# Space elevator ? How can it work?

"Space Elevator" has been in my Google Alert for quite some years now, and I have noticed a tenfold increase in the chatter on the subject. It would appear that the concept is rapidly becoming part of the collective consciousness.
It is notable that the Japanese are looking to spend 8 billion on such a project, and while that might seem an insignificant fraction of the final cost, it makes for interesting seed money.

Whether building a space elevator is feasible can be an arguable subject, but IMHO there is little doubt that someone will try. The rewards are just too big to ignore. I won't go into the mass/lift ratio advantage here, but considering the relatively small resource outlay, the political stature and military advantage that a space elevator will afford, will ultimately be too tempting for any number of powerful nations.

As a real-estate speculator, my focus of interest is where it might be located. For logistical, physical and political reasons, my bet is the island nation state of http://pantheoanimist.blogspot.com/2008/02/ideal-space-elevator-location.html" [Broken]. The island is on the equator, minimum security issues, harbor installations, commercial runway, tarmacked road rings the island.

The only other places available on, or near the equator are either politically insecure, or have no infrastructure.

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FredGarvin
...but considering the relatively small resource outlay, the political stature and military advantage that a space elevator will afford, will ultimately be too tempting for any number of powerful nations.
I'm not sure of what you mean by that. There is nothing involved with this fantasy that would be small. The amount of resources required will be huge, especially in the manufacturing sector.

You do bring up an interesting point about the military. Not so much in its use, but in how anyone could ever hope to defend a space elevator if someone really wanted to put one out of commission.

DaveC426913
Gold Member
You do bring up an interesting point about the military. Not so much in its use, but in how anyone could ever hope to defend a space elevator if someone really wanted to put one out of commission.
Yes, this is definitely something that cannot be ignored. I think it will limit any one nation from attempting it. The space elevator is too much of a game-changer.

DaveC426913
Gold Member
By the way, I REALLY think we should make a concerted effort to popularize the nickname: It's a MAGIC BEANSTALK, or BEANSTALK for short. The name fits it perfectly.

Come on everybody, we can make a change if only we truly BELIEVE!

FredGarvin
Magic Beanstalk...I like it.

I'm not sure of what you mean by that. There is nothing involved with this fantasy that would be small. The amount of resources required will be huge, especially in the manufacturing sector.
Greetings FredGarvin - Perhaps comparable to the Panama Canal in terms or resource and effort? Was it worth it?

You do bring up an interesting point about the military. Not so much in its use, but in how anyone could ever hope to defend a space elevator if someone really wanted to put one out of commission.
Several famous quotes of different personages come to mind. The slightly misquoted General Nathan Bedford Forrest's "git thar fustest with the mostest," comes to mind, or perhaps "command the high ground" of which there are too many authors to count.

From a combative point of view, the nation-state with the space elevator would definitely hold a strategic advantage over an opponent. The loss of the bridge out of the gravity well would be regrettable, but assuming you have ferried up a considerable quantity of resources, it would be of little consequence once you have obtained the sustained ability to look down upon and strike your enemy during a crisis.
From a tactical point of view the gravity-bound opponent might think twice about initializing hostilities.

DaveC426913
Gold Member
From a combative point of view, the nation-state with the space elevator would definitely hold a strategic advantage over an opponent. The loss of the bridge out of the gravity well would be regrettable, but assuming you have ferried up a considerable quantity of resources, it would be of little consequence once you have obtained the sustained ability to look down upon and strike your enemy during a crisis.
From a tactical point of view the gravity-bound opponent might think twice about initializing hostilities.
OK, well that's an escalation even above what we are talking about. If there is the slightest hint (or even if there isn't) that the elevator will be used for strategic purposes, the whole world will rise up against them before it ever gets off the ground.

MAGIC BEANSTALK
Nice! Another possible suggestion? "http://pantheoanimist.blogspot.com/2008/04/space-elevator-and-old-testament.html" [Broken]" This name has a messianic flavor and would galvanize the religious conservatives to your side:
"...He came to the place and stayed there that night, because the sun
had set. Taking one of the stones of the place, he put it under his
head and lay down in that place to sleep. And he dreamed that there
was a ladder set up on the earth, and the top of it reached to heaven;
and behold, the angels of God were ascending and descending on it! And
behold, the LORD stood above it [or "beside him"] and said, "I am the
LORD, the God of Abraham your father and the God of Isaac; the land on
which you lie I will give to you and to your descendants; and your
descendants shall be like the dust of the earth, and you shall spread
abroad to the west and to the east and to the north and to the south;
and by you and your descendants shall all the families of the earth
bless themselves..."

(I realize we are getting a little off-topic here, but I am sure the admins don't mind a bit of humor.)

