Sci-Fi Civilian Vehicles, Equipment and Technology

So you're building a space station inside a mass of rock? Seems easier to must build the station next to the mass of rock.

It’s cheaper from a radiation and impact protection standpoint to build inside the asteroid.

You'll probably dig some of those tunnels just mining for minerals. Get to the center of gravity and the ore will come to you!

Well, my setting has planetary ring (OK, stellar ring) blocks that are useful ores, but the asteroids are used for space stations only because a) there is no other method to keep yourself safe from space radiation in my setting and b) many asteroids provide their own reaction mass, so you can coax them onto useful orbits with only a bit of mass loss as a penalty. That and some asteroids are on useful orbits already.

The general problem with space stations in the empty void is that the empty void contains nothing to build space stations with.

So if you're taking apart asteroids for the material to build spacestations, it's not that weird to churn the whole thing though a material processor and use the leftover rock and slag as radiation protection shielding.

Unless you're talking about really big ones like Ceres (which are more like dwarf planets, anyhow), i think the act of building in asteroids is basically going to be the default.

As I mentioned before, most asteroids aren't in convenient or useful locations. The problem becomes getting them from where they are to a useful orbit.

Using conventional NT Rs or near-future Ion Engines you can absolutely redirect them with reasonable costs and efficiencies. I really do not see this as a problem, unless you're trying to build absolutely enormous stations.

In fact i would argue the problem is exactly the same: building a station from scratch requires you get the resources from somewhere. You need to have the capacity to move hundreds of tonnes of materials considerable distances at virtually trivial costs in order to even start. Or you need to have rock-bottom prices for putting stuff into orbit from a planet. Building the ISS is not sustainable for any sort of actual project, let alone for a long-term habitat.

So you either move your vast quantities of material from an existing convenient location to where you want your station to be... or you move the vast quantities of materials from an existing asteroid to where you want your station to be. Same difference, IMHO.

As a final addendum: earth has closeby asteroids that would not require all that much propellant to be moved into earth orbit, and could thus also be used for orbital construction. Much cheaper than boosting individual modules up. NASA did investigate such a mission using near-future (IE, mostly much more powerful/bigger) ion engines and found it doable.

The smallest asteroid large enough to house a space station without collapsing into rubble is going to mass in the millions of tons. You can stick all the ion engines on it you want; it's gonna take a long time to move into a useful orbit.

Edited by Fighteer on May 7th 2024 at 5:07:41 AM

Just how rough is the space weather here? You generally don't need millions of tons of rock to protect you from stellar radiation!

On Earth the Earth's magnetic field works as a shield against space radiation

Not to mention about 60 miles of atmosphere. Of course, Some Of Us Still managed to get burned by Stellar Radiation in the form of UV light giving us sunburn. Of course, it's not the same has having Gamma induced cancer but it's still a good object lesson in taking radiation seriously.

Well, it's not stellar radiation like easily absorbed X-rays and far UV. It's mostly gamma rays which are not so easy to absorb. And cosmic rays about 30000 times more intense than in the Solar System, which are prone to produce secondary particles.

And such radiation easily passes through insufficiently dense matter such as air or certain kinds of steel.

You need millions of tons of that between you and a high energy cosmic radiation source just to provide sufficient protection that you don’t fry in short order.

Even lead foil has to be sufficiently thick to be proper shielding against such radiation sources.

Fortunately, millions of tons of rock that make up asteroids makes the need for lead foil quite reduced in terms of weight compared to building a similar habitat in open space.

As silly as it might look, space station could also use a radiation shield made rock and mortar taken from an asteroid, if the asteroid were too small to burrow into.

The NASA asteroid redirect pegged it at a few years. I really don't see the issue here, basically everything being asked for involves long timescales and moving vast quantities of masses to places where there's none. Whether you dig out an asteroid for radiation protection or build a very-thick-wall space station to have radiation protection, it's still the same problem.

