# Please help a confused soul (Space elevator question). **URL:** \ **Category:** Factual Questions\ **Created:** [August 19, 2005, 11:47am UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727 "2005-08-19T11:47:17Z")\ **Posts on this page:** 18\ **Page:** 3
**Author:** ![Fish\_Cheer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fish_cheer/32/17179_2.png) [@Fish\_Cheer](https://boards.straightdope.com/u/Fish_Cheer)\ **Post date:** [August 23, 2005, 11:38am UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/41 "2005-08-23T11:38:59Z")
> [@Meurglys](#): > > A large amount of **David Gerrold** ’s _Jumping off the Planet_ is set near or on a working space elevator anchored in Equador. Any good? ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [August 23, 2005, 12:46pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/42 "2005-08-23T12:46:30Z")
> [@Northern Piper](#): > > Here’s another confused soul checking in: what will hold the space elevator up?? Basically it would be counterweighted - an asteroid or extending the cable itself furthur out. It would essentially behave as a tetherball being swung around in a circle. The problem, as mentioned, is not only do you have stresses from the tension between the earth and the counterweight, you also have tidal forces on the cable as gravitational forces will change along the entire length. I don’t believe that weather or terrorism would be as much of a problem as people think. The required strength of a space elevator cable would be such that it would take extraordinary actions to sever the cable. It’s not like a couple of Arab dudes could sneak up to it and go _snip_ with a pair of wire cutters. Multiple cables and a high factor of safety would also go along way to ensure safety. More troubling would be oscillations set up along the cable - due to weather or the crawlers themselves. As for falling out of the sky, some suggest that atmospheric friction would cause this particular Big Dumb Object to settle relatively softly. Not come screaming out of the sky like a meteor. Even still, you would have 10s of thousand a miles of nearly indestructible cable to clean up. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [August 23, 2005, 1:17pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/43 "2005-08-23T13:17:11Z")
> [@Enola Straight](#): > > In the book 3001, Arthur C. Clarke (or whoever :rolleyes: ) postulated the existance not only of space elevators, but a solid geosynchronous-orbital ring. > > This system would make obsolete all sattelites, rocket launches, and take over most radio transmission (save for local transmission, and near the poles.) > > Perhaps that will give an indication of cost/benefit. Just realized something…there has to be some “give” due to movements of tectonic plates. ---
**Author:** ![micco](https://avatars.discourse-cdn.com/v4/letter/m/5f8ce5/32.png) [@micco](https://boards.straightdope.com/u/micco)\ **Post date:** [August 23, 2005, 1:57pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/44 "2005-08-23T13:57:30Z")
> [@Shalmanese](#): > > Except that, yknow, its kind of pointless having a space elevator if nothing can get near it. Once you want to actually use it for something, then the inspection process is going to be a nightmare because any random bomb put on it will destroy it. It may well be that the cost of getting something up costs 5c a lb but the inspection will cost $1000 per lb. Whatever inspection costs are required may seem high compared to sending a package around the world via post service or container ship, but compare to the current process of putting payloads in orbit. Anything sent up via the space shuttle or even commercial booster is extremely secure and there are very few people vetted and qualified to handle those packages. Certainly if you maintain even the same degree of high security on space elevator payloads, you still have a huge benefit from reduced transport cost. ---
**Author:** ![Meurglys](https://avatars.discourse-cdn.com/v4/letter/m/258eb7/32.png) [@Meurglys](https://boards.straightdope.com/u/Meurglys)\ **Post date:** [August 23, 2005, 3:21pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/45 "2005-08-23T15:21:18Z")
> [@Fish Cheer](#): > > Any good? The main characters (whiny young brothers, as I recall) didn’t appeal to me much. I finished it but didn’t feel the need to continue the trilogy. (_Bouncing off the Moon_ & _Leaping to the Stars_) I mentioned it because he does go into some (made-up!) detail of his Skyhook and how it operates. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [August 23, 2005, 3:30pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/46 "2005-08-23T15:30:18Z")
But currently, we send a miniscule amount of stuff into space so we can justify the costs. And the price of losing a shuttle is miniscule compared to the cost of losing an elevator. ---
