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The Quest to Build an Elevator into Space

58 points by Thevet 12y ago

lotsofmangos 12y ago
I been trying to think about this from a different angle and have been trying to work out how long you could make a self-supporting fuel and oxygen line by putting a lightweight triangular gantry with three small adjustable rocket engines and a fuel pump every hundred meters or so. This wouldn't need stupid materials as it would not be under the same tensile loads, but it will have a maximum length that depends on overall fuel consumption of the structure vs the flow rate of pipe you can haul. Also, it would be constantly burning fuel, so it has pretty high running costs. edit - you could also make an electric version of the same thing that pumps a reaction mass like water, but then you need to be able to fire it very fast out of the nozzles otherwise the water line becomes unwieldy very quickly, so I figured using chemical fuel might make things simpler.
- civilian 12y ago
  Yeahhhhhh that is not an effective strategy at all. Rockets upon rockets. It sounds like an idea hatched in Kerbal Space Program. The best "ground powered" structure would be the space fountain: http://en.wikipedia.org/wiki/Space_fountain http://en.wikipedia.org/wiki/Space_fountain
  - lotsofmangos 12y ago
    Back of an envelope calculations seem to indicate that a 200km one is possibly feasible using normal petrol, tho I wouldn't like to bet on geostationary. The space fountain has it's own issues, such as engineering the deflector and making the giant electromagnetic tube. What I am suggesting is far simpler. edit - and the I had the idea before Kerbal came out, so if it is total madness, I promise you they are not to blame.
- stcredzero 12y ago
  There was an informal JPL study that was posted to rec.arts.sf.science a very long time ago, that found that a 100km high exponentially tapering tower could be practically built by using highly pressurized balloon tanks of boron. (Practical meaning, conceivably affordable by a superpower, with a chance in hell of actually happening.) People have also studied using dynamically supported structures. We could probably build the Lofstrom Loop and it would bring the cost of going into LEO to space elevator levels. http://en.wikipedia.org/wiki/Launch_loop http://en.wikipedia.org/wiki/Launch_loop Still, not a chance in hell of it happening in the US. China might be crazy enough to build it.
virtue3 12y ago
I think the counter argument to the space elevator magic material was always that if you could make something that light and that strong... use it to make cheaper/lighter rockets.
- Florin_Andrei 12y ago
  The energy per kilogram lifted to orbit is vastly different. It's order(s) of magnitude cheaper (in terms of energy) to lift stuff into orbit. Making the rocket from lighter materials won't matter, since the rocket is almost entirely fuel anyway.
  - virtue3 12y ago
    The issue with rockets is that it takes x amount of fuel to get to your destination once in orbit and x amount of fuel to get the craft and the destination fuel to orbit. It's why rockets generally work best in stages (you just drop the extra support structure needed for the fuel). It's really an exponential problem. Every lb of infrastructure you remove from the rocket makes it _much_ more practical. See my comment above about having magic space elevator materials available anyway. Steam rockets and the like start to seem very practical at that point. And probably less insane than a cable all the way to space.
- shalmanese 12y ago
  The Space Shuttle is already 96% propellant to 4% structure (http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html http://www.nasa.gov/mission_pages/station/expeditions/expedi...). You're going to get much appreciable gains from lighter rockets.
  - virtue3 12y ago
    I was being kind of sparse in details, sorry. Having a material that can self support itself into orbit can potentially unlock practical variations of: http://en.wikipedia.org/wiki/Steam_rocket http://en.wikipedia.org/wiki/Steam_rocket whose main problem is: The simplest design has a pressurised water tank where the water is heated before launch, however, this gives a very low exhaust velocity since the high latent heat of vapourisation means that very little actual steam is produced and the exhaust consists mostly of water, or if high temperatures and pressures are used, then the tank is very heavy. Although, that would also require the material to be very heat resistant as well. Which might be problematic. Compressed air might also work at that sort of level of material as well. At least for initial launch stages until you need to switch over to another type of propellant (or a more controllable engine).
