More on Space Elevators

finally writes "Space elevator news is being reported on Space.com and Yahoo. I, for one, am really excited about the project. I was wondering if any of the broad range of talents and skills that we have here have thought of doing a sort of open source assistance to this project by means of donating time and knowledge." We did a big story last week on this space elevator conference.

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[stak]

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Jetsons Homes

[displague]

From what I read on the last report, these carbon nanotube string type things will run out between Earth and Space (gravity and centripital force keeping the line secure) with the ability to support a few tons of stuff on them...

Why can't we make small Jetson's style homes on the line... Everyone can live 5 miles up..

The only thing that I can see as negative about this is that driving to work you will see all of these shiny vertical lines above the landscape heading out into the sky...

Re:Jetsons Homes

[Will_Malverson]

The only thing that I can see as negative about this is that driving to work you will see all of these shiny vertical lines above the landscape heading out into the sky...

Nah... The only place you could put one of these would be at the equator, and the tower would be thin enough as to be invisible from more than a mile or two away. Once you get two or three up, and find that you still don't have enough capacity, it probably becomes cheaper to strengthen existing elevators rather than building new ones.

Re:Jetsons Homes

[WolfWithoutAClause]

Why can't we make small Jetson's style homes on the line... Everyone can live 5 miles up..

Nope. Don't forget these cables hang down from orbit.

So to make this work, you have to thicken the cable above you to take the extra weight. 38000 km of nanotubular cable is not cheap...

Re:Jetsons Homes

[macdaddy357]

Since the space elevator is from a sci-fi novel, why not use materials from a comic book, like adamantium. The fact that it doesn't really exist is such a minor detail. Let's focus on the big picture.

Re:Jetsons Homes

[216pi]

Please remember that the Space Elevators are unidirectional... once you are up at home, you can't come back to earth except you are using a parachute or wait at the next space shuttle bus stop...

Re:Jetsons Homes

[Alranor]

I thought the whole point of a space elevator is that it's bidirectional, so that you can use the PE of the mass coming down to offset the energy you need to put into lifting something into orbit, and this make it essentially "free" (with the exception of frictional losses and so on) to lift things into orbit ??

Re:Jetsons Homes

[216pi]

As I've read in this thread and I think on their website, too, it is mainly a one way system and not used like a normal elevator on earth...
While something comes down, nothing can go up. It's faster to deorbit and reenter by falling, because the next cargo lift can happen concurrently. Since it takes four hours to get to lower orbit and about a week to reach higher orbits (36.000km or so) it would take too long to wait for the cabin that takes me down to seven11 to get a beer.

Re:Jetsons Homes

[hplasm]

Noooo....the whole point is that the up and down cars counterbalance each other, so only a fraction of the energy required to lift the cab + contents is needed, else it would cost an arm and a leg to hoist the dam stuff up the cable, might as well use a rocket...

You want to donate?

[Spudley]

Let me get this straight... this space elevator initiative is a purely commercial effort. They may be planning to spend billions, but the desired end result will be that they get a near-complete monopoly on space launches(*). ...And you're suggesting donating time to help them?
Hmmmmm....... I think anyone with a budget in eight figures can afford to pay their programmers.

(*) The word "launch" is probably wrong here, but I couldn't think of an alternative.

Re:You want to donate?

[ceejayoz]

Getting one up will lead to other industrial groups trying to get their own up. Competing space elevators would be a Good Thing (TM).

Anyways, I'd rather have a group of private companies doing it than NASA, given their recent success rate and Congress' cost-cutting measures.

Re:You want to donate?

[WolfWithoutAClause]

Actually the budget is 11 figures... ;-)

"A billion here, a billion there, sooner or later it adds up to real money."

From the mouth of the master...

[Will_Malverson]

Arthur C. Clarke said that we'd build a space elevator about 50 years after everyone stopped laughing. With stories like this, I think it's safe to say that we've stopped laughing.

