4 ms·

Here's something that I've been mulling around for some time: Instead of a vertical structure, as pretty much every single space elevator contains, why not mak

Here's something that I've been mulling around for some time: Instead of a vertical structure, as pretty much every single space elevator contains, why not make one that is tangential to the surface of the planet? Yes, it will be substantially more materials, but if made such that the 'tail' of the elevator is trailing the rotation of the planet, it might be partially self sustaining. (Think of a string attached to the edge of a merry-go-round whipping outwards) One would literally pick a point on the planet and build due west. Due to the curvature of the planet, after X number of miles, you'll be several miles up in the air. Is this not anymore farfetched than a 100km tall tower?

celticninja 11y ago
so the spining of the earth would propel your cargo up/down the elevator into orbit? One thing is that west, east, north, soyth up and down are really on relevant on earth. As soon as you are talking about space everything is up(or down) but in relaity regardless of which whay yo go to get there you are fighting against gravity. I assuem this would be the reason your idea would not work but i may be wrong.
delinka 11y ago
Think of going vertical like just attaching a line to a geostationary satellite (but one in much lower orbit.) Now put a larger mass where the satellite is. It's supposed to be like putting a ball on a string and flinging it about in circles - the mass (ball, station) actually helps hold the connector (tether, tower, cable, w/e) "up" while counterweighting against the central anchor (your hand, earth.) There's no drag in space, so trailing Earth's rotation isn't necessary.
- jdblair 11y ago
  You can't have a geostationary satellite in "much lower orbit." The orbital period of a satellite is set by its altitude. A lower orbit means a shorter period. Since a geostationary satellite is one with an orbit above the equator and a period of 1 day, so its orbit matches the earth, and the period is set by the altitude, a geostationary satellite can only exist in one orbit. That's why the geostationary band is getting a bit crowded.
deleted 11y ago
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berntb 11y ago
Old idea, people has been talking about railroad tracks up a mountain for a long time. (I'm hellbanned, but this might have been banned anyway. :-) )
vidarh 11y ago
Grab a plank or any other long, relatively firm object. Hold it straight out to your side. Now hold it straight up. Now you see why it is more far fetched. (Edit: actually, just try it with your own arm for 30 seconds or so) Not only is it far harder, but it doesn't take much length before even quite solid objects will start bending massively and exerting far more stress. E.g. doesn't take more than 150kg or so before the steel weight bars at my gym has a noticeable bend. We still do not have materials technology advanced enough for a regular space elevator. Trying build one where gravity is actively working in a direction where there's no support seems unlikely to help matters.
- tomswartz07 11y ago
  Surely. I didn't necessarily mean a free-standing object that was anchored at only the base. Another commenter pointed out a project very similar to what I was thinking: StarTram: https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram It has supports and launches the vehicle using maglev; basically a big, tangential, spaceship cannon that launches into orbit using fixed structures.
  - echelon 11y ago
    Looks similar to the "launch loop" concept. https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop
  - riemannzeta 11y ago
    Heinlein had a similar idea, which he described in The Moon is a Harsh Mistress http://www.quora.com/How-feasible-would-the-catapults-from-the-moon-is-a-harsh-mistress-by-Robert-Heinlein-be http://www.quora.com/How-feasible-would-the-catapults-from-t...
    - logfromblammo 11y ago
      The moon also has lower escape velocity than Earth. Lower lunar gravity makes every method of reaching orbit easier.
TheLoneWolfling 11y ago
Yes, substantially so. First off, the way stresses work it is substantially easier to build straight up than in any other direction. And secondly, you're missing something. Namely, that the only reason why a string attached to an edge of a merry-go-round whips tangentially is because of air resistance. In a vacuum, or if the air was moving with the merry-go-round, the string would be radially-pointing. (There's also a component of "the merry go round is slowing down", but that also isn't particularly relevant.) As such, it makes no sense to build something this way. About the only case where not building straight up would make sense is if you're slightly off of the equator - in which case you should move to the equator. Although I suspect you have the wrong impression of a space elevator. You don't build up, you build down. You have a satellite / asteroid / etc in geosynchronous orbit. You start spooling out two lengths of wire - one down, one up. When the lower one reaches the surface, you anchor it. Then attach a counterweight out beyond geosynchronous orbit.
- jfoutz 11y ago
  I wonder if it's cheaper to do it with everything moving. a weight with a long cable spinning like Thor's hammer at a given altitude. A payload catches the cable, steals some angular momentum to get kicked up to the next altitude, with the next hammer. If it's close enough to earth, i think the cable will get some induced current, which could spin a gyroscope in the hammerhead, getting some angular momentum back. Actually, i just wonder if this approach has a name, seems like every harebrained idea i've ever had was thought of fifty times before by much smarter people. edit Skyhook! cool.
- abduhl 11y ago
  Actually, building straight down is substantially easier than straight up. You are incorrect with your statement about "the way stresses work". The reason it is substantially easier to build straight up is due to our implicit basis where up is towards space. This is getting rather high level but stresses are actually tensors and hence are dependent on the chosen basis. If your basis has up pointed towards the north then it is substantially easier to build a different direction than up. This may seem like a semantic argument but it is actually an extremely important distinction when discussing any tensor (position, velocity, stresses).
danielweber 11y ago
I think that's https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram. It doesn't have the diagrams I remember, though.
jerf 11y ago
The short answer is, atmosphere. All the designs I've seen for that involve imparting a lot of velocity near the ground where atmosphere is really wrecking up your day. It isn't even the drag necessarily (although that doesn't help), it's the turbulence. You can't expect to reliably hit targets from a significant distance, like hoops, if you're going through the air. If you're on the moon, the idea makes a lot more sense in a lot of ways.
JoeAltmaier 11y ago
Might as well build a railgun launcher at that point?
logfromblammo 11y ago
The supports for the thing are what will kill you. At 1km from the tangent point, you're only 8cm above sea level. At 10km, you're 8m above. So far, so good. At 100km, you're 784m up. At 1000km, that support is 78km tall. The only economical way to do even part of it would be to build an evacuated acceleration track up the side of an existing mountain. The west face of Chimborazo in Ecuador is probably the ideal location for something like that. But you would need to accelerate at 23g for about 283km (51s) in order to reach escape velocity without any additional boost after the launch vehicle exits the track. That would be strictly for unmanned missions. Accelerating at 3g for 283km (139s) to a height of 6268m above equatorial sea level would achieve 4080m/s, of an escape velocity of 11170m/s. You get 465 m/s for free by being near the equator. That leaves a delta-v of 6625 m/s. If your launch vehicle used RS-25 rocket engines, that means an extra 13% of your total launch vehicle mass can be cargo instead of propellant. The acceleration track would effectively substitute for the first stage of a rocket. In order to reach escape velocity externally at 80 km above the equator (7850 m/s), you need 250 seconds at 3g (29.42 m*s^-2) of acceleration, which takes 1850 km. This is why the launch loop uses tethers instead of towers, and supports itself mainly with tension rather than compression.
- meatysnapper 11y ago
  Ecuador really has very good geography for building space-launch structures (9 very large mountains over 5000m). Probably the perfect place to build something, if you were gonna build it.
- vectorjohn 11y ago
  I think an unmanned only launcher is all we need. The reason anything in space is so expensive is not just getting the people up, it's all the shit they need. If we can launch fuel, parts, habitats, etc. for cheap, it would make the rest of space achievable. Achievable-ish.

