Interstellar Travel (No Matter Where To) Is Theoretically Possible And Doesn’t Even Take Long

[flexy]

When I was a kid I was very much into astronomy, but I have forgotten the one or the other astonishing thing. Like recently, I re-learned that our "closest neighbor" spiral galaxy, the Andromeda Galaxy, is 2.5 million light years away. I had this crazy number in my head for the recent weeks, it simply wouldn't in my head.

2.5 million light years. If your ship would go at 100c (100 times the speed of light), you'd still need 25,000 years to even get there. WTF! There is this neat software "space engine" where you can sort-of fly around in space at insane speeds, you can play around with it so you'll see what ludicrous speed you would have to set so you see even moment happening towards the Andromeda Galaxy. So, say, I set my virtual ship going at 1,000c (which is already an un-imaginable speed to begin with, now judging from our current available tech), I'd still sit here 2500 years until I arrive. And let's not mention other galaxies which are 30,40 or more million light years away.

So I dumped the idea of possible travel to other galaxies entirely and concluded that this would absolutely, never, ever be even possible, not even remotely.

But boy was I totally wrong!

Because I forgot...and I am totally perplexed now when I read this, the effect of time dilation at relativistic speeds! Yes I knew what time dilation is, but I simply didn't consider this!

Wikipedia says that traveling to the Andromeda galaxy, due to time dilation for those on the ship would only require 28 years! (This is 14 years constantly accelerating a ship to 1g, and then halfway into the journey decelerating at 1g).

In other words, besides the massive problems that relativistic space travel would bring (mostly: enormous, or better, ludicrous amounts of energy required), it is "in theory" possibly to travel literally anywhere in the visible universe in an astonishing short time, like a few decades at most. WTF!!

The concept like a "constantly accelerating space craft" doesn't sound too Science-Fictiony to me either, keywords EM drive, or whatever other potential method to somehow harvest energy during flight. The biggest problem at traveling at "almost" 1c (which would be all that's needed) would then likely be not to crash into whatever matter might be in the way, because this wouldn't be pretty.

All of a sudden, the universe has become a lot "smaller", realizing that traveling anywhere is indeed not "impossible because of the distances involved" which I thought previously.

 

[Chaotic42]

9.81 m/s/s * 14 years = 4.33402821 * 10^9 m/s = 14.456762c

I don't feel like busting out the serious math here, but just going by quick back of the napkin calculations, at 1g we could hit 0.99c in a little over 350 days. At 5,000 metric tons for a ship, 1g requires 49 meganewtons of thrust, so you'd need about 30 AJ-26 engines burning for about a year to get up to speed and about a year to get back down. Of course they'd be prone to time dilation as well.

If you strap on a NASA NEXT engine, which produces 236 mN of thrust, it would take almost 200,000,000 years to get up to 0.99c.

Of course, 0.99c will only get you about a 1/6.3 dilation. If you wanted to get there in 28 years, you'd need a factor of about 1/90000 (ignoring time for acceleration). So we're looking at 0.99999999993c, so tack on another four days or so.

But then that's just the ship. An AJ-26 consumes about 517kg of fuel per second. So that's 948,765,312,000 kg of fuel for the voyage....

In other words, getting to 0.99999999993c with current technology in a reasonable amount of time is difficult.

 

[Mike64]

And also, still sticking only with conceptual issues, that's 28 "relativistic years". Which would be "fine" if you planned never (for practical purposes) to have any contact with Earth ever again, otherwise, not so much...

 

[SMOGZINN]

9.81 m/s/s * 14 years = 4.33402821 * 10^9 m/s = 14.456762c

At 5,000 metric tons for a ship, 1g requires 49 meganewtons of thrust...So that's 948,765,312,000 kg of fuel for the voyage....

But you have to push all that fuel as well, so ship's weight has increased to 948,770,312 metric tons....which is going to require considerably more thrust...

In other words, getting to 0.99999999993c with current technology in a reasonable amount of time is difficult.

I'm fairly certain we can change the word 'difficult' to 'impossible'. In fact we can hardly even imagine a technology that would realistically allow it. People dream of FTL travel, but we can't even find a way to do near light speed travel.