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China lands Chang'e-4 on far side of Moon

planetary.org

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Re: China lands Chang'e-4 on far side of Moon

#141

Post by Latteland »

Symmetry wrote: post #120
hanoz wrote: post #103

Earlier quoted context omitted.

So how can this craft orbit a point that is not a gravity well but a gravity hill, so to speak?

It's a gravity saddle! From Earth's perspective it's a hill in the r direction but a well in the phi/theta directions. To orbit at a location always visible from Earth it needs to move in the phi/theta directions but moving the the r direction doesn't help, so it doesn't.

And you clearly know this but i had to refresh my own knowledge of spherical coordinates - https://en.wikipedia.org/wiki/Spherical_coordinate_system

Re: China lands Chang'e-4 on far side of Moon

#142

Post by Rooster61 »

metta2uall wrote: post #135
bluGill wrote: post #128

Earlier quoted context omitted.

I'm not sure I agree. While there are obvious benefits to cooperation, competition has benefits too. I think the best cooperation is in terms of emergency rescue, backup communications, and sharing scientific results. Emergency rescues mean compatible docking systems to that if an opportunity arises technical problems don't stop the rescue. Of course actually catching something in space in time to pull off a rescue i…

The USSR and USA started cooperating in the 1970s and this has had very good results. For example being able to get to the ISS after the Space Shuttle accident, and arguably in easing political & military tensions. They continued to compete as well.

> very good results

with diminishing returns. Post-Apollo funding was/is but a shadow of NASA's glory days. As soon as the military interest is gone, it's inevitable that a program will lose financial support.

Re: China lands Chang'e-4 on far side of Moon

#144

Post by bluGill »

computerex wrote: post #90
adventured wrote: post #36

Earlier quoted context omitted.

> Is this what a space race feels like? No. New Horizons capturing Ultima Thule is not a large enough event to warrant the Chinese feeling like they need to compete with it. Spectator wise, it's a nice event for anyone that likes astronomy. It will be ignored by most of the people on the planet, just as the Chinese landing on the far side of the moon will be. These are not seminal moments in space history.

> These are not seminal moments in space history. Intercepting a 20 km object in the Kuiper Belt, the farthest body ever explored by mankind, isn't seminal? This also happens to be the first encounter with a planetesimal. It gives us a unique window into planetary formation. This is a very huge accomplishment.

Correct, but the average person doesn't care. They might have read about it and gone "neat", but they have already forgotten about it.

Re: China lands Chang'e-4 on far side of Moon

#145

Post by Rooster61 »

metta2uall wrote: post #140
bluGill wrote: post #131

Earlier quoted context omitted.

I have long said that the real reason for the international space station is to give Russia cover to keep their space engineers working. That is unemployed ex-soviet space engineers are are vulnerable to evil dictators offering them a job designing ICBMs (when you have no money/food moral considerations are less important)

That was part of it though I think space engineers would never have been unemployed or out of food - just reassigned to much more boring projects. Russia also has ways of ahem "discouraging" unauthorised trade of military secrets. With China's ICBMs, aren't they already advanced enough that collaborating on space exploration with NASA won't teach them much ICBM technology that they don't already know?

I think the ICBM utility has been played out. The new concern seems to be defense of space in and of itself. Exhibit A: Fearless Leader pushing through the Space Force creation. New field, new theater of war, new way to line defense contractor's pockets.

Re: China lands Chang'e-4 on far side of Moon

#148

Post by computerex »

eps wrote: post #124
computerex wrote: post #88

Earlier quoted context omitted.

No they weren't. What's your source? Their solution (N1) had inherent flaws that would have taken a long time to work out.

Documentary on the subject that interviewed people from the project. What's your source for the "would have taken a long time" bit? Edit - ok, read up on it and N1 was not indeed flightworthy. There is however little information on the nature of technical issues and how long they would've taken to resolve. The program collapsed first and foremost because of the politics and personnel/finance issues.

The N1 used closed loop cycles, which was something new at the time and was a lot harder to get right. Also the n1 had some 30 engines that all had to operate perfectly so the inherent risk of failure was higher. The rocket was never even man rated.

Re: China lands Chang'e-4 on far side of Moon

#149

Post by sthomas1618 »

dempseye wrote: post #52
tanilama wrote: post #41

Earlier quoted context omitted.

The story behind Chang'e is also interesting. Essentially, she is the wife of a legendary hero, Hou Yi(后羿), who saved the mankind from dying of drought due to the presence of nine Suns, by shooting all but one of them down. Chang'e stole the Immortal Pill, and eat it alone without her husband knowing. After she ate it, her body became to float and she flied to the moon, to live there alone forever as her punishment,…

The trisolarian plot in Cixin Liu's The Three Body Problem also seems to have borrowed from this myth.

Having read (and enjoyed) that trilogy, I'm not making the connection. Which part?

Re: China lands Chang'e-4 on far side of Moon

#150

Post by ecp9 »

arduanika wrote: post #5

"...and if the dam breaks open many years too soon..." Perhaps interesting to note the origin of this name for spacecraft. The legend "Chang'e flies to the moon" (嫦娥奔月) lies behind the Mid-Autumn Festival (featuring mooncakes, as it were). Point is, the names of Chinese space missions are every bit as carefully steeped in tradition as, say, Mercury/Gemini/Apollo.

Thank you for making the valid point that those asian people have a history and traditions as well.

Like seriously? This is the top voted comment?

Sometimes I seriously wonder about HN.

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