h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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There are already a number of proposals on the 'Bakery to build space elevators. Why add another one?
Well, this one does not rely on exotic materials, uses locally available resources (including energy), and construction could even be automated.
A cone is a simple geometric form that is very sturdy
in the vertical plane. Clumps of heavy particles naturally form cone shapes, from gravel piles to volcano caldera. In theory a solid cone shape could be scaled up to truly enormous proportions, say 20km high, with a 40km diameter at the base. This would make escape from Earth's gravity well considerably easier.
Practical issues: a) Construction time b) Availability of Materials c) Energy d) Cost, and d) Location.
Destined for the Sahara desert, I propose the creation of a thousand or so construction robots, each with solar furnace (large parabolic mirrors) production lines designed to melt sand into 'natural' glass (obsidian) extruded form, layed out in a prescribed, concentrically circular pattern, 40km wide at the base. This would be gradually (over decades) be filled in layer by layer until the cone is complete. Accuracy would be ensured with GPS. The construction robots would either include excavators for loading sand into hoppers, or this function would be managed by separate machines.
Rather than build a solid cone (which, according to my rough calculations based on the dimensions described above, would require something like 8378 *trillion* cubic metres of glass), the robots would create a 'laminate' structure; appearing in cross section as something like an inverted family tree - reducing the sheer volume of sand required, while retaining relative structural strength.
Hey, might as well think big! :^)
(Added 30 mins later: Just noticed "Space Mountain", and comment about mountains only being able to be 10km high or so without "liquifying rocks" underneath. Hmmm. I wonder if the laminar design of this glass cone would overcome that problem?)
How to get your vehicle to the top
Solar_20Powered_20Wind_20Turbine
Parachute up. [Worldgineer, Apr 29 2005]
Is glass a liquid or solid?
http://math.ucr.edu...al/Glass/glass.html
It's, um, a glass. [Worldgineer, Apr 30 2005]
Google search "glass flow myth"
http://www.google.c...n&q=glass+flow+myth
No it doesn't. [waugsqueke, Apr 30 2005]
Pyramids Save the World
http://dilbert.com/...mids_save_the_world
Scott Adams has a similar idea [xaviergisz, May 30 2014]
[link]
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How can blowing sand be prevented from getting into the construction robots? |
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That's a good question. One possibility is sealed 'clothing' around the joints and openings. Another problem is sand blasting effects on the mirrors (maybe diamond coating the mirror would fix that). |
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I know how to stop the rock (or glass)
from liquifying: cool it. |
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[builds huge air conditioning plant next
to huge artificial mountain. huge aircon
plant starts to melt.] |
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Kudos for researching your own idea
and the possible flaws in it. [+] |
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"Glass" in this country means ice cream. |
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I've enjoyed everything you've posted, [Adze]. |
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Why the name "Adze," [Adze]? Isn't that a wood tool of some sort or is that "adz?" |
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Thankyou, [bristolz]. Adze is the closest thing I have to a nickname; It's an informal contraction of Adam (yours truly). I also enjoy the association to the carving tool you mentioned. |
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Back to the idea for a moment. I've been
thinking about my off-the-cuff
comment about cooling. Since you
intend building the structure with
stronger materials than rock, you can
slope the side more steeply and get a
higher structure. Possibly just as
importantly, you can leave air gaps (as
mentioned in the idea). |
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If you construct the pyramid to take
advantage of air convection you could
take in air from the surrounding desert
and use it to cool the base of the
pyramid leaving it to escape from the
top. This, again allows you to build
higher and gives you an updraft from
the top of the pyramid that can assist in
launches. |
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As an aside, give free choice of
material, I wonder what would be best
to put at the bottom of the pyramid. |
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//air convection and steeper slope // |
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Yes, you could use air convection for transportation or power generation as well (install wind turbines near the top), with cooling as a bonus. I was just thinking today that it might be possible to put a hyperbolic curve in the cone shape, so that the base is still very broad, but the slope steepens only gradually until near the middle, where it rises dramatically. This might solve the weight problem, as the "maximum mountain height" formula apparently assumes an upright rectangle shape. |
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//give free choice of material, I wonder
what would be best to put at the
bottom of the pyramid//
Blair, Howard, Kennedy. |
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Also might help with desert migration... |
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Adze--It’s a simple matter to design it so that the compressive stress is constant all the way up...but that doesn’t get you there. The attraction of the (totally bonkers) space elevator idea, is that it gets you into synchronous orbit. Going up 20 km or 100km or 500km doesn’t do that—you still have to accelerate to orbital speed. |
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[ld], assuming adequate strength (ok, big assumption), couldn't the launch vehicle ride up the side (on the inside)? |
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//It’s a simple matter to design it so
that the compressive stress is constant
all the way up//
Surely this
means that the pile is going to have get
exponentially wider (I mean, the base
flares out - faster than a simple cone).
