4 ms·
This is something I've thought about on and off for awhile. For completeness, I believe that the speed of light is a hard limit (and no I don't believe in any
by cletus 4y ago
This is something I've thought about on and off for awhile.
For completeness, I believe that the speed of light is a hard limit (and no I don't believe in any end-runs around this like warp drives, folding space or wormholes). Secondly, I accept the laws of thermodynamic.
Given this traveling between stars takes an incredibly long time. At a high percentage of c you get time dilation but that's not actually a practical travel speed for a few reasons:
1. The energy cost of accelerating to 0.99c and decelerating at the other end is extraordinarily high;
2. If you even can get to that speed, small objects in the interstellar medium become life threatening; and
3. Beyond about 0.86c gas in the interstellar medium actually creates drag making acceleration even harder.
Given the reaction mass problem, it creates a big question of how you'd actually travel between stars. The more you carry the more energy you need to accelerate and decelerate it. It's likely you'd need fusion at a minimum and possibly some far-future tech (eg antimatter, black holes).
So what do you do? Well, there are rogue objects not bound to any solar systems. We've seen some of these. We can't easily detect them so can only speculate on how many there are but it's likely to be a fairly large number.
So what if you opportunistically wait for one of these objects to travel through the Solar System and then hitch a ride? Imagine a planetoid 100 miles in diameter. That's likely all the resources you'd need. It then becomes less of an issue that it might not reach another star for 100,000+ years because your attitude is that this is a new home.
Obviously you still have to match velocities with this object but that's vastly easier to do with a bunch of people and equipment than it is with those same things plus all the same materials that are already traveling at intersellar speeds.
- zikzak 4y agoYou still need to accelerate and decelerate and you need to alter the course of this object to match your course. But you get all the resources for almost free. How would this compare to a raft of asteroids you select in your home system to have the exact stuff you need and the accelerate it? I realize there's differences in mass here but I am asking is it material given the scope? Because you are kind of guessing what is going on with that rogue planetoid but the asteroids you could select at your leisure and also hollow out easily while you are in your home system with access to orbital factories, etc. Anyway, fun thought experiment! I totally agree that you would have to approach this as if this is your new home and you MIGHT get to a planetary system you could also colonize at some point. Generations in that idea might seem as foreign as living on a colony flotilla.
- cletus 4y agoEven on the issue of accelerating and decelerating to a system you fly through or near, in the case of a colony ship you would need to carry that fuel and pay the energy costs for housing it, accelerating it and decelerating it. With a rogue planet you should be able to refuel from that rogue body so your fuel payload required is really only to get to the rogue planet.
- pvg 4y agoIf you've solved the energy problem of accelerating most of a human colony and its gear to interstellar object speeds, do you really get much from trying to hitch a ride on such an object? You've also presumably solved energy storage so the time spent waiting for a suitable object you might as well spend on storing energy to accelerate an object at hand.
- andyjohnson0 4y agoGood point. The only advantage that occurs to me is that you could spend the journey (waves hands) converting the interstellar object into reaction mass to enable deceleration at the other end. And maybe also for course correction, because the object is very pretty unlikely to be going anywhere interesting just by chance
- pvg 4y agoI typed slapdash things into Wolfram Alfa just to get a sense of the kinetic energy of something like a 100km metal sphere buzzing as at 40 km/s (it's a screaming chonker of an overestimate but hey) and got something like a millionth of total yearly solar output or 1/5th of lunar kinetic energy (orbiting earth). As D. Wooderson famously said, we're talkin' some fuckin' muscle, to ride such a thing. If you have it, you might even be better off just taking the moon instead.
- cletus 4y agoSo for a colony to last centuries in interstellar space with little to no prospect of resupply of any kind, you have to build in an awful lot of redundancy. You also need to cater for growth. You need a lot of infrastructure for long term care (eg hospitals). What you're building is living quarters for a thousand years over multiple generations. But for a rogue planet you need far less. Consider the Moon. It has lava tubes. You can seal these, fill them with air and live in them. You don't need to accelerate that living space. Sure you still need to bring some things but it's far, far less. What's more, if you have several such settlements in different lava tubes you have automatic redundancy. A single catastrophe won't snuff out the entire colony. So for a true interstellar colony you really have to build a fleet because a single colony is too big of a failure mode.