hyp0 12y ago
Wait... most of the energy of going into orbit is in accelerating to orbital speed (lateral), not getting away from earth (vertical). An elevator's top, in a geosynchronous orbit) rotates much faster than the bottom (describing a larger circle, covered in the same time). Therefore, a payload moving up the elevator would either need to be accelerated laterally somehow, or it would bend the elevator over. There's no getting away from needing the energy for lateral acceleration - it must be supplied somehow. Piping fuel up (instead of blasting it up in a rocket) may be more efficient, but consider that its mass too will need lateral acceleration. \edit Fuel in the form of electricity plus reaction mass, to be sent at extremely high velocity, would probably have the least mass, and so minimize this effect (I think, high voltage electricity, to reduce the current, because the electron mass itself may have an effect at these scales!). Another alternative, for the reaction mass, is earth-encompassing rings at different altitudes. You can accelerate it without throwing it away. Of course, at lower altitudes, you can just use air... maybe there's even enough (for this purpose) at quite high altitudes... Finally, I think the basic solution has been a counter-weight: as one goes up (needs to speed up to orbital velocity), one comes down (needs to slow down from orbital velocity). If it was just one elevator each, the accelerations would be imparted at different points, twisting the evelator. But I guess a series of elevators - or even a continous elevator (like a conveyer-belt... or escalator...) would smoothen out this effect as much as you like, and only needs electricity to power it... and, any acceleration of the electron mass would also balance out, because they also go up and down in a circuit (or down and up for space solar panels). Sorry, nothing to see here. EDIT I see now a reply mentions this solution, upvoted.
- Florin_Andrei 12y ago
  What if there's constant up/down traffic on two opposite sides of the ribbon? Wouldn't ascending cars try to pull the ribbon "back" (from orbital direction), whereas descending cars would try to push the ribbon "forward"? I'm pretty tired now and I can't think very well, but my gut feeling tells me the two effects would compensate each other to a pretty large fraction of 100%.
  - desdiv 12y ago
gpsx 12y ago
So what happens if the cable snaps? I assume this would happen at the height of a geostationary orbit where tension is the highest. And this is an ungodly tension so I assume it would be pretty violent. On top of that the cable will not fall straight down because the top of the cable is traveling much faster than the bottom (you could view this as the coriolis effect). It seems you would have 22,236 miles of cable wrapping itself around the earth.
- badsock 12y ago
  It's more of a ribbon than a cable - it would float gently down.
  - gpsx 12y ago
    The tip would be going over 5000 mph relative to earth, not including the speed because of the snap. I don't know if it would float gently, but it probably would burn up once it hit the atmosphere.
- 3rd3 12y ago
  http://gassend.net/spaceelevator/breaks/ http://gassend.net/spaceelevator/breaks/ https://en.wikipedia.org/wiki/Space_elevator_safety https://en.wikipedia.org/wiki/Space_elevator_safety
geuis 12y ago
When I talk about this and people ask why, and when people comment "why", this is my response. The space elevator is the Panama Canal of our time. People dreamed of building it for close to a hundred years before it was finally achieved. Multiple companies and countries tried and failed. Once it was achieved, it changed the world. This is so much more important. Instead of just linking two hemispheres, the space elevator opens up all of space to us. It's like the Bering land bridge 20k years ago or first cheap ships that could reliably cross the Atlantic. It's all of those things a thousand fold.
nathanathan 12y ago
I would like to know if electromagnetic flux pinning is strong enough to use instead of a cable. I'm imagining a scenario where pairs of rotating superconductor panels in orbit lift a giant solenoid into space by flux pinning its magnetic field as they rotate upwards.
- adaml_623 12y ago
  You're probably going to have to draw a diagram to get your basic concept across a wee bit better.
  - nathanathan 12y ago
