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And given the density of Venus' atmosphere, here is a fun thought experiment. It may be possible to make 'titanium' balloons for longer term operation. The wou
by ChuckMcM 6y ago
And given the density of Venus' atmosphere, here is a fun thought experiment.
It may be possible to make 'titanium' balloons for longer term operation. The would work by creating the balloon envelope on earth, have a sealing mechanism that you activated in orbit so they had vacuum inside. And then drop them into the atmosphere.
Same idea a glass floats on fishing nets[1] except with titanium (so they can withstand the compression forces given they have a vacuum inside). It might be useful/necessary to put some additional structure inside the envelope for strength but like eggs, the sphere is a pretty good shape for distributing compressive force.
Anyway, put a number of them on tethers attached to the instrument payload and drop it off into the atmosphere once you've gone trans-sonic with parachutes or retro rockets. The platform will then fall to the point where the lifting force of the floats is equal to the weight of the platform.
Ideally the titanium would be impervious to the atmospherics's corrosive effects.
[1]https://en.wikipedia.org/wiki/Glass_float https://en.wikipedia.org/wiki/Glass_float
- xadhominemx 6y agoVenus’s atmosphere is 100x denser than earth’s, so you could just seal the metal balloons at sea level pressure and it wouldn’t really make a difference. Or you could seal them in a vacuum on earth. Not sure why you would need to feel them in space.
- simcop2387 6y agoWeight and volume. The air has weight so it'll cost more to launch. The volume would also make them more difficult to launch. Assembling or unfolding in space near earth would allow you to make them larger and inspect them before they leave for venus.
- minitoar 6y agoI could see reusing an empty fuel tank or something as a cute way of doing this.
- ChuckMcM 6y agoOh I like that idea! Tricky to get it through the deceleration phase into the atmosphere but it would have a lot of volume. You would want some way to detach the engines (less mass) after you slowed down while still sealing the tanks.
- thaumasiotes 6y ago> Assembling or unfolding in space near earth would allow you to make them larger and inspect them before they leave for venus. Don't we want them to be rigid spheres?
- tempestn 6y agoYes, but you could still construct it in orbit. Imagine building four quadrants, spooning them together for launch, then fusing ("cold welding") them into a sphere in space.
- thaumasiotes 6y agoIt is surely better to construct them here, where we have all our tools, and if really necessary pump them out here. There just isn't an advantage to doing it in space. You end up paying more to create a lower-quality sphere. And what weighs more - the air that got trapped in the sphere when we made it, or the machine we sent up to space to assemble a sphere there?
- withjive 6y agoSeems quite short sighted to assume space manufacturing processes would not improve - or we would not want to improve them. Cold weld it in space, it's not that difficult with some engineering. Space X?
- thaumasiotes 6y agoThe assumption is that no matter how much space manufacturing processes improve, ordinary manufacturing processes will improve more than that. This is pretty well guaranteed.
- tempestn 6y agoIt's not just the weight that's an issue, but also the volume.
- zhoujianfu 6y agoDoes anybody have any thoughts on how feasible it would be to make a metal “vacuum sphere” that floated in earth’s atmosphere? That’d be pretty cool! How huge would it have to be? Would it have to be made of titanium? Aluminum? Stainless steel? How good are those materials at withstanding a vacuum (or partial vacuum) if the diameter was say... 50m? I feel like at some size it must work, as the volume of air displaced goes up with r^3 and the surface area of metal only goes up with r^2. If people here can do the math, maybe I could build one in time for next burning man...!
- tryauuum 6y agoreminded me of a mythbusters episode where they created a lead balloon
- bagels 6y agoVacuum would be pretty difficult. The strength requirements literally outweigh the buoyancy.
- ChuckMcM 6y agoThe challenge is that Earth's air isn't dense enough. That said, the math is "easy" density is volume/mass, vacuum adds no mass, so it is just material mass / volume. A 20cm diameter diamond sphere that was .5mm thick would have a mass of about 41g, a 20cm diameter sphere of air at sea level and "room" temperature is about 50g. So you would get 9g of "lifting force" from such a balloon (assuming I did all the calculations correctly). And experience about 2,900lbs of compression force. Any air in the sphere would add weight.
- bananasbandanas 6y agoIf you're interested in some fiction with this concept: In Neal Stephenson's 'Diamond Age' humans have mastered assembly of individual atoms in basically arbitrary ways. They use it (among other things) to create flying airships with an envelope made of diamond with a vacuum inside. Found it to be a fun read in general.