Why do they have to hang straight down?

[Mick D.]

I have a pretty decent knowledge of the physics involved in the construction and use of a Spave elevator. I know that they need to orbit in Geosync orbit so the cable doesn't change length. I know that the cable is actually hanging down to the Earth from the center and being pulled away from the Earth out at the tip of the cable beyond Geosync orbit.

But, the one thing that has always bugged me has been why the cable itself has to hang straight down from orbit. This places the "Ground" based end in much less practical areas. Couldn't there be multiple cables hanging down and strung like Christmas lights to northern and sorthern areas that would be more likely to use them. They would need to balance the weight to keep the orbiting cable in the correct spot, but with 4 or more anchor points it would provide multiple ways to orbit and redundency(sp) in case of catostrophic failure.

Any insight in this would be helpful. As far as I can tell the only problems would be the added weight and thus tension, but I haven't done the math and don't know how much stronger the cable material would need to be.

Re:Why do they have to hang straight down?

[WolfWithoutAClause]

But, the one thing that has always bugged me has been why the cable itself has to hang straight down from orbit.

The trouble is that the combination of rotation (which pulls at 90 degrees to the axis of the earth) and the earths gravity (which pulls directly towards the earths center)- the combination ends up pulling the end weight so that it is above the earths equator. The cable below that goes from the attachment point on the earths surface up to there.

You can move the endweight only a small amount from the earth end- the radius of the earth is only 6700 km, but GEO is 38000km, so the geometry for moving the end weight around doesn't add up.

So basically, the endweight is in the plane of the equator. So the cable comes off at an angle from the earths surface- and heads off to the weight beyond GEO. At the equator the angle is 90 degrees. But as you go north or south, the angle is lower, and the angle means that the tether is longer and weighs more, as it droops under gravity (there's little rotation force at low altitude to compensate, so it does it quite a lot.)

So if you go very far north you find that the cable leaves the earths surface horizontally... there's no point in going further north than that. Exactly how far north this happens depends on how heavy the cable is, and how much tension there is in the cable at ground level. So you can increase the tension and pull it up off the ground again. But by doing so, you are losing payload by doing this- the extra tension to make this work could be used to lift payload up the tether.

It's a bit oversimplified, but that's the main idea. You can do it, but it's probably not worth doing it.

$10 billion is *nothing*!

[GPS Pilot]

This first space elevator could be built for between $7-$10 billion

People, put things in perspective. Since design work began in the early '70s, the U.S. has spent about $180 billion on the Space Shuttle program. What do we have to show for it? Certainly not reliable, low-cost access to space. The space elevator will change everything. Especially considering the fact that you can use it to lift materials for additional space elevators -- making the construction cost for subsequent space elevators lower than for the first one.

$10 billion for our first space elevator would be the bargain of the millenium.

Re:$10 billion is *nothing*!

[J'raxis]

$10 billion - just a few billion less than this monstrosity.

Re:$10 billion is *nothing*!

[FunkMonkey#9]

Since design work began in the early '70s, the U.S. has spent about $180 billion on the Space Shuttle program. What do we have to show for it?

Oh, how about major advances in many areas of science and technology, such as materials science, aerodynamics, propulsion... or were they developed independently of that $180B?

Should anyone working on a Space Elevator work to reinvent the wheel in areas where the amassed body of knowledge has already been covered by other projects? No?

A lot has been taken away from the Space Shuttle program to be applied in other fields, significantly increasing the bang-for-your-buck factor of a lot of things we can take for granted when we start new projects.

Well, you could i think.

[Unknown Poltroon]

I have NO qualifications to make a wild guess about this, but: Im guessing you could hang them, say one in the us, one in south america, as long as the points are eqidistant from the equator. However, as for the catastrophic failure, i think ithis would increase the problem, like if one side of a cable bridge snaps, the remaing side cant handle the load anyway. Some of the other ideas with rotating cables might be a better idea.

