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Atomic Station

Been a good long while since I did a new station. I realized out of nowhere yesterday that a stylized Atom symbol is actually pretty easy to make rotationally stable if you lock the ‘electrons’ in place. The high surface area to volume should make this thing relatively easy to power and shed heat from with solar panels and radiators.

If gravity in the electrons is ~1g, then on the rings it varies from 1g down to about 0.2g. The living surface in the ‘nucleus’ is at 0.15g or slightly lower than lunar surface gravity. Of course, the nucleus could rotate at a different speed than the rings and be connected to them with magnetic bearings or something similar, but I still tend to prefer physical connections even if I don’t show them here.

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Another Domed City

Decided to keep playing around with city designs for large moons or small planets. 

If gravity’s low enough, it’s probably a good idea to have a high gravity area for exercise. Last week I showed rotating rings sunk into a crater. That’s almost certainly not necessary for support. The amount of structural support necessary to hold down a large pressurized dome on a planet or a moon with a minimal atmosphere should make the weight of a rotating neighborhood insignificant by comparison. And by having pairs of rings rotating in different directions, net torque from friction should be minimal.

I like the idea of using canals for transport. Water’s a nice thing to have a large supply of for a number of reasons, so you may as well put it to use.

And a dome doesn’t have to be isolated. A cylinder will hold in air almost as easily as a sphere. And I’ve driven down enough highways with farms on either side, that it seemed nice to recreate the concept after a fashion. It’s a short tunnel here, but there’s nothing that would keep it from being hundreds of miles long if the builders wanted.

And there’s more than one model for a road. Or a canal.

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Moon City

Specifically Callisto, in terms of what math I did. This is an idea I’ve had for a while. Just because you planted your domed city on a rock big enough to have its own gravity doesn’t mean you can’t have neighborhoods with higher apparent gravity within that city. And that might actually be necessary for health purposes. This animation shows a city with two 1-g rings and two 0.5-g rings. The rotation speed should be more or less accurate for a ring radius of approximately 900 meters. In reality, you’d probably want the ring segments to be sealed off from the rest of the habitat’s atmosphere, probably sealed torus shapes in slightly larger toruses filled with no air. The faster ones are moving at about 340 km/h relative to the ground. Or maybe you like super-hurricane winds. I don’t judge.

(the animation is a bit jerky because I screwed up and moved the camera before saving the final frame. I might fix that eventually)

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Spring/Summer Project

So it’s been a while since I’ve played around with aquaponics. I had fun back then, but also eventually ran out of time and found a few issues. This year I’d like to ease back into it. Actually not aquaponics this time (because the fish are a major failure point and their most accessible feed is obnoxiously unsustainable), just hydroponics using coffee grounds and other kitchen waste for a nutrient source. And I want to try and make a basic system that is: 1 - cheap and can be replicated with easily available or substituted parts, 2 - reliable, 3 - very easily maintained and repaired, and 4 - operates automatically for at least a day with no human intervention or electric controls.

Here’s my basic conceptual model for the water flow:

A reservoir on top holds a day’s worth of water. Siphons are used to transfer water from the reservoir to a grow bed. When that bed is filled, its own siphon begins to drain it, and triggers a balance (not pictured) dropping its outflow to the minimum water level position of the bed and at the same time lifting the reservoir’s siphon outlet to cut off flow into the bed. This repeats with each bed until the bottom bed drains and restarts flow from the reservoir. Once a day water is lifted or pumped from the bottom reservoir to fill the top and ensure that the system can continue operating. New water is introduced as needed.

A solar or wind pump could lift the water as well, operating whenever the relevant energy is available and relying on system capacity to cover downtimes. Compost is placed in the beds in perforated and capped cylinders so that the flood and drain activity keeps the material moist and aerated to be rapidly broken down by worms and bacteria.

The two reservoirs can be kept shaded, covered, and insulated for temperature control and to minimize evaporation and prevent mosquitos.

My first step is to play around with the siphon and balance system on a desktop scale to see what works. We’ll see if I stick with it. Hopefully the balances will be much less sensitive to flow rate than the loop siphons I was playing around with before were.

