Slow Space Elevator

[McCoy]

Re: Slow Space Elevator

 

The carbon nanotubes that everyone talks about for this project do not yet exist. They MAY soon, they may not.

Until super-super strong and super-super light nanotubes exist the space elevator is sci-fi.

Actually carbon nanotubes do exist. They are not yet long enough to make a strong enough tether, but there is no theoretical reason they can't be. Requires inprovements in manufacturing techniques, not a major physics breakthrough.

[Kristopher]

Re: Slow Space Elevator

 

Significant goof in the article. First' date=' it's the Coriolis [u']effect[/u]; it is NOT a force. Second and more important, it refers to the effect of moving north or south; in or out is simple inertia.

 

As others have said, this "bug" has been known about for a long time.

 

People go on weeks-long cruises just to land up where they started. Why is a week long "cruise" to outer space somehow inconceivable?

 

Because you can't go out on deck, or go to the pool, or lock yourself in your private cabin, or...

[Kristopher]

Re: Slow Space Elevator

 

Physics is sound. Just a matter of finding a strong enough material to make the tether, and it looks like carbon nanotubes will do.

 

Big problems are political, getting it past the NIMBY's.

 

We've been over everything that's wrong with the concept, and it's a long, long list.

 

And really, with a "ribbon" that long, it's in a LOT of people's back yards if something goes wrong.

[jtelson]

Re: Slow Space Elevator

 

Actually carbon nanotubes do exist. They are not yet long enough to make a strong enough tether' date=' but there is no theoretical reason they can't be. Requires inprovements in manufacturing techniques, not a major physics breakthrough.[/quote']

 

I work in AT process development specifically focusing on Nanotechnology. We're a long way out from tubes that can be used for this and there will have to be a couple of major breakthroughs to get there. I know there are a lot of news stories with people talking about how close this stuff is but close on the advanced tech scale is under 2 decades if we get lucky.

[McCoy]

Re: Slow Space Elevator

 

We've been over everything that's wrong with the concept, and it's a long, long list.

 

And really, with a "ribbon" that long, it's in a LOT of people's back yards if something goes wrong.

With a "ribbon" that long, 99% will burn on atmospheric reentry if anything goes wrong.

[tkdguy]

Re: Slow Space Elevator

 

But how much damage will the remaining 1% do? And the passengers are still SOL. Of course, that's the case right now when something goes wrong during the flight, but when the general population is involved, the public outcry will be even greater than when a handful of specially trained individuals are involved.

[McCoy]

Re: Slow Space Elevator

 

But how much damage will the remaining 1% do?

I'm going to say absolutely none outside a hundred mile radius of the anchor point, so if attached mid-ocean as currently envisioned, that's a pretty empty back yard.

Of course' date=' that's the case right now when something goes wrong during the flight, but when the general population is involved, the public outcry will be even greater than when a handful of specially trained individuals are involved.[/quote']

Huh? Lots more people have been killed in airplanes than space shuttles, I hear almost no public outcry about that.

[Vondy]

Re: Slow Space Elevator

 

Legally, there's nothing like a relevant precedent for its status. What national entity (if any) is responsible for it? Who provides police (and naval) protection (pirates, anyone)? Who pays when damage or loss of life occurs on or around it? Who collects the fees for hoisting stuff up (and pays the penalties for loss of a payload)? Who insures the thing, and its cargo?

 

I completely disagree. Its seems pretty simple. Who pays for those things with any other structure (oil rig) or massive ship (supertankers, supercarries) in international waters? The same goes for management, access, security, fees, and insurance. Who manages those for oil rigs and supertankers, or super-carriers? Who insures cargo using land, air, or sea? Because the answer to that will ultimately be the answer to this. The nation or corporation that builds it will be the stakeholder that will have to stand and deliver (and reap the benefits) on the details you mention. If its a multinational or joint megacorp project those details will be handled by a treaty-contract between the relevant stakeholders. And insurance, the train goes up instead of across. If there is a profit margin in it - which is the only way this will be worthwhile anyways - some insurance company will step up.