So, even if the top is only one atom
across, aren't you going to run out of
ground-space before you reach a great
enough height?
I'm thinking
that, for a simple cone, the total volume
of material increases as the cube of the
distance below the tip, whilst the cross-
sectional area increases only as the
square; hence, the stress at the bottom
of a conical mountain is much higher
than at the top). |
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I mean, you can design for constant stress, but that doesn't mean there's a material that can take it. Glass would be a VERY BAD choice, as it's brittle and has that nasty tendency to flow under pressure. Because it's a super cooled liquid, essentially. Anyway, this idea is just an oversized pyramid, which is why Adze put it in Egypt.
If you want to minimize launch costs, you put the launch pad on the equator, as the French do. It’s not worth the expense to put it on a mountain. Just consider Mount Everest, only five miles up. Think about hauling a rocket to the top of that, then magnify the difficulties by ten or a hundred for this glass pyramid. |
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Just attach a parachute, and use a solar tower design. |
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[ldischler] I understand your points. However, it was not the intention to suggest this structure as a way to achieve orbit without an orbital boost; merely a way to cut down on fuel requirements. As a rough example, you could build the equivalent of a Saturn 5 rocket without the first two stages. I'm not saying you wouldn't need a rocket at all.
P.S. The Sahara is in Mali, Chad and Sudan (southwest of Egpyt). |
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Wind at altitude is a killer. You'd need some B.A. engineers to work out how to get around this. Perhaps Wind relief tunnels in the structure? They would need chambers for direction probably.
//Blair, Howard, Kennedy.//[Basepair] Which floarkin' Kennedy? I really don't get it & any Kennedy I can think of draws up anger that they be included in such a scheme of yours. I know they were not perfect, any of them, but would we be where we are now or worse without them?
I think there are some attempts to incorporate polymers into ceramics that may aid in the feasibility of this idea. I really don't know how far they have gotten to date, though. |
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//As a rough example, you could build the equivalent of a Saturn 5 rocket without the first two stages.//
How do you figure that? |
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[ldishler] As I explained, if you start at a higher point, you need less fuel to get into orbit. The Saturn 5 used 3 stages so that it didn't have to carry the full weight of the rocket into orbit. |
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Correct me if I'm wrong (I'll be the first to admit I'm not a rocket scientist), but my understanding is that the need for such a big rocket in the first place was because a) you need a lot of fuel to carry a heavy payload into orbit, and b) a lot of fuel means more weight - which in turn, means a bigger rocket. If you don't need a lot of fuel to get into orbit, you don't need a big (3 stage) rocket. |
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Adze—Even from the top of your tower you still have to accelerate to 17,000 mph to get into low earth orbit. That’s partially true for the space elevator too, except the acceleration is accomplished by a transfer of momentum from the elevator to the passenger, and you don’t reach orbital speed until you’re 22,300 miles out, in synchronous orbit, traveling at just under 6,000 mph. That’s still a lot of momentum, and people forget that you’ll have to make it up somehow, like with jets spaced along the elevator. And then you’ll have to feed propellant up to the jets with massive pumps, and then, with nothing to dampen it, the whole affair will begin the gyrate like the Tacoma Narrows bridge. Not that it will ever get to that point, because it will destroy itself during construction. |
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Note for [zimmy]: Blair, Howard and Kennedy are UK political party leaders. Am inclined to think they'd crack under pressure. Given their talents, I suggest we put their feet in concrete and use them as surrogate baby-hugging points in the foyer. |
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[Pa've] no, you wouldn't, although it's a fun idea. The view at least would be impressive. Make it a steep cone, though, or we'll end up using Africa. |
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[ld] the traditional solution to the momentum problem is to have another elevator going down at the same time as the one going up, to balance it out. Filled with... some stuff, to balance out the weight of passengers. Other passengers, probably. Which is fine when it's a mature technology, but in teh beginning might involve employing people to go up and down on the lift all day just to balance things out. Cool. |
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Moom--You can't use a counterweight here. Unlike an ordinary elevator, the momentum in question is directed perpendicular to the structure. |
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// I see the fundemental problem of this idea as being that glass is a solid, but like [ldischler] said, glass is a liquid. It seems solid to use because at rom temperature, its rate of movement is very small. This property was discovered when measuring the glass pains in some ancient cathedral, I can't remember which, but the glass was thicker at the bottom than the top. // |
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Glass is not a liquid. That's baloney. |
