Space elevator ? How can it work?

In summary, the concept of a "Space Elevator" has been discussed as a potential way to transport materials into space, specifically to the Space Station. Recently, a company won a $900,000 prize for their design of a mile-long cable that can be climbed in under 4 minutes using power transmitted from a ground-based laser. However, there are still many challenges to overcome, such as creating a strong enough cable and developing a reliable power system. The cable would be attached to a geostationary platform, not the Space Station, and there is ongoing research on how to get payloads up the cable using methods like lasers. Some concerns about wear and tear on the cable and the feasibility of the project have been raised, but there
  • #36
LURCH said:
I have no doubt that a strong enough material will be developed. However, for a space elevator to be possible around the earth, we would have to first eliminate all of the sattelites in low Earth orbit. There is no point on the equator over which these sattelites will not eventually pass. When they do, they will strike the elevator shaft at about 15,000 miles per hour. If we hadn't done sattelites first, a space elevator would be possible. But as far as I have seen, no one has ever addressed this situation adequately. And, as the situation currently stands, a space elevator is simply not possible.
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.)
 
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  • #37
IMHO, It'll never happen.
for gosh sakes, we can't even agree on putting up wind towers without some group pitching a hissy fit about "issues"
I have real problems with all current nano tech. there ia a lot of it going on, but very little health and safety understanding. nano fibers pass right thru most living tissue. now, string a massive amount of it together, hang it in the air, subject it to intense light, heat, wind and radiation and tell me it won't sluff nano particles into the air.
another thing that no one has addressed is the electrical charge that it would pick up. anyone remember the shuttle experiment with dragging the cable?
http://istp.gsfc.nasa.gov/earthmag/wtether.htm
from what I heard, they almost blew the whole electrical system due to the massive emf ramp up
think on big long carbon resistor.
how many golfers and fishermen get hit by lightning thru their carbon graphite accessories?
that thing would probably drag lightning in on an unbelievable scale.
spend the $$$ on the aircraft industry, with their proven track record of slow, but positively forward advancement
best bang for the buck and absolutely the safest

dr
 
  • #38
dr dodge said:
spend the $$$ on the aircraft industry, with their proven track record of slow, but positively forward advancement
best bang for the buck and absolutely the safest
Other than the VentureStar, what is the aircraft industry's solution to achieving orbit?

The industry's delta vee is shy by a factor of 10. (2,500mph vs. 25,000mph)

Space shuttle doesn't count; it's just a rocket.
 
  • #39
all I was saying is that some technology that generally works well, exists in the aircraft/aerospace industry
its a lot closer than a 200 mile vertical cable, built out out of untried material by a technology that we don't have. (I like the nanobot idea best)

personally, I think its going to be real hard to beat the rockets for quite some time

dr
 
  • #40
dr dodge said:
all I was saying is that some technology that generally works well, exists in the aircraft/aerospace industry
its a lot closer than a 200 mile vertical cable, built out out of untried material by a technology that we don't have. (I like the nanobot idea best)

personally, I think its going to be real hard to beat the rockets for quite some time

dr

Rockets are rapidly reaching a point of diminishing returns. You don't see any more Saturns going up do you?
 
  • #41
the rockets weren't/aren't good for heavy lift, and that's where the real need is.
but for most mid to small stuff they will probably be used for many years

dr
 
  • #42
I don't really like the idea of a space elevator. Lots of technical challenges, lots of cost, in the end you have an untested expensive system that you put into some sort of geosynchronous orbit, and if it crashes down after a week you have nothing to show for it.

Why not focus on a space gun? We have the technology to launch projectiles into orbit, and having the majority of the propulsion system on the ground where it is easily repairable is a definite benefit. I guess the idea is just not trendy enough to be researched.
 
  • #43
chayced said:
I don't really like the idea of a space elevator. Lots of technical challenges, lots of cost, in the end you have an untested expensive system that you put into some sort of geosynchronous orbit, and if it crashes down after a week you have nothing to show for it.
Not true, not true! You have a huge, trench-shaped impact crater that goes almost all the way around the equator!
 
  • #45
chayced said:
Why not focus on a space gun? ...I guess the idea is just not trendy enough to be researched.
It is researched.
the research goes something like:
V2 = U2 + 2as

Assume a 100m long barrel, and an escape velocity v of 11km/s
a = V2/2s = 11,0002/200 = 600,000m/s2
a = 62,000g
There is also the small matter of air resistance when the payload leaves the (presumably evacuated) barrel and enters the ground level atmosphere at > Mach30.
 
  • #46
dr dodge said:
personally, I think its going to be real hard to beat the rockets for quite some time

Agreed.

DaveC426913 said:
Rockets are rapidly reaching a point of diminishing returns. You don't see any more Saturns going up do you?

Non-sequitor. While it's true that rockets are providing diminishing returns, that has nothing to do with the lack of current viability in the tether arena. Rockets are here and now. Tethers are several decades away, if not a century.
 
  • #48
LURCH said:
Please tell me they don't propose a space elevator on Mars?!

It has certain advanatges, you don't have to wait for the butterflies
 
  • #49
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.
 
  • #50
ok, I have been thinking about this (I know, VERY dangerous)

Wouldn't surface tension of the gases of the Earth's atmosphere follow the cable higher up the cable. That could potentially cause odd plasma reactions when it got to space. transmitting power up it would require it to either be 2 cables next to each other, or some sort of induction/coax kind of deal. and it would have to be like trying to push massive megawatts thru a tera-ohm resistor.
OK, we make the cable, how are we supposed to get it to the earth. upper atmosphere winds would drag it around all over while we are trying to get it to the ground. think about lowering a piece of fishing line off your roof to touch a 1/4 inch square a basketball on the ground. even on a zero wind day, you'd have to send out so much extra cable just to finally get a grip on it to drag it back to the point of attachment. at the point in time that we were just ready to attach it to the earth, the static on that thing would be...well
How much slack would it need to allow for the wobble of the earth? The pulling on the cable would try to pull the satelite out of orbit on the way up, and shove it out on the way down. you'd need a spool of cable the size of the moon, and a tensioner the size of rhode island to keep the cable tension correct.
IMHO, the following formula applies:

elevator idea+(many$$$$$$$$)=stick and deceased equestrian

dr
 
  • #51
"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" . 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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  • #52
Gfellow said:
...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.
 
  • #53
FredGarvin said:
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 anyone nation from attempting it. The space elevator is too much of a game-changer.
 
  • #54
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!
 
  • #55
Magic Beanstalk...I like it.
 
  • #56
FredGarvin said:
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.
 
  • #57
Gfellow said:
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.
 
  • #58
DaveC426913 said:
MAGIC BEANSTALK
Nice! Another possible suggestion? "http://pantheoanimist.blogspot.com/2008/04/space-elevator-and-old-testament.html" " 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.):smile:
 
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  • #59
DaveC426913 said:
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.
 
  • #60
Gfellow said:
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...
 
  • #61
FredGarvin said:
...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.
 
  • #62
dr dodge said:
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.
 
  • #63
mugaliens said:
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.
 
  • #64
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.)
 
  • #65
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.
 
  • #66
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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  • #67
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
 
  • #68
mugaliens said:
Proponents must learn that technology doesn't drive adoption. Econonomics drive adoption.
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.
 
  • #69
mgb_phys said:
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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  • #70
mugaliens said:
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?)
 

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