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China prepares mission to land spacecraft on moon's far side (phys.org)
149 points by dnetesn 3 months ago | hide | past | web | favorite | 83 comments

The lander plans to transmit data to Earth using a relay satellite orbiting at the Earth-Moon L2 halo orbit: http://www.planetary.org/blogs/guest-blogs/2018/0519-change-...

The relay satellite included two micro-satellites for the moon, only one of them survived: http://www.planetary.org/blogs/guest-blogs/2018/20180615-que...

That Earth-Moon L2 halo orbit is cool, I didn't even know that was a thing.

[edit] I mean I was aware of Lagrange points, but not the practicality of the halo orbit. This is a nice explanation:


Yeah, it instantly makes sense if you calculate the force at the Lagrange point and notice the vector points back at the exact L point when you're in the vicinity - and then you go, hmmm, looks like it might be possible to orbit that thing.

Will L2 congestion become a problem once JWST and a few more missions join this craft? Will we have to manage that orbit like we do with geostationary?

An interesting point from that page:

>A full n-body dynamical system such as the Solar System does not contain these periodic orbits, but does contain quasi-periodic (i.e. bounded but not precisely repeating) orbits following Lissajous-curve trajectories. These quasi-periodic Lissajous orbits are what most of Lagrangian-point space missions have used until now. Although they are not perfectly stable, a modest effort of station keeping keeps a spacecraft in a desired Lissajous orbit for a long time.

https://en.wikipedia.org/wiki/Halo_orbit "Halo orbits can be thought of as resulting from an interaction between the gravitational pull of the two planetary bodies and the Coriolis and centrifugal accelerations on a spacecraft."

Perhaps we’ll get another Space Race with China. At a point, the United States was spending over 4% its budget on NASA:


The money would probably be better spent on several projects (e.g. AI, hypersonic flight).

His useful hypersonic flight may be?

With air being so dense and power-dissipating, it might be more economical to do a sub-orbital jump than to push through the atmosphere at 7M. For short-range military applications, iirc, hypersonic rockets exist.

Really useful.

You've gotta consider how much things change as you get higher into the atmosphere. The obvious thing is that atmospheric oxygen begins to become insufficient to operate engines as you go higher up, so you need engines that use a different oxidizer than atmospheric oxygen which is extremely complex. And even the efficiency and characteristic of engine exhaust changes radically depending on atmospheric density and the characteristics of its exhaust. In other words an engine that works great at sea level might work awfully when you start to get to a fraction of the same pressure.

There's an immense amount of flexibility in being able to travel hypersonic. The SR-71 Blackbird is an amazing example of the potential. First flown back in 1964 (!!) it was capable of hitting around mach 3, some 2200 miles per hour. That's 6 hours to get from one side of the Earth to the other. It's really quite remarkable how much our overall transportation technology seems to have stagnated since the 60s. I'd like to imagine everything is just classified but everything from the SLS to the F-35 to even things like the Zumwalt just seems to indicate that we've simply technology regressed. Kind of disconcerting to imagine the reasons for that.

All current military hypersonic (Mach 5+) weapons are ballistic missiles. No one has demonstrated sustained hypersonic flight through the atmosphere but that's probably coming in a few years.

NASA does a lot of work on hypersonic flight. Lots of sources to link to, here's an article from a few years ago:


That’s Nasa’s quiet supersonic project.

Hypersonic is five or six times the speed of sound.

It would of course be nice to have both.

I'd rather see them spending it on NASA than on the military.

Ironically, these were mostly the same thing during the space race. I watched a USAF training video on re-entry mechanics[0] a while back that really drives this home in an almost dizzying context switch. It goes from the mechanics of delivering a thermonuclear payload in one sentence, to returning humans to earth in the next.

[0]: https://www.youtube.com/watch?v=c_bkY7-9c8s

There is no way a space race like the one during the Cold War can appear again. Nonetheless the term space race is often used by the media just because it sounds more dramatic.

It doesn’t have to be the same type. This time the military could be involved. Its budget is approaching NASA’s.


