Comment by h0l0cube | Hacker News Reader

Comment by h0l0cube | Hacker News Reader

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> preserve the planet in its pristine state

For those that have jumped straight to the comments this isn’t the flavor of TFA:

> The moon hosts several sites of extraordinary scientific importance (SESIs) to astronomy.

> Only within the last 20 years have astronomers discovered locations on the moon where conditions are ideal for the study of the early universe. The far side of the moon, for example, is one of the most radio-silent places in our solar system, as radio transmissions and interference from Earth are blocked. From there, radio telescopes can peer into the universe’s past to a time before the stars formed—or search for evidence of technologically advanced alien life, writes the Guardian.

> But because of the far side’s mountainous terrain, scientists say the installation of telescopes is possible at only three sites—and one in particular is rich in helium-3, which space mining companies have identified as a key element in quantum computers and fusion energy.

> Another scarce resource are the moon’s “cold traps,” located along craters near the north and south poles, where sunlight hasn’t been able to reach for billions of years. Among the universe’s most frigid places, they are the perfect location for infrared telescopes, which are specifically designed to operate at extremely cold temperatures. These could potentially collect images of Earth-sized exoplanets, and seismometers placed at cold traps could measure the moon’s own movement amidst gravitational waves.

> > But because of the far side’s mountainous terrain, scientists say the installation of telescopes is possible at only three sites—and one in particular is rich in helium-3, which space mining companies have identified as a key element in quantum computers and fusion energy.

A while ago, I saw a page that did the maths, and it worked out that the abundance of He3 was so low (at best 50 parts per billion), that even if we assumed a perfect fusion reactor (which we don't have) and noted the energy density of fusion fuel, it made slightly more sense to separate the metal and oxygen in the lunar regolith, catapult the resulting metal ingots to earth, and then generate energy from magnetically decelerating them (and even more if the ingots were shaped into liquid oxygen tanks). Likewise, one could get more energy from burning that metal as if it were coal than from fusion of the He3 in the same volume of regolith, because the particle density of He3 is so low.

I have not been able to find a link to that page since reading it, so unless someone here can remember where it is, I may have to re-do the maths and blog about it myself.

I always find that the reality of space exploration is so much more disappointing than my 1970s science fiction. When I was a kid I dreamed of farming on Ganymede and mining on Mars. The technology of today is AMAZING, but space is looking more and more barren.

Well, we have put hundreds of billions of person-years into developing technology suited to Earth. If we find a reason to put in the investment into these other environments, those sci-fi dreams may still come true!

These places surely cannot be scarce in the universal sense? Are they even scarce in our own solar system?

I think it actually might be the best spot because the far side of the moon is always positioned facing away from earth.

Is there anywhere else in the solar system that can claim that?

Always facing away from Earth, but not always facing away from the sun. Not my field, so I don't know how important interference from solar RF is.

If you're building on this scale, why not put two on opposite sides of, say, Deimos? The delta-v between there and LEO is less than the delta-v between the lunar surface and LEO: https://upload.wikimedia.org/wikipedia/commons/9/93/Solar_sy...

Wow! TIL. At first I thought you must be reading the map wrong, but you're right. Landing on Deimos does indeed seem to require less delta-V than landing on our own moon, assuming that this map is correct. And that seems to hold even without aerobraking.

14917 ms-1 [Moon] v. 14520 ms-1 [Deimos], if I'm reading it right.

It's because Deimos basically doesn't have a gravity well to overcome. You're just getting alongside it in orbit. It's not really landing at all.

I don't know if it's possible to make this map to scale, but it's hard to read right now.

There's an orbit that's always dark to Earth: https://en.wikipedia.org/wiki/Counter-Earth

A telescope in that orbit would never see earthlight, like one on the moon.

Communication with earth in that orbit would be a bit of a pain tho, right?

Some might see that as a benefit! But yeah you'd want a satellite orbiting in the L4/L5 Lagrange point of the Earth/Sun system. It would seem stationary to both Earth and Counter-Earth/L3.

> Is there anywhere else in the solar system that can claim that?

I know Mercury shares this. Not super useful, except at the boundary.

I'm 90% sure you're mixing up two other things, about planets in the goldilocks zone of red dwarfs being tidally locked to their host star?

Mercury definitely isn't tidally locked to the sun, and its sidereal day isn't a whole integer fraction of Earth's year.

I'm not 100% certain without doing some algebra, but don't think it's even possible for one planet to be tidally locked to any planet in a different orbit, be that Mercury to Earth or otherwise, owing to the distance not being constant while angular momentum has to be.

(If two planets share an orbit, there are an infinite number of trivial solutions).

Indeed, you are correct.

https://www.quora.com/Is-Mercury-tidally-locked-so-that-one-...

There is more info about what is and is not:

https://en.wikipedia.org/wiki/Tidal_locking

> Are they even scarce in our own solar system?

That doesn't really matter at the moment, because even if places like these are common, the only practical ones we can reach are on the moon.

But a lot more of them would be practical if we had a launchpad on the moon, no?

We don't have one now.

Let's not let our imaginations run away. There's a lot more that needs to happen to have a launchpad on the moon compared to an observatory.

"the installation of telescopes is possible at only three sites"

The far side of the Moon is bigger than Russia. I have my doubts about such a categorical claim as "only three sites are suitable for telescopes".

On Earth, we build observatories in mountainous terrain regularly.

Maybe a telescope has to rise above the harsh and damaging lunar dust. After construction of anything on the moon, I'm concerned about the 20 micron, glass-like, dust. Lunar dust is not weathered, like Earth dust. Once you are out of the lunar "atmosphere", the dust remains in low orbit for a long time.

Just put the telescope in space. It's a lot easier, despite the difficulty.

Have at it: https://cseligman.com/text/moons/moonfar.htm

The issue might be landing anywhere near it to construct the telescope. We are probably pretty far away from landing on the near side of the moon and then building roads or train tracks to the far side and creating a flat area.

When in orbit around the moon, you have complete freedom to choose the landing site.

If you're worried about communication, a relay satellite is way cheaper and easier than cables or roads.

There's no need to build roads or tracks from the near side to the far side.

Don't you need a large flat area to land safely?

In principle, no; in practice, a few recent attempts to land on a mild slope have immediately fallen over, so we clearly need some practice.

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