Plans for Space Elevator

[Patrick Degan]

I'm sorry, but the Beanstalk/Space Elevator concept sounds sort of like the underwater cities they used to talk about when I was a kid: theoretically possible, perhaps physically possible, but with so many attendant difficulties in engineering and insufficent commercial value that it would never be practical. In terms of surface-to-orbit transport, ground-based laser rocket launch impellers running off the power grid or even the old Boeing concept of the high atmosphere transport/shuttle combination along with expendible rockets makes far more sense.

[Enlightenment]

I'm sorry, but the Beanstalk/Space Elevator concept sounds sort of like the underwater cities they used to talk about when I was a kid: theoretically possible, perhaps physically possible, but with so many attendant difficulties in engineering and insufficent commercial value that it would never be practical.

There are certainly engineering problems associated with the construction of a beanstalk[1] but the economics are a different matter. It costs IIRC around $100,000 USD to put 1 lb into orbit using the Shuttle. Expendable lift costs are around half that. Generally suggested cost figures for lifting things into orbit using a beanstalk are around $10/lb. While this figure is pure running costs and does not include repayment of capital costs it's quite clear that a beanstalk could undercut conventional launchers into the ground and still turn an operating profit hand over fist. Assuming enough business, earning--say--$9990 in revenue per lb lifted will deal with capital expenditures quite nicely.




[1] I hereby nominate myself for the understatement of the year award....

[Nova Andromeda]

How would the cable be maintained? I'm talking specifically about locating and fixing failed segment strands.

--What if instead of a single cable with two ends you had a belt attached to wheel setups on both ends. One could then continuouly turn the cable and replace old segments at both ends after a certain period of time. They would do this by having excess lenghts of cable at either end on spools (which are continuous with the belt), stopping the belt every so often, and replacing the spool. The old spools could be "recycled" in some manner if they can be properly tested for bad portions.

[Warspite]

The concept of a Space Elevator is nice... for sci-fi.

Let's see... One rigid (possibly) structure going from sea-level to orbit, with an economically viable payload-carrying capacity (100 tons) and a receiving orbital facility:

First it needs a LOT of restricted airspace, you don't want some airplane cliping it's wings into it... Let's say 100 nm all around, so forget about Europe and most of USA and SE Asia... There goes most of the potential customers. Yeah, Guiana is in the South America, but if you want a feasible Space Elevator

Second, it's better to be placed in the Equator... So, South America or Africa... ummm, more western capitalists taking advantage of poor Third-World country [ /sarcasm mode]... Maybe... The supporting infrastructure could put off investors.

Third, it needs a good, stable anchoring, in the middle of a stable tectonic plate, to forego earthquake-dynamic damping systems, with a solid rock bed... Remember, the Twin Towers started what? 100 ft bellow the surface? In the rock bed of lower Manhattan... So, this one would have to find a VERY good rock bed, without fissures and be buried DEEP, at least the foundations...

Fourth, still assuming a compressive (rigid) system, the atmosphere is a dynamic system, what if the structure is subjected to powerfull winds? A cylindrical tower is good, but still subjected to enormous stresses due to vortices, and if it goes through a jet stream layer? Those are high-velocity winds, hence more dynamic loads, in an already assimetrically loaded member... The picture is not getting pretty...

Fifth, the elevator himself... Are people going in it? If they are, what happens if it fails? Not everyone knows how to use a parachute, and a fall from 60,000 ft is a long one... Even from 10,000 ft...
OK, braking systems exist for normal elevators, but this is not a nornal elevator, elaborate failsafes need to be introduced, increasing weigth and investment.
Does it enters the atmosphere slow enough to prevent ionization? If not, then it needs a heat shield, increasing weight... again.

Sixth, the orbital facility... Well, it's on the receiving end of a rigid pole, thousands and thousands of feet long, someone else can figure it out...

Conclusion: it's not feasible, although a nice ideia, and the technologies involved could be fruitfull into other uses... But, naaaaahhhh!