The only real difference is whether constructed radiation defense (so water tanks, thick radiation shields etc) is superior to just using raw mass from an asteroid. Which, i think, depends a lot on the nature of the radiation.

^ Stopping the solar wind in terms of radiation shielding is cheap as chips if you just throw some rock in the way. Especially if the mineral content is not uniformly conducive to having electric or magnetic fields induced in them.

Meaning it’s dirt cheap to use asteroids as radiation shelter so long as it’s not a virtually pure lump of iron, cobalt and nickel.

Which most of them aren’t.

Stopping cosmic rays and high energy radiation like gamma rays blasted out of quasars, black holes, supernovae, or other astronomical phenomena requires more of an expense but utilizing physical barriers like rock or naturally occurring magnetic fields can bring the cost of the subsequent shielding down quite considerably.

sure i agree, but thats not quite what i meant. You're stuck with moving mass around because you still need to build a space station. That's the default. For some kinds of radiation (like relatively slow charged particels) a magnetic shield may be able to be built quite cheaply. Not every material behaves the same with regards to the solar radiation either. A really big living station may have enough plain water on board for life support and enough fuel for ships and stationkeeping that it can simply use it as radiation shielding. Some polymers are also very effective at stopping certain types of radiation, and so are a low-mass solution.

High-energy particles are not so easily stopped so you need a lot of mass. Here simply adding more mass is equally effective whether this is hull, liquid tankage, or dead rock.

So my question here is: what exactly is the radiation that's so prevalent in the solar system that you need so much shielding to begin with? Because if it's mostly regular solar wind, it would be easier to strip asteroids for materials and build space stations from that, leaving the useless rubble behind. If there's also still substantial high-energy particles, then the rock is very valuable mass shielding and you'd simply move the entire asteroid, disassemble it, and use the slag and rock for shielding.

Don't get us wrong, it's perfectly possible to turn asteroid rock into purpose built rad shielding and you'll probably be doing that in the long run. Rather, making the habitat inside the asteroid is a good shortcut and works as a temporary lodging while a full spinning colony is made. It's like how in a lot of colony-builders you start with communal housing and limit facilities and later move on to luxury suites for everybody.

edited for clarity.

Edited by Belisaurius on May 9th 2024 at 3:58:16 AM

In our solar system, ultraviolet. Planet Earth isn’t affected as much as a spaceship or station would be because it bends in our magnetic field and is heavily absorbed or deflected by the layers of our atmosphere. What ultraviolet radiation reaches the surface is mostly only sufficient to cause things like a nasty sunburn.

Mostly.

Also solar wind which includes a veritable boatload of alpha and beta radiation. Most of this is deflected by Earth’s magnetic field. These are a pain the ass because these are forms of ionizing radiation which can cause quite a few physical or chemical changes in things. There are pockets of this solar wind known as the Van Allen radiation belts where Earth’s magnetic field has trapped or slowed enough solar wind to create a hazard for anything trapped or passing through for a prolonged period.

Also the solar wind is energetic enough that it is confirmed able to strip off matter from other celestial objects. Fortunately this is mostly atmosphere it’s capable of doing to but it can do so nonetheless. (Just ask Mars.)

Beyond that is high energy radiation. Most of it is cosmic sources diluted by the vastness of space but our Sun does put out a sizable amount of x-rays and gamma rays.

All of that has to be shielded. Like ultraviolet, planet Earth’s magnetic field and atmosphere do most of the work at preventing harm to life on the surface from these sources. No such mojo in space however.

Who said anything about the solar system?

Also, magnetic fields are not quite as effective as people think. For one thing, there are sizable holes at the magnetic poles - hence the aurora. For the other thing, extremely energetic particles have too much inertia to be deflected by a magnetic field. Finally, gamma rays aren't magnetic and will penetrate any magnetic field short of a magnetar-strength one.

& yea no maybe i wasn't clear but i meant what's so different about radiation in this hypothetical solar system that requires heavy solar wind shielding.

