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Relativistic Spaceship

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Re: Relativistic Spaceship

#381

Post by bhickey »

wholinator2 wrote: post #252
bhickey wrote: post #236

Earlier quoted context omitted.

Briefly: No. I read a paper on the topic a few years back. My recollection is that once you go faster than about 0.3c it becomes impossible to shed heat faster than you gain it from collisions with Helium. I'll try to dig it up.

I'm interested if that's physically impossible or just currently technologically impossible

Here's one paper on the subject. There are others, but I've run out of steam for trawling through Scholar and arXiv.

Radiation hazard of relativistic space flight https://arxiv.org/abs/physics/0610030

Re: Relativistic Spaceship

#382

Post by noduerme »

mihaaly wrote: post #361
noduerme wrote: post #350

So, this does seem to take the angle I'm flying at into account. If I'm accelerating to 99.9% the speed of light, and I yaw 180deg the view, I start "decelerating". What happens if I keep maximum acceleration and pitch up 90deg? The software seems to keep flying on the original vector. Is this a bug or is it intended to be a simulation of how light would behave under those circumstances?

Not the way I see it. If I accelerate modestly (0.2m/s2) to just above 30% of c where the movement is noticable enough and then put the direction of travel just beyond one of the corners (e.g. just beyond the top right) by turning the view then the direction of travel will move slowly towards the center of the screen on its own - giving a slight sense of turning in the beginning - as one would expect of current veloc…

>> the diagonal of the two can never go beyond c

Sure, from the observer's system (home planet "stationary" the speed is measured from) it can't go faster than c... but that's where I don't think it's accurate. From the flyer's perspective, if you're close to c (as viewed from home) and suddenly accelerate at a 90deg angle, that shouldn't bleed off your speed forward, or be limited by your speed forward. Only from the distant viewer's perspective would those two velocities combined max out at c. From your perspective they wouldn't.

Re: Relativistic Spaceship

#383

Post by nurumaik »

bocytron wrote: post #369

> Now you are staring into the big bang in all its glory; make sure to wear safety squints. Wait what? That's not true right? All the light we see is concentrated in one point but it's not really the big bang that we see, it's an illusion, is that correct?

It's blue-shifted microwave radiation from big bang. You see it in one point because doppler effect is directional

Re: Relativistic Spaceship

#384

Post by tsimionescu »

eru wrote: post #335
tsimionescu wrote: post #324

Earlier quoted context omitted.

Wouldn't your water and food then become highly radioactive over time? Even if no, it would mean your shield will be gradually consumed. Not sure this is the best idea.

Your fuel is the outermost layer of your shields (modulo whatever is necessary to keep the fuel in place. But you might use magnetic fields perhaps). That's basically free shielding: you have to carry the fuel around anyway, so you might as well put it to good use. If you run a nuclear fusion reactor, you won't really lose much of the mass of your fuel, unless you want to. Eg you could use the helium you produce as t…

Your fuel still gets consumed, so you still can't rely on your fuel as the main form of shielding. Towards the end of your journey, your rocket is approximately 0% fuel. And at the point of highest speed, before you start decelerating, it is roughly 50% fuel.

And you are entirely wrong about the isotopes of hydrogen. Tritium is highly radioactive, with a half life of ~12 years. And it is not just hard, but virtually impossible to isolate tritium out of water. So if any tritium forms (which is an extremely common by-product of any fusion reactions which might happen, and the most common decay product of heavier hydrogen isotopes), it will render your water quite poisonous for human consumption, virtually irrevocably.

Re: Relativistic Spaceship

#385

Post by aerique »

denton-scratch wrote: post #360
MilStdJunkie wrote: post #26

Earlier quoted context omitted.

Every proton would have the energy of a baseball. It's bananas. Granted, space is really empty, but it's not that empty, somewhere around a hundred atoms per cubic meter. Your ship might look like a very, very long shooting star. Probably dialing the speed down a touch would be worth it for whatever your shielding material is, but who knows? We're talking miracle engines here. I think in the "Valkyrie" ship-on-a-stri…

> somewhere around a hundred atoms per cubic meter. Wikipedia says that intergalactic space contains less than one hydrogen atom per cubic meter; and that most of the baryonic matter in intergalactic space consists of hydrogen and helium atoms. If I've understood it correctly... https://en.wikipedia.org/wiki/Outer_space

Yes, but that's intergalactic space not interstellar space. We've not even begun exploring the latter :-)

Re: Relativistic Spaceship

#387

Post by satvikpendem »

jcul wrote: post #379
satvikpendem wrote: post #250

Earlier quoted context omitted.

Indeed. Have you read the rest of the series? It just gets crazier and crazier.

The rest of the hail mary series?? Or Three Body? I have read two of the three body books, but I wasn't aware of a sequel to project hail mary, would be very excited if that's the case!

The rest of the three body problem series.

Re: Relativistic Spaceship

#389

Post by boxed »

ivolimmen wrote: post #386

Nice visualization except for the fact that traveling backwards does not show anything...

Isn't that correct though? The light gets redshifted away from the visible spectrum quite fast and after not very long there's nothing to see. Unlike when going forward where there's plenty of extreme red light that can be blueshifted into the visible spectrum (and eventually past it).

Re: Relativistic Spaceship

#390

Post by aerique »

daedalus_j wrote: post #177
jcadam wrote: post #125

Earlier quoted context omitted.

Could use such a ship as a time machine (well, that only goes one way).

The Forever War novels have this as a key plot point, if you're interested in that sort of thing.

Not to mention the comic is pretty good as well!
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