Then if you wanted could you cook up a partial pressure atmosphere for the spin shell? Using magnetics to keep the small world centered in the spin shell, and can the air be like an air bearing?
Could you fly aircraft from the little world to the interior of the shell and land at the equator? Of course a crash might rupture the shell, so I anticipate that the shell would have many layers and some method to patch a hole.
As far as Nitrogen goes I guess you might have spaces with a higher pressure and Nitrogen.
If you have a sphere for a shell, then you have various spin gravity gradients which could accommodate various industrial processes.
You could actually have microgravity at the poles, if you had subshells that could be counter spun.
But the interior of the shell does not have to be pressurized, in some cases I simply imagine multiple shells with pressurized compartments where needed. This would be less vulnerable to accident and military actions.
Done
]]>To get to the ocean a tunnel method is needed, I suppose that would be a first base.
Getting to the ocean, you might do the things you have suggested. Now I wonder about a simple spherical shell to spin around the moon.
A simple version is just that a sphere, that is outside of the moon and spins and has artificial gravity on its equator.
Doing this then something needs to be done about the stability of ice. and the sea.
Frankly I want the shell to be quilted sort of multi-layer, so that rupture is less dangerous. I originally thought that the interior of the shell would not be pressurized. But now I wonder if it can tolerate a certain level of O2. Maybe as high as 1/3 g???
The notion of a mega satellite for Ceres invokes magnetic bearings. So here I am supposing the moon might have magnets that point magnetic north poles outward, and the shell would point magnetic north poles at those magnets.
You have a sort of an air bearing if the distance between the shell and the moon is enough. Don't know if we can get away with it though.
If you could have a 1/3 bar or maybe less O2 atmosphere you could use air breathing aircraft to pass from the moon to the shell.
Granted, you could probably have towers at the spin poles that would allow trams between the moon and the shell.
So, the shell would have enough gravity at its "Equator" whatever sufficient gravity were.
The outer shell could have a rectenna on it, and power plants may send power to the apparatus. I know solar is not popular for Saturn, but concentrating mirrors are simple and can be rather thin, so solar is not ruled out for Saturn and company.
And in the Saturn system we have Nitrogen for making a greater atmosphere simulation.
Done
So, notions of modifications and concerns are welcome.
Done
My profile for the moon is probably not correct, but it is hard to get the correct information.
https://phys.org/news/2024-02-mimas-tin … ocean.html
OK, hard to get the information I want but just now I think that perhaps 90% of the moon is melted or rock. Not that much rock, but still if it were even 5%, then that is something.
The anti-humans don't want our germs anywhere in space. Basically they wish we were dead, I think. The want their servants to serve them and then be dead, I think.
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]]>At -100°C, the thermal conductivity of ice is 3.5W/m.K. Mimas has a radius of 200km and the ice shell is expected to be 30km thick. By my estimates, the temperature difference between the sea and the surface, must be at least 150K. To keep the sea liquid, about 8GW of heat must be generated by core-ocean interactions. Maybe tidal flexing induced by the gravity of Saturn and its other moons provides this heat.
But 8GW is not a huge amount of heat on a planetary scale. It is the heat generated by two 1400MWe nuclear reactors. In the future, a human colony of a million people could generate this sort of waste heat. And a small icy world gives that colony a place to dump waste heat without huge radiators. So aquaforming is something we may be seeing a lot of.
It occurs to me that an ice shell 100km in diameter and several km thick in a gravity field of ~0.001g, has both a short radius of curvature and low compressive shell stress. It should be possible to inflate an air bubble between the ice layer and the ocean that humans can live in. Because the ice layer is curved, it should function as an arch.
]]>Indy 100
Hidden ocean discovered beneath the surface of moon
Story by Harry Fletcher •
4h
I would not go so far as to make a high pressure atmosphere under such a shell, just a method to reach the ocean.
For instance, if you harvested the ice shell to fill up aqua habitats, you would eventually reach the ocean, and then with robots you could mone the core.
If Calliban wishes he might do some calculations of conditions of such a terraformed world.
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]]>If you have a radiator of metal perhaps, and you discharge evaporation into it, then the air pressure inside can be kept low, by freezing.
If the shape of the radiator were basically a cylinder, when the level of frost was high then you could pull a sock over it as thermal insulation.
Then you could allow the air pressure to build up inside, and so the cooling output from the heat source you want to sink, could melt the ices. So, maybe a phase change cooling in this part of the cycle?
Of course, then you need a method to draw off the fluids that result from melting or evaporating the ices.
Rinse and repeat.
I just got up so maybe there is a flaw, but please let me know what you think.
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]]>For bodies some 40% more massive than Ceres, the effects of scale height are enough to provide a counteractive force that will restore a displaced shell. On these worlds, pressure containing shells could be built without the need for any physical connection to the central body. For smaller worlds, cables or towers would be needed to physically anchor the shell in place and prevent it from displacing and impacting the surface. Roy doesn't seem to have accounted for the compression that would result from a displaced shell. Given that speed of sound is only 343m/s under standard conditions, any movement of a planet sized shell will compress the gas underneath faster than it can escape. This has nothing to do with scale height and would provide an additional restoring force. So I think his shell concept could be applied to smaller bodies than he anticipates.