    I've asked about the concept here as well: http://forums.xkcd.com/viewtopic.php?f=18&t=109979 http://forums.xkcd.com/viewtopic.php?f=18&t=109979 I suggested a two designs and the one I mentioned on hn has an ascii drawing about halfway down the page.
Sebpereira 12y ago
I believe lifting cargo outside orbit is not the greatest strength of an orbital elevator, instead it most useful feature would be on gathering sun rays which have not been diminished by the atmosphere. But there are many challenges to achieve that: http://io9.com/5984371/why-well-probably-never-build-a-space-elevator http://io9.com/5984371/why-well-probably-never-build-a-space...
- jessriedel 12y ago
  The atmosphere only attenuates sunlight by a factor of order unity. Won't it always be much, much cheaper to build slightly larger solar panels?
weavejester 12y ago
An alternative to a full space elevator is the rotovator or rotating sky hook. Instead of building a single tethered cable that reaches up to geostationary orbit, you instead build shorter, untethered cables that rotate end over end in their orbit. These structures can then be used to assist conventional rockets. Place a rotovator in low orbit, then send up a suborbital rocket to hook onto the end of the cable when at its lowest point. Detach half a rotation later, and the rocket is flung into a higher orbit. There's a more detailed discussion here: https://www.reddit.com/r/technology/comments/2h07ku/japanese_company_obayashi_announces_plans_to_have/ckoc2j6 https://www.reddit.com/r/technology/comments/2h07ku/japanese...
- 3rd3 12y ago
  https://en.wikipedia.org/wiki/Momentum_exchange_tether https://en.wikipedia.org/wiki/Momentum_exchange_tether
trhway 12y ago
i wonder why before various unobtanium requiring structures we wouldn't try some rail/coil gun in a [close to] vacuum tube going several kilometers up a mountain. After all, 2000 years ago it was possible to build that http://en.wikipedia.org/wiki/Roman_aqueduct http://en.wikipedia.org/wiki/Roman_aqueduct , so building something like it up the Kilimanjaro (or any other mountain near equator like this http://en.wikipedia.org/wiki/Nevado_Sajama http://en.wikipedia.org/wiki/Nevado_Sajama) should be pretty doable today. Or how about just this http://en.wikipedia.org/wiki/Project_Babylon http://en.wikipedia.org/wiki/Project_Babylon for starters - was worked on by a guy who knew what he was doing: "The barrel was to be 156 metres (512 feet) long, with a bore of 1 metre (3.3 feet).[3] Originally intended to be suspended by cables from a steel framework, it would have been over 100 metres (300 feet) high at the tip. The complete device weighed about 2,100 tonnes (the barrel alone weighed 1,655 tons). It was a space gun intended to shoot projectiles into orbit, a theme of Bull's work since Project HARP."
- tfgg 12y ago
  One cool proposal is StarTram [1], which has a long (100km+) maglev run in an evacuated tunnel to a linear accelerator up the side of a mountain, ending in a magnetohydrodynamic "window" to keep the atmosphere out, launching out the end fast enough to reach orbit. The acceleration of the first plan (30g) is too much for humans, so it'd initially be for cargo only. The second stage is a crazy-awesome magnetically levitated tube that exits at an altitude of 22km, and gives low enough accelerations that a human could survive. [1] https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram
- aruggirello 12y ago
  Nice, somewhat like Jules Verne's From the Earth to the Moon's: http://en.wikipedia.org/wiki/From_the_Earth_to_the_Moon http://en.wikipedia.org/wiki/From_the_Earth_to_the_Moon
- 3rd3 12y ago
  https://en.m.wikipedia.org/wiki/Spacegun#Technical_issues https://en.m.wikipedia.org/wiki/Spacegun#Technical_issues
DennisP 12y ago
People got enthused about this after Brad Edwards, mentioned in the article, led a NASA study on space elevators about a decade ago, which found it to be surprisingly feasible. Here's their final report (pdf): http://www.niac.usra.edu/files/studies/final_report/521Edwards.pdf http://www.niac.usra.edu/files/studies/final_report/521Edwar... The material would be carbon nanotubes a couple centimeters long, bound together by a reasonably strong epoxy. They estimate a cost in the low tens of billions of dollars, by using seven shuttle flights to deploy a minimal elevator, and using that to pull up additional elevator material. They examine a lot of practical issues and find solutions for them.
- noir_lord 12y ago
  We live in a world where an individual has the resources to make a credible stab at a space elevator....that is amazing.
deleted 12y ago
[deleted]

