Space elevators a fantastic idea that maybe someday could be reality?

[rtxoff]

Anyone of you guys heard of them?

Would be awesome if we could build one.

[Streetwind]

They're widely regarded as the crowning achievement of space development. Both because there is nothing better for hauling stuff out of our gravity well, and because they're absolutely insanely difficult to build. They require materials we simply do not have, period. Though there's some hopes for future improvements in that area.

At least, that's true for an Earth-based space elevator. On the other hand, there's a company that has been argumenting that a lunar space elevator is viable with today's technology.

. Sadly that was back in 2013 and there has been absolutely no progress since, and they're even struggling with sending out Kickstarter rewards. Still, it's a fun concept.

[Nibb31]

Space elevators, railguns, rotovators, launch loops, and all those other exotic launch methods have also been discussed to death in these forums.

http://forum.kerbalspaceprogram.com/threads/58691-Space-Elevator-or-Mass-Driver-Railgun-or-something-else

http://forum.kerbalspaceprogram.com/threads/81147-Next-Generation-launch-technologies-achievable-with-CURRENT-technology

Insanely expensive, impossible with modern materials, and probably only really useful for hauling cargo, because of the transit time. 36000km is quite a long distance to travel. It will probably never be very practical.

Most of these launch methods have in common that they are megastructures that would costs trillions to build. The engineering involved goes way beyond anything we have ever done and there simply isn't enough demand to justify the cost and financial risk.

[lajoswinkler]

Yes, they're nothing new. And we can't build them. They're impossible even with the soon to come cutting edge technology. Too bad, they'd be very cool.

[Seret]

Anyone of you guys heard of them?

I'd assume most people on this forum would be at least familiar with the idea.

IIRC NASA were actually funding a competition to do some investigative work on the technologies required (beam powered climbers, etc). The main problem is materials though, there's nothing that can be manufactured in the required quantities a high enough tensile strength for the cable, let alone for an acceptable price.

[Aghanim]

In the near future? No.

In the far future? Probably

[Nibb31]

In the near future? No.

In the far future? Probably

I really doubt it. To reach geostationary altitude in less than a week, your elevator car would need to propell itself vertically at over 200km/h on pinch rollers that would also need to support the weight of the elevator, the payload, the engine, the power source. Even if we could manufacture a 36000km long ribbon with carbon nanotubes, the heat and friction constraints of those rollers on the ribbon material are staggering.

If we had the materials to build a space elevator, then we could also build all sorts of reusable vehicles that would be faster and much more flexible. If we had a power source as light, powerful, durable, and compact as what is required to power a space elevator train for a week, then we would have much better propulsion modes than rockets or pinch rollers to reach space.

[softweir]

One substantial issue to overcome for manned space-elevator use is radiation. Astronauts get a dose of radiation as they travel through the Van Allen belt, but it is trivial because the transit time is so short. However, in a space-elevator, the transit time is much longer and the radiation dose correspondingly higher. Shielding is heavy and would slow the transit even more! It's a wonderful idea and I would love to think they could happen, but I really, really have any hope they will.

[Mazon Del]

What appears to be one of the issues that some of you are caring about a lot is travel time. We don't NEED the space elevator to be fast enough to get something into orbit inside of a week. Especially given that we don't have enough infrastructure and such using space right now. The earliest space elevators could take a month to reach orbit and STILL be useful enough to shut down the rocket launch space industry. We just don't have any foreseeable needs (beyond missiles) to get to orbit RIGHT NOW, we can wait. Of course the longer it takes the more expensive it is for a PERSON to go because the person has all those needs people tend to have, food, water, etc. You would in effect be paying for a hefty cruise ticket just to reach orbit. Yes the radiation shielding for these speeds would need to be somewhat bulky, but since we are not going super fast, we can go with low speed high torque motors and ignore the problem, or you could just ship up less people per trip and devote the space/mass used for them and their food/etc for shielding.

[Nibb31]

The longer the trip, the heavier the vehicle needs to be. Making it a cruise ship with massive shielding simply turns the elevator into a behemoth that is going to need even more power to fight gravity and put even more strain on the tether and is going to require a massive counterweight.

Also, because elevators cannot cross each other on the same tether, you can only have one vehicle at a time either going up or down, therefore taking 2 weeks (or a month) for the elevator to do a round trip limits the total payload capacity of the system. I really don't think there is any demand for month-long cruises to GSO and back that would justify the upfront cost of building the thing. The solution to this is multiple tethers, with an even more massive counterweight. However, there are practical limits to all of this...

No, the whole idea is highly impractical for manned trips. It could really only be used for cargo, which means that you would still need some high-speed manned GSO shuttle vehicle for it to be of any use. Now, if an infrastructure exists for economical frequent and fast manned launches to GSO, then it makes much more sense to share the cost of that infrastructure with cargo launches rather than to build a separate expensive space elevator system. Besides, you would need to maintain a redundant launch vehicle infrastructure anyway for when the elevator is out of order or for emergencies.