I think a more probable concept to shell worlds is the tunnel world. A large asteroid like Vesta could be riddled with tunnels and cavities as a result of mining activities. These could be hundreds or even thousands of metres in diameter. If these are more than about 200m beneath the surface, the overbearing weight of the rock would contain the upward force resulting from pressurisation.
Tunnel worlds could be built up incrementally as a byproduct of the mining needed to build space habitats. They aren't things that necessarily require a dedicated effort to build and can start small, growing bigger as excavation removes more material. This makes them a more probably outcome in my opinion.
The conventional shell might eventually be used to enclose outer solar system objects like KBOs. These bodies are 50% water ice by mass. A sufficienctly powerful thermonuclear heat source could be used to melt this ice. An inflatable skin would then be placed over the surface and inflated with air to low pressure. The liquid water will then be pumped from beneath the skin onto its surface, where it would freeze into solid ice. As the ice layer thickens and its weight increases, air pressure will grow to balance it, allowing net zero shell stress. Eventually, we have a mostly rocky world, with a gap of say 10km between its surface and a thick icy shell above, with the weight of the shell largely balanced by air pressure, leaving only a weak compressive stress within it. Waste heat removal would favour keeping most of the above the shell liquid. So the roof itself will need enough integrity to prevent water from draining out of tge shell onto the ground.
]]>If so, then do they pull in gasses and dust from the interstellar medium?
If so, then do they do a slow fusion???
I understand that Neutron stars may explode from time to time, if materials from a companion star is deposited on their surfaces. However, I am wondering if white dwarfs might be fed by a trickle of Hydrogen and Helium, so as to have a continuing fusion at a very low lever.
I don't know of course, that is why I post this.
Done.
]]>There are two possible reasons for shelling a planet (In these cases the shell is supported by atmospheric pressure underneath
1) to provide a surface for inhabitants to stand on Venus, Saturn, Uranus, Neptune
2) to prevent the gases in the atmosphere from escaping into space Mercury, Moon, Pluto
also 2a) to conserve gases required to produce a 1 bar habitable atmosphere on the World's surface (Mars)
One exception would be Jupiter, it presents a special problem, is gravity at the top of the atmosphere is significantly greater than the gravity at Earth's surface. If you take the square root of Jupiter's mass in Earth masses, you get the radius of the shell around jupiter in Earth radii that would be required to have a surface with 1 Earth gravity, the problem is this radius is greater that the actual radius of Jupiter, so atmospheric pressure could not support this shell, some other mechanism would be required to support it, a dynamic compression mechanism most likely which transfers the weight of the shell onto the atmosphere of the Planet Jupiter below. The surface area of this shell would equal 318 times the surface area of Earth, since Jupiter has 318 times the mass of Earth, this is more difficult that Saturn where the shell would simply rest on top of its atmosphere, it would also be easier to obtain the atmospheric components of a breathable atmosphere on top of a Saturn shell than a Jupiter shell, since the Saturn shell rests on top of Saturn's atmosphere, and one can simply mine out all the nitrogen, oxygen, carbon, and water from deep in Saturn's atmosphere. Since Saturn condensed out of the original solar nebula, then all those gases found in Earth's atmosphere are available in sufficient quantities in Saturn's atmosphere. Since the planet holds onto hydrogen, it would also hold onto all the gases that are heavier than hydrogen. Convection would keep the gases mixed despite the heavier components of the atmosphere, so what one would do is extract the nitrogen from the 0.01% ammonia in Saturn's atmosphere, the carbon dioxide would exist at a lower level in Saturn's atmosphere where it could exist as a gas instead of as dry ice, oxygen would come from water clouds deep below as would the water as well. Since Saturn has 95 the mass of Earth and most of it is in gases, that means even if a gas exists only in trace amounts as a percentage of Saturn's atmosphere, there is enough atmosphere there that we can obtain as much of those gases as we need. A shelled terraformed Saturn would require 95 times the breathable atmospheric mass of Earth's atmosphere since its surface area is also 95 times that of Earth and an atmosphere under an Earth's gravity would stack just the same as it would on Earth.
The next problem is providing adequate sunlight Saturn's diameter is 120,536 km. One could build a solletta ring around Saturn that concentrates sunlight around Saturn to warm it up. If the Solletta ring was 3,900,000 km in radius and 1,280,000 km wide it could gather enough sunlight and concentrate it on Saturn enough to warm up Saturn's artificial surface so it warms up Eventually the planet would absorb enough heat so that its atmosphere would expand outward, so hopefully the shell would be made of stretchable material. I imagined a similar solletta ring around Venus, but in this case it would be only 39,000 km in diameter and 12,800 km wide, the main task for that solletta would be to shield Venus from too much sunlight and give the planet a 24-hour day/night cycle by reflecting sunlight around the planet and illuminating the right hemisphere with reflected sunlight on the inside of the Solletta.