58 points by Thevet 12y ago

I been trying to think about this from a different angle and have been trying to work out how long you could make a self-supporting fuel and oxygen line by putting a lightweight triangular gantry with three small adjustable rocket engines and a fuel pump every hundred meters or so. This wouldn't need stupid materials as it would not be under the same tensile loads, but it will have a maximum length that depends on overall fuel consumption of the structure vs the flow rate of pipe you can haul. Also, it would be constantly burning fuel, so it has pretty high running costs. edit - you could also make an electric version of the same thing that pumps a reaction mass like water, but then you need to be able to fire it very fast out of the nozzles otherwise the water line becomes unwieldy very quickly, so I figured using chemical fuel might make things simpler.

civilian 12y ago
Yeahhhhhh that is not an effective strategy at all. Rockets upon rockets. It sounds like an idea hatched in Kerbal Space Program. The best "ground powered" structure would be the space fountain: http://en.wikipedia.org/wiki/Space_fountain http://en.wikipedia.org/wiki/Space_fountain
- lotsofmangos 12y ago
  Back of an envelope calculations seem to indicate that a 200km one is possibly feasible using normal petrol, tho I wouldn't like to bet on geostationary. The space fountain has it's own issues, such as engineering the deflector and making the giant electromagnetic tube. What I am suggesting is far simpler. edit - and the I had the idea before Kerbal came out, so if it is total madness, I promise you they are not to blame.
stcredzero 12y ago
There was an informal JPL study that was posted to rec.arts.sf.science a very long time ago, that found that a 100km high exponentially tapering tower could be practically built by using highly pressurized balloon tanks of boron. (Practical meaning, conceivably affordable by a superpower, with a chance in hell of actually happening.) People have also studied using dynamically supported structures. We could probably build the Lofstrom Loop and it would bring the cost of going into LEO to space elevator levels. http://en.wikipedia.org/wiki/Launch_loop http://en.wikipedia.org/wiki/Launch_loop Still, not a chance in hell of it happening in the US. China might be crazy enough to build it.

virtue3 12y ago

I think the counter argument to the space elevator magic material was always that if you could make something that light and that strong... use it to make cheaper/lighter rockets.

Florin_Andrei 12y ago
The energy per kilogram lifted to orbit is vastly different. It's order(s) of magnitude cheaper (in terms of energy) to lift stuff into orbit. Making the rocket from lighter materials won't matter, since the rocket is almost entirely fuel anyway.
- virtue3 12y ago
  The issue with rockets is that it takes x amount of fuel to get to your destination once in orbit and x amount of fuel to get the craft and the destination fuel to orbit. It's why rockets generally work best in stages (you just drop the extra support structure needed for the fuel). It's really an exponential problem. Every lb of infrastructure you remove from the rocket makes it _much_ more practical. See my comment above about having magic space elevator materials available anyway. Steam rockets and the like start to seem very practical at that point. And probably less insane than a cable all the way to space.
shalmanese 12y ago
The Space Shuttle is already 96% propellant to 4% structure (http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html http://www.nasa.gov/mission_pages/station/expeditions/expedi...). You're going to get much appreciable gains from lighter rockets.
- virtue3 12y ago
  I was being kind of sparse in details, sorry. Having a material that can self support itself into orbit can potentially unlock practical variations of: http://en.wikipedia.org/wiki/Steam_rocket http://en.wikipedia.org/wiki/Steam_rocket whose main problem is: The simplest design has a pressurised water tank where the water is heated before launch, however, this gives a very low exhaust velocity since the high latent heat of vapourisation means that very little actual steam is produced and the exhaust consists mostly of water, or if high temperatures and pressures are used, then the tank is very heavy. Although, that would also require the material to be very heat resistant as well. Which might be problematic. Compressed air might also work at that sort of level of material as well. At least for initial launch stages until you need to switch over to another type of propellant (or a more controllable engine).

