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The "moon in a bubble" idea led me to think - why not make a REALLY big balloon - around the earth?
The earth's atmosphere would support it. Make it very transparent - don't want to make global warming worse! Most of it would be very thin, but at a few spots we'd thicken it up enough to hang an
elevator from it.
Now I'm not sure how best to take advantage of this for getting into space - maybe put a long mag-lev system up there, taking advantage of the near vacuum to get craft up to orbital velocities.
out of the bubble
http://lofi.forum.p...l-the-air_2049.html
Spaceballs stealing air inside the planet's shield. [the great unknown, Jun 27 2007, last modified Jun 29 2007]
Moon in Bubble
Moon_20inside_20soap_20bubble
For different reasons. [neelandan, Feb 27 2009]
[link]
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"Why not," you say. As the idea's author, I think you're more obligated to answer "why" than "why not". |
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Saves people like me coming along and asking why. Which I'm doing, btw. |
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Notes waugs is talking to TomRC, when globaltourniquet is that-a-way... Tom - may I call you Tom?... Ever seen this mentioned in Science Fiction? |
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//don't want to make global warming worse!// |
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Then don't put a balloon around the earth. Fishbone. |
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// It already is in a bubble. Can you spell 'atmosphere' ?// |
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One of the methods that atmospheric planets use to regulate their temperatures is by losing the higher speed particles from the upper atmosphere in a process similar to evaporation. Putting a balloon around the atmosphere would be the planetary equivalent of going for a run wearing rubber trousers. |
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Why put Earth in a bubble? I thought I answered that in the original message - it is an alternative to various schemes to hang 40000km long elevators from orbit under tremenduous stresses, yet which can only come down to earth at the equator. |
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Use the earth-bubble to hold up a number of elevators, anywhere on earth, and only about 60km long. Once you are out of the atmosphere, getting up to orbital speed is much easier - especially if the bubble provides support for the spacecraft while it accelerates horizontally. |
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Temperature balancing the atmosphere is an interesting issue - but I doubt that cooling due to loss of atmosphere is a very significant effect - not enough molecules escaping to do anything, else we'd have long ago run out of air. Heat radiation is far more significant - hence the need to make the bubble transparent to heat radiation, as I said in the first message. |
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[thumbwax] No, I've never seen the idea of putting the earth in a bubble in science fiction. |
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I do recall having read one story where the moon was in a bubble - to hold in a terraformed atmosphere. |
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But I don't recall ever reading anything where a planetary bubble was used as a stepping stone into space, which is the key point here. |
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Please keep in mind that this is being proposed in much the same "mega-engineering" spirit as the various space elevators - which are far more dangerous, IMO - they CAN fall, as was described in on of the "Mars" novels, and the results would not be pleasant. |
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A space elevator is one tall object, that if it falls, will land in a relatively small area. <relative to the Earth's surface.> |
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What you're proposing is something that will completely cover the earth, thus being much more widespread in its damage if it falls. |
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If it is supposed to be strong enough to hold a number of elevators, then it's going to be very heavy indeed, and will make one hell of a mess. I don't think you've thought about the consequences, when calling a plain elevator 'more dangerous'. |
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All of this being an exercise in the properties of Unobtanium anyway... |
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[StarChaser] A falling space elevator has considerable angular momentum and LOTS of energy. It will not fall in a single spot - it will wrap almost all the way around the earth like a ~4km/sec bandsaw until it burns off. |
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Now if you want nice straight canals running across S.America and Africa, you may think this is a good thing. But in the process it would unleash super tsunami and toss enough water vapor and dust into the air to make nuclear winter look wimpy - hello ice age. All that energy ends up as heat - so you get something akin to a continuous line of hurricanes as well. |
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An earth bubble would have a huge mass - but most of it would be around a micron thick. If a big piece ever falls on you, take a moment to tear a hole and step through as it drifts slowly down. The 60km elevators falling would be bad - but only bad, not "ending-life-as-we-know-it" bad, as with the space elevator. |
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A rip in the bubble shouldn't cause it to fall as long as it is closed within a day or two. (Vs one hit on a space elevator and down it comes.) As a safety feature, loose-hanging carbon nanotube fibers could connect points on the surface - so if a meteror zips through horizontally and makes a big rip, the fibers would grow taut as the rip opens, and hold the bubble together. Patch it sometime this century and it shouldn't be a problem. If you're really paranoid, use two layers separated by a few hundred meters. |
