What do you think? Living on Jupiter and its Moons.

[MatterBeam]

Hi!

I've got a series running on my ToughSF blog where I describe the how and why of living on other planets.

The latest entry is for our largest Gas Giant and its 67 moons.

How to Live on Other Planets: Jupiter

A look at how we could colonize Jupiter and its Moon. Fittingly long for our largest planet!

Description

Jupiter is big. It masses more than twice of all the other planets combined. Appropriately, it has the lion's share of the moons in our solar system: 67 as of today's count. A faint planetary ring crowns this behemoth.

Layered like a big hydrogen snowball.

In interstellar terms, Jupiter is a rather average gas giant. It is mostly hydrogen, with about 25% helium and rare traces of other elements. The only solid surface is its core of metallic hydrogen, kept at the crushing pressure of 200GPa. Further extremes are reached at the centre of the planet. 

The upper atmosphere is more interesting. A mix of ammonia, water and even some sulphides makes for a diverse colour palette. The 1 bar (100000 Pascal pressure) 'surface' of Jupiter is at a hot 67 degrees Celsius. The top of the atmosphere, at 1000km altitude, is so hot that it glows during the night. In between are multiple layers of frigid hydrogen gas. 

Unlike most planets, Jupiter has a very dynamic cloud and storm system. It is powered by the rotation of the planet, thereby moving clouds at over 45000km/h. The Great Red Spot is one of the largest features, at 12000km tall and up to 40000km wide. 

These features are even more impressive from the view point of Jupiter's moons. The largest are called the Galilean moons: Io, Europa, Ganymede, and Callisto. All but Europa are larger than our Moon, and two are larger than Mercury. 

Jupiter follows the 'orbital spaghetti' school of moon systems

Accompanying these moons are a plethora of smaller bodies, such as Amalthea (167km), Himalia (170km) and Thebe (100km).

Habitability

Living on Jupiter's solid surface is not possible. 

The transition to metallic hydrogen that creates a solid surface involves temperatures and pressures that no habitat or spacecraft can resist. It might be possible, however, to float in the upper atmosphere.

Jupiter will offer titanic vertical landscapes.

Generating lift will be difficult. Filling balloons with the lightest gasses, such as hydrogen and helium, will not work as the atmosphere is already composed of those same gasses. A 'lighter than air' balloon does not exist here! The problem is compounded by Jupiter's gravity: 2.5G. This means that you would need to produce much more lift than on Earth.

The only solutions to generating lift would require the continuous use of energy: hot gasses are less dense than cold gasses, so something like a hot air balloon would work. A quick calculation tells us that if we try to maintain the altitude where pressure is 1 bar (Earth's sea level pressure) on Jupiter, the temperature is about 180 to 200K and density is 0.16kg/m^3. If we can heat up the air inside a hot air balloon to a blistering 450K (the maximum safe temperature of Kevlar), the density inside the balloon would be 0.08kg/m^3. This would provide a terrible lift to volume ratio of 1kg per 12.5m^3 of hot gas. In comparison, a helium balloon on Earth provides 1kg of lift per 0.9m^3. Even then, most of the lift capacity on Jupiter would be lost to the heavy insulation the balloon would require.

The other option would be mechanical lift: helicopter blades or wings. Obviously, these cannot be made large enough to support a large habitation base. With the Jovian atmosphere nearly eight times less dense than our atmosphere and with 2.5 times more gravity, an airplane would have to travel twenty times faster to take off, or require wings twenty times bigger and heavier.

Hypersonic... at liftoff?

Something like a 737-800 would have to travel at 7500km/h (Mach 6) to stay in the air!

Even if hopeful colonists manage to stay in the air, they will find themselves in the Jovian equivalent of a desert: no useful volatiles, poor energy resources and exacting living conditions.

Jupiter's atmosphere is starved of water and oxygen-containing compounds. They, along with elements such as sulfur or nitrogen, are held in the lower atmosphere, where pressures of 10 bars or greater make their extraction difficult. 

Considering the issues with generating lift and finding resources, habitats on Jupiter would have to stay very deep in the atmosphere. There, they trade crushing pressures and high temperatures for denser air and access to wispy clouds of ammonia and water.

