Coriolis Fountain

Completed 2019-11-08. Available releases:

The only known way to get gravity when your spacecraft is in freefall is to spin it. This has given rise to the concept of an O'Neill Cylinder: a cylinder that spins around itself, such that you can walk around on the inside and forget that you were ever in space.

Although envisaged as truly enormous structures, constructing even a modest-sized O'Neill cylinder would be a significant undertaking. So, we build small. Instead of tens of kilometers in radius (or indeed, larger), we could start with a mere 50 meters. Rotating at 4.229 rpm would produce one standard gravity at the floor.

Spin gravity has the disadvantage that the smaller you build it, the more trajectories appear to deflect in the rotating frame. This is called the Coriolis Effect, and it can make people nauseated (at-least, allegedly, and if they aren't adapted to it). It's certainly noticeable when the spacecraft is this small.

The designers of this habitat have used the Coriolis effect to design a beautiful fountain with a loop in it. Here, the water is launched at 109° from spinward (so, slightly "backward") at 8.7 m/s. The water travels almost exactly 4 meters high before landing in the fountain again as the habitat wall rotates around to intersect the water's inertial straight-line path.

I can't take credit for the concept (that goes to an artist so insufficiently cited that all I have is the name: Tye-Yan "George" Yeh, who made an illustration ultimately here), but the mathematics of this solution come from a JavaScript calculator I wrote myself to solve these sorts of problems. You can play with that here.

Here, I've drawn the 50 meter habitat with the fountain. Everything is roughly the right size/shape/scale—this is sortof what it would actually look like! The habitat is sparsely furnished; I guess they're still building it (or I'm too lazy to draw more stuff).

There is an enormous window into empty space in the background. This deserves special mention because it's fairly unrealistic: it would have to be heavily shielded against radiation and micrometeorites. However, it does let natural light in, which is a big aesthetic plus. Maybe the inhabitants are filthy rich, and will spare no expense for the view. That would also help to explain why such an expensive space station has such a low apparent population—you're paying for the ambiance, as well as the locale, you see.

Sunlight is white. It only appears yellow on Earth because the blue is scattered out, making the rest of the sky blue (N.B. we can answer XKCD (https://xkcd.com/1145/) as to why it isn't violet: sunlight has less violet than blue, and the human eye is terribly insensitive to violet, so the blue dominates). But anyway, I drew streaky rays of light in yellow for effect. If you like, the window was deliberately tinted to make the environment more-appealing. I don't even have white watercolor (the very notion is, perhaps unfairly, widely scorned).

Note also that the stars are not visible, given the dynamic range. Indeed, you mostly only see a reflection of the interior.

Artistically, this is watercolor and gel pens over pencil sketches.

This marks the first usage of a new brush set I got—six different brushes (out of sixteen) were used. The brushes aren't amazing, but they're pretty good—and certainly far better than what I had before. The paper is decent-quality sketch paper—not watercolor paper—which means it wrinkles and tears and doesn't absorb paint the right way. But it's the paint itself that is truly terrible: this is the kind of stuff you pick up for $5 at the grocery store in the greeting cards section. This stuff doesn't layer correctly, cover or lift well, and is generally a pain to work with.

I definitely don't really know what I'm doing with watercolor, so I'm fairly pleased with how this came out. I even sortof understand the basic technique. Nevertheless, you can see blotches everywhere, which is a technique I call "augmenting your mistakes by making more mistakes". In my defense, these paints are, again, terrible. Even I know enough about watercolor to tell that. The shadow on the back rim is the clearest example: I spent several hours tediously painting, correcting, and touching-up—and yet it still looks blotchy and uneven. Under the circumstances, I think it's fair to say anyone would be limited by these tools.

One thing I was pleased with was the colors' saturation. The blue was especially intense. I initially tried to tone down the colors, before I remembered to embrace the impressionistic feel. After all, it's not like I can get realism instead.

The people, I sketched out using the (surprisingly decent) method of "draw a triangle, then add a head and arms". If you look carefully, you might be able to spot some people I didn't add color to (because I didn't like how they looked, composition-wise, in the end). The streaks of light are a fan brush. The fountain spout is mostly gel pen, washed through with thin blue.

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