we're technically an interstellar species. sadly, that doesn't mean much, yet

Our spaceships have left the solar system and are heading to the stars. If we want to follow them, we're going to have to reinvent everything, ourselves included.

Dear reader, congratulations. You, yes you, are now part of a species that was able to leave its solar system and send spacecraft to other stars. With any luck, our very first emissary to the cosmos, Voyager 1, will buzz by our nearest stellar neighbor Proxima Centauri in just 16,000 years. Our second and fourth — Voyager 2 and Pioneer 10 — will pass by it in 18,000 and 20,000 years, respectively. Pioneer 11, our third, will pass Gliese 905 in 34,000 years. Our fifth and final so far, New Horizons, is headed in the same direction at a similar velocity as Voyager 2, and should reach its destination in a similar time frame.

If we were silicon organisms that lived for millions of years, those would be impressive velocities and accomplishments. But we’re not, and if we were, our metabolism would most likely be so glacial that we wouldn’t have built these craft in the first place, since we’d evolve and move on literally geological timescales. So, as carbon-based humans we can only look at all the zeroes and groan. Maybe pop sci headlines calling us an interstellar species are being way too generous. Maybe the title they bestow on us is the participation trophy of deep space exploration. Maybe that lofty claim should be reserved for when we actually manage to reach another star.

But what would that take? How would we become an interstellar species? Turns out, we have some idea of what might be involved, how the technologies in question will need to work, and understand that if we do decide to venture away from our cozy blue home in the Orion arm of the Milky Way, we’ll have to profoundly change what we are, and the experience will change us even further. If you’re still with me, strap in for a quick preview of the distant future in which the explorers we will be discussing would be farther removed from us than we’re removed from the first humans to invent the basics of agriculture.

“scotty, we need more power!”

It’s pretty much common knowledge now that trying to navigate even our little solar system with chemical rockets is like trying to propel yourself with particularly strong flatulence. In the short term, we’re going to need nuclear rockets. In the medium term, we’ll need antimatter-catalyzed nuclear rockets. In the long term, we’ll need a warp drive, or something very much like it, relying on power from miniature black holes to alter the topology of space and time around our spacecraft, or at least keep a steady rate of acceleration until special relativity acts like a governor in a supercar and slows us down to a velocity acceptable to the laws of physics.

Oddly enough, we already know how to make antimatter and use it to power rockets and spacecraft. We just need to figure out how to mass produce this admittedly, very expensive and dangerous fuel on demand so it doesn’t sit in a magnetic or laser trap, itching to loose power for a nanosecond so it can obliterate any matter it touches by literally unwinding it down to point particles, converting the forces holding it together into gamma rays, light, heat, and sound. Spacecraft usually function best when they don’t explode, and astronauts tend to function at their best in intact spacecraft, not as wisps of radioactive gas floating through space.

Of course, even relativistic spacecraft will only get us to the stars so fast, which is why we’re already experimenting with the Casimir force — a phenomenon that allows us to use magnets and lasers to make seemingly empty space even more empty — to see if we can bend the fabric of the cosmos enough to circumvent the limitations of general relativity. Now, that’s going to come with a catch because even the best and most stable warp bubbles also can’t just teleport us across the cosmos, and their interaction with real space would generate internal tsunamis of radiation that craft inside of these bubbles would need to learn to either harness or redirect.

cruising the stars in cosmic hot rods

That brings us to another interesting fact about the spacecraft of the future. As we’ve learned in middle school, space is pretty much empty. This is why the shape of, say, a space station doesn’t matter. There’s no air resistance, so as long as you gave your starship a good push, it will continue moving in the opposite direction of the thrust basically forever. And this is true. To a point. Once you start hitting a few percent of the speed of light, you’re still moving through mostly empty space, but fast enough to hit the extremely sparse atoms of gas and dust on a regular basis. Hit about 10% of the speed of light in the inner solar system and the friction will disintegrate you.

What does that mean for the spacecraft of the far future? Well, they’ll be sleek and extremely aggressively shaped. From relativistic travel to warp bubbles, the faster you need them to go, the more they’ll have to resemble hypersonic gliders of today. Since they’ll also need very large engines, reactors, and cargo bays to support long duration missions and generate tremendous amounts of energy, they’ll be very large as well. Just imagine a DARPA Falcon HTV-2 the size of the Burj Dubai screaming through an aurora borealis-like shower of subatomic particles, maybe leaving blue shockwaves of Cherenkov radiation in its wake, and you’re most of the way there.

Forget all that “hard science fiction” in which ugly metal cylinders and boxes full of humans in bulky spacesuits touch down on alien worlds. Our interstellar craft will absolutely kick ass in extraterrestrial design competitions and put any retro-futuristic atompunk illustration to shame. Oh, and it’s probably a good idea to mention that they will almost certainly be heavily armed and have crews with military training on board, just in case we come in peace but some alien species out there doesn’t want us there in said peace or not. We may not want to need weapons, but we’ll certainly want to have them, given the high potential for nasty surprises.

don’t you forget you forget about them

Another major difference between typical sci-fi stories and likely reality? Interstellar missions will not be one-and-done. You simply can’t send generation ships to other solar systems, then wish them the best of luck. No, a successful landing is just how you establish a beachhead. You’ll have to keep sending new prototypes, materials, instructions, software updates, and, perhaps most importantly, people. If you fail to support outposts around other stars, you risk technological decline, inbreeding, and upticks in disease and genetic defects thanks to the island effect.

In other words, a colony on an exoplanet is kind of like a puppy. It’s an expensive, long term commitment, not a Christmas present. And that’s not just because you need ongoing support and communication networks spanning dozens, if not hundreds of light years. You may not even be supporting humans as you know them. In order to cope with the rigors of radiation, low gravity, and all the horrible things they do to the brain, blood, bones, heart, and the immune system, our astronauts will need to be… different. This is something we knew since the 1960s, and given that neither human biology or physics changed much in half a century or so, this point still applies.

Bottom line is that it’s entirely possible that we will become a truly interstellar species at home in multiple solar systems. But humans who traverse the stars in 30,000 years won’t be like us. They’ll tear through the cosmos on impossibly sleek craft wrapped in quantum fields, be more machine than meat, and modified with engineered viruses to protect themselves from radiation and the ill effects of constant changes in gravity. At that point, there may be literally trillions of these seemingly alien creatures swarming the galaxy, Earth reduced to nothing more than a primeval myth told by their parents as far as they’re concerned.

If we play our cards right, we will outgrow this cosmic cradle and explore the stars for fun and profit, though unlikely to be defined the same way we define profit today. And if our post-human descendants come across Voyager 1 or 2 on their travels, and find out that we let that little piece of metal leave our heliosphere and called ourselves an interstellar species, they would laugh until they got their equivalent of hiccups. Who could blame them? After all, they’d be completely right.