**Author:** ![Oslo\_Ostragoth](https://avatars.discourse-cdn.com/v4/letter/o/a9a28c/32.png) [@Oslo\_Ostragoth](https://boards.straightdope.com/u/Oslo_Ostragoth)\ **Post date:** [August 23, 2005, 3:46pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/47 "2005-08-23T15:46:05Z")
(Excuse me because I haven’t read the entire thread, but…) As I recall, one of the early concepts for a space elevator was that a cargo container descending to earth would be “counterbalanced” by a mass ascending to a higher orbit. I have no idea how that would work with cargo weight differences up/down. ---
**Author:** ![micco](https://avatars.discourse-cdn.com/v4/letter/m/5f8ce5/32.png) [@micco](https://boards.straightdope.com/u/micco)\ **Post date:** [August 23, 2005, 4:13pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/48 "2005-08-23T16:13:01Z")
> [@Shalmanese](#): > > But currently, we send a miniscule amount of stuff into space so we can justify the costs. And the price of losing a shuttle is miniscule compared to the cost of losing an elevator. My point was that even if the inspection costs are a “nightmare”, equaling or exceeding the procedures in place for current payloads, you still have enormous benefits in other aspects of the system. Yes, perhaps inspection issues would get worse than they are with the current system, but cost per payload weight would go down, volume would go up, and many other issues would improve compared to the current system. I don’t think anyone is proposing that a space elevator would replace our current space shuttle and other boosters with exactly the same mission specs. That is, we’re not going to build something as massively expensive as a space elevator would be just to conduct the missions we’re conducting now (a relatively small number of commercial launches per year). We’d build an elevator in order to enable a massive increase in the number of “launches” and payload weight, on a scale that may not even be practical with chemical boosters. If security and inspection requirements are a “nightmare”, that’s one small downside for enabling the many benefits. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [August 23, 2005, 4:14pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/49 "2005-08-23T16:14:19Z")
Raising and lowering payload in the manner of a traditional counterweight seems unlikely to me. To do that, you would need a cable running from the top of one payload cab, over a pulley and down to another cab; and that’s in addition to the main tether that anchors everything in place and guides the cab up and down. That’s an awful lot of extra complexity. I think most of the designs for this have it operating more like climbing a ladder than a traditional elevator. And you could still recover the energy from anything descending the tether by using the electric lift motors as generators. (What **Oslo** describes is actually similar to the original elevators on the Eiffel Tower. From the second level to the top used to take two seperate elevators, which largely balanced each other. You’d ride one elevator halfway up as the other was coming down, change from one to the other at the midpoint, and continue up as the first elevator descended.) ---
**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:** [August 23, 2005, 8:24pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/50 "2005-08-23T20:24:41Z")
I don’t think you’d end up with huge expanses of indestructible cable if the thing somehow (through accident or sabotage) fell. Aren’t fullerenes still flammable? I would expect the cable to burn on re-entry. As for counterweights, one nifty feature of a space elevator is that you wouldn’t need pulleys. You can (partially, at least) counterbalance one payload going up with another payload going up. Anything below the geostationary point will fall downwards, but anything above it would “fall” up. So one could have a second cable shorter than the main cable, with cars permanently attached at intervals along it, which would move up and down parallel to the main cable. Move up one step, transfer over to a waystation attached to the main cable, move the moving cable down one step, then get on the next car up. If you have equal masses going both directions (which could just be rocks from the Moon or Mars, if you have nothing else worthwhile to send back) and you’re willing to accept a large number of layovers, you can make the energy cost of the system arbitrarily low. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [August 23, 2005, 8:45pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/51 "2005-08-23T20:45:37Z")