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this could actually prevent global warming with UV filtering. unfortuately it would need rather more substantial protection due to the large numbers of tiny meteorites and other bits of crap that hit our atmosphere |
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Well, this one gets my "Wrong in so many ways" vote. [Also thinks TomRC has been reading too much Kim Stanley Robinson; remember, that stuff is conjecture, not hard science.] |
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[chud] Most meteors would cause very tiny holes. Anything big enough to create a significant hole is a threat to the planet anyhow. The standard argument thrown out for similar objections to the space elevator is "we'll have nanotech repair robots fix it". Apply the same solution here with equal validity (or lack thereof). |
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[DrCurry] Feasibility with today's technology is now a requirement for half-bakery entries? Gee, then toss out everything in "other:space:elevator" - and most of "other:space". An amazing number of people are seriously pushing the idea of building a space elevator (sometime in the next 50-100 years) which I consider insanely dangerous. Hence this alternative proposal. |
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[UnaBubba] It isn't intended to hold in atmosphere - it is intended as a safer alternative to 36000km+ space elevator proposals. |
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Here's a little change that could make this idea useful: Instead of putting this bubble around the Earth, construct it around planets that don't have enough gravity to maintain an atmosphere and use it as a terraforming tool. |
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[moved vote to neutral -- still dislike the original idea but see potential in a spin-off] |
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Here's my two cents. The bubble, due to gravitational forces exerted upon the surface (even at a micron thick, this Mylar bubble would weigh in at billions of tons), the bubble's surface would necessarily contract. This would in turn increase atmospheric pressure on the ground to the point where our heads would pop like pimples. Great idea, TomRC. Save planet Earth by killing all the humans. (actually the best idea I've heard all day. Let's bubble up!) No croissant for you! |
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[muttboy] I make it around 100 million
tonnes (ish), but my maths won't get
any further. But surely a micron thick
world-size skin of mylar has about the
same mass as (say) a metre thick world-
size skin of atmosphere? So, it's not
going to have any perceptible effect on
air pressure for that reason.
But, a different problem. What keeps
this bubble centred on the earth?
Surely it would be unstable - if one side
gets a tad closer (metric or imperial
tads - either way) to the earth's surface,
and the opposite side gets a tad further
away, then the nearer side get's pulled
more (closer to the earth's centre-of-
mass) while the further side gets pulled
less and....before you know it, you'll
have shrink-wrapped half the globe.
I'm not saying that's a bad thing, but... |
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This seems less feasible than
space elevators because its
bigger. Still, it's an
interesting idea. It's like an
inside-out vacuum balloon. It
could help prevent helium loss
from the atmosphere. It
wouldn't fall to earth as
Basepair describes. Solid
spheres don't do that because
the gravitational attraction in
the opposite direction cancels
it out exactly, but they can
drift. The bubble should be
more stable because if it keeps
its shape, falling to earth
means raising a lot of the
atmosphere high off the ground. |
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As to why not, apart from other
reasons, it's vaguely
claustrophic. No matter where
on earth you go, you're still
inside. |
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I don't want to say this is a great idea, but is it really that much worse than any other ideas about getting into space? I mean, *that* much? |
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<caspian>, I'm not convinced this sphere WOULD keep its shape. Through the magic available to those who do not have to build their ideas, it will simultaneously be able to support elevators while being gossamer thin. If I've understood the underlying idea, TomRC envisions atmospheric pressure keeping the balloon inflated, and this provides the rigidity of the system. As holes begin to apear in the fabric (due to meteorites, Martians, and rogue nations trying to launch traditional space programs), some atmosphere will leak out. Even if these holes are patched through a maintenance program, every time it happens there will be less air inside than before, and more air "resting" on the outer surface. Sooner or later, the skin would have enough slack in it for a portion to droop to earth. I'm picturing the under-inflated red rubber balls we played with in the schoolyard, with the caved-in part. |
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I think we're going to have to build rigid rings into the fabric of the balloon, probably supported from the earth's surface on giant pillars or arches. Of course, we could build ONLY the giant arches, dispense with the bubble, and have McDonalds sponsor the whole thing. |
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[theins] some of your questions were
answered already. However, the
question of //what do you do if one
part of the bubble gets close to earth//
is interesting. |
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If we were dealing with a rigid shell, I
can see that there might be an inherent
instability causing it to "fall" and make
contact with the earth on one side
whilst rising and being further away on
the opposite side. In other words, the
Earth does not necessarily remain
centred in a shell (?). |
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Conversely, the atmosphere is of course
distributed more or less uniformly, and
shows no tendency to become
"lopsided", ie, Earth remains centered in
its atmosphere. |
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So, if you built an atmosphere-
supported bubble, would it behave like
a shell and be unstable, or like the