At least, at those depths, the habitats would not have to worry about radiation hazards or meteorites. These same hazards make living in close orbit around Jupiter very hazardous. Automated factories would suffer from rapid degradation of their electronics, so even an unmanned presence is unsustainable.  

Moons of interest

Living in or around Jupiter does not seem to be worthwhile, at least with conceivable technology. Staying on one of the moons orbiting the gas giant would be the better deal... but which of the moons is the most promising target for colonisation? 

We will look at the Galilean moons first. Together, they represent 99.997% of the mass orbiting Jupiter. 

Io

Io is the Galilean moon orbiting closest to Jupiter, at just further than the distance the Moon orbits our Earth (421000 vs 384000 km). It is a remarkable moon in many ways, but habitability is not one of them: it is the most geologically active object in the Solar System, but also the driest (least water to mass ratio). Its distinctive yellow tint comes from the sulphur compounds churned out by volcanoes and shot up to 500km from the surface. The volcanoes themselves are incredible peaks, like the Boösaule Montes reaching twice Mount Everest's height at 17km!

Volcanic eruptions in low gravity are spectacular.

This moon is a champion in another statistic: density. At 3528kg/m^3, it is the highest in the solar system, surpassed only by a few metallic asteroids. 



Io orbits Jupiter in a mere 42.5 hours, wobbling enough to cause tidal forces to lift the surface by as much as 100m. As it does this, it flies through the most intense parts of the gas giants magnetosphere and gets bathed by 3600 rem of radiation per day.

This is 6 times the level that caused Chernobyl workers to die in months, every day. The safe limit is 360 times lower. 

This is 18000 times the yearly radiation we encounter on Earth, per day!



In terms of temperature, the surface varies between sulphur ice fields at 143K (-130 C) and volcanic spots hot enough to melt steel at 1922K (1649 C). Io has an extremely thin atmosphere, composed mainly of the scorching remains of volcanic emissions. It glows in the day and collapses as snowfall when the moon passes behind Jupiter. 

Due to the ions being stripped away by Jupiter's magnetosphere, Io builds up an incredible charge across its surface, reaching 400 million Volts. Lighting strikes discharge a potential of 3 million Amperes on Jupiter's end. 

The plasma torus visualized

In other words, Io is a fascinating place, with a great many potential uses, but it is worse for colonisation than even the sun-facing side of Mercury or the acidic hell of Venus. 

The rest is available here.

Tell us what you think!

 

Edited February 22, 2017 by MatterBeam

[UnusualAttitude]

A very interesting read. I've always found that Callisto looks like a surprisingly promising place to explore, or even settle, at least compared to other places in the outer system. It's funny how science fiction has traditionally focussed on the other Galilean moons (Ganymede and Europa), which are arguably more interesting, but would be infinitely more hostile places to live.

And there lies the biggest challenge. As far as I know, we can't yet even imagine how to shield crewed spacecraft from such high levels of radiation, unless our future means of propulsion allows us to encase everything in several metres of water or ice. That, and the huge delta-vee requirements to reach the inner moons.

I do enjoy your blog. Without wanting to give too much away, this entry will be particularly useful for the next part of the Logs. Camwise will have to pack his iodide tablets.

Edited February 22, 2017 by UnusualAttitude

[Findthepin1]

It says that Ganymede's gravity is over twice the gravity of the Moon, but the Moon's gravity is 1.622 m/s^2 and Ganymede's gravity is only 1.428 m/s^2, which is less than the Moon.

[Tyko]

I wonder if you could make a vacuum balloon (filled with nothing) that would create enough lift for a reasonable size. We don't have the material science to create it today, but perhaps in the future.

[MatterBeam]

3 hours ago, UnusualAttitude said:

A very interesting read. I've always found that Callisto looks like a surprisingly promising place to explore, or even settle, at least compared to other places in the outer system. It's funny how science fiction has traditionally focussed on the other Galilean moons (Ganymede and Europa), which are arguably more interesting, but would be infinitely more hostile places to live.

And there lies the biggest challenge. As far as I know, we can't yet even imagine how to shield crewed spacecraft from such high levels of radiation, unless our future means of propulsion allows us to encase everything in several metres of water or ice. That, and the huge delta-vee requirements to reach the inner moons.

