# Space siphon (Space elevator V2.0)

In my readings a new concept came up, that of a space siphon. The idea is to get water from the earth’s oceans to the moon, then Mars and Venus all without external energy. Object is terraform and providing resources at those places in the meantime.

So this breaks into 3 parts:

1 - Possibility of the ‘free’ trip to space (at the expense of the earth slowing). This is not a ‘true siphon’ as in it’s not just a tube of water pulling itself along. The concept is that the water moved up beyond geosync would generate a force pointing away from the earth, that force would be used to pull the water behind it, including the water all the way from the surface. The siphon is long enough that the claim is that the outward beyond geosync is greater then the total inward to the surface. The means of this force transfer is not mentioned, but it seems to be individual cars perhaps on a conveyer belt (though that last part is not mentioned), and not a continuous stream. Does the energy equation work out (which i assume it would)? Is there a known theoretical way to have this work?

2 - (regardless of part 1) Getting that water to the moon and beyond? Could it be just released to be flung accurately to it’s target?

3 - What happens on the moon, mars assuming the water does make the trip, does it snow, rain, get pounded by a great big ice rock, get a atmosphere of humidity?

Your environmental impact statement should be interesting.

IF I understand correctly - and that’s a big if…

The water moved up beyond geosync would have to be moving faster than the rotation of the earth in order to stay in that elevated orbit or it sinks back down to the geosync orbit altitude. How do you propose to have your space elevator move faster than the speed of the earths rotation?

And now that I think about it that means that all the water underneath the geosync orbit will pull the entire column down. Not to mention how are you going to pump it up that high to begin with? That’s gonna be one heavy ass column of water.

Someone page Stranger on a Train

In Larry Niven’s Rainbow Mars the ancient Martians developed biological “space elevators” – giant trees – that transport water to the top of the atmosphere by a combination of capillary action and some other processes. Once it gets up there, it boils off into space. It’s a slow process, but it eventually dehydrates Mars. Something to consider.

You can’t suck water higher than 10 meters, so you’ll have to push it or use other forces such as capillary action.

Why did they want to do that?
And for the OP, also, why would you want to siphon Earth’s water anywhere? It’s really useful stuff and we sort of need it. You want to terraform planets, there’s lots of raw materials there or in space that would (probably) allow you make the water, given the availability of pretty much unlimited solar power.

I don’t recall – it’s been a while since I read it. I think they really wanted the biological space elevators, and the water loss was an unforeseen and unexpected byproduct.

http://en.wikipedia.org/wiki/Rainbow_Mars

This has plot details:

http://www.sfsite.com/04a/rain54.htm

Exactly. Kind of a problem for this plan.

1. Not ever going to happen - pick up a gallon of water, now multiply that by a gazillion. How off earth are you ever going to lift it in the first place?
2. You’re going to need to continually adjust the path of the water to intercept your targets - you’re moving and they’re moving
3. Massive blocks of ice will hot the moon, Mars would likely get hit by blocks and have water vapour in the atmosphere and Venus will likely see impressive chemical reactions as the water screams through its acidic atmosphere.

Also note that as the water will cool and freeze as it moves into space how exactly are you going to aim it anyway?

This is even weirder that rocket launching blimps.

Hey, now you’re on to something!

Yes, it could be done, for an arbitrarily-low input from what we usually think of as energy sources. But there’s no free lunch: You’re actually just tapping into a different energy source, the rotation of the Earth. As you’re carrying water (“pumping” is probably the wrong term) into space, you’re slowing the Earth’s rotation. You could make up for this, if you’re worried, by carrying an equal mass of some other material from your destination back to Earth.

You mean there no free launch

I agree with the rest of the people that the scheme in the OP is an awful way to get water to Mars. Much easier to just hijack a comet or steal some of the rings of Saturn or something.

He might think that limit is set by turbulence in the pipe or leaks or something

Actually you can’t suck water even centimetres.

The syphon limit is around 10 metres because that’s as much as atmospheric pressure can *push * against gravity (assuming earths surface level gravity and its standard air pressure )

But that’s only relevant if you’re pumping it, which we aren’t here. It’s irrelevant that water is a fluid: The same technique could be used on any sort of payload. You’re just packing the water into big tanks, and then putting those tanks in elevator cars strung together with the same high-tensile-material that the elevator cable is made from.

If you extend a space elevator past geosync, then its farther end will be moving faster than Earth’s escape velocity. Such extended elevators have been proposed for launching spacecraft. IIRC, if you have materials strong enough to build an Earth-to-space elevator in the first place, you can get enough acceleration to reach Saturn orbit that way.

Interesting idea, but a really bad idea to terraform using earth’s water.

Here’s an illustration showing the volume of water the earth holds compared to the sphere of the earth itself.

I don’t know about you, but I think we should use water that’s already on the other planets or elsewhere in space.

Sheesh, my reading comprehension seems to be broken. :smack:

The term ‘siphon’ threw me too, despite the description.

What’s being described is a centrifuge - using the Earth’s rotation to lift things against gravity.

Assuming the engineering details are possible (strong enough materials, reliable enough mechanisms), it’s possible, but you’re not only stealing water from the Earth, you’re slowing its rotation too.