Another possible use for space elevators is as a spacecraft launcher/receiver. Since it extends well past geosynchronous orbit, the endpoint will be moving faster than orbital velocity. If you release a ship or cargo container from there, it will be able to leave Earth’s orbit for little or no energy. You regain the energy expended the same way you do for the elevator cars; incoming vessels grab onto the end and let it decelerate them ( presumably with some sort of hook and cable arrangement ). ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 24, 2005, 1:37am UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/52 "2005-08-24T01:37:02Z")
One problem with space elevators that often seems to get neglected is that a load ascending or descending the elevator will exert significant lateral forces on the structure; you’re changing the orbit of the load, you have to change the velocity i.e. add/remove energy - like a ballet dancer’s spin slowing when the arms are outstretched - a load ascending the elevator is going to tend to lag behind the rotation of the Earth; a load descending is going to try to push forwards. It isn’t solved by sending a load up at the same time as one coming down, becuase you just have big forwards forces at the top and big reverse forces at the bottom - they don’t cancel out. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [August 24, 2005, 1:54am UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/53 "2005-08-24T01:54:58Z")
Wouldn’t those lateral forces be proportional to the vertical speed of the load? Presumably, if you slowed down, you would give more time for the tower/cable/structure to push the load into its succession of new ‘orbits’… ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [August 25, 2005, 1:26pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/54 "2005-08-25T13:26:17Z")
> [@Mangetout](#): > > One problem with space elevators that often seems to get neglected is that a load ascending or descending the elevator will exert significant lateral forces on the structure; you’re changing the orbit of the load, you have to change the velocity i.e. add/remove energy - like a ballet dancer’s spin slowing when the arms are outstretched - a load ascending the elevator is going to tend to lag behind the rotation of the Earth; a load descending is going to try to push forwards. > It isn’t solved by sending a load up at the same time as one coming down, becuase you just have big forwards forces at the top and big reverse forces at the bottom - they don’t cancel out. Wouldn’t it be more like an ant moving along a ballet dancers arm given the relative masses? I can’t imagine it would be too significant. ---
**Author:** ![Steve\_MB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steve_mb/32/5339_2.png) [@Steve\_MB](https://boards.straightdope.com/u/Steve_MB)\ **Post date:** [August 25, 2005, 5:18pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/55 "2005-08-25T17:18:14Z")
> [@bobk2](#): > > I apologize in advance for this sort-of-hijack, but…is it at all possible that the geo-stationary orbit of Jupiter actually lies within the bounds of Jupiter itself? No – if it were, then the portions of Jupiter beyond that point would be rotating at faster than orbital velocity, and get flung off into space. ---
**Author:** ![Merijeek](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Merijeek](https://boards.straightdope.com/u/Merijeek)\ **Post date:** [August 25, 2005, 6:13pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/56 "2005-08-25T18:13:11Z")
> [@Polycarp](#): > > The solution is therefore a Beanstalk **longer** than Clarke-orbit elevation, with the “counterweight” portion further out thant Clarke orbit undergoing centrifugal force sufficient to counteract the pull of gravity on that part of the Beanstalk below Clarke orbit, producing a net effect of a long, skinny satellite in Clarke orbit. (Note that anything elevated beyond Clarke orbit would achieve a significant portion of its launch velocity simply by being flung from the Beanstalk at that point, giving further savings.) In that case, wouldn’t such a force have an effect (albeit a really really tiny one) on the Earth’s orbit? -Joe ---
**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:** [August 25, 2005, 9:31pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/57 "2005-08-25T21:31:20Z")
Any method of getting things off the planet will have an effect on the Earth’s orbit, and a space elevator in particular would also have an effect on the Earth’s rotation. But first of all, the effect would be so miniscule as to not worry about, and second, it’d be cancelled out by any payloads you receive from points beyond. ---
**Author:** ![ENugent](https://avatars.discourse-cdn.com/v4/letter/e/4af34b/32.png) [@ENugent](https://boards.straightdope.com/u/ENugent)\ **Post date:** [August 25, 2005, 10:05pm UTC](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727/58 "2005-08-25T22:05:19Z")
There is a lot of information on this subject available [here](http://www.liftport.com/faq.php). [Previous page](https://boards.straightdope.com/t/please-help-a-confused-soul-space-elevator-question/317727.md?page=2)