hyp0 12y ago

Wait... most of the energy of going into orbit is in accelerating to orbital speed (lateral), not getting away from earth (vertical). An elevator's top, in a geosynchronous orbit) rotates much faster than the bottom (describing a larger circle, covered in the same time). Therefore, a payload moving up the elevator would either need to be accelerated laterally somehow, or it would bend the elevator over. There's no getting away from needing the energy for lateral acceleration - it must be supplied somehow. Piping fuel up (instead of blasting it up in a rocket) may be more efficient, but consider that its mass too will need lateral acceleration. \edit Fuel in the form of electricity plus reaction mass, to be sent at extremely high velocity, would probably have the least mass, and so minimize this effect (I think, high voltage electricity, to reduce the current, because the electron mass itself may have an effect at these scales!). Another alternative, for the reaction mass, is earth-encompassing rings at different altitudes. You can accelerate it without throwing it away. Of course, at lower altitudes, you can just use air... maybe there's even enough (for this purpose) at quite high altitudes... Finally, I think the basic solution has been a counter-weight: as one goes up (needs to speed up to orbital velocity), one comes down (needs to slow down from orbital velocity). If it was just one elevator each, the accelerations would be imparted at different points, twisting the evelator. But I guess a series of elevators - or even a continous elevator (like a conveyer-belt... or escalator...) would smoothen out this effect as much as you like, and only needs electricity to power it... and, any acceleration of the electron mass would also balance out, because they also go up and down in a circuit (or down and up for space solar panels). Sorry, nothing to see here. EDIT I see now a reply mentions this solution, upvoted.

Florin_Andrei 12y ago
What if there's constant up/down traffic on two opposite sides of the ribbon? Wouldn't ascending cars try to pull the ribbon "back" (from orbital direction), whereas descending cars would try to push the ribbon "forward"? I'm pretty tired now and I can't think very well, but my gut feeling tells me the two effects would compensate each other to a pretty large fraction of 100%.
- desdiv 12y ago

gpsx 12y ago

So what happens if the cable snaps? I assume this would happen at the height of a geostationary orbit where tension is the highest. And this is an ungodly tension so I assume it would be pretty violent. On top of that the cable will not fall straight down because the top of the cable is traveling much faster than the bottom (you could view this as the coriolis effect). It seems you would have 22,236 miles of cable wrapping itself around the earth.

badsock 12y ago
It's more of a ribbon than a cable - it would float gently down.
- gpsx 12y ago
  The tip would be going over 5000 mph relative to earth, not including the speed because of the snap. I don't know if it would float gently, but it probably would burn up once it hit the atmosphere.
3rd3 12y ago
http://gassend.net/spaceelevator/breaks/ http://gassend.net/spaceelevator/breaks/ https://en.wikipedia.org/wiki/Space_elevator_safety https://en.wikipedia.org/wiki/Space_elevator_safety

geuis 12y ago

When I talk about this and people ask why, and when people comment "why", this is my response. The space elevator is the Panama Canal of our time. People dreamed of building it for close to a hundred years before it was finally achieved. Multiple companies and countries tried and failed. Once it was achieved, it changed the world. This is so much more important. Instead of just linking two hemispheres, the space elevator opens up all of space to us. It's like the Bering land bridge 20k years ago or first cheap ships that could reliably cross the Atlantic. It's all of those things a thousand fold.

nathanathan 12y ago

I would like to know if electromagnetic flux pinning is strong enough to use instead of a cable. I'm imagining a scenario where pairs of rotating superconductor panels in orbit lift a giant solenoid into space by flux pinning its magnetic field as they rotate upwards.

adaml_623 12y ago
You're probably going to have to draw a diagram to get your basic concept across a wee bit better.
- nathanathan 12y ago
  I've asked about the concept here as well: http://forums.xkcd.com/viewtopic.php?f=18&t=109979 http://forums.xkcd.com/viewtopic.php?f=18&t=109979 I suggested a two designs and the one I mentioned on hn has an ascii drawing about halfway down the page.