The Trump Administration wants a Space Force, for example:


we used to invest $3 into infrastructure and science for every $1 in entitlements spending. Now we spend $5 in entitlements for every $1 in infrastructure/science

And people wonder why the US is falling apart and technological advances have slowed down.

We're living hand to mouth instead of investing in the future. The sad thing is that many of our problems could be solved permanently via technology rather than government.

Instead of creating the automobile people are trying to make horses faster

The US is wasting trillions fighting wars in other countries.

China is wasting trillions building infrastructure in other countries.

Wasting money on infrastructure is better than wasting on wars. The government of the U.S. need to learn better.

The problem with war is that no matter which side wins, both side will always in some way hate each other (Once war started, it will never end).

While even in the worse scenario, locals can still benefit from the infrastructure. Booming strategy is something Chinese people play very well.

And people wonder why the US is falling apart and technological advances have slowed down.

I don't think anyone wonders why it's happening. They just feel powerless to change anything.

Have technology advances slowed down? Or are we just not advancing in the big, exciting really of "blowing shit up"?

We are now advancing mostly in the ability to manipulate, exploit and make miserable almost everyone, via adtech.

That's an inevitable result of devoting the efforts of so many of our brightest to attracting eyeballs.

It feels like we slowed down in the important areas. Software? Web Apps? We're doing great. Anything space related? Eh. In theory we get to claim SpaceX so I guess that counts but most people couldnt tell you what NASA's been up to recently...

There was that landing on Mars two weeks ago...

nice and vague

abolish government, libertarian paradise, ???, solve problems

I wouldn't say "vague". He cited the differential in dollar amounts and drew a conclusion from the data presented. That sounds specific to me. I think you may have overreacted to his point. You should have debated the merits and demerits of welfare spending versus R&D investment. Instead you accused him of something he never advocated for.

duxup 3 months ago [flagged]

Would we fund it even then?

I would expect some nationalistic fervor that would help fund a space race would come from US conservatives.

But in the US the "conservative" side of politics seems more interested in short term tax cuts for corporations, dismantling government, and hating on immigrants, and other Americans...

I have my doubts the US would step up.

Accepting your blatant mischaracterization of conservative US politics as true for a moment, I think given the choice between "othering" folks in the US or a country on the other side of the world that most people know nothing about, politicians of any stripe would prefer the latter.

"I think given the choice between "othering" folks in the US or a country on the other side of the world that most people know nothing about, politicians of any stripe would prefer the latter."

I don't know what you're trying to say.

Show me reigning US conservatives who aren't espousing those ideals cited. Go on, I'll wait. Even the libertarian puritans like rand paul have fallen in line with the socially and economically regressive republican platform of today.

The only ones willing to stand up to the hypocrisy of Trump and actually represent conservatism have been sidelined consistently.

The tech gap is too big, despite media hype, don't think China can even catch up.

You can land on the moon with 60s technology, what basis is there for not being able to reach that?

In space flight some of the most advanced technology even to this day was developed in the 60's and 70's. Things like NERVA[1], the NK-33[2], and the Saturn V[3], were developed back then and are still more efficient or bigger then similar technology we have today. The 60's and 70's were the golden age of spaceflight.

[1]: https://en.wikipedia.org/wiki/NERVA

[2]: https://en.wikipedia.org/wiki/NK-33

[3]: https://en.wikipedia.org/wiki/Saturn_V

So, you’re saying the world’s second largest economy, soon to be the first, can’t catch up in 10-20 years?

The US only spends $20 billion a year on NASA.


If you keep breaking the guidelines we'll ban the account.

> Please don't impute astroturfing or shillage. That degrades discussion and is usually mistaken. If you're worried about it, email us and we'll look at the data.


Ok I'll refrain myself next time. I'm hoping you monitor suspicious activities and accounts on here, including where the trails ends up, because I assure you weird things are happening. There's an unnatural tendency to favor a view as of lately.

> It may also carry plant seeds and silkworm eggs, according to the official Xinhua News Agency.

Is there any scientific/experimental reason for this, or is it just a symbolic gesture?


Seems like an experimental attempt to create a "Moon Surface Micro Ecosystem". Not sure how legit it is though.

According to this article, they try to build a mini biosphere: https://www.telegraph.co.uk/news/2018/04/13/china-plans-grow...

