Shell-Worlds: How Humanity Could Terraform Small Planets

[rhoenix]

One day, humans could re-make a world in Earth's image.

Engineering an inhospitable world into a livable one, a process known as terraforming, could be a successful way to colonize another world after a long, interstellar journey, said Ken Roy, an engineer and presenter at last week's Starship Congress in Dallas, Tex.

Roy's terraforming vision hinges upon what he calls "shell worlds." Upon arrival at an ideal planet, humans would literally encase the alien world inside of a protective shell made from Kevlar, dirt and steel. [Shell-Worlds: How Humanity Could Terraform Small Planets (Infographic )]

"We have a central world. We put an atmosphere on it," Roy said. We can have the "composition, temperature, pressure of our choosing. Let's assume we want 'Earth-normal,' and we put a shell around the central world to contain this atmosphere. The atmosphere then exists between the shell and the central world. The outer part of the shell is essentially a vacuum."

While the planet's gravity would remain unchanged, the rest of the world could be made very similar to Earth after importing vital materials, Roy said. The new world could even have some benefits not afforded on Earth, such as:

Industry and facilities that could benefit from access to a vacuum could use a port that connects to the outside of the shell.
Ultraviolet radiation from a star would not be a problem since the world would be fully encased in the shell.
The heating, cooling and the length of a day on the world would not be dependent upon the orbit of the planet around a star.
The shell would provide radiation protection.
The world would provide an almost limitless playground for design. For example, cities could hang down from the interior of the shell.

A small planetary body like Mars or even Pluto would be a great candidate for the shell world treatment, Roy said.

Martian gravity is about one third that of Earth's, and the surface area of the Red Planet is equal to the land area of Earth. Mars has no magnetic field; plate tectonics seem to be non-existent, and the planet's core is frozen, Roy said.

While all of these factors might seem to add up into an inhospitable world, they actually make a Martian-type planet a great candidate for shelling.

"That is not a bad thing," Roy said. "It means you don’t have to deal with volcanoes and earthquakes. I'd say that's a good thing."

Roy admits that these kinds of worlds wouldn't be perfect. The creation of a habitable shell world would be an intensive process; large amounts of nitrogen and water would need to be imported or produced on the planet, and the construction of a shell itself would be a vast undertaking. But it might be preferable to other ways of terraforming, he said.

Traditional terraforming methods used on a Mars-like body would require mirrors that reflect sunlight down onto the planet's surface, simulating a greenhouse effect for a small planet.

If the world's manufactured atmosphere is designed to provide Earth-like conditions on the surface of the traditionally terraformed home, then engineers would need the equivalent of about half of the mass of the Earth's atmosphere imported to Mars, Roy said. That atmosphere would also bleed off into space eventually.

A Mars-sized shell world would only require about 6.6 percent of the mass of Earth's atmosphere, a much more manageable amount of material.

Shells could provide the next step once humans actually reached a Mars-sized planet orbiting another star, Roy said.

"Getting [to another star] is half the battle, but you also have to give thought to what you do once you get there," he said. "One of the objectives of travelling to another star … is colonization. It's unlikely that once we get to an alien star system, we'll find a world that we can move into."

Ah, plans are afoot already. Maybe we can do a test-drive of this sort of thing on Earth's moon Luna.

[frigidmagi]

I'm of the opinion that it would be honestly easier to drill into the moon. As that is actually something we could pull off today.

Also, fuck me a that would be alot of Kevlar and steel to make a shell around Mars.

[rhoenix]

I'm of the opinion that it would be honestly easier to drill into the moon. As that is actually something we could pull off today.

Also, fuck me a that would be alot of Kevlar and steel to make a shell around Mars.

Yeah, I'm guessing this would be far easier with much smaller masses, since that would be a LOT of material.

And hey - if 3D printing keeps advancing the way it is, we can mine the moon and use the material directly to 3D print the shell. I think that would be a good test case.

[Lys]

There's a vast quantities of materials nobody's using out on the asteroid belt, and even more out in the Kuiper belt. Making a shell around a planet should be logistically possible for an advanced Kardashev type-I civilization. It's mostly a matter of time and effort, and giving Mars an Earth-like atmosphere requires vast quantities of materials anyway. The only question is whether our descendants will be better able to focus on large scale, extreme long term mega-engineering projects than we are.

