Sunlight is powerful. Whenever light shines on something, it creates pressure.
And you can use that pressure to move a spacecraft.
The process of making a spacecraft begins with the unicorns. You can make a solar sail out of anything lightweight and reflective enough, but unicorn hair is the best material. We have six unicorns at our ranch—Viduria, Sabelia, Sarustia, Aenarian, Salorsia, and Vidosion. There are a few different types of unicorn hair, graded by its coarseness—different types are useful for different things. Salorsia’s a type D, for instance. You use that for structural support and reflective parts.
I was really scared the first time I went to harvest unicorn hair.
“They’re so big. They’ve got such sharp horns.”
“Sure, but they’re smart enough to know what you want. They won’t hurt you.”
She’s been working with unicorns for twenty years, so I figured she knew what she was talking about. She did—Viduria just kind of looked at me for a moment and then let me go ahead.
Once it’s harvested, the unicorn hair goes to the darkroom and gets processed in a bath of plant-derived chemicals. This makes it more reflective and ‘grows’ organic electronics in the fibers. Different fibers get treated differently to make different parts for the spacecraft—some become solar panels, some can change color to adjust the flight characteristics of the vehicle, some get made into the control computer. You adjust what grows where by shining different colored lights on the fiber as it gets cranked from one spool to another. The darkroom has several machines for this purpose.
I used to work in the darkroom but didn’t like it. The machine jams up sometimes, and then you have to open it up in the dark and find the problem and untangle everything. And you have to waste as little unicorn hair as possible since it takes so long to gather enough of it. And not spill chemicals everywhere. Or trip over anything. Did I mention that it’s dark? It’s kind of annoying.
Then it goes upstairs to the Weaving Room, where skilled weavers turn the unicorn hair into solar sail fabric. The entire weaving room is filled with a tense silence as the weavers carefully work.
I was never very good at weaving. I spent all my time in the weaving room doing inventory work and odd jobs. I /was/ actually pretty good at that. One of the first things I did was reorganize the shelves to make everything easier to find.
“You can’t weave, but for that we’ll make you an honorary weaver,” one of my coworkers said.
Once the weaving is done, the sail is attached to its wooden support frame. Solar sails have to be large to catch enough light, and the workshop at the ranch is small. So we build them in sections and assemble them in a bigger workshop off-site. That’s where I work now—Final Assembly. Working on the ranch was nice, but I like it here better.
Once the vehicle is done, we send it up the space elevator. It’s also made of unicorn hair: a braided rope thousands of miles long.
We finished putting the sail together yesterday. This is the first time I’ve been in charge of the entire construction process. This one’s headed for the asteroid belt.
There it is, coming over the horizon. The power of the sunlight is blowing it out into the Solar System.
What's Real:
Solar sails are real and several have been launched. They use the force produced by photons reflecting off of objects. This force is small, but with a large and reflective object you can get enough of it to be useful. A notable recent solar sail is LightSail 2, launched in 2019 by the Planetary Society.
Space elevators are based on the idea of having a vehicle climb some sort of cable from Earth’s surface into space, instead of launching things with a rocket. They could exist in the future, if we can figure out how to make strong enough materials. Most science fiction writers just hand-wave through the ‘making strong enough materials’ part, so I figured I’d use unicorn hair in this story since unicorns are cool. You can learn more about space elevators here.
Flexible electronics and fiber-based computers are also things that could exist in the future. There’s some research going on now to find ways to make this technology practical.