[Nyrath]

Re: Slow Space Elevator

 

But how much damage will the remaining 1% do?

from http://en.wikipedia.org/wiki/Space_elevator_safety#In_the_event_of_failure

 

...in most cable designs, the upper portion of any cable that fell to Earth would burn up in the atmosphere. Additionally, because proposed initial cables have very low mass (roughly 1 kg per kilometer) and are flat, the bottom portion would likely settle to Earth with less force than a sheet of paper due to air resistance on the way down.

[Basil]

Re: Slow Space Elevator

 

Because you can't go out on deck' date=' or go to the pool,[/quote']

But you can look at Earth and the stars.

 

or lock yourself in your private cabin' date=' or...[/quote']

Who/what says you wouldn't be able to?

 

Anyway, a cruise isn't the best thing to compare it to. Emigration to the USA, Canada, Australia, etc., before the days of long airplane flights is a better comparison. A month or two to a new life; done before, no reason it wouldn't happen again.

[tkdguy]

Re: Slow Space Elevator

 

Here's the reasoning behind my last comment.

 

I see this project being a tough sell for the public. The physics may be sound, but I see most people being wary of it. Most people haven't even heard about it. Also, the cost will be astronomical, which is already a big minus.

 

True, people die in plane crashes, but by now, people are used to air travel. This will be new and untested technology. If you get a high death toll the first time something goes wrong, it will take a lot more convincing to get it back on track.

 

Again, I'm not trying to come off as a naysayer. I'm just stating the challenges I think the people involved will face (public perception in addition to the physical challenges) when they try to get it off the ground, so to speak. I may be wrong; that's just how I see it right now.

[Nyrath]

Re: Slow Space Elevator

 

I see this project being a tough sell for the public.

Agreed.

 

And you didn't even mention the ever-popular "why should we spend money on outer space when there are so many problems we could spend money on right here in our own country?"

 

My personal take on that last bit is those problems tend to be infinite money-sinks that can easily absorb all of a given country's money but with no visible effect.

[McCoy]

Re: Slow Space Elevator

 

I see this project being a tough sell for the public. The physics may be sound' date=' but I see most people being wary of it. Most people haven't even heard about it. Also, the cost will be astronomical, which is already a big minus.[/quote']

That was sort of my point, Political problems > Technological problems.

[Kristopher]

Re: Slow Space Elevator

 

That was sort of my point' date=' Political problems > Technological problems.[/quote']

 

Despite the guy who works with the stuff telling us that we're at least two decades and multiple breakthroughs away from it being anything like possible?

[Kristopher]

Re: Slow Space Elevator

 

from http://en.wikipedia.org/wiki/Space_elevator_safety#In_the_event_of_failure

...in most cable designs' date=' the upper portion of any cable that fell to Earth would burn up in the atmosphere. Additionally, because proposed initial cables have very low mass (roughly 1 kg per kilometer) and are flat, the bottom portion would likely settle to Earth with less force than a sheet of paper due to air resistance on the way down. [/quote']

 

Part of this that always gets me is that any breakthroughs that make a material that's strong enough in all ways and yet only weighs about 1 kg per kilometer possible, somehow don't apply to any kind of SSTO project, according to the spacevator proponents.

[McCoy]

Re: Slow Space Elevator

 

Despite the guy who works with the stuff telling us that we're at least two decades and multiple breakthroughs away from it being anything like possible?

Yep. Barring a major misunderstanding in our current knowledge of the way molicules work, the material is possible. Solving the political wranglings and the NIMBY's fears of the sky falling may not be.

