Hypothetically, spacecraft are some day built capable of surviving reentry into Jupiter’s atmosphere. The craft slow down from orbital velocity to rest relative to the atmosphere and deploy gas filled balloons, floating in the clouds of Jupiter.
Could human astronauts live in water tanks and survive the 3 G? Obviously, water tanks are used a simulator for zero gravity but they aren’t physically the same thing - the 3 Gs would still be pulling on every bit of tissue in a person, just their entire body would be evenly supported by the water as they float there.
Would liquid ventilation help any with this? (the humans are breathing liquid instead of air - works in rats though no human trials are listed)
Humans have quite a bit of experience breathing gas at 3x normal pressure. Scuba divers do it all the time.
So I don’t think breathing would be a problem.
Such astronauts night want to change the composition of the gas mixture to something other than normal Earth air proportions to achieve something closer to normal Earth partial pressures of oxygen and carbon dioxide.
But everyday living in high gravity could be a problem for all sorts of other physiological reasons.
Assuming (falsely) that 3G is equivalent to three times the pressure, it’s equivalent to SCUBA diving to about 66 feet, because you add 1 atmosphere per 33 feet depth.
But the pressure really depends on where you stop (altitude). The pressure will increase as you go lower; meanwhile the gravity will decrease. So it’s really just a matter of buoyancy design of the “landing” craft.
Off the top of my head, getting out would require something exotic. I don’t think it’s impossible - but you would need extremely high ISP and extremely high thrust.
The only way I can think of that would give the needed performance would be a large network of satellites in jupiter orbit would have very large laser arrays and mirrors. They would focus their light, tuned to whatever has the best transmissivity through Jupiter’s atmosphere, onto the back of the rocket trying to leave. Ablative propulsion like that can have several thousand ISP, and also very high thrust/weight since the rocket is not carrying the energy source (the rocket would just be a very long stick of some kind of solid propellant, with the payload on top)
Or, antimatter - but we can work out the numbers for ablative laser propulsion right now, since it is nothing special and achievable on a small scale right now. We don’t know how to even store significant quantities of antimatter in a 3G gravity field…
You’d build the satellites by sending self replicating factories to some of the moons of jupiter. You’d build the self replicating factories and the interplanetary vehicles in a self replicating factory on Earth’s Moon. You’d build the first self replicating factory on Earth. A self replicating factory is a huge room of robots and general purpose machine tools that can make everything used in itself… We’d make such robots work at a software level by using the advanced AI methods that Google and other researchers have recently developed, where neural networks that can reliably learn to perform complex tasks are finally beginning to work on a practical scale…(so you wouldn’t have to explicitly program the robots with every tiny motion needed to make the many thousands of distinct products a self replicating factory would need)…
Note that Jupiter’s gravity is ‘only’ 2.54 Earth gees at the cloud-tops; this might not seem much less than 3 gees, but I suspect you’d be glad of the difference if you went there. You might need some kind of Iron Man suit to help you move around, even if you were confined to the gondola of a hot hydrogen balloon.
Three gees is survivable for short times even without buoyancy tanks or the like. Amusement park rides routinely exceed four gees, and fighter pilots routinely go as high as ten. Mind you, it wouldn’t be fun, and you’d probably get a lot more heart attacks than you would on Earth, but it could be done.
Ignoring Habeed’s proposed liquid tanks and just talking about living in a habitat on Jupiter …
Once you’re used to it, 3Gs is only a minor problem for sitting, leaning to & fro, and moving arms & head. Eating, peeing, & pooping will probably work about normal. Going from sitting to lying down for sleeping would be easy. Going the other way would be work, but doable. In other words, being a couch potato or a telecommuting office worker would be not all that physically challenging.
I wonder whether sleep would be disrupted; the normal breathing reflex is pretty gentle and may not be strong enough to ventilate adequately. I’d bet sleeping on your back would be all but essential to survive the night.
I think walking would be very, very difficult bordering on impossible for all but the strongest humans. A few short steps would be a full workout even for them. Certainly they’d be pretty fragile and unable to lift much additional load beyond their own body. A trip and fall would almost certainly be a fracture or concussion on impact.
In all I think we’d do better to send the humans to places with noxious atmospheres but compatible G forces. Send the robots where the Gs are incompatible with people even if the place is otherwise “Class M”.
First. look up David Blaine - 10 days in a water tank (breathing with an air hose) was very damaging to his skin. Your skin is not designed to handle long-term water exposure.
Another suggestion I’ve seen - Freon (now illegal) with oxygen dissolved might be an acceptable substitute. There have been experiments with mice submerged in Freon with high oxygen content dissolved in it, and once the lungs fill up with that, you can breathe properly. Freon being close to water density, would help with buoyancy. The suggestion I saw was that it would work for very high pressures (deep deep sea diving) and also in extreme maneuvers for spacecraft - because of the neutral buoyancy, you could subject, say, a fighter spacecraft to extreme G-forces and the occupant would not become a smear across the interior wall.
IIRC some humans had experimented with breathing Freon and said the worst part was filling the lungs, almost deliberate drowning… until you realize you can breathe again.