Redefining "Long commute"

[phamlen]

The Highlift website suggests "Travelling at average speeds of anywhere from 120 km/h to 160 km/h, the length of a voyage to low Earth orbit might be as brief as four hours." Considering that here in NYC, we have people who commute 3 hours each day, we should consider anchoring one near Grand Central Station. I can just hear the talk:

"Yeah, well, we were looking at a place in Poughkeepsie, but then we realized the commute would only be about 30 minutes longer. Plus you should see our views!

Re:What happens when the cable breaks?

[shrikel]

Actually the cable is more like 60,000 miles long. The idea is to use a substance that will NOT break easily. And if it did break, it wouldn't crash down like steel, it would float down like paper. They're taking this into consideration. Look at their faq on their website.

Space Elevetor more difficult that reported

[Anonymous Coward]

I found this (http://flightprojects.msfc.nasa.gov/pdf_files/ele vator.pdf) report from NASA of the state of Space Elevetor technology. There are a number of technological problems that must be solved before we can build a space elevator, and I think that given time we will overcome all of them. However, there are two non technological hurdles that must be jumped. The first is space junk. There are more than 8700 pieces of 10mm+ sixed space junk. All of them are a threat to the safety of the space elevator and most need to be cleaned up before we deploy a space elevetor. The other big hurdle is politics. Not many people are going to be keen on the idea of having 20 tons of cable deangling above their heads. If the space elevator snaps at the right (that is wrong) place then you'll have 22,000 miles of cable tumbling out of space. Also, it will have to be an international effor with some heavy duty security requirements. All that has to be sorted out before construction begins.

I personaly would love to see a space elevator in operation in time for me to actualy take a ride. But I persoanly think the 15 years mentioned is too optimistic.

Re:Space Elevetor more difficult that reported

[bassburner]

If the cable were to break wouldn't it fly outward like a shotput because of centripital force? Obviously, only the part that disconnected would go outwards, but if all else fails the cable could be detached at the base or some other key point. It's been quite a few years since physics so I may be way off here.

Re:Space Elevetor more difficult that reported

[tiedyejeremy]

"At the heart of the space elevator is a ribbon that stretches some 62,000 miles (100,000 kilometers) from Earth to space.

That seems like a lot more than "22,000 miles of cable tumbling out of space"
which makes your point more frightening. Though, I believe the centrifugal force will keep the string pointing out, not crashing down. So, if the wire breaks, does the climber just rocket out to space? If so, then, does it really need to be that high to accomplish the goals?

Re:What happens when the cable breaks?

[MindStalker]

The current thought is to design the cable so that incase it does break it should crumble into many pieces and mostly burn up in the atmosphere with just the last 10 miles or so actually falling, which would be an ultra thin cable hitting the ocean (plans are to have it be in the middle of the ocean for obvious reasons) So yes, probably small tidal wave from this cable, but nothing catostrophic and huge meteor shower, but nothing catostrophic if done properly.

Re:What happens when the cable breaks?

[the_skuncle]

More fiction and speculation has been written on this subject than you could throw a stick at.

K.S. Robinson blew the counterweight off of his space elevator in his awesome mars series, and it encircled the equator almost three times. By the time it was almost completely down, the heat from re-entry and pressure of impact caused the carbon whiskers to turn into pure diamond and bucky-balls (Buckminster Fullerenes).

Now, sure I know that it is only fiction, but so was 'Twenty Thousand Leagues Under The Sea' when it was written.

I also read a crappy book that placed the elevator on the polar axis instead of on the equator. It was written by some famous British guy who had written piles of stuff for Dr. Who and Red Dwarf among others. It answered the nagging question as to why I hate TV Science Fiction; There's virtually no science involved at all.

Just my $0.02

They don't, but it's easier that way

[Spamalamadingdong]

Since everything is going to the same destination anyway, and the dynamics of e.g. the lunar and solar tides would tend to stress paired skyhooks pretty badly unless you winched them in and out to compensate, it's probably simpler to just have one.