celticninja 11y ago

so the spining of the earth would propel your cargo up/down the elevator into orbit? One thing is that west, east, north, soyth up and down are really on relevant on earth. As soon as you are talking about space everything is up(or down) but in relaity regardless of which whay yo go to get there you are fighting against gravity. I assuem this would be the reason your idea would not work but i may be wrong.

delinka 11y ago

Think of going vertical like just attaching a line to a geostationary satellite (but one in much lower orbit.) Now put a larger mass where the satellite is. It's supposed to be like putting a ball on a string and flinging it about in circles - the mass (ball, station) actually helps hold the connector (tether, tower, cable, w/e) "up" while counterweighting against the central anchor (your hand, earth.) There's no drag in space, so trailing Earth's rotation isn't necessary.

jdblair 11y ago
You can't have a geostationary satellite in "much lower orbit." The orbital period of a satellite is set by its altitude. A lower orbit means a shorter period. Since a geostationary satellite is one with an orbit above the equator and a period of 1 day, so its orbit matches the earth, and the period is set by the altitude, a geostationary satellite can only exist in one orbit. That's why the geostationary band is getting a bit crowded.

deleted 11y ago

[deleted]

berntb 11y ago

Old idea, people has been talking about railroad tracks up a mountain for a long time. (I'm hellbanned, but this might have been banned anyway. :-) )

vidarh 11y ago

Grab a plank or any other long, relatively firm object. Hold it straight out to your side. Now hold it straight up. Now you see why it is more far fetched. (Edit: actually, just try it with your own arm for 30 seconds or so) Not only is it far harder, but it doesn't take much length before even quite solid objects will start bending massively and exerting far more stress. E.g. doesn't take more than 150kg or so before the steel weight bars at my gym has a noticeable bend. We still do not have materials technology advanced enough for a regular space elevator. Trying build one where gravity is actively working in a direction where there's no support seems unlikely to help matters.

tomswartz07 11y ago
Surely. I didn't necessarily mean a free-standing object that was anchored at only the base. Another commenter pointed out a project very similar to what I was thinking: StarTram: https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram It has supports and launches the vehicle using maglev; basically a big, tangential, spaceship cannon that launches into orbit using fixed structures.
- echelon 11y ago
  Looks similar to the "launch loop" concept. https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop
- riemannzeta 11y ago
  Heinlein had a similar idea, which he described in The Moon is a Harsh Mistress http://www.quora.com/How-feasible-would-the-catapults-from-the-moon-is-a-harsh-mistress-by-Robert-Heinlein-be http://www.quora.com/How-feasible-would-the-catapults-from-t...
  - logfromblammo 11y ago
    The moon also has lower escape velocity than Earth. Lower lunar gravity makes every method of reaching orbit easier.