Edited June 20, 2014 by Nibb31

[Aethon]

I read somewhere recently that a moon elevator is technologically feasible now ( I can source it if I hafta but donwanna ). For a super interesting discussion on this subject by some very smart people ( sorry no Henry Spencer ) see this old, ugly Usenet archive.

http://yarchive.net/space/exotic/tower_launch.html

[Streetwind]

I read somewhere recently that a moon elevator is technologically feasible now ( I can source it if I hafta but donwanna ).

You could start by reading the second post in this thread...

[Aethon]

You could start by reading the second post in this thread...

I read every post in the thread thank you. Edit- Thread in the post ( "What are you doing in this wep of the noods- neck of the wape... What are you doing here?" ).

Source : http://www.space.com/24905-moon-elevator-lunar-exploration-liftport.html

More from Usenet : http://yarchive.net/space/exotic/tethers.html

- - - Updated - - -

Edited June 20, 2014 by Aethon

[Mazon Del]

The longer the trip, the heavier the vehicle needs to be. Making it a cruise ship with massive shielding simply turns the elevator into a behemoth that is going to need even more power to fight gravity and put even more strain on the tether and is going to require a massive counterweight.

Also, because elevators cannot cross each other on the same tether, you can only have one vehicle at a time either going up or down, therefore taking 2 weeks (or a month) for the elevator to do a round trip limits the total payload capacity of the system. I really don't think there is any demand for month-long cruises to GSO and back that would justify the upfront cost of building the thing. The solution to this is multiple tethers, with an even more massive counterweight. However, there are practical limits to all of this...

No, the whole idea is highly impractical for manned trips. It could really only be used for cargo, which means that you would still need some high-speed manned GSO shuttle vehicle for it to be of any use. Now, if an infrastructure exists for economical frequent and fast manned launches to GSO, then it makes much more sense to share the cost of that infrastructure with cargo launches rather than to build a separate expensive space elevator system. Besides, you would need to maintain a redundant launch vehicle infrastructure anyway for when the elevator is out of order or for emergencies.

The vehicle does not need to be a cruise ship sized vehicle, that would certainly be impractical (though imagine watching THAT slowly climb!). My comment about the "cruise ship" was that years ago it wasn't that big of a thing that it would take 10+ days to cross the Atlantic. Pricey to do so in comfort and technically pricey at all. But people did it because it was the best way to do it. If the best (cheapest, safest, etc) way to get into space is to take a 3 week journey to get up, then that is what you do. Again, for the next 20+ years the primary cargo going into space is going to be just that, cargo. People will be the minority. Once we have a Mars or Moon colony going, then we might see an influx, but again, it’s a one(ish) way trip that could already be followed by months of travel. Who cares if it takes a month to just go straight up?

In order to make the system work at all you already need a massive counterweight, most designs envision using a captured asteroid for that purpose.

For going up and down, you are forgetting something. Getting DOWN from space has always been the cheap and easy part. Getting UP is the expensive side. You could, if you wanted, have two elevators, one for up and one for down. OR you can just come down the ye olde fashioned way with a heat shield and some parachutes. Hell, considering how cheap things would be compared with today, you could likely have craft make powered descents through the upper atmosphere instead of just slamming into them. Go slow enough, no reentry burn.

Chances are if we built a space elevator right now, we'd still have people funding shuttle-esque vehicle development, if only because the military would not want to rely on a single point of failure for access to space for troop deployments. Can anyone say Orbital Drop Shock Troopers?

The point is, dollar for dollar, the space elevator will ALWAYS be more economical than shuttle vehicles as long as we don't have antigravity available to us. We just need to learn to accept that going to space may take longer that the 10 minutes it takes astronauts.

[luisair]

Mazon Del +1

[Mazon Del]

Mazon Del +1

I shall protect and cherish this +1. It is mine and I will call it Steve.

[Awaras]

For going up and down, you are forgetting something. Getting DOWN from space has always been the cheap and easy part. Getting UP is the expensive side. You could, if you wanted, have two elevators, one for up and one for down. OR you can just come down the ye olde fashioned way with a heat shield and some parachutes. Hell, considering how cheap things would be compared with today, you could likely have craft make powered descents through the upper atmosphere instead of just slamming into them. Go slow enough, no reentry burn.

An elevator car going down could use some form of regenerative braking to generate power for the cars going up. The elevator would open many possibilities for asteroid mining, orbital industry and similar endeavors, and at some point the amount of stuff going down the elevator might exceed the mass going up, making the elevator a net PRODUCER of power...

[Mazon Del]

One of the things I remember reading a while ago on the space elevators was that one of the problems the units are going to have is the fact that they will be constantly generating power passively. You have a 30,000 km long semi-superconducting tether, as it moves around its going to pick up a charge. As the Earth rotates, the tether moves through the Sun's magnetic field, generating a charge. As the tether shifts around (winds on the Earth, orbit shifting for debris avoidance, etc) it will generate a charge from the Earth's magnetic field. There is even some research to suggest that it will be sucking up any charged particles near it. So power should theoretically never be too much of a problem.

Honestly, something I had never considered is, as the tether moves through the Sun's magnetic field...what does that do to the Earth's rate of rotation and the Earth's orbital velocity about the sun? Obviously it should do very little...but how little?