Sebpereira 12y ago

I believe lifting cargo outside orbit is not the greatest strength of an orbital elevator, instead it most useful feature would be on gathering sun rays which have not been diminished by the atmosphere. But there are many challenges to achieve that: http://io9.com/5984371/why-well-probably-never-build-a-space-elevator http://io9.com/5984371/why-well-probably-never-build-a-space...

jessriedel 12y ago
The atmosphere only attenuates sunlight by a factor of order unity. Won't it always be much, much cheaper to build slightly larger solar panels?

weavejester 12y ago

An alternative to a full space elevator is the rotovator or rotating sky hook. Instead of building a single tethered cable that reaches up to geostationary orbit, you instead build shorter, untethered cables that rotate end over end in their orbit. These structures can then be used to assist conventional rockets. Place a rotovator in low orbit, then send up a suborbital rocket to hook onto the end of the cable when at its lowest point. Detach half a rotation later, and the rocket is flung into a higher orbit. There's a more detailed discussion here: https://www.reddit.com/r/technology/comments/2h07ku/japanese_company_obayashi_announces_plans_to_have/ckoc2j6 https://www.reddit.com/r/technology/comments/2h07ku/japanese...

3rd3 12y ago
https://en.wikipedia.org/wiki/Momentum_exchange_tether https://en.wikipedia.org/wiki/Momentum_exchange_tether

trhway 12y ago

i wonder why before various unobtanium requiring structures we wouldn't try some rail/coil gun in a [close to] vacuum tube going several kilometers up a mountain. After all, 2000 years ago it was possible to build that http://en.wikipedia.org/wiki/Roman_aqueduct http://en.wikipedia.org/wiki/Roman_aqueduct , so building something like it up the Kilimanjaro (or any other mountain near equator like this http://en.wikipedia.org/wiki/Nevado_Sajama http://en.wikipedia.org/wiki/Nevado_Sajama) should be pretty doable today. Or how about just this http://en.wikipedia.org/wiki/Project_Babylon http://en.wikipedia.org/wiki/Project_Babylon for starters - was worked on by a guy who knew what he was doing: "The barrel was to be 156 metres (512 feet) long, with a bore of 1 metre (3.3 feet).[3] Originally intended to be suspended by cables from a steel framework, it would have been over 100 metres (300 feet) high at the tip. The complete device weighed about 2,100 tonnes (the barrel alone weighed 1,655 tons). It was a space gun intended to shoot projectiles into orbit, a theme of Bull's work since Project HARP."

tfgg 12y ago
One cool proposal is StarTram [1], which has a long (100km+) maglev run in an evacuated tunnel to a linear accelerator up the side of a mountain, ending in a magnetohydrodynamic "window" to keep the atmosphere out, launching out the end fast enough to reach orbit. The acceleration of the first plan (30g) is too much for humans, so it'd initially be for cargo only. The second stage is a crazy-awesome magnetically levitated tube that exits at an altitude of 22km, and gives low enough accelerations that a human could survive. [1] https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram
aruggirello 12y ago
Nice, somewhat like Jules Verne's From the Earth to the Moon's: http://en.wikipedia.org/wiki/From_the_Earth_to_the_Moon http://en.wikipedia.org/wiki/From_the_Earth_to_the_Moon
3rd3 12y ago
https://en.m.wikipedia.org/wiki/Spacegun#Technical_issues https://en.m.wikipedia.org/wiki/Spacegun#Technical_issues

DennisP 12y ago

People got enthused about this after Brad Edwards, mentioned in the article, led a NASA study on space elevators about a decade ago, which found it to be surprisingly feasible. Here's their final report (pdf): http://www.niac.usra.edu/files/studies/final_report/521Edwards.pdf http://www.niac.usra.edu/files/studies/final_report/521Edwar... The material would be carbon nanotubes a couple centimeters long, bound together by a reasonably strong epoxy. They estimate a cost in the low tens of billions of dollars, by using seven shuttle flights to deploy a minimal elevator, and using that to pull up additional elevator material. They examine a lot of practical issues and find solutions for them.

noir_lord 12y ago
We live in a world where an individual has the resources to make a credible stab at a space elevator....that is amazing.

deleted 12y ago

[deleted]