The space elevator

[pendell]

Seen on NBC

For more than half a century, rockets have been the only way to go to space. But in the not-too-distant future, we may have another option for sending up people and payloads: a colossal elevator extending from Earth’s surface up to an altitude of 22,000 miles, where geosynchronous satellites orbit.

NASA says the basic concept of a space elevator is sound, and researchers around the world are optimistic that one can be built. The Obayashi Corp., a global construction firm based in Tokyo, has said it will build one by 2050, and China wants to build one as soon as 2045. Now an experiment to be conducted soon aboard the International Space Station will help determine the real-world feasibility of a space elevator.

Here's hoping it's built soon. I'd love to get to orbit in my lifetime!

Respectfully,

Brian P.

[Grey_Wolf_c]

Seen on NBC



Here's hoping it's built soon. I'd love to get to orbit in my lifetime!

Respectfully,

Brian P.

I mean, I'd love to see one built, but that article is long on the basics and very, very short on the details. Last I heard, the longest single walled carbon nanotube was a couple of cm long. This article doesn't claim any advances in that area, and that is the crucial one. Until we have a way to manufacture 100000 km of it, the elevator won't get off the ground. And the article doesn't fill me with confidence in that area- it reads like a VC verging on scam.

In all honesty, I'd sooner believe that the first of these we will see will be the lunar one, if at all.

Grey Wolf

[BeerMug Paladin]

I'm betting we'll see this the same year as the Hyperloop, cold fusion and the Mars outpost/colony/whatever. So never.

I'd love to be proven wrong though. The more wrong the better! Are scam-tech businesses are on the rise or something?

[Mando Knight]

Until we have a way to manufacture 100000 km of it, the elevator won't get off the ground.

They'd need a launch vehicle able to get it off the ground, too--even if the tether is a mere 5 tons per kilometer, the total mass of a GSO space elevator would be around 180 kilotons, and most of that would have to be deployed from space--a feat that would require over a thousand Saturn V-like super heavy-lift launch vehicles to do it sequentially.

The requirements for a lunar space elevator are utterly insane, and unlikely to ever occur without some kind of coplanar orbital ring as some kind of "please don't think about these numbers"-sized interface.

[Lvl 2 Expert]

They'd need a launch vehicle able to get it off the ground, too--even if the tether is a mere 5 tons per kilometer, the total mass of a GSO space elevator would be around 180 kilotons, and most of that would have to be deployed from space--a feat that would require over a thousand Saturn V-like super heavy-lift launch vehicles to do it sequentially

Ones you have a line up that can hold its own weight plus a bit it gets easier, though not simpler. More strands of material can be added by crawlers climbing up the cable. That way you can use the advantages of a space elevator to build (the later parts of) your space elevator.

[Sermil]

Ones you have a line up that can hold its own weight plus a bit it gets easier, though not simpler. More strands of material can be added by crawlers climbing up the cable. That way you can use the advantages of a space elevator to build (the later parts of) your space elevator.

But you still need to get it up there in order to deploy it. The crawler would move down, not up.

[Mando Knight]

Ones you have a line up that can hold its own weight plus a bit it gets easier, though not simpler. More strands of material can be added by crawlers climbing up the cable. That way you can use the advantages of a space elevator to build (the later parts of) your space elevator.

Just that first weight-supporting line would require at least as much lifting power as would take to put a Nimitz-class carrier into orbit. Depending on the mass of the cable, probably the same amount of lifting power as putting all ten of the Nimitz-class carriers into orbit, and maybe their fleet groups besides.

[Lvl 2 Expert]

But you still need to get it up there in order to deploy it. The crawler would move down, not up.

Unless they're strong enough crawlers. it would allow us to feed the strands/fibers in some kind of well organized manner.

Sure, that first cable would still be super heavy and really hard to place, but we can't even make a suitable material yet, so we're talking relatively far future anyway. Judging by the pace of materials science making stronger materials available over the past century or so I doubt any of us will get to see even a start to a project like this. The pace of lifting capacity into space increasing since the moon landings just confirms this at that point. It might be an even bigger problem, but it's still a problem.

Those companies can claim stuff about 2045 all they want, but most technologies that are supposedly about 20 years away either take much longer or never happen at all.

The cool thing about a space elevator is that there's seemingly nothing fundamentally impossible about it. There are some big impracticalities, but in some other ways it's extremely practical, so that sort of balances out. It's a thing that could really be in our future. Just not around the corner.

[Eldan]

They'd need a launch vehicle able to get it off the ground, too--even if the tether is a mere 5 tons per kilometer, the total mass of a GSO space elevator would be around 180 kilotons, and most of that would have to be deployed from space--a feat that would require over a thousand Saturn V-like super heavy-lift launch vehicles to do it sequentially.