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Suddenly Vaccinated

My job at the grocery store finally did something right and let me get vaccinated on Wednesday (single shot, J&J). Once they opened up the eligibility, it was probably only 5 minutes on the computer and 40 minutes in a grungy temporary storage room at one of stores waiting for my turn and then waiting to be sure I wasn’t going to pass out or break out in hives.

The good news I can tell my immune system is doing something. A day later I’ve got a slightly elevated temperature and heart rate, the barest hint of a headache, and just enough soreness in every muscle I own to be really annoying. I’m resting up and drinking water, so there won’t be a post today, or probably again until the second week of April since I’m taking a vacation soon.

Be well.

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Shamrock Station

Forgot to add this to my queue. Nothing too special this week:

It’s just a slender spinning ring space station with shamrock shaped habitats facing the center of the ring, and a set of six elevator towers where the bottom two thirds of the towers have the same shamrock habitats circling the station in pairs that ascend in a double helix.

You could build physical radiation shielding on this sort of station, but it would be extremely wasteful. So it’s probably best to assume electromagnetic shielding in this case.

I’m not sure if I’ll get around to posting next week. I kind of want to draw a solar system map focused on travel times and typical energy costs for trips, but I might have to sit around doing some math and checking my assumptions for moving around in the kuiper belt first. We’ll see.

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Project Dandelion

So generation ships. It’s been a few years, but I’ve brought them up before. My basic thought for an interstellar settlement effort is this: don’t send a completed city or ship, send a small seed ship along with the tools and raw materials to bootstrap itself into a thriving city that arrives at its destination just as it’s running out of space and materials for growth.

Something that might look like this in it’s various stages:

The grey sphere represents the ore-pile sent with the original ship, and the four ships show the growing colony as it expands from 200 people to 500 to 1000 to 10,000 just in time to arrive at one of the nearest stars. The ore pile doubles as micro-meteorite shielding in the direction of travel, which for a habitat traveling at percentage levels of light-speed is somewhat more critical than might otherwise be the case.

The hemisphere shows the parachute for a medusa style nuclear pulse rocket used to brake the ship at its destination, and the little blue sphere shows the final colony collapsed for deceleration, into a form where it can serve as the initial hab in a bolo-style station that will be the start of a much larger city in it’s new solar system.

The nice thing about this general idea for an interstellar spaceship is that aside from the engine itself, and the impossibility of immigration or emigration, the basic model of running and growing the city itself is identical to that of how most of the stations I draw would be built and expanded over time. So, ideally, by the time someone decides to take their city to another solar system humanity will already have experience on building, expanding, maintaining, and upgrading multi-decade or even multi-century habitat projects.

The other thing to consider is the 200-10,000 population range and the size of the ore pile is built around a 2-400 year trip using nuclear pulse propulsion with a large enough reserve of uranium at the far end to actually decelerate the thing. That’s probably somewhere between realistic to optimistic for the initial trip. Barring fundamental changes in physics, the rocket equation is cruel. On the other hand, once the initial trip has been made you can build the infrastructure to use laser-pumped solar sails for both the start and the stop parts of the trip and cut the mass of the ship (and hopefully the travel time) way down.

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Don’t take the Stairs

This one’s about 2.7 kilometers in diameter, and has a surface area over 80 square kilometers which would let it fairly easily support everything a population over 1.75 million would need and still dump the heat without having to get into silly tricks or getting stuck using serious business heat pumps and having to deal with the extra energy and heat from running those. Of course, since it’s hanging on the end of a 10-20 km tether, there’s much more surface area than that available for power generation and heat rejection available, as well as plenty of other places to dump the energy hog activities like heavy industry and agriculture. But 1.75 million is a decent and conservative estimate.

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Tree in the Void

Here you go, a space station habitat that’s meant to look like a tree. Not pictured is the support cable or counterweight, or really much of anything but a stylized habitat.

This one has a radius of approximately 1.7 kilometers and a surface area somewhere north of 22 square kilometers. Using last week’s logic, if heat’s the limiting factor it could potentially host a population of just over a half million people. That’s about what the drawn living space is appropriate for, assuming that the leaves have a single story of building space underneath the open public space.

Here’s an x-ray to call out the individual leaves inside a bit better:

You know, I was talking to my mom on the phone last week about rock-climbing for some reason and we both brought up our deep fear of heights that makes our bodies tense up when we even see people on television leaning over a great big void of nope. And yet, for some reason, I keep doing things like this to the residents of my imaginary space stations:

The small drop is only a hundred meters or so, the big drop is over a kilometer.