 

Part of this that always gets me is that any breakthroughs that make a material that's strong enough in all ways and yet only weighs about 1 kg per kilometer possible' date=' somehow don't apply to any kind of SSTO project, according to the spacevator proponents.[/quote']

Problem with SSTO is not the weight of the vehicle, it's the weight of the propellant. Breakthroughs in material science are not going to change that. Running a car up a beanstalk doesn't require propellent. Use electric motors and beam energy via laser or (better) power them off a "third rail." Don't have to have all your fuel on board before you lift the first inch.

 

As far as SSTO, we could build a mass driver today. Knew a couple of guys that wanted to build a demonstration of principle device that could throw a (IIRC) 25kg payload into LEO. (Mass drivers are not practical for crewed missions, again IIRC the payload in their demonstration device would have been subjected to something like 30 G's.) They coudn't get permission to build it. Not funding, permission. Seems that as it was able to throw a payload to LEO, it could also hit any point on the surface of the Earth, and that violated some treaty.

[Kristopher]

Re: Slow Space Elevator

 

Yep. Barring a major misunderstanding in our current knowledge of the way molicules work' date=' the material is possible. Solving the political wranglings and the NIMBY's fears of the sky falling may not be.[/quote']

 

Now, when someone says to me "multiple decades and multiple breakthroughs" seperate us from something being made, that doesn't tell me it's possible. Hypothosis is all well and good, but if no one ever finds a way to make the stuff in a way that makes the spacevator possible -- lots of it in very long chains -- then it's just handwavium.

 

Problem with SSTO is not the weight of the vehicle' date=' it's the weight of the propellant. Breakthroughs in material science are not going to change that. Running a car up a beanstalk doesn't require propellent. Use electric motors and beam energy via laser or (better) power them off a "third rail." Don't have to have all your fuel on board before you lift the first inch.[/quote']

 

Ironically, a spacevator that's going to lift people is going to make some kind of quick-lift vehicle with a lot of delta-V on board and decent cargo capacity all the more necessary -- it's not like you can send up another "cable car" if something goes wrong with the first one, or the ribbon.

 

The kind of materials that would make the spacevator possible would reduce the amount of weight taken by the structure of an SSTO drastically, allowing more fuel to be carried, and the amount of vehicle weight that needs to be lifted -- X-33/VentureStar failed largely because various parts could not be made both light and strong enough at the same time. And a very similar type of vehicle would be needed making those fast or short-notice trips if it were stationed at the ISS or a successor structure. Any such vehicle without re-entry capability strikes me as foolhardy in the extreme.

 

Trips times of weeks or months can be made to sound reasonable if one compares them to the times taken by colonists and explorers in the past, travelling by ocean vessel. But no one emmigrates, let alone commutes, by transatlantic liner in 2008. If there's a faster way to get around, people will take it, and the attempts to replace the hypothetical spacevator with something better began sometime before 1980...

 

But hey, I guess it's fashionable to take shots at thrust-lift vehicles, especially the reusable kind, right now. Even the new moon and Mars program is taking a step backwards to capsule-style systems.

[McCoy]

Re: Slow Space Elevator

 

Now' date=' when someone says to me "multiple decades and multiple breakthroughs" seperate us from something being made, that doesn't tell me it's [i']possible[/i]. Hypothosis is all well and good, but if no one ever finds a way to make the stuff in a way that makes the spacevator possible -- lots of it in very long chains -- then it's just handwavium.

 

The kind of materials that would make the spacevator possible would reduce the amount of weight taken by the structure of an SSTO drastically' date=' allowing more fuel to be carried, and the amount of vehicle weight that needs to be lifted -- X-33/VentureStar failed largely because various parts could not be made both light and strong enough at the same time. And a very similar type of vehicle would be needed making those fast or short-notice trips if it were stationed at the ISS or a successor structure. Any such vehicle without re-entry capability strikes me as foolhardy in the extreme. [/quote']

Pick a standard. If "it's just a hypothesis until we actually do it," then SSTO is just as much handwavium as the beanstalk. In both cases, the technology needs work. In both cases, we are unaware of any reason why it cannot work.