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If there is the slightest hint (or even if there isn't) that the elevator will be used for strategic purposes, the whole world will rise up against them before it ever gets off the ground.
Do you believe the US would have placed a man on the moon if the USSR was not on the agenda? Major resource hungry efforts by nation-states have a combative proponent. They may never mention it, but it is still there.
Ideally, the space elevator ought to be an international effort - perhaps it might happen that way. However, if that does not occur, the advantage afforded to an individual nation-state would eventually be too great a temptation.

FredGarvin
Greetings FredGarvin - Perhaps comparable to the Panama Canal in terms or resource and effort? Was it worth it?
Greetings to you as well.
Like I have mentioned before, the Panama Canal is not even close in the terms of what is required. The pieces and abilities to build the canal were already in place and understood. There just needed to be a huge man power commitment (and money). With the bean stalk we are talking about using materials that have not been invented yet, and building techniques that do not exist. Once we figure that out we have to figure out how to do it on a massive scale. Then you bring in all of the other issues also mentioned like satellites, etc...Honestly, I can not think of anything on this planet that is a good comparison to what needs to be done. Perhaps the Great Wall of China...

...huge man power commitment (and money). With the bean stalk we are talking about using materials that have not been invented yet, and building techniques that do not exist.
I put it to you that we have emerged into a new paradigm. The adept control of manpower and resources was the great triumph of the past two centuries, a tool we now take for granted. The flower of our epoch is the additional thrust of efficient research towards a given end.
When Kennedy told the world the US was going to put a man on the moon in a decade, the NASA science staff were gobsmacked. Although it is what they wanted, they had not really taken the time to sweat the details. However, it turned out to be a confirmation that this paradigm was upon us.

The REAL issue comes down to, 'is it worth it?'.

As a rule, nation-state military systems tend to be conservative and usually remain complacent unless there is an imminent and obvious threat. Seen in this light, the space elevator can be dealt with in three ways:
1. A space elevator race could ensue between nation-states.
2. An agreement might be forged to share costs and build an international space elevator, the advantage being that no individual nation-state gains an overall advantage.
3. Agreeing amongst themselves not to build it at all, which would suggest a conspiratorial component historically uncharacteristic of such entities.

OK, we make the cable, how are we supposed to get it to the earth.

You build the geosynchronous location, along with the counterweight, then slowly lower the cable while simultaneously extending the counterweight further out. Once the cable is anchored on Earth, you can extent the counterweight further in order to apply tension along the length of the cable.

DaveC426913
Gold Member
You build the geosynchronous location, along with the counterweight, then slowly lower the cable while simultaneously extending the counterweight further out. Once the cable is anchored on Earth, you can extent the counterweight further in order to apply tension along the length of the cable.
You stopped reading halfway through his sentence. He explains why he thinks getting it to Earth might be problematic.

There are about 400 satellites in geosynchronous orbit. At present, launch costs run from $4K to$40K per kilogram dependent upon dependability of launch. Taking \$10K/kilogram cost as a near-future cost for rocket launches, how much will the cost equivalent of a space elevator be to amortize 4000 satellites to break even with rocket lauch profits? (Hint: you need to know the average mass of a satellite.)

The folks I work for make boxes that cost the customers x dollars apiece. At the premium launch dependability demanded, the customer pays 0.2x to get it to orbit. For this particular component, launch cost is only 1/5 of payload cost. I don't see any significant economic advantage for a marginal price break to develop this technology.

Agreed, Phrak - Not in the case of your customer and their product, no.

Before anyone, private or government, begins to work in ernest on the space elevator, there will have to be demonstrable economic benefit over current Earth to LEO launch platforms.

It's not necessarily a pipe dream, but it's both a long way off, and may never be economically viable.

One principle tenet of management is to ensure technology is developed in support of business goals, principles, and practices, and never becomes a driver of those business rules. This holds as true for the space program as it does for Company X looking to upgrade aging computer systems. Define the need, then find the best solution.

Occasionally, it'll be something as exotic as the space elevator! Given the fact my alma mater's entire computing storage across all university and student-owned storage passed the 1 TB hurdle in 1986, I agree that a 1 TB external hard sitting on my desk is ridiculous! Yet I have two of them. Go figure.

But I didn't buy them because they existed. I bought them because I do daily incremental, and weekly full backups of my computer's 120 GB hard drive, of which about 80 GB is full of user data. I swap out the TB drives weekly, storing them off-site, as I've literally decades of data on them.

I bought them because my needs were such that I needed two 1 TB drives, not because 1 TB drives were "cool," or that I had money to blow. They're simply a safe and effective tool to ensure my computing requires would continue relatively unabated in the event of theft or fire.

Given that my off-site storage is only a mile away, however, I think I'm pretty susceptible to nuclear holocaust...

...but I'm hoping and praying against all hope that will never be the case! LoL!