The requirements for a lunar space elevator are utterly insane, and unlikely to ever occur without some kind of coplanar orbital ring as some kind of "please don't think about these numbers"-sized interface.

I think they probably meant one from the lunar surface to moon stationary orbit.

[Eldan]

I've seen a few hopeful proposals about parking a carbonaceous asteroid in GSO and then manufacturing the cable there, which could with some luck safe on launch costs. BUt then, we have even less of an idea on how to manufacture something like that in orbit.

[deuterio12]

The cool thing about a space elevator is that there's seemingly nothing fundamentally impossible about it. There are some big impracticalities, but in some other ways it's extremely practical, so that sort of balances out. It's a thing that could really be in our future. Just not around the corner.

Still waiting for flying cars to become common. And for that we actually have working prototypes, but there's just too many "big impractilities".

There's also the bit where it's not enough to build the space elevator. You need to keep it in one piece. But we live in a time where terrorists easily get all sorts of bombs and rocket launchers, and a space elevator would be the biggest target in human history.

Even assuming nobody blows it up willingly, there's also the chance of simple accident, and something that size would be pretty messy if it collapsed, so you'll need security measures well beyond the norm.

[Grey_Wolf_c]

There's also the bit where it's not enough to build the space elevator. You need to keep it in one piece. But we live in a time where terrorists easily get all sorts of bombs and rocket launchers, and a space elevator would be the biggest target in human history.

This "danger" is way overblown. The standard plan is to put it in the middle of the Pacific. Terrorists would not have an easy access to it. Much less with high explosives or rocket launchers.

Even assuming nobody blows it up willingly, there's also the chance of simple accident, and something that size would be pretty messy if it collapsed, so you'll need security measures well beyond the norm.

It is lighter than a feather. Everything above the breaking point - i.e. most of it - would fly off into space. The rest would float down, the top bits likely burning up in the atmosphere, and the rest could just be spooled in as it went down, more than likely.

Honestly, the biggest danger to it breaking would be the financial cost of rebuilding it.

Grey Wolf

[Eldan]

Still waiting for flying cars to become common. And for that we actually have working prototypes, but there's just too many "big impractilities".

There's also the bit where it's not enough to build the space elevator. You need to keep it in one piece. But we live in a time where terrorists easily get all sorts of bombs and rocket launchers, and a space elevator would be the biggest target in human history.

Even assuming nobody blows it up willingly, there's also the chance of simple accident, and something that size would be pretty messy if it collapsed, so you'll need security measures well beyond the norm.

I still think people just have too many requirements for a flying car. And they keep adding more. They seem to want a helicopter which is silent, safe, shaped like a car instead of aerodynamic and no harder to control than an actual car. And also transports five people and their luggage, like a car.

[deuterio12]

This "danger" is way overblown. The standard plan is to put it in the middle of the Pacific. Terrorists would not have an easy access to it. Much less with high explosives or rocket launchers.

The middle of the pacific, aka international waters, how exactly are you going to enforce any kind of perimeter?

It is lighter than a feather. Everything above the breaking point - i.e. most of it - would fly off into space. The rest would float down, the top bits likely burning up in the atmosphere, and the rest could just be spooled in as it went down, more than likely.

Just what we need, more space debris in orbit hitting satellites/space stations and being a danger to future missions.

Honestly, the biggest danger to it breaking would be the financial cost of rebuilding it.

That alone is pretty big, since the only advantage of building it is saving costs, but that demands holding in one piece for quite a bit of time.

I still think people just have too many requirements for a flying car. And they keep adding more. They seem to want a helicopter which is silent, safe, shaped like a car instead of aerodynamic and no harder to control than an actual car. And also transports five people and their luggage, like a car.

Well of course they call it flying car because it's supposed to have all the advantages of a car plus flying.

But point still stands, we've had flying vehicles for decades now and nobody managed to develop a proper personal version anybody can just afford and use inside a city. People were expecting jetpacks and true hoverboards and whatnot too by now.

[pendell]

Here's Obayashi's concept , dated 2014. There are considerably more details but they do note the technology is not currently in place to allow them to implement the plan. I'll throw it out to the group as to whether the projected technological advances are realistic in the time frame or not.

They are conducting an elementary test this year.

A team of researchers from Japan's Shizuoka University and other institutions will conduct the first test in space this month as part of a project to build a space elevator, Japan's The Mainichi reported last week. The space elevator essentially ferries people and cargo shipments in an elevator car travelling on a cable connecting Earth to a space station.