In a nutshell? no. The amount of work it takes is basically the same. As mentioned before, asteroids are mostly rubble piles. Ones that are sufficiently big and solid (like metallic ones) are rare, and certainly unlikely to be in a useful location. You also still need a shitload of material to build the space station. So the most likely scenario (aside from, again, Ceres-likes) is that you simply deconstruct a bunch of asteroids for their carbon, volatiles, water, and other useful stuff, build a space station with that, and use the leftover rubble as radiation shielding.

You might want spin gravity on your rubble pile too (and your asteroid-coated station would not be dust-coated: you'd want some sort of binder or else every visiting spacecraft is a hazard), if gravity is a concern.

Edited by devak on May 12th 2024 at 8:51:36 PM

I keep telling people that Tunnelling Shields mean that you can dig through loose piles of gravel without dealing with a collapse but everyone ignores that part.

edit:Spelling.

Edited by Belisaurius on May 12th 2024 at 12:32:02 PM

You can't just say "tunnel boring shielding" without at least a cursory explanation of how it works, because none of the existing systems work on a loose pile of rubble.

That's key here: lots of asteroids are not merely rubble, but have extremely weak gravity too. Any existing mechanism that uses pressure to hold it together (like metallic or concrete shields) is immediately out. The engineering nightmare of trying to pump in some sort of cement slurry, i won't even start on that. Existing tunnel technology is there so all the rock (or gravel/sand/etc) does not fall on your head. Putting up some sort of structure is enough. On an asteroid, both the act of mining and the act of placing these structures would disrupt your asteroid and potentially turn it into a rubble cloud. IE, useless.

Common theories for asteroid mining involve simply scooping it up in a big unfolding bag and using the pressure of the bag to hold it together (and then some sort of outlet to mine it with). The problem is that this makes it really hard to bore the sort of neat tunnels you want.

The only real exception here is asteroids big enough to hold together with gravity (e.g. like Ceres) or made of likely non-rubble material (metallic, like Psyche) but i already noted they're rare and unlikely to be where you want them to be.

Edited by devak on May 12th 2024 at 9:42:37 PM

So you're issues is A) a lack of external pressure and B) lack of air and gravity making moving ore difficult and C) the asteroid falling apart due to mining pressure?

Well the first one is a non-starter. If there's no external pressure you can hold the entire structure together with brackets. The ISS holds 15 PSI with 3mm of Aluminum with polyurethane reinforcement and a second redundant outer aluminum skin. There's no reason a tunneling shield can't use that rather than concrete blocks.

The second part is a more significant matter but frankly one that needs to be confronted no matter what kind of mining technique you use. You've got to get ore to the smelter somehow and whatever technique you use will generally work no matter what kind of mining scheme you use. I'm thinking sandwiching the ore between two conveyor belts or an auger pump in a rifled pipe.

Third issue is an issue only for the smallest of asteroids. The moon Phobos took an impact big enough to form the Stickney Crater despite being only 11 km across on average and there are dozens of asteroids bigger than Phobos. 2 Pallas, 511 Davida, 3 Juno, all bigger than Phobos and plausibly big enough for multiple mining colonies, all digging into the asteroid dust to escape solar radiation.

Gonna note that spin gravity on a hydrostatic body isn't easy - unless the hydrostatic body has Earth-like gravity, spinning it up to the degree needed for spin gravity will cause it to fall apart. Having the habitat spin in a circular tunnel-like system makes the whole thing way more complex to build and there is drag/friction between the spinner and the tube/asteroid to contend with.

In a system where space radiation is a concern, it might just not be possible to have artificial gravity.

As for which systems would have space radiation, there are plenty of potential systems. Systems whose central star isn't a main sequence star but a neutron star, for example. Systems located close to active galactic nuclei or neutron stars, for another example.

Edited by SeptimusHeap on May 13th 2024 at 8:49:11 PM