Fun fact: This is not the first time a space program has flown on another planet. The Soviets launched weather balloons on Venus during the Venera missions [1]
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.
Don't we want them to be rigid spheres?
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?
Cold weld it in space, it's not that difficult with some engineering.
Space X?
This is pretty well guaranteed.
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...!
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.
On the subject of Sci-Fi, there's also a vacuum airship featured in one of Edgar Rice Burroughs' Tarzan novels - 'Tarzan at the Earth's Core'. It is of course much less scientific than Stephenson's version though.
https://en.wikipedia.org/wiki/Vacuum_airship
This is a plot element in Neal Stephenson's The Diamond Age, as well as several other fictional appearances (Edgar Rice Burroughs, Azhar Abidi, Peter Watts, and Iain M. Banks all use the trope).
There are no materials known with sufficient strength to withstand compressive and buckling forces. Not even diamond.
Lightweight stiff structures (honeycomb, something resembling aerogel, perhaps) are other options, but seem unlikely as well.
Gas-filled airships or balloons benefit from the fact that low-density gasses (by either chemical composition or temperature in the case of hot-air balloons) exert a countervailing pressure to balance atmospheric pressure, but with a lower mass, hence providing buoyancy. The internal pressure actually provides some (or much) of the structural rigidity of most airship variants. Any vacuum airship would have to make up for this factor, again, increasing strength (and material mass) requirements.
The idea sounds relatively sound to me. One could construct a sphere out of aerogel cones, and the external pressure would reinforce it. Not sure how practical it would be to build such a thing, though.
At some point, since volume grows slower than volume, I expect you can make the envelope relatively thick without sacrificing density. That's also the idea behind Cloud nine: https://en.wikipedia.org/wiki/Cloud_Nine_%28tensegrity_spher...
Square-cube law. Mass scales with surface area, lift scales with volume. Large balloons (conventional, not vacuum) are simpler and more efficient than small ones.
As to materials, a tremendous problem with areogels are that they're exceedingly friable. Any friction, flexing, or stress will crumble the gell to a powder. I suspect this is why the gel hasn't taken off as it had been projected to. I did some very-early 1990s work in the space and aerogels were a noted emerging technology thought to have applications in, e.g., mobile home, pre-fab housing, and RV designs. For the most part, fibre-based insulation or expanded-foam (polystyrene) insulation remains the standard, largely because road and other vibration don't reduce your insulation to a few inches of fine dust at the bottom of wall cavities.
Material properties are complex, and represent interesting trade-offs between afforded capabilities and imposed constraints.
Speaking of flight and picking the nits here — looks like Wikipedia also isn‘t completely correct here:
> It is planned to make the first powered flight on any planet beyond Earth
...arguably the first _powered_ flights were done by the sky cranes of Opportunity and Perseverance
Not the Apollo 11 lunar module? In contrast to the sky cranes it actually lifted off again.
Figuring out something that works well in Mars' thin (but still there) atmosphere, especially a helicopter, is really impressive. The celestial body classification is just a cherry on top.
Edit: Phantom 4 is 1.3 kg and blades are 45g
Also, Isaac Asimov considered the system a dual-planet system as the Moon's path around the sun is at no point convex nor retrograde.
1% is an arbitrary threshold and solar orbit is dependent on external circumstances rather than the Earth-Moon system itself.
> Earth-Moon centre of mass is inside Earth, so, it's
> obvious that the Moon is orbiting the Earth, not both
> orbiting something else.
I'd tend to say that separating them further would tend more towards planet-moon. Yet doing so moves the system's center of mass outside the larger body, so would actually push the system into the dual-planet definition by that criterion.
The barycentre of the Sun and Jupiter isn't inside of the Sun.. so does that mean Jupiter doesn't orbit the Sun?
But Flight? A rocket has no fixed or rotating wing providing lift, so maybe not.
The first flight was in 1903, not 300 BC China when they used sky lanterns.
The first powered flight was in 1903, with the criteria that it was not gravity assisted, that it was sustained and that it was controlled. No one is claiming that it was the first flight ever.
https://www.nytimes.com/1985/06/12/us/soviet-drops-weather-b...