This test is the first exploring the movement of a container on a cable in space. Two ultra-small cubic satellites measuring 10 centimeters on each side connected by a steel cable about 10 metres long will be carried from Kagoshima's Tanegashima Space Center to the International Space Station on Sept. 11.

From there, the connected satellites will be launched and a motorised container acting as an elevator car will travel along the cable and have its journey recorded via a camera attached to the satellites.

Details on the Chinese plan are far more sketchy , which I suppose is not surprising.

Respectfully,

Brian P.

[Grey_Wolf_c]

The middle of the pacific, aka international waters, how exactly are you going to enforce any kind of perimeter?

The same way you enforce any other perimeter. Except it is easier to tell who is and isn't supposed to be there.

Just what we need, more space debris in orbit hitting satellites/space stations and being a danger to future missions.

Yes, because the problem here is that debris of this and not of everything else. Do you object to every rocket launch on that basis, or are you simply grasping at straws?

Also: flies off into space. Not "sticks around in close Earth Orbit".

That alone is pretty big, since the only advantage of building it is saving costs, but that demands holding in one piece for quite a bit of time.

If this one is "pretty big", why didn't you bring it up in the first place?

No, you are just grasping at straws.

Here's Obayashi's concept , dated 2014. There are considerably more details but they do note the technology is not currently in place to allow them to implement the plan. I'll throw it out to the group as to whether the projected technological advances are realistic in the time frame or not.

Same issue: depends on the unproven existence of a 150 GPa tensile strength tether material capable of being built up to 100000 km long. The details are there, but they are the same details from the wiki page: start with a single thread deployed, and build it up with climbers. Nothing really new, unfortunately.

Grey Wolf

[halfeye]

The last time I heard about this, the "cable" was going to have to be about a mile wide at it's widest point (which is quite near to the Earth (about the top of the atmosphere?)), just to support it's own weight. It's not going to happen with even the best materials we have now.

[Grey_Wolf_c]

The last time I heard about this, the "cable" was going to have to be about a mile wide at it's widest point (which is quite near to the Earth (about the top of the atmosphere?)), just to support it's own weight. It's not going to happen with even the best materials we have now.

Errr... no? The current designs won't use tapering at all - the ribbon will be equal thickness all the way through, as far as I know. And in any case it would be widest at geostationary orbit (that's where the center of mass needs to be), which is 35000 km away, well outside the atmosphere (100 km).

ETA: it is hard to find the width of the ribbon, but we're talking less than a meter, as far as I can tell.

ETA2: See this paper

Grey Wolf

[factotum]

Also: flies off into space. Not "sticks around in close Earth Orbit".

With a space elevator, if it snapped for some reason then the part attached to the ground would totally fall down into the atmosphere, not off into space...for a start, it can't fly off into space because it's attached to the ground!

[Grey_Wolf_c]

With a space elevator, if it snapped for some reason then the part attached to the ground would totally fall down into the atmosphere, not off into space...for a start, it can't fly off into space because it's attached to the ground!

That's what I said:

It is lighter than a feather. Everything above the breaking point - i.e. most of it - would fly off into space. The rest would float down, the top bits likely burning up in the atmosphere, and the rest could just be spooled in as it went down, more than likely.

Of that, I'm only uncertain about the spooling it in bit (this assumes the breaking is caused by space debris shearing it - thus my comment about "most of it").

Grey Wolf

[Grey_Wolf_c]

The requirements for a lunar space elevator are utterly insane, and unlikely to ever occur without some kind of coplanar orbital ring as some kind of "please don't think about these numbers"-sized interface.

That's not a space elevator. This is a lunar space elevator. It could be built out of kevlar.

Grey Wolf

[halfeye]

Errr... no? The current designs won't use tapering at all - the ribbon will be equal thickness all the way through, as far as I know. And in any case it would be widest at geostationary orbit (that's where the center of mass needs to be), which is 35000 km away, well outside the atmosphere (100 km).

ETA: it is hard to find the width of the ribbon, but we're talking less than a meter, as far as I can tell.

ETA2: See this paper

Grey Wolf

Yeah, wikipedia seems to say a tapering one would be widest at geostationary orbit, that's odd, I distinctly remember it tapering dramatically from about the top of the atmosphere, maybe it gets more slowly wider from there upward.

I do like the idea of space elevators, but I'm pretty sure we can't make them yet. I'm convinced that for loads that weigh more than an ounce, the maximum thickness (or overall thickness if untapered, you're not going to make it narrower by not tapering it), is going to be much more than a metre (if a ribbon, cross sectional area equal to more than a metre squared).

[Grey_Wolf_c]

Yeah, wikipedia seems to say a tapering one would be widest at geostationary orbit, that's odd, I distinctly remember it tapering dramatically from about the top of the atmosphere, maybe it gets more slowly wider from there upward.

