On the feasibility of traveling to Proxima Centauri B


So, as everyone has heard by now, scientists this week announced officially the discovery of a (maybe) Earth-like planet orbiting our nearest neighboring star, Proxima, which has been dubbed Proxima Centauri B (heretofore referred to as PCB). Aside from us Babylon 5 fans being excited as hell (Proxima colony?! The Centauri?!) everyone else was too because this planet looks to be in the Goldilocks zone of its host star, appears to be rocky and isn’t unfathomably bigger than Earth. In other words, so far (and it’s early so things could change) it appears to have a lot of the characteristics we expect of a planet that could support life.

But, the bigger reason for the excitement is simply because of its relative closeness to us. “WE COULD ACTUALLY GO THERE!” exclaimed the Internet in unison.

But could we? Could we really get there?

If you wanna TL;DR this thing, here it is: no, not with today’s technology, at least not in a time frame that would do us much good. But, that’s a pretty nebulous statement, isn’t it? Exactly how long WOULD it take? Exactly how long COULD it take it if we really pushed our technology in the near future? What IS a “useful” time frame anyway?

Well, I’m no scientist of course, but I do play one on the Internet so, thanks to the magic of Wolfram Alpha, lemme see if I can throw down some numbers and come up with something a little more concrete.

First, some basic facts that we’ll need, and note that I’m going to round everything here just to make the numbers a little cleaner, but they’re all very close to actual, certainly close enough for our purposes here:

  • PCB lies 4.3 light-years from us, which is 25 trillion miles
  • The speed of light (C) is of course 186,000 miles per second, which is about 670 million MPH (apologies to all my non-American friends, but I gotta calculate with what I know, and I don’t know kilometers – I was educated in the American educational system after all!)
  • 1% of C is therefore 1,860 miles per second, or 6.7 million MPH (why this matters is something I’ll come back to shortly)

With those basic facts we can now do some pretty simple math (which I’ll probably screw up somehow none the less, but that’s what comments are for!). First, let’s use that 1% figure I mentioned. Traveling at 6.7 million MPH, how long does it take to reach PCB? Well, that’s just the distance to PCB, 25 trillion miles, divided by 1% C (6.7 million MPH), which yields 3.7 million, and that’s in hours. Ok, so, how many days is that? Just divide by 24 obviously and we get 155,000 days. And how many years is that? Divide by 365 (screw you leap years!) and we find it’s 425 years.

Ok, that’s a long time for a little trip around the galactic neighborhood. Never underestimate how mind-bogglingly big space is!

Even at 1% C that’s not really feasible for us to do, even if technologically we could achieve it. But, that depends on what “feasible” means, doesn’t it? Well, beyond the technology, I would suggest that “feasible” refers to being able to get there, one way, in a single human lifetime. That’s really what most of us want after all, right? We want someone to go there and be able to report back what they find. We could of course send automated probes, and logically that’s what we’ll wind up doing at some point (whether this planet or some other yet to be discovered). But, a probe isn’t as good as a person to most people. It certainly doesn’t capture the imagination quite like humans going does. Our rovers on Mars continue to capture my imagination for sure, but I’m big-time itchin’ for someone to step foot on the red planet and use the human capacity for poetry to describe it to me (and I’d go in a heartbeat myself and cut out the middle man entirely!)

That’s the baseline assumption here: we want to be able to get there in a single human lifetime. In order to make this easier, let’s be a bit cold about it and say that we don’t care about coming back, nor of our intrepid explorers being able to survive there for very long, and “lifetime” we’ll define as a long human life. So, given that, what kind of speed do we need to be able to accomplish? Well, now you know why I did the 1% of light speed calculation: it makes it easy to extrapolate out! We just divide 425 by the percent of C we’re going to travel to see how many years it would take at each level. And, doing so yields the following table:

  • 2% = 212
  • 3% = 142
  • 4% = 106
  • 5% = 85
  • 6% = 71
  • 7% = 61
  • 8% = 53
  • 9% = 47
  • 10% = 43

Given that the current average human lifespan across the entire planet is around 71 years, we probably don’t want to send anyone that will be older than that upon arrival to have the best shot of, you know, everyone actually being ALIVE by the end! That means that we can’t send anyone older than 18 (53+18=71). That’s probably too young though, we probably want people in their 20’s realistically so as to have enough time for training (not to mention someone theoretically old enough to make the choice to go and understand the ramifications). That means no older than 24 at 9% C and we can go up to 28 at 10%. So the sweet spot is probably right in there.
So, to put it plainly: we probably need to go 9% or 10% C and send no one older than 28 to have any chance of this working. Let’s call it the 10/28 rule ?
But, how realistic is 10% of C for us? Well, NASA’s Juno probe is recognized as the fastest man-made object, attaining a top speed of 165,000MPH. That works out to about .02% C. So, it’s 50 times too slow.

D’oh 🙁

And that doesn’t even account for acceleration and slowing down, things which are inherently more important for us squishy meatbags than our hardened technological creations.

This all tells us that we’re probably not doing this with current technology, not if we want to send people. In fact, it doesn’t seem even remotely possible if we just wanted to send just a probe. Even though a probe allows us to accelerate and decelerate much faster, making the overall average speed of the trip better, the bottom line is we still can’t touch these speeds whether there’s people on-board or not. I don’t honestly know how much faster than Juno we could pull off today, but I’d be willing to bet even 1% C would be a (likely impossibly) tall order. Therefore, we have to look to theoretical propulsion if we want to make this trip in any fashion. That’s always tricky of course because being theoretical, quite obviously, means that they aren’t real yet, and might never be. We don’t know FOR SURE they’ll work or what kinds of problems we might encounter even if they do.

However, the thing that’s encouraging is that there are quite a few theoretically propulsion systems on the drawing boards that aren’t what would be considered by most to be fantastical. We’re not talking warp drives or wormholes or anything like that. No, we’re talking things like nuclear propulsion, plasma drives, solar sails, fusion, things that we either know work and just need to be scaled up (which makes it a pure engineering challenge) or things that we have every reason to believe is feasible given some time to develop (fusion). If we said, for example, that we have 100 years starting from today to create the technology needed get to PCB, that wouldn’t seem impossibly far-fetched. Highly optimistic, yes, and we almost certainly wouldn’t be talking about sending people, but it wouldn’t sound utterly ridiculous. And you’ll note that 100 years isn’t too much longer than a typical human lifetime – it’s right around 1.5 human lifetimes in fact. That, in theory, puts this within the reach of the unborn children of someone alive today. That’s not so bad!

So, in summary: the bad news is that we’re not going to PCB, whether people or just technology, with what we have now. We’re simply too slow at the moment. The good news however is that we do have some ideas currently being developed that might have a shot at doing it in a generation or two AND getting there in a semi-reasonable time frame AND which aren’t pure science fiction. There’s a ton of if’s and’s and but’s that you have to qualify that optimism with, but it’s probably not an outright impossibility in the foreseeable future. That’s pretty exciting!

Speaking as someone who would sacrifice arbitrary body parts to be able to see this planet in his lifetime whether with his own eyes or through technology, I’m depressed. My children have an outside shot… maybe… and my grandchildren a better shot still, but that doesn’t help me 🙁

I guess I’ll just go buy a PS/4 and play No Man’s Sky. Seems that’s as close as any of us alive today is ever going to get.

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