Complex Numbers

Ain't Goin' Nowhere

And now to crush all your dreams...

Why interstellar travel is so damn hard  
Basic physics goes a long way towards explaining why a pair of theoretical rocket engines may never come to fruition.

Rocket science is easy. Newton figured that shit out. Action. Reaction. F=ma. There, done; what made "rocket science" a synonym for supergenius?

Well, it turns out there's a lot of details to work out. Who knew?

Ever since we imagined the technological sophistication to send ourselves hurtling at escape velocity away from the Earth and toward some unknown pinprick of light in the unending vacuum of open space, obsessive individuals and paranoid governments have spent billions of dollars trying to figure out how to get as far away from our home planet as possible.

That's a cynical way to look at it. The idealist version is we're curious and want to explore. Need to explore, actually.

As for the next big thing, the general idea that the American government has run with for the past 70 years—from Project Orion to Project Longshot to Project Prometheus—has involved strapping small nuclear bombs to the backs of rockets and hoping for the best.

It occurs to me that some people might not have heard of these things. I forget that not everyone reads science fiction. Yes, there have been serious proposals to use nuclear bombs for rocket thrust. Look it up if you don't believe me.

Needless to say, none of these have ever been built or are likely ever to be built; they were dreamed up with a future civilization in mind, one that had conquered the problems of nuclear fusion and international cooperation but still had no control over the Earth’s inevitable solar doom

That's rich. My turn to be cynical: Should we survive all the looming catastrophes such that we have to start worrying about the Sun heating up and destroying Earth (not something to worry about for, oh, half a billion years at least, so don't start sweating yet), we will figure out a way to engineer the Sun before we figure out international cooperation.

As long as there are some people who think pineapple is just fine on pizza and others who think it's an abomination, there will always be war and conflict.

If you’re wondering why taking a trip to another star is incredibly difficult, blame physics. Conservation of momentum (or Newton’s third law, depending on how you want to look at it) requires a rocket to poop out some amount of mass at some speed (AKA explosive fuel) for the rocket to move. The sticking point is that the fuel still has to push the remaining fuel still unpooped and connected to the payload.

Gotta love those technical terms.

This predicament can be turned into a formula that relates the change in speed to the amount of mass pooped out. It’s called the Tsiolkovsky rocket equation, named after the father of modern rocket science.

This is the same Tsiolkovsky who, after looking at all the math needed to lob rockets into space (he lived about 100 years ago), said "fuck it, what if we built a really tall tower?" Only he said it in Russian so no one listened.

It can tell you that if you have a chemical propellant and you’re going to eject your fuel at, say, the maximum velocity of a nuclear fireball — around 100 km/s — and you want to travel 4.25 light-years over to Proxima Centauri, you’re going to need to have ten thousand trillion trillion trillion trillion times more fuel than payload if you want to get there in around one hundred years. Not to mention that we’d need double the fuel and time to slow down enough to take data from or drop passengers near the star. For a 1 kg payload, the fuel would roughly account for the entire mass of the universe.

This is the kind of shit that space-based science fiction loves to hand-wave around, to the point where people are all like, "Why don't we just invent warp drive?" Like that's easy. I mean, sure, maybe? We're actually pretty clever when we try to be. But we barely have the vaguest glimmerings of a theory of how such a thing would be possible. Meanwhile, it's a plot device, nothing more.

The sheer weight of the scientific difficulties facing interstellar travel is humbling, if not existentially depressing. Many space nerds have put their hopes in harnessing exotic engines that utilize badly understood (or entirely misunderstood) physics that might obviate the fuel problem. Two of them, the EmDrive and the Mach Effect Thruster, have been hyped by everyone from NASA to National Geographic as the solutions to our interstellar detention. It’s too early to say if either of them is a pipe dream, but their tantalizing likelihoods fade every day.

The article goes on to describe these technologies, mostly in plain language (what do you expect from an article that calls rocket exhaust "poop?") so it's worth reading; I won't copy much more of it here.

For his part, Shawyer seems to be doing great: after receiving a patent for the EmDrive in late 2016, he formed a joint venture with some guys who have been trying to make flying cars happen for more than a decade.

AKA "doing holy work."

Before you comment with links, yes, I know there are flying car prototypes out there. I don't care. I want my consumer-model flying car. It's 2021 and I still don't have a flying car. I was promised one long before now.

For the foreseeable future, we will have to settle for a less glamorous, less hopeful kind of interstellar travel.

Still, there's always the possibility of new breakthroughs in physics. Like I said, we can be clever. History is littered with ideas that just waited for technology to catch up, and others that seemed impossible until someone made them possible. Unfortunately, it's also littered with bullshit, but we tend to forget things like "riding a dew-powered ship to the Moon" (which was actually the basis for one of the earliest "trip to the moon" stories) in a kind of collective confirmation bias.

So I'm not saying warp drive can never happen. And we certainly shouldn't stop imagining what we'll find when we finally have a way to head out there.

Mini-Contest Result!

Lots of great comments from yesterday! Some of them I might actually try. And I appreciated all the comments; some of y'all are overachievers. I said I'd pick one winner, though, and that's going to be...

Sharmelle'sThankfulExpressions for her Bacon, Sausage, Runny Yolk, Hashbrown Sandwich

While I'm not actually a fan of runny yolks, it's trivial to simply cook the egg more thoroughly. And I do love me some breakfast. So a MB will be sent your way soon! But like I said, that wasn't the only one I liked, so thanks again for the ideas! I'll do this again sometime soon, so there'll be more chances.