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China's Jade Rabbit lunar rover dies on moon

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Re: China's Jade Rabbit lunar rover dies on moon

#51

Post by lutusp »

Pxtl wrote: post #33
lutusp wrote: post #2

This is a shame, but most people -- even in space programs -- don't appreciate how cold the Moon's shaded areas become. It's now estimated that these areas get to 26 Kelvins -- that's 26 degrees above absolute zero. To get a sense of how cold this is, Pluto's average surface temperature is seven degrees warmer . Also consider that, because of the specifics of the Moon's orbit, a given area stays shaded for just over…

That said, temperature works differently in hard vacuum - with no air to conduct/convect the heat away, isolated objects don't actually get "cold" the way they would in a pool of liquid nitrogen or something. Notice you don't hear about the ISS freezing at night.

No, actually, a vacuum is an ideal environment for radiating heat away -- better than an atmosphere, certainly. Surfaces in lunar shadow really do drop to an extremely low temperature over a period of days.

Re: China's Jade Rabbit lunar rover dies on moon

#52

Post by lutusp »

mpyne wrote: post #49
unspecified wrote: post #38

Earlier quoted context omitted.

The ISS is only in shade for 45 minutes at a time, which is orders of magnitude less than a lunar night. But speaking of that: how long is too long to spend at 26K in a vacuum? Are there any good articles/videos that talk about what happens to various materials at such extreme temperatures in a vacuum?

I think the point of the parent comment was that simply being in a cold vacuum doesn't make you instantly cold. That still requires a process of heat transfer, which occurs in a fluid via conduction, convection, and radiation. When immersed in a vacuum the conduction and convection heat transfer paths are sharply reduced, so the question then becomes how fast do you cool off via radiation alone? I'm not a physicist s…

As it turns out, even on earth's surface, radiation is a more efficient heat transfer method than conduction and convection through the air. Objects under a clear sky quickly drop below air temperature in many circumstances.

Re: China's Jade Rabbit lunar rover dies on moon

#53

Post by officemonkey »

shitgoose wrote: post #24
oftenwrong wrote: post #21

Earlier quoted context omitted.

>To get a sense of how cold this is, Pluto's average surface temperature is seven degrees warmer. That doesn't give me a good sense because I have no idea how Pluto's average surface temperature compares to typical on-Earth temperatures that I have experienced. This gives me a better sense: 26 K = -247.2 C

Is that with the windchill?

No atmosphere, therefore no wind, thus no windchill.

Re: China's Jade Rabbit lunar rover dies on moon

#55

Post by beachstartup »

trekky1700 wrote: post #28
cygwin98 wrote: post #25

Earlier quoted context omitted.

Not surprised. He has been bashing China for a while, which is the trending topic in the mainstream media anyway. Though I do wish some of the media agencies strike out of the group-thinking, and examine what NASA has been up to for the past decade, and what needs to be improved in terms of space exploration.

I haven't seen any trend of bashing China, unless of course reporting honestly is bashing. NASA, despite its huge budget cuts, in the last decade has operated three rovers on Mars, landed one new one (via spectacular jet crane awesomeness). They've built new types of rockets, taken pictures of the universe, continued to do valuable research in science and space. Continued to be a major contributor to the ISS. And muc…

the US, english-speaking media tends to only point out extremely good, and extreme bad things about china.

this paints a really extreme (go figure) picture of china. some people think it's the most amazing place on earth and some people think it's some kind of post apocalyptic hellscape.

as always, the truth can be found by actually going there, something most people with very strong opinions about china have never done and probably never will do, in all likelihood

Re: China's Jade Rabbit lunar rover dies on moon

#56

Post by Dylan16807 »

lutusp wrote: post #51
Pxtl wrote: post #33

Earlier quoted context omitted.

That said, temperature works differently in hard vacuum - with no air to conduct/convect the heat away, isolated objects don't actually get "cold" the way they would in a pool of liquid nitrogen or something. Notice you don't hear about the ISS freezing at night.

No, actually, a vacuum is an ideal environment for radiating heat away -- better than an atmosphere, certainly. Surfaces in lunar shadow really do drop to an extremely low temperature over a period of days.

You changed the entire context by sticking the word 'radiating' in there. Yes vacuum is fine for radiation, but radiation is much slower than physical contact with standard pressure air.

Re: China's Jade Rabbit lunar rover dies on moon

#58

Post by df41 »

dengnan wrote: post #12
demallien wrote: post #8

Well that sucks. Is anyone here a big follower of the Chinese space programme? I follow "western" space efforts pretty closely, but with heavy military involvement, a preoccupation with face-saving, and the language barrier, I find the Chinese programme nigh on impossible to track. Do they have the same sort of spending split that NASA has with respect to the manned v. unmanned programmes? Or does their unmanned prog…

We, Chinese, do not know too much details either. It is hard for us to know details about the spending. I tried to google it with key words like "Chang'e budget", but found nothing useful. However, I did found an article about the history[0]. Here is some fact: Back to 90s, there were Chinese scientists suggesting for lunar exploration. But the projects requires a budget around 1.5B, which was declined by the prime m…

I spent 2 minutes with google and it seems the closest I could get is this: http://news.qq.com/a/20120625/000134.htm Basically it says the total spending on manned space missions is less than RMB 40B from 1992 to 2013. That translates to about 6.7B in current ratio.

2 NEST to send man to space. Not too bad IMO.

Re: China's Jade Rabbit lunar rover dies on moon

#59

Post by sounds »

1morewebdev wrote: post #41
lutusp wrote: post #2

This is a shame, but most people -- even in space programs -- don't appreciate how cold the Moon's shaded areas become. It's now estimated that these areas get to 26 Kelvins -- that's 26 degrees above absolute zero. To get a sense of how cold this is, Pluto's average surface temperature is seven degrees warmer . Also consider that, because of the specifics of the Moon's orbit, a given area stays shaded for just over…

Suppose China were to send another Rover up in the next 5 years, and it found this one. In theory, could this one be repaired? Or will the "electronics self-destruct" be thorough by then?

Some assumptions I have to make are:

• The RTG in Yutu (the rover already up) will last that long

• Yutu does not move, get struck by a meteor, or other normal events in space that will damage it further

• The team who understands Yutu is still around in 5 years

Then China could, in theory:

• Assemble a rover with the repair parts on board

• Launch it to the moon

• Land on the moon intact

• Locate Yutu

• Do a remotely-operated repair

There's a lot of risk in each of those steps. It might be an interesting mission to push the boundaries of tele-operated robotics etc. Realistically it seems less expensive to launch a second rover that has been improved based on the lessons learned from Yutu. Hopefully China can think of lots of things to improve the second time.

Interesting thought experiment, though.

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