I do like the idea of space elevators, but I'm pretty sure we can't make them yet. I'm convinced that for loads that weigh more than an ounce, the maximum thickness (or overall thickness if untapered, you're not going to make it narrower by not tapering it), is going to be much more than a metre (if a ribbon, cross sectional area equal to more than a metre squared).

Err... the paper I linked to is from 2006 (so recent, as these things go) and with tapering, it is 5-12 cm wide. The thickness of the ribbon is measured in microns. If you disagree, by all means present your own math.

Grey Wolf

[halfeye]

Err... the paper I linked to is from 2006 (so recent, as these things go) and with tapering, it is 5-12 cm wide. The thickness of the ribbon is measured in microns. If you disagree, by all means present your own math.

Grey Wolf

I don't have maths, but I am sceptical of that paper. It says an early proposal was 5 to 11.5 cm wide, there isn't any sign of a mass of the climber for that, so maybe it's a prototype with a one ounce climber?

I remember a lot of discussions of this, it's something that we ought to do sometime, but as you say carbon nanotubes aren't ready yet, and I really doubt it can ever be that thin.

[Lvl 2 Expert]

Yeah, wikipedia seems to say a tapering one would be widest at geostationary orbit, that's odd, I distinctly remember it tapering dramatically from about the top of the atmosphere, maybe it gets more slowly wider from there upward.

The tapering would be to make the cable stronger. The lowest point isn't weighed down by a lot of cable beneath it, so it doesn't need to be as strong. As you get really high up you probably also need less strength again because you're getting close to geosynchronous orbit and thus weightlessness. Where the weight needs to be in order to stay in orbit can be adjusted through other means, like a counterweight station. The weight distribution will cause all sorts of stresses in any scenario which the cable also needs to be able to stand up to, but the cable might also need to be able to be swung out of the way of meteorites, so it's pretty exotic and strong material in any case.

[Tvtyrant]

What do you think the chances are a trillion dollar space elevator is going to be knocked out by a 10K rocket? Any system that relies on an exposed super structure that by its nature doesn't stay in one place is going to have security problems.

Put it over the south pole maybe?

[Grey_Wolf_c]

What do you think the chances are a trillion dollar space elevator is going to be knocked out by a 10K rocket? Any system that relies on an exposed super structure that by its nature doesn't stay in one place is going to have security problems.

Put it over the south pole maybe?

You can't. It has to be on the equator, or very close to it.

The chances of randomly being hit by a rocket are practically nil. If you mean "targeted with ICBM", then still quite a hard problem, because as I have been saying, this is a very narrow target. They could aim at the station on the other end, but the ISS has survived so far, I don't see why this would be any different.

Also: not even close to a trillion dollars. Price tag is expected in the tens of billions

Grey Wolf

[Knaight]

The chances of randomly being hit by a rocket are practically nil. If you mean "targeted with ICBM", then still quite a hard problem, because as I have been saying, this is a very narrow target. They could aim at the station on the other end, but the ISS has survived so far, I don't see why this would be any different.

You can just blow something up in the air nearby - it's really not a hard target to shoot down, and it relies on the usual day to day defenses. The vast majority of stuff can't survive a missile strike, and just needs nobody to choose to fire missiles at it. It's the same way that every time you walk down the sidewalk you're relying on everyone driving to choose not to veer out and hit you.

Personally, I'm reasonably confident in this line of defense.

[Mando Knight]

If you mean "targeted with ICBM", then still quite a hard problem, because as I have been saying, this is a very narrow target.

An ICBM would make destroying the setup child's play--all of those are loaded with nuclear weapons, so you don't need to actually hit the elevator cable itself (even if they do manage to make it astonishingly thin), you just need to detonate the warhead nearby. It would also easily be capable of destroying the counterweight station itself if the flight path was calibrated for an orbital target instead of something on or near the ground.

Of course, if someone is both willing and able to fire an armed ICBM at a target, you have much bigger problems than losing an expensive space station--you'd be in the middle of a global thermonuclear war.

[Tvtyrant]

You can just blow something up in the air nearby - it's really not a hard target to shoot down, and it relies on the usual day to day defenses. The vast majority of stuff can't survive a missile strike, and just needs nobody to choose to fire missiles at it. It's the same way that every time you walk down the sidewalk you're relying on everyone driving to choose not to veer out and hit you.

Personally, I'm reasonably confident in this line of defense.

Most targets don't cost billions of dollars and consist of thin cables hanging in the air. We also loses tens of thousands of people to exactly your scenario a year, and we are a lot cheaper then space elevators.