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Thread: To build a suspended 'earthscraper'

  1. #1
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    To build a suspended 'earthscraper'

    Is there any theoretical or practical reason why this 'earthscraper' could not be built?

    Or is it an early April Fool's joke?

    http://www.dailymail.co.uk/sciencete...-asteroid.html

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    It's just a space elevator without the ground anchor. Same practical problems as that proposed structure, with the addition that the lower end, where the weather is, is not firmly held in position.

    Grant Hutchison

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    Radical skyscraper design from a New York City firm will be built from the sky down....
    I won't be holding my breath.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    So far, we don't have a material strong enough to hold even its own weight from that high up. ... plus we'd have to avoid the orbiting space debris ... though I guess with a lot of effort that could get cleaned up.
    Forming opinions as we speak

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    Quote Originally Posted by antoniseb View Post
    So far, we don't have a material strong enough to hold even its own weight from that high up. ... plus we'd have to avoid the orbiting space debris ... though I guess with a lot of effort that could get cleaned up.
    Space elevators have that capability. The can bend by hundreds of km, like a guitar string, with nodes, to avoid debris. This has been worked out in pretty good detail.

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    Quote Originally Posted by grant hutchison View Post
    It's just a space elevator without the ground anchor. Same practical problems as that proposed structure, with the addition that the lower end, where the weather is, is not firmly held in position.

    Grant Hutchison
    It's considerably worse, actually, since it's in an inclined orbit. It wouldn't just tend to wander slightly, it'd constantly be dragging through the atmosphere at considerable airspeed...I'm not sure it'd even stay subsonic.

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    Yeah, in the picture they show it hanging straight down... Not likely!

    I wouldn't want to be in it when a window breaks.

    And I'd also mention that it assumes we can capture an asteroid and put it into earth orbit.

    It's obviously just a speculative idea. But the Daily Mail loves that kind of stuff.
    As above, so below

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    If you're going to go to that much trouble, buid a space elevator. Peronaly, I wouldn' lett these clowns build a garage for me. Daily Mail should be ashamed.
    Last edited by John Mendenhall; 2017-Mar-29 at 06:53 AM.
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

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    I actually missed that it was from the Daily Fail!
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    wd40, for the sake of us all, please please please please please stop taking that atrocious rag seriously!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    wd40, for the sake of us all, please please please please please stop taking that atrocious rag seriously!
    I used to know somebody who worked there. It was a steady job, but he wanted to be a paperback wri----ter.
    As above, so below

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    Quote Originally Posted by wd40 View Post
    Is there any theoretical or practical reason why this 'earthscraper' could not be built?
    Newp.

    Quote Originally Posted by wd40 View Post
    Is there any theoretical or practical reason why this 'earthscraper' could not be built?
    On the list of answers to "we've built a space elevator, now what do we do with it?" This would be pretty far down.

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    Quote Originally Posted by VQkr View Post
    Newp.


    On the list of answers to "we've built a space elevator, now what do we do with it?" This would be pretty far down.
    Lack of a sufficiently strong cable material.

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    Quote Originally Posted by DaveC426913 View Post
    Space elevators have that capability. The can bend by hundreds of km, like a guitar string, with nodes, to avoid debris. This has been worked out in pretty good detail.
    But if the upper part is flexing around like that, won't the lower end swing like a pendulum do? Not to mention damping the waves along the length induced by weather while maintaining that movement desired for avoidance.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by cjameshuff View Post
    It's considerably worse, actually, since it's in an inclined orbit. It wouldn't just tend to wander slightly, it'd constantly be dragging through the atmosphere at considerable airspeed...I'm not sure it'd even stay subsonic.
    Well, the orbit they've drawn (shown in the linked article) makes no sense but, yes, a circular geosynch orbit inclined at 41 degrees (to reach overhead New York) should have a ground track that just tickles the speed of sound as it crosses the equator.

    But the ground track shown is deeply strange because:
    1) It extends to 41N, but nowhere near 41S, which implies it's either under thrust or not orbiting the centre of the Earth
    2) It's asymmetrical, implying an elliptical orbit, and the wide loop is in the N, which implies that it has the faster ground track in the northern hemisphere - but the text says it's moving at its slowest over New York
    3) If it is moving at its slowest over New York it needs to be at apogee in that location - which implies that the tower will be out of the atmosphere at that point, if it's not to hit the surface during southern hemisphere perigee

    Grant Hutchison

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    Wouldn't atmospheric drag be a deal-killer? The asteroid would require constant thrust compensation, though perhaps less than what it took to get it in orbit. I wonder where it would place on the Torino scale?
    We know time flies, we just can't see its wings.

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    Aliens. I'm not saying it's aliens, but it's aliens. That's the only way to do it.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    Quote Originally Posted by grant hutchison View Post
    Well, the orbit they've drawn (shown in the linked article) makes no sense but, yes, a circular geosynch orbit inclined at 41 degrees (to reach overhead New York) should have a ground track that just tickles the speed of sound as it crosses the equator.

    But the ground track shown is deeply strange because:
    1) It extends to 41N, but nowhere near 41S, which implies it's either under thrust or not orbiting the centre of the Earth
    2) It's asymmetrical, implying an elliptical orbit, and the wide loop is in the N, which implies that it has the faster ground track in the northern hemisphere - but the text says it's moving at its slowest over New York
    3) If it is moving at its slowest over New York it needs to be at apogee in that location - which implies that the tower will be out of the atmosphere at that point, if it's not to hit the surface during southern hemisphere perigee

    Grant Hutchison
    That's how I read it, that apoapsis is in the north. Perhaps they reel in part of the suspension cable closer to periapsis.