If we go for a flexible system... It gets worse.


Nobody would get me into one of those, no way!

[Ewo]

How would the cable be maintained? I'm talking specifically about locating and fixing failed segment strands.

--What if instead of a single cable with two ends you had a belt attached to wheel setups on both ends. One could then continuouly turn the cable and replace old segments at both ends after a certain period of time. They would do this by having excess lenghts of cable at either end on spools (which are continuous with the belt), stopping the belt every so often, and replacing the spool. The old spools could be "recycled" in some manner if they can be properly tested for bad portions.

I don't think that they would even be using a cable to get the elevators up that high. You would be in that elevator forever. Maybe they plan on using some sort of booster to get it up there. Plus, I, personally, would be deathly afraid to ride this thing. What is the largest freestanding structure we have? From the pic, it is going to be hard to make something that won't fall over if a big gust of wind comes along. Doesn't the CN tower sway in the breeze?
I think it is a cool idea but it is going to be ages before it becomes a reality. I am not going to say never but I imagine past 2050 at least.

[TrailerParkJawa]

I would also think that space travel or at least putting something into orbit would have to be a daily occurance for this to even be a reasonable thing to build. Thats why its such a great idea for sci-fi cause in Traveller 2300 they have stutterwarp drives would allow ships to travel several light years per day.

[Warspite]

I would also think that space travel or at least putting something into orbit would have to be a daily occurance for this to even be a reasonable thing to build. Thats why its such a great idea for sci-fi cause in Traveller 2300 they have stutterwarp drives would allow ships to travel several light years per day.

When the "daily occurance" of going into orbit happens, the transport would still be much more safe, and cheaper, than building the elevator.

[Nova Andromeda]

--I just wanted to add that my cable repair system could also be used to exchange "orbital" mass with "ground" mass. Currently, we waste all the potential energy when we land say the shuttle. However, the elevator would solve that problem to a great extent.
-I would also add that the biggest worry is the cable being cut by terrorists or a stray plane. One would have to stock the orbital part with enough propelant to put it in geosyncronise orbit if that happened.

[jegs2]

http://www.msnbc.com/news/837772.asp?cp1=1

Pretty interesting, neat idea they have.

What a juicy target for terrorists that thing would be...

[Darth Wong]

What a juicy target for terrorists that thing would be...

No kidding. What happens if you load up a Cessna with high explosives, fly next to the cable, and blow yourself up?

[Nova Andromeda]

What a juicy target for terrorists that thing would be...

--I was thinking a military base with good antiaircraft defenses would be sufficient to stop the terrorist. Besides, hitting a skyscrapper would do far more damage.

[Warspite]

What a juicy target for terrorists that thing would be...

--I was thinking a military base with good antiaircraft defenses would be sufficient to stop the terrorist. Besides, hitting a skyscrapper would do far more damage.

Are you kidding? An orbital facility with a BIG cable attached to it isn't "damage-able" enough? At least, a skyscrapper can fall with a small footprint, a Space Elevator would create havoc for miles...

Besides, a military base implies stright security, resulting in an added, unnecessary expense.

[Enlightenment]

A few points that some people here seem to be misunderstanding:

An orbital elevator--aka a beanstalk--is a high-tensile strength cable that extends from ground level to at least geostationary orbit. The structure must be at least 35,000km in height and will be 'supported' by centrificial force rather than ground-based foundations.

It is theoretically possible to design a beanstalk that will hover above the ground and impose no force load on its anchorpoint. In practice a certain degree of upward tension will be necessary to reduce wind sway. Under no circumstances would exceptionally strong bearing rock be required for the anchorpoint. Indeed, it'd even be possible to fix a beanstalk to a floating platform at sea.

Beanstalks must be anchored at the equator. Connecting a beanstalk to Europe or any part of the United States isn't physically possible.