atmosphere and remain centred? |
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what would it be made of? I suggest
chewing gum... lots of it. In fact, this is
so dim-witted that I'm awarding it this
croissant for making me laugh. |
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Seriously, though, //if you built an
atmosphere- supported bubble, would it
behave like a shell and be unstable, or like
the atmosphere and remain centred?// |
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While enough atmosphere remained inside it should be stable like the atmosphere, since the mass of the combined balloon/contained-air object is mostly air. If too much leaked out it would lose its spherical shape, and would be unstable, but in a different way to the spherical shell. [gardnertoo] described how it could happen. |
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it would remain stable but pulled mostly toward the moon like the rest of the atmosphere -if it didnt leak, and everything does. I would suggest a giant snot bubble instead of chewing gum but only if sufficient custard could not be scraped up. bah. |
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I can just picture all the baby otters and ducks with shrinkwrap all over them. Oh the humanity! |
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Anyway, most space elevators are just reasonably sized high tensile cables with a counterweight on top, not some huge mammoth tower of steel or whatever. If one of them fell down, such a thin cable would burn up before it hit the ground. And the counterweight would generally simply fly off into space, no matter where you cut the line. So they really aren't dangerous in any way. it's just a little bit of cable hitting the ground at low speed near the bottom, which would most likely be in the ocean anyway, since you have to move the elevator around to stay away from storms. |
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Yours would either be so thin that while gravity didn't pull it down hard enough to counteract atmospheric pressure, it would also not be thick enough to hold any elevators OR it would be thick enough to hold elevators, but then would also have to maintain its own integrity against gravity, which is virtually impossible and insanely expensive, and also subject to drifting a few miles off course and then wiping out humanity when a bubble half the mass of Earth smashes into us. |
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But what happens when some malicious alien sticks a pin in the bubble? |
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Ptthhhhwwwww - we'd end up somewhere near the Crab Nebula. |
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I like this. I never noticed it before, for some reason. And it seems original and workable. |
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The stability issues that have been raised are valid, but can easily be solved. All it needs is some cables going up to the bubble to keep it from going upward at any place. Obviously, if a constant-volume sphere is coming down on one side, it's going up somewhere else. Think of it as a spherical bicycle rim with the cables as spokes. (Yes, the cable tension will increase the overall pressure slightly.) |
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The elevators and their cables do the same thing as the stabilizing cables, so elevators all over the world would also keep the bubble in place. So stability is not an issue. |
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Otherwise, it's comparable to a plastic high-altitude balloon. Most of it is flimsy as hell, but the technology to support a heavy load has been around for fifty years at least. |
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Getting the damn thing up would be the worst part. I can see that distributing the parts around the world and having a zip-and-seal day, then sucking all the atmosphere down through the elevator holes while paying out cables. Better to have parts held up by helium while assembling, although working a panel at a time could be tricky--hmm--with helium balloons and massive blowers, it could be done. [+] |
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----------
Since this is getting renewed interest in 2007, I'll post a few responses. |
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The mass is of course a major issue - no question about it, this is mega-engineering, though far short of Dyson Sphere levels. Still, not for the faint of heart. |
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Holes punched by space debris would be *almost* inconsequential, compared to the surface area and volume of Earth's atmosphere. With nanotech, those holes could be quickly repaired. If - after a million years - enough air escaped to let the bubble fall 1km, a new bubble could be built 1km higher, before disassembling the old bubble. Probably that could be made into a continuous automated process. |
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A whole-Earth bubble could not go off-center, because Earth's gravity keeps the atmosphere distributed fairly evenly, with or without the bubble - the weight of the bubble is not sufficient to counteract the Earth's air pressure. The only way it could get to ground level would be for a large fraction of the Earth's atmosphere to get above it. |
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Objections that a thin bubble could not support the weight of an elevator or mag lev launcher either missed the idea that the bubble would be a bit thicker near those and taper to thinness only further away, or do not understand that virtually all forces applied to perpendicular to a bubble (e.g. weight of an elevator) are translated by deformation of the bubble counter-acted by air pressure, into force through the surface of the bubble. The bubble should have reasonably high tensile strength everywhere and fairly high strength right under anything heavy resting on the surface - but need not be very thick elsewhere, because the force of the weight would be spread over such a huge area. |
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Note that the common concept of what a space elevator might be like has shifted dramatically since this idea was 1st posted (and yes, a few people were proposing "thin and light" SEs even back in 2002 - I just was not yet aware of them). |