Once you're up to the level of traffic which justifies multiple skyhooks, you might be better served by a launch loop or orbital ring, aka Skyrail. You could have a whole bunch of those operating simultaneously.

Space junk perhaps not as bad

[Spamalamadingdong]

There will be micrometeoroids in any event, which require a redundant tether (braided and interconnected) so that one hit doesn't take the whole thing out. The other factor is that the same transport network which allows easy access also allows systems to remove junk from orbit. Something as trivial as a squirtgun, hitting a passing piece of junk with a cloud of vapor and ice crystals, would destroy and/or deorbit most hazardous objects. You could use a laser system to detect and deorbit the ones which pass too far away to hit with material deflections.

Re:Space junk perhaps not as bad

[lommer]

"Something as trivial as a squirtgun, hitting a passing piece of junk with a cloud of vapor and ice crystals, would destroy and/or deorbit most hazardous objects."

You mentioned the problem inherent in your own proposition just there: ice crystals. The crystals would only have to be 5mm in area on one face to become as bad a problem as the space junk they are supposed to be deorbiting... and in the coldness of space on the dark-side of the earth, these would occur far too frequently.

I think a more promising solution would be some sort of automated cleaner system that uses armor similar to what the british have been developing for use on their tanks. Basically the cleaner is armored with a capacitor, the inner plate be live and the outer plate being "ground", when a piece of space junk impacts the outer shell, it makes a connection between the two plates of the capacitor, thus causing thousands of amps to flow through it - vaporizing it instantly. You could just have a dozen cleaning machines sporting shields such as these running around in space smashing into objects.

Re:What happens when the cable breaks?

[WolfWithoutAClause]

I also read a crappy book that placed the elevator on the polar axis instead of on the equator. It was written by some famous British guy who had written piles of stuff for Dr. Who and Red Dwarf among others.

Who? Who? Go on tell us, so we can laugh at them ;-)

Multiple cars?

[Myco]

I've read a lot of discussion on /. about these things, but I have yet to see anyone mention the question of how many cars can run on a space elevator at once. Obviously, if only one car can run at once, that seriously limits your traffic and efficiency. The main difficulty I see with multiple cars is what happens when they need to pass each other. Does anyone have any ideas for solutions to this, or other reasons why multiple cars wouldn't work?

If cars aren't allowed to pass, you could still send them along in batches, though. As long as you have ample storage for them at each end. Shouldn't be a problem -- space is big.

Re:Multiple cars?

[spike hay]

Actually, with this system, unlike other elevator concepts, it is only a one-way ticket. To get down, you have to have a vehicle capable of surviving reentry.

Re:Multiple cars?

[lommer]

One could use the idea that another poster had - two angular tethers instead of one. Then one tether is reserved for traffic goin up and the other is for traffic coming down. The trick would be keeping the tethers far enough apart that congestion doesn't occur at the space end of things but balancing this with transportation costs incurred from having the tethers' earth-side attatchments far apart.

Of course, one could just have two space elevators beside each other, the transport between the two in space would not be difficult to managae. For that matter, a REALLY wide space-station-end could just be used with two vertical tethers...

I have no ideas regarding the feasability of these suggestions, but they're a start.

Re:Multiple cars?

[iktos]

The one we were discussing last year was designed for one 20 ton car (12 ton payload) every 97 hours.

Re:What happens when the cable breaks?

[charlie763]

How about we put together some sort of system that maintains the tension on the cable so that if the tension falls it will keep pulling the line. If we can pull the cable in as fast as it is falling there would be no problem. Since the terminal velocity of something so lite pulling it in at it's terminal velocity should be no problem.

a small problem

[Goldsmith]

All this space elevator talk is fine and dandy, but where are they going to get these nanotubes?

I've read that some car company in Japan is providing them with carbon nanotube technology to build this out of. No mention of what company, or what process is being used.