There is more than enough cable in a beanstalk for it to wrap itself around the earth several times over in the event of a catastrophic failure. However competent design can eliminate most of the ground risks by engineering the beanstalk such that it will break up into segments short enough to burn up upon reentry rather than reach the ground. Note that reentry burnup doesn't apply to the lower few hundred kilometers and as such it is desirable to mount the anchor point on the east coast of a landmass such that--in the event of a catastrophic failure--the first few hundred KM of beanstalk vaporize nothing but ocean and a few unfortunate ships.


For a bibliography of published papers on orbital elevators, see
http://lifesci3.arc.nasa.gov/SpaceSettl ... PBI120.HTM.

[TrailerParkJawa]

Even if you could engineer the beanstalk to cause minimal damage in the event of failure, the risk of failure and the ensuing costs would probably prevent it from being built.

[Enlightenment]

Even if you could engineer the beanstalk to cause minimal damage in the event of failure, the risk of failure and the ensuing costs would probably prevent it from being built.

No argument. No one is ever going to build any of the high-end space access or space utilization projects--including beanstalks--that used to be staples of 19xx SF. There's just no economic reason to risk the money and humanity has long since lost its nerve for doing things just for the hell of it.

[TrailerParkJawa]

No argument. No one is ever going to build any of the high-end space access or space utilization projects--including beanstalks--that used to be staples of 19xx SF. There's just no economic reason to risk the money and humanity has long since lost its nerve for doing things just for the hell of it.

I agree that we loose our nerve for doing things just for the hell of it. Seems to come along with affluence, IMO. China is building the worlds largest dam project that will radically change not only the Yangtze but have a tremendous social impact. A project like that can only happen in a country where the people are relatively unaffluent or lack freedoms.

Mabye a beanstalk would be built if the Earth was under some sorta dictatorship. No need for Environmental Impact Studies then.

[Evil Sadistic Bastard]

What a juicy target for terrorists that thing would be...

No kidding. What happens if you load up a Cessna with high explosives, fly next to the cable, and blow yourself up?

Or a suitcase nuke?

[XaLEv]

Suppose something happens to the beanstalk, and it starts to come down. Would releasing it on the 'ground' help any? Would it fly away, or come back down?

[jegs2]

Even if you could engineer the beanstalk to cause minimal damage in the event of failure, the risk of failure and the ensuing costs would probably prevent it from being built.

I can already envision droves of lawyers lining up and licking their chops...

[Warspite]

Suppose something happens to the beanstalk, and it starts to come down. Would releasing it on the 'ground' help any? Would it fly away, or come back down?

It would still come back down, and worse, you wouldn't had any control on where the cable would crash. A cable with miles of length is still heavy, no matter what's is made of... (except perhaps, aerogel...)

[TrailerParkJawa]

I can already envision droves of lawyers lining up and licking their chops...

Last night on the news, I saw that the Enron collapse has generated a billion dollars in legal fees!

A physical collapse of the beanstalk would probably keep lawyers in business for life.

[Asst. Asst. Lt. Cmdr. Smi]

How much would it cost? I'm guessing a few hundred billion.

We won't be sending civilians into space anytime soon, so until then, it would be cheaper to use shuttles. A space elevator might be more effective in the long run, but that's if you have a lot of people using it.

Before we do that, we have to get rid of all the space junk, just becuase it damages millions of dollars of equipment, and can be life-threatening.

[TrailerParkJawa]

How much would it cost? I'm guessing a few hundred billion.

I would imagine something like that would cost closer to a trillion dollars. But I could be wrong. What would power the thing?

[Asst. Asst. Lt. Cmdr. Smi]

How much would it cost? I'm guessing a few hundred billion.

I would imagine something like that would cost closer to a trillion dollars. But I could be wrong. What would power the thing?

I dunno. They'll probably use solar panels in space.

[Sienthal]

Yah...They had an article like this a few months ago in either Popular Mechanics or a similarly named one. Good to see it put into motion.