Back to the space elevator concept: Noteworthy concept! Proponents must learn that technology doesn't drive adoption. Econonomics drive adoption. If it's cheaper in the long run, and only well-proven to be so, it will be adopted. Otherwise, it will remain a "gee whiz" technology, neat, but not economically useful.

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an elevator space race...could you imagine
the satelites would have to be swerving around like a race at sears point.
the earth would look like a daisy from space.

can a geosat have an eliptical orbit, or will they always be a (somewhat) perfect circle?
what linear distance is the actual wobble of the earth?
we'd need to handle that slack, and keep a constant even tension

dr

mgb_phys
Homework Helper
But sometimes technology drives economics.
Just like your Tb harddrives and fast internet connection chnages the economics of selling movies container ships change the economics of where you build stuff.

If you can put somethign into orbit for the same price as airmail it's likely to have some unforseen economic effects beyond what we currently use space for.

But sometimes technology drives economics.
Just like your Tb harddrives and fast internet connection chnages the economics of selling movies container ships change the economics of where you build stuff.

Oh, I agree! I wouldn't be working from home without it! However, technology is an enabler, not a driver. As an enabler, it's certainly changed the variables in the economnic equation of whether to work from home or sit in a corporate office.

If you can put something into orbit for the same price as airmail it's likely to have some unforseen economic effects beyond what we currently use space for.

Absolutely. Currently, space elevators are not technologically feasible. If/when they become technologically feasible, they may or may not ever become economically feasible.

Given unlimited funds we might accomplish all sorts of technical feats! However, our funds are limited, so we follow (more or less) the most economical approach.

As for our use of space, communication satellites were once considered the heat, but advances in fiber optics (the ocean floors are littered with them) have resulted in fiber carrying nearly all global communication traffic. NASA would love to sell you space, but aside from exploring, there's exceedingly little space offers at economically more favorable rates than we can achieve here on Earth. As for manned exploration, those unmanned Martian rovers are still kicking!

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Otherwise, it will remain a "gee whiz" technology, neat, but not economically useful.

It's pretty 'gee whiz' to me, otherwise I wouldn't be posting to see if someone can show me wrong.

But I still want to see the equations for things like required tensile strength and things like that (this is, after all a physics forum) so I don't have to derive them.

(And what would the unloaded diameter of the cable be as a function of height such that each element of the cable is under the same tension, anyway?)

mgb_phys
Homework Helper
but aside from exploring, there's exceedingly little space offers at economically more favorable rates than we can achieve here on Earth.
If transport was cheap enough there a bunch of alloys and materials that would be easier to make in zero G, access to infinite vacuum and cold might also be handy industrially.

It's going to have to get a lot cheaper than the Shuttle though !

there will have to be demonstrable economic benefit...
Proponents must learn that technology doesn't drive adoption. Econonomics drive adoption. If it's cheaper in the long run, and only well-proven to be so, it will be adopted. Otherwise, it will remain a "gee whiz" technology, neat, but not economically useful.

Finding an immediate economic reason would be nice and I'm sure that there are SE proponents who might expand on that, but as unpopular as my comment might be, the foremost priority is tactical. If it is not an international effort, some nation state - US, China, Japan, will make the move. Whoever does it will insist it is economic in nature, but the fact is that the owner of the SE gets to decide what goes up.

LURCH
This is an area of lively study. The cable is heap big flexible and can be maneuvered. Simulations have been done that show the cable can be moved out of the way of any satellites. (Don't assume that it is as simplistic as I describe. There's a lot more to it.)
I do believe it is possible, and even probable, that the materials to build a space elevator will soon be developed. However, the simple construction of an inanimate tether would be a gargantuan engineering challenge. The idea that we could ever build one that spends its entire operational life performing a combination of dodge ball and hula dance is beyond the limits of mike credulity.

At this point putting a space elevator on mars is the equivilent to putting a Starbucks there. When it does become possible it will probably be ancient technology.
The beanstalk on Mars would have the same problem I'm concerned about with an earth based system, but on steroids: the satellite it would have to dodge is Phobos!

DaveC426913
Gold Member
The idea that we could ever build one that spends its entire operational life performing a combination of dodge ball and hula dance is beyond the limits of mike credulity.

How many satellites is the cable actually likely to encounter?

Consider that, with all the satellites we currently have in orbit, we almost never have collisions. We almost never worry about the ISS colliding with anything.

Granted, the cable is a line instead of a point, which multiplies the odds. But what do you get when my multiply "very-nearly zero" by even a largish value? You get "something a little more than zero".

Your intuition is not a reliable yardstick in this case.

If transport was cheap enough...

Aye, there's the rub.

It's going to have to get a lot cheaper than the Shuttle though !

Unfortunately, it will require several hundred heavy lifts simply to construct it! That doesn't seem to daunt http://www.liftport.com/" [Broken], however. Their FAQs page addresses most of the concerns raised here.

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