 

When a vehicle must be > 80% fuel by weight, it is difficult to get "drastic" improvements by making the sides of the fuel tanks lighter.

 

Ironically' date=' a spacevator that's going to lift people is going to make some kind of quick-lift vehicle with a lot of delta-V on board and decent cargo capacity all the more necessary -- it's not like you can send up another "cable car" if something goes wrong with the first one, or the ribbon.[/quote']

No, if something goes wrong with a cable car in mid trip, you are just as royally screwed as if something goes wrong in an airplane (or for that matter, a SSTO rocket) in mid flight. Mid-trip rescues probably are not practical.

 

Trips times of weeks or months can be made to sound reasonable if one compares them to the times taken by colonists and explorers in the past' date=' travelling by ocean vessel. But no one emmigrates, let alone commutes, by transatlantic liner in 2008. If there's a faster way to get around, people will take it, and the attempts to replace the hypothetical spacevator with something [i']better[/i] began sometime before 1980...

Currently if you want to get from New York to Los Angeles, most people go by air. But you can still take a bus, take a train, or rent a car. All have offsetting advantages and disadvantages.

 

How long does it take a supertanker to get from the Persian Gulf to North America? We are talking a freight train here, not a commuter train. Bottom line is not how fast you can get a payload to Clarke orbit, but how cheap. Beanstalk represents a massive capital investment, but once compleated could lift payloads for pennies per kilogram.

 

But hey' date=' I guess it's fashionable to take shots at thrust-lift vehicles, especially the reusable kind, right now. Even the new moon and Mars program is taking a step backwards to capsule-style systems.[/quote']

Straw man! You're the one who brought up SSTO, no one was mentioing it, much less taking shots, until you did.

 

Since a beanstalk has to be built from the top (or actually the middle) down, it does involve delivering a metric buttload of material to Clarke orbit, which means either mass drivers (and their resulting political complications) or improved rockets. Beanstalks will not replace rockets any more than cargo ships replace airlines.

[Lawnmower Boy]

Re: Slow Space Elevator

 

 

Since a beanstalk has to be built from the top (or actually the middle) down, it does involve delivering a metric buttload of material to Clarke orbit, which means either mass drivers (and their resulting political complications) or improved rockets. Beanstalks will not replace rockets any more than cargo ships replace airlines.

 

 

But if we have rockets that good, what do we need a space elevator for? It's like building a rapid transit line. It would be nice to whiz up to geostationary orbit in the relaxing comfort of a subway car, but unless the traffic pays the fare set by the construction cost, it's a white elephant.

[McCoy]

Re: Slow Space Elevator

 

But if we have rockets that good' date=' what do we need a space elevator for? It's like building a rapid transit line. It would be nice to whiz up to geostationary orbit in the relaxing comfort of a subway car, but unless the traffic pays the fare set by the construction cost, it's a white elephant.[/quote']

Again, freight to Clarke orbit at least an order of magnitude cheaper than SSTO.

 

You want to launch a satellite. You can get it to LEO tomorrow for ten million dollars, or Clarke orbit next week for one million. Which do you pick?

[The Weapon]

Re: Slow Space Elevator

 

Good point. I can see equipment and even satellites being launched into orbit that way. I doubt people will want to spend weeks just getting into orbit and living in the elevator all that time.

 

[correction: got sums and data wrong]

Cost to get into orbit is about $1950/lb. or $4.30/g for the cheap options. For a 70 kg person being paid $500,000 year (probably the median for someone working in space factories) his transport costs = 70kgs * $4300/kg /($500,000/year) = about 219 days pay. So taking 4 weeks to arrive as opposed to a day is worth it if the cost is reduced by about 12%. Of course you have to factor in food, but his waste is going into the hydroponic garden anyway right? For freight of course it's even more worth it since the cost of delay is only (cost of materials * interest rate).