There are sometimes I’m actually glad that I’m too lazy to make properly rendered images.

In happy news, I actually have a bit of a queue of posts built up after a week of feeling inspired. I’ll even be briefly revisiting my generation ship concept in a couple weeks.

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Big Station 3

Ok, it’s time for some power and heat estimates to get my population estimates for the Big Station. Spoiler alert, our limit turns out to be something like a billion people. I'll be simplifying things a bit, but let’s get started:

For the sake of making pretty pictures, I typically depict large fractions of the walls of most of my stations as transparent. In reality, I don’t actually believe that it’s a good idea to build things that way. Instead, I prefer to imagine lighting the 'outdoor’ areas of my stations with LED or similar displays that mimics whatever sky the residents desire, and the interiors of the buildings within the stations in roughly the same way we do currently.

The actual exterior of the station would be coated in radiators, solar panels, and whatever other equipment is necessary and beneficial. Only dedicated viewing areas would have transparent walls.

So, with that in mind, I’m using the entire skin of the 1g habitat as radiator surface for my estimates, and I’ve added in a potential mirror array that would allow that skin to radiate to empty space, assuming that the plane of the station’s rotation cuts through the Sun. The mirror array also effectively shades the station from the Sun, which is nice.

To find out how much heat we need to dissipate, we’re only going to consider two things: per capita energy usage assuming modern US consumption rates and the additional energy cost of the artificial lighting needed for the outdoor and agricultural areas. The other major source of heat would be the light of the Sun, but the mirrors should handle the overwhelming majority of that.

Energy usage is from the US Energy Information Administration, and as that link will surely die sooner or later I’ll summarize. Total per capita usage is 309 MMBtu, of which 65.7 is residential, 56.4 is commercial, 100.2 is industrial, and 87.1 is transportation. The total number works out to 90600 kwh, or a steady need of 10.34 kw.

The Stanford Torus study estimated a need for roughly 150 square meters of space per capita, of which roughly 50 were for agriculture and 22 were for other outdoor areas. We’ll keep the farm space the same and bring the park and road space to 75. With a lighting efficiency of 100 lumens per watt, and an average lighting intensity of 600 lux (lumens per square meter) in the public spaces, and 17,000 lux for the agricultural areas, that gets us an additional .45 kw for the open spaces and 8.5 kw for the farms. (The lighting assumptions are the same I used here.)

All up, we’ll say we’re looking at a per capita energy usage of 20 kw. Assuming solar power, an efficiency of 40%, and 1350 watts per square meter of sunlight, that’s 37 square meters of solar panels. And that gives us our first population estimate: if we were to power the whole silly thing with solar collectors set up as a cylinder with the same dimensions as the mirrors, we’d have 9.45 billion square meters of solar panels, or enough to support 255 million people. But we don’t have to rely on attached solar panels for our power, and if we do we can just park it closer to the Sun, so lets take a look at another estimate.

The 1g hab has an outer radius of 50 km, an inner radius of 46 km, and a height of 70 km. That’s 42,000 square kilometers or 42 billion square meters of radiator. If I use the assumptions I had when I first took a close look at the topic, we’re looking at an operating temperature for our radiators of 311 kelvin. That would mean we need about 42 square meters of radiator per person, and can house about a billion people. If we used the temperature that the ISS seems to use for its radiators, we’d be looking at something more like 625 million people. On the other hand, if the skin of our station was just painted black and had the same temperature as the air inside it, it could host 800 million people.

So what to assume? Eh, a billion is a round enough number. That’s a population density of 45,000 people per square kilometer of outer station surface.

It is worth keeping in mind, however, that the world’s per capita energy usage is less than a fifth of the US rate and that the best lighting I can find with a quick search today gives twice the light per watt as I assumed here. Taken together, we’d be looking at more like 3 billion people.

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Big Station 2

Following up on last week’s post. No math yet, but a few prettier pictures of my 50 km radius station that’ll host up to 4 billion people:

I didn’t file the edges off, but there’s a bit of detail of the outer habs:

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Big Station

It’s been not quite a year since I decided to drop out of trying to keep a regular posting schedule while dealing with extra hours at the grocery store and constant low level anxiety about the safety of my friends and coworkers thanks to the plague. I’d like to start easing back in, but it’ll probably be a slow process.

