or Apollo astronauts etc.), but here comes the hairy part of taking off from the Moon, 1st major launch from a major solar system object since Luna 24 of 1976:pic.twitter.com/lyrV6mbzL6

So after ~2 days of surface operations the ascent stage will have only 1 chance to get to the right rendezvous orbit (15 x 200 km towards the orbiter at 200 km circular per a 2014 paper). Then it has to dock w/ it - never tried robotically that far from Earth.pic.twitter.com/d3f73nYjFR

Those who have read the details of the @NASA/@ESA Mars Sample Return mission plans would probably have a headache on this. Now the Chinese are attempting s/t only slightly easier all by themselves.pic.twitter.com/RJD6CLk0CX

It appears the docking mechanism is some sort of "soft docking" one with claws on the orbiter/return capsule side. The sample container would slide (?) into the return capsule and then automatically sealed. Quite tricky to get that right it seems...pic.twitter.com/HbeGj4C4eh

The orbiter would wait for ~10 days before making the TEI burn (can't remember why). Another 5 days would pass before they come across Earth around December 16-ish. The return capsule would separate from the orbiter at ~5000 km altitude.pic.twitter.com/jbHzIOsPH2

Then came the hottest part of skip re-entry - so hairy that the Chinese rehearsed w/ the Chang'e 5-T1 mission way back in Oct./Nov. 2014. After bouncing back to 140+ km high the capsule would make a 2nd dip into the atmosphere before landing.pic.twitter.com/y3GwdgtBRt

Well, that's it for my (way later than planned) walk through. Since the Chinese are full of stresses of risk we don't know what kind of coverage we'll get through to landing on the Moon and back. Sit back and wait is all we can do. ¯\_(ツ)_/¯pic.twitter.com/RvWcSPEL8P

Ah, I can end this thread with the REAL launch window and target T-0! **T-0 is set for 20:30:12 UTC.** Launch window extends to 21:15:07 UTC.pic.twitter.com/85xkSCpyjf