Heh, new explanation for lack of advanced civilizations. They all eventually make a space elevator, and then plunge into their stars because they stopped the planet accidentally.

[Aethon]

A relevant point from Usenet :

From: Hans Moravec <[email protected]>

Newsgroups: sci.space.tech,rec.arts.sf.science

Subject: Re: The Problem with Space Elevators

Date: Mon, 04 Dec 2000 22:47:43 -0500

Jason Goodman <[email protected]>:

> Which brings up my other point. Having a cable much longer than

> geosynch is *useful*. You can launch a spacecraft toward any

> planet in the solar system by simply climbing up to the right

> height, and letting go at the right moment. No rockets, no

> fuel(*), just push the right button on the elevator. "Second

> floor: Mars, the Asteroids.... Third floor: Jupiter, the Trojan

> Colonies... Fourth Floor: Saturn..."

>...

> (*) It's not a free ride to the planets. The energy to accelerate

> the spacecraft comes from slowing down the cable. You have to put

> energy back into the cable somehow, and rockets mounted to the

> cable might be the best way to do so. But they can be *good*

> rockets...

No rockets necessary. The cable "leans" a little from coriolis

force as the spacecraft rides up it. The lean puts a torque

on the earth through the anchor. Momentum and energy is

transferred from the earth to the spacecraft through the sideways

component of the leaning cable force vector acting on the

upriding spacecraft. Some sway remains after launch, but there

are damping effects, eg electromagnetic.

If you feel guilty about stealing earth's rotational energy to

launch you to Saturn, assuage your guilt by returning the same

way. As you grapple your way down the cable to synchronous

altitude against the centrifugal force, and then coast down with

gravity below synchronous, the cable leans the other way and

your energy and momentum are returned to mother earth.

[Dedjal]

Would not. Geostationary orbit be outside of earths protected sphere?

If so, the hauling cargo up would not do ISS any good, since they would need to launch a vessel up to the station, retrieve stuff, fly back to safety at the ISS.

[SargeRho]

Using Ion Engine-powered tugs to bring the stuff down from GEO to LEO would still be cheaper than launching the payload via Rocket.

[Awaras]

Would not. Geostationary orbit be outside of earths protected sphere?

If so, the hauling cargo up would not do ISS any good, since they would need to launch a vessel up to the station, retrieve stuff, fly back to safety at the ISS.

Well, if humans want to leave the cradle that is the Earth, we are going to have to figure out how to protect ourselves without the help of the Earth's magnetic field. Compared to the kind of infrastructure we would need, the ISS is just an inflatable raft. Besides, LEO is getting crowded enough already. And hey, if you've got a space elevator, what's stopping you from building your GEO base with 10 cm lead walls?

Edited June 21, 2014 by Awaras

[Aghanim]

I really doubt it. To reach geostationary altitude in less than a week, your elevator car would need to propell itself vertically at over 200km/h on pinch rollers that would also need to support the weight of the elevator, the payload, the engine, the power source. Even if we could manufacture a 36000km long ribbon with carbon nanotubes, the heat and friction constraints of those rollers on the ribbon material are staggering.

If we had the materials to build a space elevator, then we could also build all sorts of reusable vehicles that would be faster and much more flexible. If we had a power source as light, powerful, durable, and compact as what is required to power a space elevator train for a week, then we would have much better propulsion modes than rockets or pinch rollers to reach space.

Its that long? I thought that space elevator is fast... Halo tricked me again

[Seret]

I really doubt it. To reach geostationary altitude in less than a week, your elevator car would need to propell itself vertically at over 200km/h on pinch rollers that would also need to support the weight of the elevator, the payload, the engine, the power source.

Much of the appeal of a space elevator is that you don't lift the engines or power source. That stays on the ground. Lifting the propulsion and fuel would offer no advantage over a rocket.

Even if we could manufacture a 36000km long ribbon with carbon nanotubes, the heat and friction constraints of those rollers on the ribbon material are staggering.

Most serious designs I've seen assume maglev.

[Nibb31]

Its that long? I thought that space elevator is fast... Halo tricked me again

By definition, if you want it to stay in orbit attached to a permanent ground station, a space elevator must be linked to a station in geostationary orbit, which for Earth can only be 35,786 km above the equator.

Much of the appeal of a space elevator is that you don't lift the engines or power source. That stays on the ground. Lifting the propulsion and fuel would offer no advantage over a rocket.

Then you need a way to send the power to the climber car. This means either very very long wires (36000km worth of the thinnest copper wire would be heavier than a nuclear reactor) or beamed power (laser or MW...). Now, if you have the technology to beam power over such long distances to a climber vehicle, then that same technology could be used to power a launch vehicle and you wouldn't need to mess with megastructures and nanocarbon tethers in the first place.

Most serious designs I've seen assume maglev.

Most of the serious designs I've seen assume superlong superlight nanocarbon tube ribbons (because it's the only material that has the potential to maybe one day be strong and light enough for the application) and small solar powered roller-propelled climbers. I don't see how a maglev design would help you fight gravity while remaining light and strong.