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An amorphous or non-crystalline solid, I thought. And the cathedral glass thicker at one end than the other was (is) due to some way they made the glass at the time. |
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I once read (in a checkout line, of course) that the pyramids were built upside down, with the thick ends up. The article said aliens had used them as landing pads and then flipped them to prevent the Egyptians from following them to their home planet. It didn’t mention cathedral glass, but I didn’t read the whole thing. |
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how deep in the sand would you need to set the pointy bit so that the pyramid didn't tip over? |
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Of course, given that the pointy end was down, some sort of force field was required to keep the thing from plunging into the earth or just falling apart. It seemed to me a bit complicated, but there it was, in black and white. |
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[Bristoltz], you wand [waugs] are both partially right. |
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Glass is a non crystalline solid, meaning that in theory it will "flow" over time. However, this flow is much smaller than most people think--the cathedral windows are not thicker at the bottom because of glass flowing, but because of poor manufacturing techniques--it was impossible to get a perfectly flat piece of glass, and given what they did have, the logical choice is to put the thicker end at the bottom so it is supported better. |
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"Glass is not a liquid. That's baloney." |
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"An amorphous or non-crystalline solid, I thought." |
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[5th Earth], what part of these statements is only partially correct? |
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"[Basepair] Which floarkin' Kennedy?"
as [moomintroll] pointed out, he is
a UK political leader (well, that's a bit of
an exaggeration but no
matter).
What puzzles me is,
what's a "floarkin' "? |
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To clarify the glass liquid thing: |
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Glass does not ever flow at room temp and pressure. The cathedral windows are because the manufacturing technique they used at the time was to place a blob of metal on a spinning wheel until it formed a disc. Then they cut the disc into squares, which would always be somewhat uneven. They would then simply put the thicker side on the bottom of the frame, because it was less likely to fall out. |
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If you are still skeptical about that, it is possible to go to some more obscure old buildings (like old mediocre houses), and find windows where the thick part is actually on the top or the sides, because the contractors weren't paying attention. |
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Furthermore, there was a 30 year or so long experiment (maybe even longer than that) where a meter long thin glass rod was laid across a gap and hung with weights almost to the point of breaking. The most precise measuring implements of the time (probably sub-millimeter) were unable to detect any change of curvature whatsoever during that time. And that is unsupported glass under pressure. Not a big thick slab sitting happily in a window someplace. |
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So no. It does not normally flow (maybe under high pressure it does) |
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And yes, I realize this is a two year almost bump. But I very much dislike the glass myth |
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[ldishler] //That’s still a lot of momentum, and people forget that you’ll have to make it up somehow// |
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I thought this issue could easily be avoided by oversizing the cable and reeling the space station out a little bit. I actually have always imagined the cable being constantly reeled in and out from the ground station to compensate for effects like this. |
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I may have missed this in the foregoing
annotations but... |
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Surely the issue is not the mechanical
properties of this 20km high man-made
mountain. The issue, it seems to me, is
that you are going to build it on the
surface of the earth. The earth is
basically a big blob of hot gooey stuff
with a thin crunchy crust. |
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Building this thing on the earth's crust
is pretty much like trying to construct a
garden shed on the skin of a large
bowl of custard, Shirley. |
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I think the reason why the Sahara desert is used is because it is a large source of sand & on the equator. I would think if you want a plentiful source of building material, try below the earth's crust & use some of that nickel etc. instead. But you can only make some things so big. there will be a point that something will get too big to support it's own weight. That's why skycrapers need steel frames; stone will break if it has too much weight. You can try to honeycomb or hollow the cone or something else to give it a better weight/height ratio, but I don't think you can get higher than everest. |
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Someone here proved conclusively that you cannot build an edifice more than four miles high. I believed it at the time but now I suspect it's rubbish. If we'd put Everest there we'd have built something 5.5 miles high. |
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