I do enjoy your blog. Without wanting to give too much away, this entry will be particularly useful for the next part of the Logs. Camwise will have to pack his iodide tablets.

Real research, such as the Human Outer Planet Exploration study (HOPE: Article, Wiki), points to Callisto. Fiction usually focuses on arid Mars or thick-atmosphered Titan, which are lesser candidates. One fact I haven't seen picked up is that Callisto contains large deposits or rock and metal just sitting in the ice like Swiss cheese. 

For protection against radiation, just stay far away from Jupiter itself. Ganymede's equator is protected by a weak magnetic field, and Callisto is far away enough, that radiation levels fall to 1 rem per day. We naturally get 300 rem per year, and astronauts are allowed up to 25 rem per mission. All in all, a Jovian inhabitant can work a full business year outside of his or her habitat without being worse off than in the ISS.

You Camwise logs is always interesting, and I look forward to an... ah, colonization attempt.... of Jupiter?

3 hours ago, Findthepin1 said:

It says that Ganymede's gravity is over twice the gravity of the Moon, but the Moon's gravity is 1.622 m/s^2 and Ganymede's gravity is only 1.428 m/s^2, which is less than the Moon.

Sorry, this is a mistake and I'll have it corrected shortly. Thanks for picking it up!

31 minutes ago, Tyko said:

I wonder if you could make a vacuum balloon (filled with nothing) that would create enough lift for a reasonable size. We don't have the material science to create it today, but perhaps in the future.

Vacuum balloons have been proposed, but calculations show that they'd need super-strong carbon-nanotube or graphene-based walls to survive 1 bar of pressure. I suppose they could work in the much thinner upper atmosphere... but consider this: bouyancy is the difference in density. Even if your internal density is 0 (vacuum), the external density is still very low. It might never be practical to build such balloons, even if the super-materials exist.

[Tyko]

2 hours ago, MatterBeam said:

Vacuum balloons have been proposed, but calculations show that they'd need super-strong carbon-nanotube or graphene-based walls to survive 1 bar of pressure. I suppose they could work in the much thinner upper atmosphere... but consider this: bouyancy is the difference in density. Even if your internal density is 0 (vacuum), the external density is still very low. It might never be practical to build such balloons, even if the super-materials exist.

Assuming you can make them they'd work in Jupiter's atmosphere. The question is "how deep within the atmosphere do you go before you hit equilibrium between lift and weight". It's really a submarine for all intents and purposes

[YNM]

Just now, Tyko said:

Assuming you can make them they'd work in Jupiter's atmosphere. The question is "how deep within the atmosphere do you go before you hit equilibrium between lift and weight". It's really a submarine for all intents and purposes

Vacuum dirigible would only equalize in vacuum, naturally.

All depends on payload weight.

[Tyko]

Just now, YNM said:

Vacuum dirigible would only equalize in vacuum, naturally.

All depends on payload weight.

Assuming you have a rigid structure that you could evacuate of gas, you could control buoyancy by pumping gas in and out. It's just a submersible 

[YNM]

2 minutes ago, Tyko said:

Assuming you have a rigid structure that you could evacuate of gas, you could control buoyancy by pumping gas in and out. It's just a submersible 

Well, as much as a shipliner can bounce up and down the sea level as payloads comes and go despite keeping the hull dry.

 

For OP : I think I don't like living underground... dammit if you have such scenery outside, why not live at surface ? Ah yes I'd be fried after a few days. Good luck.

Edited February 22, 2017 by YNM

[Tyko]

28 minutes ago, YNM said:

Well, as much as a shipliner can bounce up and down the sea level as payloads comes and go despite keeping the hull dry.

Not quite. A surface ship is floating at the interface between two very different densities - the air above and the water below - this causes it to bob up and down along with waves. A submersible underwater doesn't bob up and down in the same way. A vacuum dirigible in Jupiter's atmosphere should be just as stable (or unstable) as a hot air balloon - subject to winds and localized changes in atmospheric pressure, but not bobbing up and down.