TheLoneWolfling 11y ago

Yes, substantially so. First off, the way stresses work it is substantially easier to build straight up than in any other direction. And secondly, you're missing something. Namely, that the only reason why a string attached to an edge of a merry-go-round whips tangentially is because of air resistance. In a vacuum, or if the air was moving with the merry-go-round, the string would be radially-pointing. (There's also a component of "the merry go round is slowing down", but that also isn't particularly relevant.) As such, it makes no sense to build something this way. About the only case where not building straight up would make sense is if you're slightly off of the equator - in which case you should move to the equator. Although I suspect you have the wrong impression of a space elevator. You don't build up, you build down. You have a satellite / asteroid / etc in geosynchronous orbit. You start spooling out two lengths of wire - one down, one up. When the lower one reaches the surface, you anchor it. Then attach a counterweight out beyond geosynchronous orbit.

jfoutz 11y ago
I wonder if it's cheaper to do it with everything moving. a weight with a long cable spinning like Thor's hammer at a given altitude. A payload catches the cable, steals some angular momentum to get kicked up to the next altitude, with the next hammer. If it's close enough to earth, i think the cable will get some induced current, which could spin a gyroscope in the hammerhead, getting some angular momentum back. Actually, i just wonder if this approach has a name, seems like every harebrained idea i've ever had was thought of fifty times before by much smarter people. edit Skyhook! cool.
abduhl 11y ago
Actually, building straight down is substantially easier than straight up. You are incorrect with your statement about "the way stresses work". The reason it is substantially easier to build straight up is due to our implicit basis where up is towards space. This is getting rather high level but stresses are actually tensors and hence are dependent on the chosen basis. If your basis has up pointed towards the north then it is substantially easier to build a different direction than up. This may seem like a semantic argument but it is actually an extremely important distinction when discussing any tensor (position, velocity, stresses).

danielweber 11y ago

I think that's https://en.wikipedia.org/wiki/StarTram https://en.wikipedia.org/wiki/StarTram. It doesn't have the diagrams I remember, though.

jerf 11y ago

The short answer is, atmosphere. All the designs I've seen for that involve imparting a lot of velocity near the ground where atmosphere is really wrecking up your day. It isn't even the drag necessarily (although that doesn't help), it's the turbulence. You can't expect to reliably hit targets from a significant distance, like hoops, if you're going through the air. If you're on the moon, the idea makes a lot more sense in a lot of ways.

JoeAltmaier 11y ago

Might as well build a railgun launcher at that point?

logfromblammo 11y ago

The supports for the thing are what will kill you. At 1km from the tangent point, you're only 8cm above sea level. At 10km, you're 8m above. So far, so good. At 100km, you're 784m up. At 1000km, that support is 78km tall. The only economical way to do even part of it would be to build an evacuated acceleration track up the side of an existing mountain. The west face of Chimborazo in Ecuador is probably the ideal location for something like that. But you would need to accelerate at 23g for about 283km (51s) in order to reach escape velocity without any additional boost after the launch vehicle exits the track. That would be strictly for unmanned missions. Accelerating at 3g for 283km (139s) to a height of 6268m above equatorial sea level would achieve 4080m/s, of an escape velocity of 11170m/s. You get 465 m/s for free by being near the equator. That leaves a delta-v of 6625 m/s. If your launch vehicle used RS-25 rocket engines, that means an extra 13% of your total launch vehicle mass can be cargo instead of propellant. The acceleration track would effectively substitute for the first stage of a rocket. In order to reach escape velocity externally at 80 km above the equator (7850 m/s), you need 250 seconds at 3g (29.42 m*s^-2) of acceleration, which takes 1850 km. This is why the launch loop uses tethers instead of towers, and supports itself mainly with tension rather than compression.

meatysnapper 11y ago
Ecuador really has very good geography for building space-launch structures (9 very large mountains over 5000m). Probably the perfect place to build something, if you were gonna build it.
vectorjohn 11y ago
I think an unmanned only launcher is all we need. The reason anything in space is so expensive is not just getting the people up, it's all the shit they need. If we can launch fuel, parts, habitats, etc. for cheap, it would make the rest of space achievable. Achievable-ish.