[Josh]

There's a vast quantities of materials nobody's using out on the asteroid belt, and even more out in the Kuiper belt. Making a shell around a planet should be logistically possible for an advanced Kardashev type-I civilization. It's mostly a matter of time and effort, and giving Mars an Earth-like atmosphere requires vast quantities of materials anyway. The only question is whether our descendants will be better able to focus on large scale, extreme long term mega-engineering projects than we are.

If a lot of the process can be automated and run essentially off-camera, I'd say yes. We pay attention to big public allocations of resources and manpower, but turning loose swarms of drones is more feasible.

[Hotfoot]

Yeah hey guys let's go to a place we can only get to via space flight and make it impossible to get to by way of space flight and horribly prone to absolute failure from basically undetectable space debris. Hooray!

[rhoenix]

Ok, then how well would Ceres serve as a test case for this sort of thing?

[Cynical Cat]

Ok, then how well would Ceres serve as a test case for this sort of thing?

Ceres is no where near the size of small planet/large moon. As planetary macroengineering projects go, it's not unreasonable, but it's still planetary macroengineering which assumes ridiculous amounts of time and resources to devote to a project. For those keeping track, a Dyson swarm is easier to pull off than this.

[Lys]

Yeah hey guys let's go to a place we can only get to via space flight and make it impossible to get to by way of space flight and horribly prone to absolute failure from basically undetectable space debris. Hooray!

There are space ports on the exterior of the shell for a reason? And on the scale of a planet it would take a really big rock impacting the shell to cause more than a minor repair job in comparison to the scale of the structure.

For those keeping track, a Dyson swarm is easier to pull off than this.

Theoretically, all a Dyson swarm requires is for you to build one drone. The principal difficulty is in making that drone, everything after takes care of itself.

[rhoenix]

I think I get what CynCat & Hotfoot's issues are - by the time we have the practicable technology to actually do this, there will likely be other (and more practical) options for doing so. After re-reading the article, and doing a bit more reading about related ideas and subjects, I'm more inclined to agree with their assessment.

A nice idea to show that someone's thinking about the future, and food for thought for scifi writers, but that's about it.

[Lys]

There being better and more economical options - such as genetic engineering plus cybernetics to minimize terraforming - hasn't ever stopped anyone from engaging in gigantic vanity projects. I mean, hell, if I had a system's worth of resources to spare I'd probably build several of those things.

[frigidmagi]

Bah, I would just drill into the planet's mantle. Now instead of needing to ship materials for the shell, I just have to move rock and soil round with shipped equipment. Is Easier! Is less maintenance! Is cheaper!

[rhoenix]

Bah, I would just drill into the planet's mantle. Now instead of needing to ship materials for the shell, I just have to move rock and soil round with shipped equipment. Is Easier! Is less maintenance! Is cheaper!

That could be interesting, for certain. Titan might be a good candidate for it; it's surface conditions are less annoying than Venus' to deal with overall. Titan's basically a big ice moon with a metal core - the core could supply some of the metal, and you'd probably be able to get more from Saturn's ring system.

[Hotfoot]

There are space ports on the exterior of the shell for a reason? And on the scale of a planet it would take a really big rock impacting the shell to cause more than a minor repair job in comparison to the scale of the structure.

Spaceports would make the system totally unsustainable, because you'd have to be able to account for the constantly changing mass of the spaceport comparative to the movement of the shell. Polar ports might be able to adjust for this slightly, but you have to find a way to make a spaceport work without ripping the shell apart under normal operations.

Meanwhile, you're looking at large and constant impacts, requiring constant resources spent not just on repair, but on maintaining atmospheric pressure. Plus the tougher you make the material, the harder you make it to keep in orbit and the more it will cost.

[frigidmagi]

Space elevators everywhere!

But seriously I'm putting my money on "DIG ME HEARTIES DIG!"

[Josh]

Eh, playing with implausible concepts can be a useful exercise as well. We have no idea what ideas might spin off, or what magic the next generations of technology will bring.