We could also shell rogue planets, the problem with rogue planets is they are very cold, and so would hold on to their hydrogen when they formed, an Earth mass rogue planet for example would be a sub-gas giant, a mini-neptune for example, its mass would equal Earth but a large portion of that mass would be in the form of the gases hydrogen and helium as they make up the primary components of interstellar gas clouds and there would be no nearby stellar radiation to blow those gases away. If we were to remove the light gases from an rogue planet, what we'd have left from an originally Earth massed planet would be something with less mass that the Earth, the radius of an Earth mass rogue planet would be greater than Earth due to its lower density and would thus have less than an Earth gravity at the top of its atmosphere. A rogue planet could be a planet like Saturn or a planet like Neptune, so the same methods we'd use to shell those would would apply to a rogue planet, the only difference would be that there would be no nearby star to focus radiation on the planet to make it habitable. One possibility is to build a double shell around a rogue planet, the bottom shell would be the surface in which you stand on, the top shell would contain the breathable gases between the two shells. On tip of the top shell would be a layer of hydrogen and helium plus fusion reactors. The hydrogen and helium would feed into the fusion reactors and the fusion reactors would provide power for the artificial illumination between the two shells.
]]>If doing as you suggest, then I would also have a chatchment shell attached to and supported by the outer shell. That shell could catch air leaking out or the outer shell propper, and keep the pressure between the double outer shell below that of molecular flow for air, and the catched leaked air could then be pumped back into the system.
That shell, and the shells you have suggested, and then below that I would eventually want built the honeycomb shell, which could hold a pressure by it's weight of at least 300 mb. It would be really cool to have a dirt surface of an asteroid with a savanna vegitation on it.
Since I have invensted nothing but imagination so far, I can afford a savanna. Keep the lions though. Don't want lions leeping at me from 1000 feet away.
]]>I quickly and with little concern for precision have calculated a few things:
0.025 g for gravitation.
0.36 km/s for escape velocity.
To hold down a full 1 bar atmosphere, you would need 1280 feet of water (More if it is ice), but that is for reference, I do not propose to use water.
But if you had building materials 4 times as heavy as water, you might need 320 feet.
That shell could be a honecomb type structure, with many cells, and of course with that much better safety factor against leaking. I suppose some of the cells could simply be filled with stony materials as balast. Some could have centrifuges in them to generate synthetic gravity.
I would think though that as it was built and made more heavy, a progression of atmosphere imposed over Vesta could be done.
10 MB, 50 MB, 250 MB, 330 MB, 500 MB and then perhaps 1 Bar.
That world is so small that perhaps support structures from the surface to the shell could be used.
So the builders would end up with a expansive living space in a honeycomb shell, a tiny world with a biosphere on it's surface, and an extensive mining operation subsurface, which might even reach to the core. The mining spaces when they were done with them could also provide living spaces as well.
]]>Maybe some super advanced civilizations could manage that.
I myself think that perhaps we might consider the Asteroid Vesta or the moon Enceladus to cut baby teeth on. Just maybe in many numbers of years our inheritors might do that.
]]>Well, internal heat dominates anyway, but - how much is the geothermal energy flux per sq.m.?
The inner heat exploitation will shrink the planets indeed.
Puffier and hotter will blend better and will be more suitable for mining, but once the bark/s set over these planets comprise 10s of Earth masses of temperature of 1000s of K. Shotcutted to 3K universum background temp. radiator the Carnot efficiency would be 99.95%, i.e. more or less extractable on "face value".
For how long this can provide, say, 300W of power per sq.m. of circum-(say)-Neptune habitat?
If for millions or billions of years then even interstellar ( rogue ) neptunes will live well in the dark...: two shells - very thin "ceiling" one + more solid floor one.
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Well, well, weeeellll, ...
Neptune's mantle and core are approx. 15 Earth masses or about 10exp26 kg
Mostly water-amonia, so we could approx. it to water specific heat.
Which is about 4KJ/kgK.
Amonia specific heat is 6-ish.
Iron ~ 0.4 KJ/kgK
Specific heat of water under hundreds of thousands to millions of bars and thousands of K temperature, I dunno, but ... lets say this total mass has average temperature of 3000K and the mass above and specific heat of 4KJ/kg.
10exp26 kg multiplied by 4KJ miltuplied by 3000K = 12x10exp29 J
5.5×10exp24 J is the total energy from the Sun that strikes the face of the Earth each year.
Neptune's 1gee shell-world would have 17 times bigger area then Earth
Lets assume better IR isolation and needed 10 times lower "solar" constant of 150-170-ish W/m2. ( to round the figures )
Thus the habitat could be powered for 10 000 years only by internal heat reservoir before sinking moons and external captured bodies to become necessary.
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