Now... if someone out there has developed a way to make long nanotubes on a bulk scale, they should really tell all the scientests out there who are working on that, they'll be glad to know it's been done. I'm sure some people in Stockholm would also be very interested.

If someone can point me to somewhere detailing how this has been achieved, that would be great. Otherwise, I wouldn't invest a dime or an hour in that company.

Incredible properties

[Bunjo]

Additional research has shown that carbon nanotubes posses incredible properties. One of those attributes is having a tensile strength 100 times stronger than steel at one-fifth the weight.

That's something. Still, if it were to break, that's a long way down. You'd probably need to reserve a several mile radius in case something were to come down.

Re:What happens when the cable breaks?

[spammeister]

Yes, but wasn't it attached to one of the "moons" (phobos or deimos i forget)? I can't relaly remember since it ahs been a couple years since i read it last (and 2,000 pages tween the 4 of them books makes me forget by the time i'm done iwth #4 what happened in #3 let alone #1). So that elevator was actually quite large because there was an actual large counterweight already in orbit with all sorts of retro-rockets and whatnot.

... but some solutions are worse and/or silly

[Spamalamadingdong]

You mentioned the problem inherent in your own proposition just there: ice crystals. The crystals would only have to be 5mm in area on one face to become as bad a problem as the space junk they are supposed to be deorbiting... and in the coldness of space on the dark-side of the earth, these would occur far too frequently.

Silly objection. Water ice sublimes rapidly in vacuum, and in order to get back to the tether it would have to make at least one complete orbit around the earth, at least half of which will be in full sunlight. Safe to say, it's not going to get back to the tether. (Water squirted out at the typical space-junk altitudes of 2000 miles and lower wouldn't get into orbit in the first place; they'd fall into the atmosphere. Might make a nice show on clear nights for people a bit to the east!)

when a piece of space junk impacts the outer shell, it makes a connection between the two plates of the capacitor, thus causing thousands of amps to flow through it - vaporizing it instantly.

The kinetic energy of most sand-grain sized space junk is enough to vaporize it if it's in a polar orbit; getting fancy with electrical discharges is just gilding the lily. The problem with that scheme is that the area you can sweep is limited to the area you can cover with matter, and you have to drag it through the upper atmosphere, avoid working satellites, and everything else. It's much more cost-efficient to have a laser "broom" to sweep stuff out of orbit; you can even keep most or all of the hardware on the ground.

wooooosh

[illerd]

That's a pretty good failsafe. Put a big ol' lynch pin at the base. If something goes wrong and it looks like the teather is going to break, pull the pin and WOOOOSH! The biggest most expensive slingshot in the history of mankind. That would be rad to watch from the moon. And if the space elevator industry caught on and more sprung up, we could use them as weapons in interplanetary wars, a la the bugs in Starship Troopers. Just put a big nuke or giant mass on the end of the teather, pull the pin at the right time and off goes your intergalactic slingshot. If we couldn't find any hostile planets to pummel we could just chuck rocks at Mars for kicks. Man, this is gonna be great.

Why in the hell....

[narftrek]

would I want to live on a cable 5 miles up? These things will be made by humans. Historically stuff made by humans break...and break often. So I am sittin on my couch watchin the Simpsons and suddenly the cable breaks and I get slingshot out into space...or worse yet I fall back down to earth in a horrible fiery crash. Gravity tends to keep my house pretty securely attached to the ground so my likelyhood of crashing into said earth is pretty low unless a sinkhole or earthquake hits. I figure that probability is WAY lower than a carbon cable breaking so I think I'll just watch the Simpsons from the ground.

Re:What happens when the cable breaks?

[the_skuncle]

No...

Not AC Clark. He's got science on his side mostly. I can't remember who it is and I have put the novel into a box in the bottom of my storage shed so I don't know his name.

I'm pretty sure that the book was called "Colony" but I can't be sure. Rest assured that it was a waste of time and money.