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On the other hand, the same "thin and light" approach can be applied to the bubble. Instead of enclosing the whole earth, enclose a hemisphere prehaps 300km across - maybe 20K tons of material. Instead of an elevator, have it support a mag-lev launcher, starting from ground level for convenience. |
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For Mars, this could be a shorter term approach to terraforming - start with a meter-sized bubble, consisting of solar-powered nanotech that will pump carbon-dioxide from the surrounding air, and inject most of it to it's interior to half-inflate itself. It'd extract a tiny fraction of the carbon to build more bubble, expanding it's diameter and height. When it gets big enough - say a mere 100km across and 50km high - it increases its thickness to add more weight, compressing the atmosphere within to approach 1 Earth atmosphere of pressure. People would only need a bottle of O2 to walk around. |
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//No, I've never seen the idea of putting the earth in a bubble in science fiction// |
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I guess you never seen Mel Brooks' Spaceballs. |
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If the outside of the balloon was somewhat reflective wouldn't this actually help reduce global warming? |
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I can't think of a reason why there would be much stress on the skin of the balloon so it could be the thickness of a normal weather balloon. |
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You could accelerate objects to orbital speed using a solar powered truck with enormous wheels that travels along the outside of the balloon. |
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The balloon construction project could involve an orbiting shuttle that reels out an elastic band around the earth and then links the 2 ends together. From here, a construction device needs to travel around the band widening it. Once the band is sufficiently wide, you draw the edges together and seal it. |
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One problem I can foresee is that the atmosphere is a good shield against solar winds/flares and meteorites, all of which would wear/tear a balloon. |
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Cool! The only problem I can foresee is DOOM, DEATH, DESTRUCTION, and maybe a little bit of APOCOLYPTIC MAYHEM. Oh, and of course, THE ULTIMATE FATE OF THE EARTH, AND OF LIFE AS WE KNOW IT, but that can be easily repaired. I think a fishbone is a small price to pay, for the survival of earth. |
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I think [TomRC] overestimates the tensile capacity of a micron thick membrane. Just saying "we'll thinken it a bit where the loads are" doesn't mean much, as you'd end up thinkening a rather significant portion of the surface. |
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Also, the ability of a thin membrane sphere to resist skin deformation is a product of tension in the skin itself. A bubble or baloon displays rigidity not because of the air pressure within, but the local (and to a lesser extent global) tension in the membrane. I'd like to see some evidence to show that a micron of any material (even some nanotube reinforced whatever you like) will suitably withstand these stresses. Also, you generally attain the necessary tension through elastic deformation of the skin. Read this as catastrophic failure any time a puncture occors. A fibre reinforced membrane may have some notch-insensitive, rip-stop properties, but once again, you're asking a lot out of your wispy baloon. |
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No bone, in fact I haven't boned anyone in ages (shutup you clowns in the back, that's not what I meant) but I really do think this is a bit on the preposterous side. |
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haha. apparently I didn't do much thinkening either. Change that to "thicken". |
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Custardguts - I think you're greatly underestimating how much the tension forces fall off as one moves away from the elevator attachment point. If the elevator attached to a ring about 10m in diameter, at 1km the tension is spread over 100x as large a circle, and so has fallen by 1/100, as can the thickness. |
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If the elevator attachment point had to be 10cm thick, it'd be down to 1mm at 1km out, and 1micron at 1000km out - still only about 2.5% of the way around the world. (Made from nanotubes, it wouldn't need to be anywhere near 10cm thick, by the way.) |
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Of course it's preposterous - today. 50 years from now, with mature nanotech - maybe not so tough. 50 years ago the idea of putting a computer on a chip of glass one cm square was "preposterous". Open your mind a little! |
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Although the whole thing is almost certainly impossible, I think that Tom has answered most of the criticisms, and that the idea holds together, so have a shrink-wrapped croissant, to counteract one of the bones. |
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I'm for this, but only if there is a giant clown blowing up the bubble and sticking Earth inside (comical trombone music in the background). |
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I see an advantage that I had not noticed earlier. If we could get all the upper atmosphere inside the bubble--no easy task--satellites could orbit a lot closer to the Earth. A launch system atop the balloon, like the rolling tractor mentioned above, would be nice. |
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However, a bit of space junk in a decaying circular orbit is going to slice across the highest part of this balloon for a mile or so. I suggest a few impact blocks made of foam, sticking up above the balloon, to catch any surface-skimming crap. (Stuff falling straight down will miss the blocks, yes, but will make less of a long gash.) |
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