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Comment by thrance | Hacker News Reader

With a ship that accelerates at a constant 1G, you can go pretty much anywhere in the universe in less than 50 (subjective) years [1]. And when I say anywhere, I mean anywhere.

[1] https://www.reddit.com/r/dataisbeautiful/comments/s4tbry/oc_...

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This comes up every time this sort of thing is discussed on HN. Sustained 1 g acceleration takes a staggering amount of fuel, and carrying enough to slow down again makes it even worse.

It's definitely sci-fi for now, but we can always imagine some far out way to store energy much more densely than antimatter. A huge amount of photons orbiting a micro black hole on its Schwarzschild radius, would only weigh as much as the black hole and let you store a potentially infinite amount of energy.

No, they would have as much mass as the black hole plus the energy of the photons (they still distort spacetime and exert a gravitational force, and have inertial mass) and you still have to move that mass with you. You may have increased your fuel density, but you haven’t reduced its mass compared to antimattter, and you still have not dodged the relativistic rocket equation.

That's exactly the point. The limiting factor to space travel is how to achieve acceleration, and not the acceleration limits of the human body.

Maybe I'm mistaken, but that graph would be for passing by places, as it doesn't include the time it would take to slow down from that constant acceleration, if you want to actually visit any other places than your zipping spaceship.

The title of the graph says it is for accelerating half way, then decelerating the other half

The CMB becomes deadly well before these speeds (the rear facing light burns you; the forward facing light nukes you). That's not even accounting for objects in space, or the light from stars, which will be amplified according to the Lorentz factor.

EDIT: here's a small discussion: https://physics.stackexchange.com/a/196171 There's a whole PBS SpaceTime episode about this, but I can't find it, rn.

A mere engineering problem.

And at high enough speeds, you don’t want to be carrying anything metal with you, eddy currents as you pass through magnetic fields will melt your wedding ring.

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