EDIT: I misunderstood your use of "bob up and down". The ship's displacement changes as it takes on or removes cargo. You're right about that. The sub or vacuum dirigible would do the same thing except it controls it's displacement by taking on or removing water (or atmosphere for Jupiter)

Didn't mean to hijack the thread   I guess it would be possible to colonize Jupiter's atmosphere. Have to figure out how to avoid the big storms

Edited February 23, 2017 by Tyko

[MatterBeam]

2 hours ago, Tyko said:

Assuming you can make them they'd work in Jupiter's atmosphere. The question is "how deep within the atmosphere do you go before you hit equilibrium between lift and weight". It's really a submarine for all intents and purposes

Quite true.

2 hours ago, YNM said:

Vacuum dirigible would only equalize in vacuum, naturally.

All depends on payload weight.

The biggest factor for a vacuum dirigible is the ratio of balloon wall mass to lifting capacity. Unless super-materials are used, it will be heavier than the lift it provides. At equilibrium, it produces sufficient lift but gets crushed by the pressure. 

2 hours ago, YNM said:

Well, as much as a shipliner can bounce up and down the sea level as payloads comes and go despite keeping the hull dry.

 

For OP : I think I don't like living underground... dammit if you have such scenery outside, why not live at surface ? Ah yes I'd be fried after a few days. Good luck.

You can live on Callisto's surface and Ganymede's equator and not get more radiation than an astronaut on the ISS. The heavy radiation happens much closer to Jupiter. 

The problem is justifying why you would take all that risk for the... ah, "looming gas giant with flashing aurorae and bright spark-like moons over your head" view.

2 hours ago, Tyko said:

Not quite. A surface ship is floating at the interface between two very different densities - the air above and the water below - this causes it to bob up and down along with waves. A submersible underwater doesn't bob up and down in the same way. A vacuum dirigible in Jupiter's atmosphere should be just as stable (or unstable) as a hot air balloon - subject to winds and localized changes in atmospheric pressure, but not bobbing up and down.

EDIT: I misunderstood your use of "bob up and down". The ship's displacement changes as it takes on or removes cargo. You're right about that. The sub or vacuum dirigible would do the same thing except it controls it's displacement by taking on or removing water (or atmosphere for Jupiter)

Didn't mean to hijack the thread   I guess it would be possible to colonize Jupiter's atmosphere. Have to figure out how to avoid the big storms

No worries, I appreciate any and all discussions here. We're all scifi fans after all!

[YNM]

3 hours ago, Tyko said:

EDIT: I misunderstood your use of "bob up and down". The ship's displacement changes as it takes on or removes cargo. You're right about that. The sub or vacuum dirigible would do the same thing except it controls it's displacement by taking on or removing water (or atmosphere for Jupiter)

Not quite true - why do you think the containers carried by such ship are towering above the deck ? They don't fill the hull to the brim with containers, and containers aren't full to the brim with heavier-than-water stuff either. Point is, I don't think changing the shape of the vacuum chamber would be easy, nor does create a new vacuum again.

53 minutes ago, MatterBeam said:

The biggest factor for a vacuum dirigible is the ratio of balloon wall mass to lifting capacity. Unless super-materials are used, it will be heavier than the lift it provides. At equilibrium, it produces sufficient lift but gets crushed by the pressure.

That's the inherent problem with vacuum dirigible.

Edited February 23, 2017 by YNM

[kerbiloid]

Not necessary rigid

Spoiler

(The artist's copyright reserved)

http://www.rusring.net/~levin/levin3d/dz.htm

but still too low difference between hydrogen and vacuum densities

[Snark]

On 2/22/2017 at 3:00 AM, MatterBeam said:

Generating lift will be difficult. Filling balloons with the lightest gasses, such as hydrogen and helium, will not work as the atmosphere is already composed of those same gasses. A 'lighter than air' balloon does not exist here!

This statement is true.  However,

On 2/22/2017 at 3:00 AM, MatterBeam said:

The problem is compounded by Jupiter's gravity: 2.5G. This means that you would need to produce much more lift than on Earth.

...this is incorrect and misleading.  For a craft that maintains lift due to buoyancy, gravity is irrelevant.  Jupiter's gravity could be 10 times or 100 times weaker, or stronger, and it would make zero difference to the question of "will this object float or sink".