Huh, interesting. I'm left wondering whether China has a Planetary Protection Officer, though of course the Moon is barren so it doesn't really matter…

It isn't just barren. It's sterilized of any Earth life that may have happened along every month, which gets up to 250 degrees F (~120 C), and even if something survives that, there's never a window of time in which something like livable conditions obtain, because once out of the sterilizing sunlight the temperature immediately heads for a decent approximation of the average temperature of the cosmos. (Doesn't seem to quite get there, but it's cold enough that you could pour liquid nitrogen on to the ground and it would stay liquid if you held it at 1atm pressure. Dunno about vacuum.) So between the extreme thermal cycling and hard radiation, even Earth's best aren't going to get a foothold up there.

This is in contrast to places with a non-trivial atmosphere or standing liquids, which may moderate the environment enough that something could conceivably live. Something could conceivably live on Mars, something that isn't even necessarily that far from some things that live on Earth. Nothing will live on the Moon. You can fling as many gallons of the scummiest pond water you can find from any pond water on Earth on the moon, and you're not going to "contaminate" it with life.

I'm sure tardigrades have fared worse and survived, at least for a little while.

Throw enough bullshit at a problem and something is bound to grow...

We really, really need more data on the responses of living creates to 1/8g. We've got all the 1g data. We've got a considerable amount of 0g data from ISS experiments. But we just don't know how living creatures respond to lunar or martian gravity. And knowing that will be very important for future colonization efforts.

Couldn’t we get that from a spinning satellite closer to earth?

Spin can indeed create (effective) gravity, but it differs due to the coriolis effect. We'd have two options: We can build a really big satellite, so as to minimize that effect -- or we could assume plants aren't sensitive to it, and hope for the best.

Needless to say, most scientists aren't fans of the second option.

Incidentally, long-term it would be possible to achieve 1g on the moon by way of a similarly huge centrifuge.

I can't grasp the centrifuge option, won't there still be two forces? It'll be more like those carnival rides than artificial gravity. A dropped ball won't fall straight "down".

On Moon?

The compartments would have to be tilted relative to the centrifuge, such that down becomes properly down.

Another option is simply using a tether and a counterweight.

There are spinning experiments on the ISS.

No, the satellites stay in orbit only because the net G they experience is 0.

I believe the parent was referring to pseudogravity via rotation ('centrifugal force')-- hence the reference to a spinning satellite.

And how this related to the proximity to the Earth? I think the OP meant being close to the Earth would result in a gravity due to the proximity.

I read it as being cheaper to get experiments there (1kg to LEO is cheaper than 1kg to soft land on the moon)

Yes, exactly what I meant. It seems a lot easier to get an experiment into orbit than onto the moon. If you connect two halves of the satellite with a long tether, you could reduce the coriolis effects, if that's really an issue.

If that's the correct meaning, then O.K. My bad.

I assume it's to provide food for the cane toads.


Don't know this time, but Chinese textbooks mentioned the radioactive space environment could cause mutations in the genes, creat new varieties.

Nice: giant worms in a world with scarce water laying in caves.

Let me know when I can buy a stillsuit and then we'll talk.

Teoretically you learn to build it yourself....

I have ridden the mighty moonworm!

You can do it more cheaply using a radioactive source on Earth. https://en.wikipedia.org/wiki/Mutation_breeding

Is this something they are trying to study, or trying to protect against?

There are already hard at work planning for a clothing factory.

It's traditionalist/nationalist symbolism of claiming the greatness, much like Russians hanging up Orthodox icons on ISS.

"hanging up"

How can you "hang" something in microgravity

Easier than in full gravity, I imagine.

Velcro, I imagine.

Duct tape.

"Its program also suffered a rare setback last year with the dialed launch of its Long March 5 rocket."

Failed, I presume.

First Long March 5 rocket succeeded in Nov '16. Second one failed in July '17

I really like the Chinese approach to space exploration. They go slow but steady and focus on interesting stuff.

When will China publish their own pictures of the satellite dish, cooling tower, and woman on the moon? <snark>



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I'll see you on the dark side of the moon.

[Adjusts glasses]


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