Which is to say, here’s a very rough first sketch of a 50km radius station:

Aside from the central ‘eye’ that should experience something like lunar gravity on its outer surface, the pressure walls of the station are all 2km in radius so that even on the 1-g layer there’s a low to nonexistent risk of getting altitude sickness by taking an elevator ride.

I plan to polish the sketch, and do some mass and population estimates over my next post or three. But for a rough idea, the last station I did of this scale had a very small fraction of the 1-g living space shown and that station had an upper  limit of housing and feeding about 350 million people.

A quick bit of napkin math with my old assumptions suggests that it shouldn’t have much trouble dumping the heat from all the activities needed to comfortably support close to 4 billion people. As that’s usually the limiting factor for population on a station design, I’ll run with that estimate for now and try to double check those assumptions now that it’s been a few years since I’ve looked at them.

No promises though.

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Pumpkin Station

Not that I’m following any sort of regular schedule again yet, but I’ll be working on Thanksgiving. So have some early pumpkins and Stay the F*ck at Home!

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Zero-G Farm

This time I decided to try to fit a farm into an actual proposed module, this time the B330 from Bigelow:

There’s only a ~3 meter radius to work with, so to keep things compact and accessible for maintenance, harvest, and other general fooling around I decided to make the planters rotate. So there are six perforated tubes filled with grow media and either periodically flooded with water or continuously flooded with highly oxygenated water. These tubes host the roots of the plants, and rotate slowly, once every 24 hours. If grow lighting is restricted to one side of the planter, this rotation simulates the day/night cycle, and can be further adjusted by altering the color of the light based on position. Each planter has a dedicated water tank that can hold a different nutrient solution based on the individual needs of the planter.

A single module should provide the equivalent of roughly 150 square meters of growing space, enough for 2 people’s worth of food.

Alternatively, if rotation isn’t needed or seems like too much of a pain, there’s this:

This time, the root zone is handled in disks, with growth on both sides of the disk. The working space for whoever enters is a bit more cramped, and the plants on the outside of the outer ring, and inside of the inner disks will be a pain to access for most people, but this layout should be less mechanically complicated and offers roughly the same amount of growing space as the other. Water tanks aren’t shown.

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Space Diet

I’ve written about growing food in space before, more than twice actually but you can go hunting for the rest if you’re so inclined.

The general rule of thumb I’ve come up with based on NASA’s assumptions for design purposes is that assuming everything works well and reliably, 50 square meters of growing surface is sufficient to provide the overwhelming majority of people with a reasonably healthy and varied diet using hydroponic techniques. Bumping that to 75 square meters, and assuming aquaponics with a fairly low stocking density of 1kg of fish per 100 liters to help ensure stability, the basic components for a zero-g system could look like this:

The bit on the right is the growing chamber for the plants, a ring of growing media hosts the roots for the plants growing both inward and outward from the ring. The water is on the left, of course.

Here’s what it could look like if the fish tank were placed around the growing area while leaving plenty of access and travel space:

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A Solution to Space Suburbia

I’ve said before and repeatedly that even in a massive O’Neill-style space station I feel like a sprawl of single-family or resident houses is a massive waste of volume and resources. That said, there’s a simple enough solution if, for some reason, you want a massive rotating space station that has a more rural development pattern than I usually depict.

Layers. Lots and lots of layers.

Above is a 20 km diameter station with fifteen 100 meter tall layers.

Each layer has an artificial sky, far enough above most observers for fairly standard-sized bulbs to effectively act as the pixels in a hi-res display.

There’s a noticeable curve to the ground for residents, but the low ceiling prevents residents from looking into each other’s back yards and helps preserve the illusion that the limits of the visible world are from a nearby ridge-line.

Apparent gravity varies between the levels, of course, but only by a maximum of 15% between the outermost and innermost layers.

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Finally Another Space Station

Well, partially anyway.

This time it’s a ring station where the main layer is stylized after a cavern with towers based on stalactites and stalagmites.

Above the cavern is open and sunny, heavily vegetated park space. I suppose that the upper layer could be expensive single-family residences with yards and such, with the lower being a high density urban environment. But that offends my delicate sensibilities. So instead there are parks for everyone.