# Space siphon (Space elevator V2.0) **URL:** \ **Category:** Factual Questions\ **Created:** [January 6, 2014, 1:51pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019 "2014-01-06T13:51:33Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [January 7, 2014, 1:48pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/21 "2014-01-07T13:48:44Z")
> [@kanicbird](#): > > - Questions still remain, 1 - can we aim it accurately enough, predict and adjust for any delta v from the sun heating this to actually hit the target. - what form will it need, a ice ball? many individual ice crystals? 2 what happens at the target? You need to include some thrust capability anyway, since otherwise your target would only be accessible when it crosses the plane of the Earth’s equator\*. You’d only be able to send one, or at best a few, pods per year to each target. > [@](#): > > - Need PR campaign to convince the public that it is a good idea. This will help combat sea level rise from global warming. Look at those cute kids enjoying that beach that hasn’t been washed away by rising ocean levels. - ETA: It would really be some sort of warped plane, but regardless, any target would only be available during a very short launch window. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 7, 2014, 4:15pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/22 "2014-01-07T16:15:15Z")
In some ways, “siphon” is a good name, since in the co-rotating frame, you’ve got a potential “hill” with its peak at geosynch height, and you’re getting matter up the uphill part of the hill by using the energy from the matter going down the downhill part. In that sense, it’s just like a siphon. And the limited launch windows aren’t too big of a deal, since you’d still get one launch window to anywhere you’d care about each day. You’d still want course-correction rockets on your payload, of course, but they’d be orders of magnitude smaller and cheaper than what you’d need without the elevator. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [January 7, 2014, 4:40pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/23 "2014-01-07T16:40:47Z")
Let’s build a few ASAP. But instead of water, we siphon all the assholes and douchebags. They’ll love Venus. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [January 7, 2014, 5:05pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/24 "2014-01-07T17:05:59Z")
> [@Mangetout](#): > > 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. The problem I see is, how do you actually transfer the earth’s rotation to the entire space elevator structure? Every payload pod being ejected from the elevator is carrying away angular momentum from the elevator. Soon the top of the elevator starts to fall behind the earth’s rotation, and bend towards the west. How do you replenish that angular momentum and keep the whole elevator straight and taut? I think the only way is to mount thrusters along the length of the elevator. Nothing wrong with that, but at that point it’s not a siphon or centrifuge, it’s a tethered rocket-powered platform for launching payloads. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 7, 2014, 5:19pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/25 "2014-01-07T17:19:54Z")
The tether is always being pulled out by centrifugal force. If you’re constantly launching, there will be some steady-state amount of deflection, but it’s not going to fall over. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [January 7, 2014, 5:32pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/26 "2014-01-07T17:32:26Z")
> [@Chronos](#): > > And the limited launch windows aren’t too big of a deal, since you’d still get one launch window to anywhere you’d care about each day. If your payload doesn’t have thrust, and you’re just relying on initial accuracy to hit a target like Mars, you’re going to only have one window a year. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 7, 2014, 7:13pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/27 "2014-01-07T19:13:14Z")
No, you’d have more than that, if your elevator is long enough. We’re used to assuming that trips to other planets must use Hohmann transfer orbits, because those are the most fuel-efficient, and with our current launch technology you need every advantage you can get. But with an efficient launcher like a space elevator, you could reach other planets at other times just by throwing harder to begin with. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [January 7, 2014, 7:23pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/28 "2014-01-07T19:23:51Z")
How are you changing the direction _out of the plane of the equator_? If I want to hit Mars, I need to wait for the plane of Earth’s equator to sweep across it. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 7, 2014, 7:54pm UTC](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019/29 "2014-01-07T19:54:57Z")
That’s simple, you just… um… Hmm… OK, yeah, that’s a good point. Though you could still get away with very low thrust requirements, especially if you make clever use of lunar flybys. [Previous page](https://boards.straightdope.com/t/space-siphon-space-elevator-v2-0/678019.md?page=1)