Humans returning to the Moon

As the ISS winds down, Lunar Gateway and other developments are around the corner


Problem is, there’s no particular reason to go to the moon. I’m a big fan of onward and outward, and the cost (in the big picture) is minuscule, but there’s better things to do out there.

Off the top of my head:

Helium 3. Isn’t the moon a possible source of fuel that can be used for further missions

Lunar Gateway. This is not a gate to the moon, it is a moon based gate to deeper space. The moon is a stepping stone where missions can resupply

In the meantime, having a station there means doing science and developing technology for deeper space exploration, in the same way the ISS has been

Probably having a lunar telescope will help with looking for planet killing asteroids

And so on, that’s just off the top of my head


I’m starting to wonder if we really ever went there


What I don’t get is how spaceships don’t suddenly find themselves a really long way from the earth once they leave its orbit. Earth travels at 67,000 mph. Why doesn’t a spaceship on its way to the moon find the earth disappearing at an incredible rate? Or does it never leave the earth’s orbit if it only travels to the moon?

Earth travels at very high speed around the sun. So does everything on or in earth. You need fuel to add to or cancel this speed out. You don’t magically get left behind just because you left earth.

In fact it’s so hard to get to the sun itself, due to the high speed, that it’s actually easier to leave the solar system then it is to get to the sun.

If you aren’t going that fast around the sun you’d fall into the sun, and that would be a bad day.

It’s all orbital mechanics. You don’t stay in orbit because you somehow reached a magical height. You stay in orbit because your sideway speed is high enough that you miss the ground while falling. That’s what orbit is, basically falling.


I’m pretty sure it is because velocity is relative. The same reason why when you’re on a teain and you jump up, the train doesn’t move quickly underneath you. Been a few decades since university physics for me, and i couldn’t find a space travel specific video in 1 minute of Google searching, but I think that’s the answer. Relative velocity

As @Taiwan_Luthiers says, orbit is basically falling, but at such a speed and distance that it is possible to take a long time to fall all the way. If orbit decays too much, eventually a satellite will hit the ground. This is why from time to time old space junk finally makes it to the ground, and why modern satellites have propulsion to help maintain orbit.

Once a spacecraft has a vector which is no longer in that sweet spot of orbital “fall”, it is not in orbit but in fact vectoring away from earth. That sweet spot depends on mass as well as velocity, so the moon whichnis more massive can maintain orbit further out without secondary propulsion

Er, I’m pretty sure.


At lower height there’s air that creates drag to slow you down. At higher orbit there’s no air that can slow you down and it can stay in orbit for thousands or millions of years. Same reason why the moon doesn’t fall and why the earth don’t fall into the sun.

In fact due to tidal interactions we are actually slowly losing the moon.


But isn’t it like being outside on top of the moving train and jumping up and the train moving quickly?

I’m not going to disagree with anyone, cos obviously we go into space. I just can’t get my head around it.

I appreciate all the explanations though. I will mull it over today as it is Sunday and I’ve got the day off to ponder such marvels.

Air resistance?



Things moving will stay moving… That’s the rule.

Unless acted upon by an outside force. Like friction, or air that isn’t moving inside the train with you.

It’s worse than that. Since there’s nothing to stop you any change in velocity, whether speeding up or slowing down, requires fuel. Which is why it’s harder to go to the sun than leave the solar system.

I think the goal is to capture them, and mine them.

And every time I see this thread, I read Hamas Returning to the Moon and think, wow, that happened fast.

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I recently went down a rabbit hole on Wikipedia, starting with

Basically all motion has to be described based using another object as a frame of reference, as everything is relative and there is no absolute frame of reference.

The reason it was a rabbit hole is because - yeah - hard to wrap my brain around some things.

fwiw, the Earth has a gravitation pull for quite some distance. The gravitation neutral point between the earth and moon is much closer to the moon, since it has weaker gravity:



I think you can go down that rabbit hole until you’re in a wormhole, but my physics is pretty rusty

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Think about this also:
“Our solar system is moving with an average velocity of 450,000 miles per hour (720,000 kilometers per hour). But even at this speed, it takes about 230 million years for the Sun to make one complete trip around the Milky Way.”

So when you leave our planet, why do not Earth and the Sun travel away from you at 450,000 miles per hour?

Because you are in the frame of reference of the Earth and the planets and the sun, you are also already moving at 450,000 miles per hour. Then if you flew away from planet Earth at 1000 miles per hour, you would actually fly at 451,000 miles per hour or 449,000 miles per hour, depending on which direction you left in.

And you can add another layer. The Milky Way galaxy is also moving away from other places at certain large speeds, but it does not matter for our local frame of reference.



Much speculation has been made over the possibility of helium-3 as a future energy source. Unlike most nuclear fusion reactions, the fusion of helium-3 atoms releases large amounts of energy without causing the surrounding material to become radioactive. However, the temperatures required to achieve helium-3 fusion reactions are much higher than in traditional fusion reactions,[3] and the process may unavoidably create other reactions that themselves would cause the surrounding material to become radioactive.[4]

Get back to me when we have even ordinary fusion.

-Gateway to what? You’re already in space; this is like crawling out of a deep hole, passing over level ground, and crawling into a shallow hole to prepare you to reach…level ground- you’re already there
-Doing science and developing technology for deeper space exploration is probably better done in space than not-space.
-Looking for killer asteroids is better when you have a clear view than when you’re perched on a rock obscuring half the sky every rotation.