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Relativistic Spaceship

dmytry.github.io

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Re: Relativistic Spaceship

#31

Post by MilStdJunkie »

AlexAndScripts wrote: post #13

I had no idea you could achieve relevant amounts of time dilation so "easily" with relatively small (1m/s) of constant thrust - such that interstellar travel becomes somewhat viable provided you can continuously accelerate for the entire trip. Googling it, it would take approximately three years of observed time for a traveller to get to alpha centauri at 1g. Could any somewhat-plausible technologies (fusion etc) get…

One gee over the course of months is insane. Even if you converted the entire "fuel" reaction mass directly into momentum, you're still carrying tens or hundreds of thousands of tons of fuel for any remotely habitable spacecraft. And no engine has perfect mass conversion. Matter-Antimatter has been simulated to be maybe sixty percent efficient, fusion is around 17%, nuclear pulse propulsion a surprising 7%, fission nuclear gas rockets might max out at 12% but those numbers are dodgy as we don't have sharp numbers on gas core reactors.

As an SF writer, it's pretty interesting, though, to think of the weird shapes a society would take when your astronauts are outliving entire civilizations. I imagine a sort of neo-Polynesian culture, with travellers never quite knowing how the place will look if they ever come back that way.

Re: Relativistic Spaceship

#32

Post by ianburrell »

JumpCrisscross wrote: post #21
AlexAndScripts wrote: post #13

I had no idea you could achieve relevant amounts of time dilation so "easily" with relatively small (1m/s) of constant thrust - such that interstellar travel becomes somewhat viable provided you can continuously accelerate for the entire trip. Googling it, it would take approximately three years of observed time for a traveller to get to alpha centauri at 1g. Could any somewhat-plausible technologies (fusion etc) get…

> Could any somewhat-plausible technologies (fusion etc) get us to that point? Nuclear thermal or nuclear pulse propulsion. No fusion needed.

Nuclear thermal or pulse, fission or fusion, aren't enough for interstellar relativistic speeds. They have way too low specific impulse. They don't even have enough for constant acceleration inside the solar system unless the acceleration is really low or the fuel ratio is huge.

Re: Relativistic Spaceship

#33

Post by Keyframe »

AlexAndScripts wrote: post #13

I had no idea you could achieve relevant amounts of time dilation so "easily" with relatively small (1m/s) of constant thrust - such that interstellar travel becomes somewhat viable provided you can continuously accelerate for the entire trip. Googling it, it would take approximately three years of observed time for a traveller to get to alpha centauri at 1g. Could any somewhat-plausible technologies (fusion etc) get…

as far as we understand, you have to eject mass in order to move there. pick your choice in that regard.

Re: Relativistic Spaceship

#34

Post by ok_dad »

Don't forget to accelerate in the opposite direction (move it down) once to see the starlight shift out of visual range! It's fun until about 95% of c then there is just blackness.

Re: Relativistic Spaceship

#35

Post by otikik »

AlexAndScripts wrote: post #15
ryandrake wrote: post #12

Great visualization of the unintuitive nature of special relativity. It's kind of mind blowing to realize that if we could accelerate our spaceship at a mere 1G continuously, we could visit the center of the Milky Way in under 20 years (spaceship time), totally do-able in a human lifespan. Of course 27900 years would have passed on Earth, so you wouldn't be able to tell anyone about your vacation.

I suppose you would also have to worry about surviving the trip - every atom in the interstellar medium would damage your ship, likely penetrating the entire way through, and electromagnetic repulsion would only work with charged particles.

My ship exterior hull is made of quadratic jergotrons, precisely to avoid that issue.

Re: Relativistic Spaceship

#36

Post by zonkerdonker »

robbomacrae wrote: post #20

This is something I've wanted to try in VR one day. Does anyone know if there is an app/game available for one of the popular headsets? Is there a technical limit to how realistic the effect could be?

Not exactly what youre looking for, but this type of game (using relavistic physics) has been attempted. Heres one built in unity that could be easily ported to a Quest line device.

https://en.m.wikipedia.org/wiki/A_Slower_Speed_of_Light

I also found this render (and game!) that show off some aspects of relativistic spaceflight. https://youtu.be/Ix1XlxF66Zk?si=8HzDH3U-CRM-erRB

I think the technical limit might be moot, better question might be how strong of a stomach you have, geometry gets pretty wacky near c

Re: Relativistic Spaceship

#37

Post by thatwasunusual »

ryandrake wrote: post #12

Great visualization of the unintuitive nature of special relativity. It's kind of mind blowing to realize that if we could accelerate our spaceship at a mere 1G continuously, we could visit the center of the Milky Way in under 20 years (spaceship time), totally do-able in a human lifespan. Of course 27900 years would have passed on Earth, so you wouldn't be able to tell anyone about your vacation.

We would also need to find a way to slow down.

Re: Relativistic Spaceship

#38

Post by floxy »

AlexAndScripts wrote: post #13

I had no idea you could achieve relevant amounts of time dilation so "easily" with relatively small (1m/s) of constant thrust - such that interstellar travel becomes somewhat viable provided you can continuously accelerate for the entire trip. Googling it, it would take approximately three years of observed time for a traveller to get to alpha centauri at 1g. Could any somewhat-plausible technologies (fusion etc) get…

"Roundtrip Interstellar Travel Using Laser Pushed Lightsails"

https://ia600704.us.archive.org/view_archive.php?archive=/24...

"A one-way interstellar flyby probe mission uses a 1000 kg (1-metric-ton), 3.6-km-diam. lightsail accelerated at 0.36 m/s2 by a 65-GW laser system to 11% of the speed of light (0.11 c), flying by a Centauri after 40 years of travel. "

"...The third mission uses a three-stage sail for a roundtrip manned exploration of e Eridani at 10.8 light years distance."

Re: Relativistic Spaceship

#39

Post by A_D_E_P_T »

~850 years of ship time at max acceleration and the universe is 10^30 years old.

At this point, only white dwarfs, neutron stars, and various stellar remnants remain. Galaxies have dissipated, and stars like our Sun are a distant memory. (If any still exist to remember them. Which is, I'll add, not out of the question. Life can cling to structures built around black holes, white dwarfs, etc., and extract energy from those bodies for a very long time.) We're a long, long way from "heat death" -- from the Universe becoming an undifferentiated entropic sea of particles -- but it is already a very different place.

Puts things in perspective.

Re: Relativistic Spaceship

#40

Post by Teever »

MilStdJunkie wrote: post #31
AlexAndScripts wrote: post #13

I had no idea you could achieve relevant amounts of time dilation so "easily" with relatively small (1m/s) of constant thrust - such that interstellar travel becomes somewhat viable provided you can continuously accelerate for the entire trip. Googling it, it would take approximately three years of observed time for a traveller to get to alpha centauri at 1g. Could any somewhat-plausible technologies (fusion etc) get…

One gee over the course of months is insane . Even if you converted the entire "fuel" reaction mass directly into momentum, you're still carrying tens or hundreds of thousands of tons of fuel for any remotely habitable spacecraft. And no engine has perfect mass conversion. Matter-Antimatter has been simulated to be maybe sixty percent efficient, fusion is around 17%, nuclear pulse propulsion a surprising 7%, fission…

What if you didn't carry the fuel? Use stationary lasers from your starting point to power your journey half way until you lasers from your destination to slow your craft down.
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