All that matters to whether a buoyant object floats or sinks is this:  Is its density larger or smaller than the surrounding medium?  If it's denser, it sinks.  If it's less dense, it floats.  Period.

It's the same thing that determines, say, where the waterline is on a ship floating in the ocean.  Imagine you can paint a line on the hull, right at the waterline, showing how deep in the water a ship floats when at rest.  Then go turn a magic knob that increases or decreases gravity by a factor of 10.  The waterline won't move even one millimeter relative to the line you painted on the hull.

This is counterintuitive to a lot of people-- they're thinking "well, higher gravity means it's heavier so it'll sink, right?"  Except that the stuff it's floating in also gets heavier, by the exact same factor, so it cancels out.

For a heavier-than-air craft that maintains lift dynamically (like an airplane), of course, gravity does matter.  A lot.  But for a buoyant craft, all they need to worry about is maintaining a density lower than the surroundings.  Gravity doesn't enter into it.

That's not to say that building a floating thing on Jupiter will be easy.    It would be really darn hard, precisely because you're trying to float in hydrogen, which is literally the least-dense gas there is.  So either you'd need a hot-air balloon (with the problem of "where do you get the energy from?"), or else a vacuum balloon (with the mechanical problems that entails, as folks have already been discussing here).   Just... gravity itself isn't the issue.

 

Also, another thing I haven't seen anyone bring up here, including the OP.  Presumably, any potential colonists would be concerned about going on a permanent one-way mission.  There has to be a way to leave.  Even if you could somehow build a stable, floating colony in Jupiter's atmosphere... how do you escape?  Jupiter's escape velocity is nearly 60 km/s.  What kind of a vehicle are you going to provide that can pull that kind of dV, at the sort of high TWR that would be required for jovian ascent?  And handle the aerodynamic heating that entails, until you can get free of atmosphere?  And not be so heavy that it sinks your floating colony while it's waiting to take off?

[MatterBeam]

On 24/02/2017 at 4:43 PM, Snark said:

This statement is true.  However, [...]here).   Just... gravity itself isn't the issue.

I'll try to be clearer next time. Both generating aerodynamic lift and using buoyancy forces is difficult on Jupiter. 

Also, another thing I haven't seen anyone bring up here, including the

OP.  Presumably, any potential colonists would be concerned about going on a permanent one-way mission.  There has to be a way to leave.  Even if you could somehow build a stable, floating colony in Jupiter's atmosphere... how do you escape?  Jupiter's escape velocity is nearly 60 km/s.  What kind of a vehicle are you going to provide that can pull that kind of dV, at the sort of high TWR that would be required for jovian ascent?  And handle the aerodynamic heating that entails, until you can get free of atmosphere?  And not be so heavy that it sinks your floating colony while it's waiting to take off?

'How to Live on Other Planets' is a series on the blog which tries to describe colonisation of the solar system without looking through the lens of Earth. It is more useful that way for SF writers or worldbuilders that have very different plans for what happens to our planet. 

I agree that Jupiter is a bad choice for colonisation, it was one of the central conclusions of the post. If it were necessary, and a main base had already been established elsewhere, then it could still be done. Low Jupiter Orbit is tough, especially when high TWR engines are required. If we start at a TWR of 1.2, Earth-equivalent TWR would be something like 3! 

Unless the setting has access to high-erformance nuclear engines, it would have to be achieved by chemical rockets. However, the latter have a poor exhaust velocity of 4.5km/s, and LJO is 40km/s, so about 42km/s deltaV is required. Mass ratio 11371. Obviously impossible. If we limit ourselves to a mass ratio of 100, then an exhaust velocity of 9km/s, which is achievable by hydrogen-propellant nuclear rockets. 

Aerodynamic heating is an issue, so ascent profile will likely be very steep, with the majority of the horizontal acceleration being done outside of the atmosphere. 

[kerbiloid]

The pure hydrogen will corrode the zeppelin construction, leak inside and fill the interior space. The will be a boom, because of oxygen.

We must not ignore Pandore-style flying islands, btw.
In a more dense atmosphere, say Earth, Venus or so.
_{(Easy to implement with KerbalKonstructs.)}

Spoiler