 

http://www.geocities.com/nini_net2000/spaceelcosts.xls

[The Weapon]

Re: Slow Space Elevator

 

 

McCoy[/b]]

Better than the crewed mission to Mars. Six people sharing what amounts to an efficency apartment they can't leave for two and a half years.

Why do I smell a reality TV show...

 

How do you vote people off in the middle of 200 million miles of vacuum? Or don't I want to know?

 

This reminds we of an episode of "Drawn together" (the world's first animated reality TV show) where one team lost the "oxygen challenge" and didn't get oxygen for a week.

[The Weapon]

Re: Slow Space Elevator

 

Actually, NIMBY isn't an issue. The elevator site has to be on the equator, and the best sites in terms of weather are in the open ocean. So there's some substantial new space and admiralty legal issues. The bottom of the tether has to be modestly mobile ... something like a deep-ocean oil-drilling rig will do, which can move a few km in a day. But you have this quasipermanent structure based in international waters, extending upward through international airspace, and out beyond the atmosphere into international space. Legally, there's nothing like a relevant precedent for its status. What national entity (if any) is responsible for it? Who provides police (and naval) protection (pirates, anyone)? Who pays when damage or loss of life occurs on or around it? Who collects the fees for hoisting stuff up (and pays the penalties for loss of a payload)? Who insures the thing, and its cargo?

 

The slower speed ... 20 to 30 days in a tens-of-tons bulk carrier isn't a huge deal. You won't have commuters, and that transit time limits its usefulness for putting humans up there, but for freight service (which might be unmanned, or have a single crew) it still wins big. It also depends on how many elevator cars you can have running on the tether at once. AFAIK those are still development questions.

 

There are design competitions ongoing now for elevator car technology, things that can climb a ribbon cable at speed using a remote power source. And making the fibers long enough to be spun into a useful ribbon is also ongoing work.

 

It's not dead yet, and at no time did I think it'd be smooth sailing in the development process.

 

Heck, I'm still wondering if there's a way to harness the electromagnetic effects the thing will create. There's a few million volts of potential difference between Earth's surface and the top of the atmosphere, and then you'll have 30,000+ km of this ribbon cable rotating through Earth's magnetic field every 24 hours, which varies if for no other reason than it's compressed on the sunward side and extended in a tail out the night side. So the time-derivative terms of Maxwell's equations mean there'll be some current generated ....

 

Not only should that work, but modifying the amount of resistance in the wires will give you effective thrust since the current will determine the energy used and the energy is taken from the rotational energy of the elevator, i.e. it's speed. Changing this locally makes the beanstalk speed up or slow down relative to the earth and can be used to correct wobbles.

[The Weapon]

Re: Slow Space Elevator

 

Because you can't go out on deck' date=' or go to the pool, or lock yourself in your private cabin, or...[/quote']

 

Private cabins aren't a problem, they don't mass that much and space is not a problem (hey advertising slogan!). A pool may be a bit much, but an electronic library/hyperfast internet connection isn't, nor a gym. Sure it's not for those who like forest views, but neither was sailing to America.

[The Weapon]

Re: Slow Space Elevator

 

Here's the reasoning behind my last comment.

 

I see this project being a tough sell for the public. The physics may be sound, but I see most people being wary of it. Most people haven't even heard about it. Also, the cost will be astronomical, which is already a big minus.

 

True, people die in plane crashes, but by now, people are used to air travel. This will be new and untested technology. If you get a high death toll the first time something goes wrong, it will take a lot more convincing to get it back on track.

 

Again, I'm not trying to come off as a naysayer. I'm just stating the challenges I think the people involved will face (public perception in addition to the physical challenges) when they try to get it off the ground, so to speak. I may be wrong; that's just how I see it right now.

 

We don't need to convince the public we need to convince the bankers. The public doesn't have to worry as long as they're not near it when it collapses, which they won't be, even if it does. The biggest problem I can see is we just made the biggest terrorist/protection racket target in the world.