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Comment by garmaine | Hacker News Reader

There will be no thousand year journies. You’d be overtaken by the generation after which left in faster ships and arrived in half the time. Make the trip in a few decades or don’t bother making it at all.

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Going faster means expending more energy. At some point it won't make economic sense to go faster, even if technically you could. Freeze dried wombs don't care whether the journey takes a thousand years or five hundred, but the costs are very different.

It takes the same amount of energy to accelerate at any speed in space. The limit is our determination really, it is possible to visit our nearby star with ~200 hydrogen bombs

It doesn't take the same amount of energy to accelerate (and later brake) to 0.5c as it does to accelerate to 0.1c.

0.1c would be sufficient for a single generation ship.

Depends on where you want to go. The universe is a pretty big place.

No it doesn't. Your mass increases the faster you go, so that more and more energy needs to be expended to accelerate more. At 50% light speed, you're 15% heavier. At 90% light speed, you're 129% heavier. At 99% light speed, you're 608% heavier. Your mass goes to infinity as you approach the speed of light, which is why the speed of light is unattainable for objects that have mass.

And objects that have to carry their own fuel have problems even at much lower speeds.

right i assumed low-relativistic speeds. also i got the number of bombs wrong, it's 300.000 not 200. Here's the relevant pbs video

https://www.youtube.com/watch?v=EzZGPCyrpSU

At the same time, you could send information, compressed, enough to accurately reconstitute the travelers in spacetime. That would take some raw materials and a plenty of energy. However, the required devices might be much more resilient to acceleration and radiation than any possible human body.

Enter K-level thinking:

What if we did send a ship on a thousand year journey, and learn more about building fast ships than if we hadn't? Such that the second ship we send, would be quicker than the first ship we'd have sent if we waited a few decades?

Hah, you made me think of this: "what's really going to bake your noodle later on is would you still have broken it if I wouldn't have said anything".

https://www.youtube.com/watch?v=eVF4kebiks4

Do you put off buying electronics knowing that next year's product will be faster than this year's? At some point you just got to say, screw it, I'd rather do this now instead of waiting for some hypothetical future where the cost-benefit ratio is at its highest.

Additionally, why do you expect the old ship cannot be retrofitted or replaced and travel sped up incrementally?

It should be easy to find a hot broadcasting object in space and rendezvous with it. The crew might face some future shock.

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