    BTW, I saw this on IFLS, so maybe it's a real news release and not a DM fiction.
    Et tu BAUT? Quantum mutatus ab illo.

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    Yes, it's a real plan released by a real architecture firm, with a history of speculative stuff as well as actual buildings. Free publicity if anyone in the media picks it up. I suspect they didn't spend a lot of time on the orbital mechanics.

    Grant Hutchison

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    Quote Originally Posted by Jens View Post
    I used to know somebody who worked there. It was a steady job, but he wanted to be a paperback wri----ter.
    Well, at least he could practice writing fiction at the Mail....

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    Quote Originally Posted by grant hutchison View Post
    Yes, it's a real plan released by a real architecture firm, with a history of speculative stuff as well as actual buildings. Free publicity if anyone in the media picks it up. I suspect they didn't spend a lot of time on the orbital mechanics.

    Grant Hutchison
    When I see some of the hideous facades here in greater Washington, I would not be surprised at anything that might be stirring in the minds of the architects.

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    Quote Originally Posted by George View Post
    Wouldn't atmospheric drag be a deal-killer? The asteroid would require constant thrust compensation, though perhaps less than what it took to get it in orbit. I wonder where it would place on the Torino scale?
    Perhaps that actually serves as an anchor, sine it;s not firmly fixed to the ground.

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    Quote Originally Posted by grant hutchison View Post
    1) It extends to 41N, but nowhere near 41S, which implies it's either under thrust or not orbiting the centre of the Earth
    Or its just not a perfectly symmetrical arrangement.
    If the cable had a vibratory node, it is not a given that its surface-based end will always be at full crest when at full southerly orbit.
    Think of how a double pendulum can peak at the top but not peak at the bottom.

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    That's a fun site. It has some interesting ideas in speculative architecture - not all of which are practical, but some of them might work given perfect materials.
    This one, for instance
    http://www.cloudsao.com/THIRD-SPHERE

    The text seems to be largely irrelevant, but the pictures look very familiar to me- maybe because I've illustrated a very similar concept for OA.
    http://www.orionsarm.com/eg-article/5553b39942829
    The basic idea here is a three-ring structure, the middle one orbiting at geostationary distance, and the innermost and outermost rings are suspended from the middle one by tethers. You live on the inner surface of the outermost ring, and the outer surface of the inner ring.

    I find it interesting to see other people coming up with the same ideas - that doesn't mean that they are practical, it just means they haven't been shown to be impossible yet. As far as the hanging skyscraper is concerned, this would be a lot easier to achieve if it hung down to a respectable distance above the atmosphere. Why you would want to do that is another matter.

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    Quote Originally Posted by DaveC426913 View Post
    Or its just not a perfectly symmetrical arrangement.
    If the cable had a vibratory node, it is not a given that its surface-based end will always be at full crest when at full southerly orbit.
    Think of how a double pendulum can peak at the top but not peak at the bottom.
    That's a big oscillation. It doesn't seem to get much farther south than 5 degrees, which implies that the bottom end is swinging through a range of at least 3800km in 12 hours (with the counterweight making compensatory excursions at the top end). The precessional forces on that would be ... interesting. I've never seen any discussion of that sort of mode in space elevators - vibratory modes are usually treated as something to be damped, and induced excursions for satellite avoidance are on the order of 10km, and presented as a single wave sent up the tether for a specific purpose, and then damped. Outside of the Mars tether in The Fountains Of Paradise I haven't seen a permanent oscillation suggested, and certainly not so large. Have you a source for that idea?

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    That's a big oscillation. It doesn't seem to get much farther south than 5 degrees, which implies that the bottom end is swinging through a range of at least 3800km in 12 hours (with the counterweight making compensatory excursions at the top end).
    Assuming a figure 8 pattern and each half of the 8 having a radius of 950 km, that puts the air speed at just under Mach 1 (assuming no wind, like jet streams!). So if the radius gets tighter in portions of the turn, which it should, the passengers will get a little bonus to their ride, apparently.
    Last edited by George; 2017-Mar-30 at 07:45 PM.
    We know time flies, we just can't see its wings.

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    Instead of a skyscraper, you should put a scoop at the bottom of this tether to collect air for export to space habitats. If there were thousands of habitats in Earth orbit they would need significant amounts of oxygen and nitrogen for pressurisation purposes; the closest source of these materials would be Earth’s atmosphere. Maybe water vapour and carbon dioxide would be worth harvesting too. Of course you’d need solar power collectors somewhere on the tether to counteract the drag.

    As a nod to the original idea, maybe a hotel somewhere on the tether would make a bit of income- but it would be a challenging place to visit.

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    Where would the sewage go? What's the evacuation plan in case of fire?

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    Quote Originally Posted by eburacum45 View Post
    Instead of a skyscraper, you should put a scoop at the bottom of this tether to collect air for export to space habitats. If there were thousands of habitats in Earth orbit they would need significant amounts of oxygen and nitrogen for pressurisation purposes; the closest source of these materials would be Earth’s atmosphere. Maybe water vapour and carbon dioxide would be worth harvesting too. Of course you’d need solar power collectors somewhere on the tether to counteract the drag.

    As a nod to the original idea, maybe a hotel somewhere on the tether would make a bit of income- but it would be a challenging place to visit.
    The same amount of energy would be needed to get the atmosphere into space regardless of how it's done. The issue "overhead".

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    Methods of getting into space that use fuel and propellant also have to lift that fuel and propellant part way into space, so they are not as efficient. A solar-powered tether lift need not use any fuel at all.

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