this post was submitted on 01 Feb 2026
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Found a calculator: https://www.calctool.org/relativity/space-travel
Assuming we want to accelerate at a constant 1g for half of the travel and then brake at 1g for the second half of the travel we would need 151 years to get there but only 9.794 years would pass on the ship. Depending on the mass of the ship we would need coupe million/billion tons of fuel (anti-matter).
Oh only a billion tons of anti-matter. Good thing we've already made a few nanograms, so in a billion years or so we'll have plenty.
Yeah, and antimatter converts to pure energy with e=mc^2 what means that 60 grams contains like Hiroshima worth of energy
In theory yes, in practice we have absolutely no idea how to actually do that and use the energy in an efficient or practical way. Even just on paper without limitations of technology or costs, we have no idea. Physics simply isn't as clean or neat like that in real life.
adding to this comment, the best way that we currently know how to extract this energy is using spinning black holes, with theoretical efficiency of ~42% (answer to the universe)(src: a minute physics video precisely on this). the naive solution to just touch them gets like 0.01-0.1% of total energy, so in bad case, we need trillion years.
How can it take 151 years to go 150 light years when not close to lightspeed most of the time? I get the 9 year thing, but 151 years seems wrong.
Smarter people than me on the internet calculate that at constant 1g you only need 2.5 years to get very close to speed of light. So I guess you accelerate fast enough and reach 'almost speed of light' very early in your travel and total time is almost as if you traveled at speed of light the whole time.
The main advantage of keeping accelerating when you're at >90% of the speed of light is that it means you arrive faster in subjective time. You could take 160 years to get there and use ten times less fuel (or thereabouts), but the subjective travel time would go up by decades.
I think having constant gravity on the ship during the entire flight is also a big plus. Designing a ship where you can live in 0g for years and in 1g for years would be like designing two ships in one.
Not that smarter when they forget you're running out of gas by the Oort cloud. Gotta spread ~~christianism~~ capitalism there and build a petrol station before we go further.
Earth’s gravity being what it is a blessing cause it means we can do interstellar travel faster.
The closer you get to lightspeed, the slower you accelerate (from an outside perspective). It's actually close to lightspeed for most of the time.
I just used the calc, it's closer to 152 years. Which I assume means acceleration at 1g for about a year to reach .999c, and deceleration for the same time.
I just confirmed with dV= a*t, a year of 1g(9.8m/s/s) gets you just over the speed of light. I think it's more complicated than that, If I remember right relativistic speeds require more and more energy to accelerate so you can't ever "reach" light speed.
Most of the journey is spent traveling very close to light speed. It's not a linear ramping up and ramping down of speed, since it takes more energy to accelerate the closer you get to light speed. Rather you quickly accelerate to near light speed and spend most of the trip working on that last small bit of velocity.
Constant acceleration at 9.8m/s^2 in a given direction will bring you close to the speed of light eventually, but yeah, I'm also not super sure how this math checks out
Imagine sitting on a spaceship for 151 years just to discover your parents' bet was wrong
9.974 years
It's only 9 years for you!
Ohhhhhhh, ok that's clever!
Imagine getting there and finding out a ship left 50 years after yours that flies faster and arrived 2 years before yours!
Just imagine sitting on a spaceship for 151 years to find out they got there first because in 151 years space travel tech has improved so much they can travel there in 35 years.
Unless we figure out FTL travel that wouldn't be possible.
Alcubierre engine.
so with the solar mass of antimatter ponies that are propelling your spaceship, please tell me how yours works in reality.
Nah, Earth ran out of ideas in the 2020s
i mean shit this isn't even my idea jerry pournelle wroute a short story about it ages ago
Maybe ChatGPT has some ideas
Time for Bussard to invent those collectors
So a bit quicker than terraforming Venus by chucking several oceans worth of ice at it, and some cyanobactera once it cools down in a few hundred thousand years.
What about accelerating 1g for 16 hours of 'day', then 8 hours of 3g 'night'. It would be one hell of a weighted blanket lol.
It's not just blanket entire body experience that force including internal organs.. So i guess sleeping with tgat would be more than just uncomfortable
I say have a spinny ship that does that with the shape of the ring. Some kind of parabolic bullshit I'm sure there's a way to get it to math without having to have a 1g ring and a 3g ring but that works too
The purpose of my idea is to average 2g without expecting people to function in 2g. Not just for the purpose of a weighted blanket
I mean, yeah. They'd probably have reasons to have stuff in the high grav areas besides sleep areas. I'm not a spaceshipologist I can't think of anything but radon to keep there tho
It would only save you a few months
And you'll only need about 320 million GWh per ~80kg person... plus 4 million GWh per kg of supplies, equipment and ship weight...
Oh and also thats just the pure energy for acceleration/deceleration, not life support, steering, thrust ineffeciencies, take off, landing etc... 😅
Great Scott!
So 340 PWh per person. A couple of guys with a static bike and a dynamo and that's it😜
Note: the Earth receives 170 PWh of energy from the Sun in a year.
Sounds feasible for a fusion reactor to provide at some point in the very distant future.
Twice the full energy the Sun gives the Earth in a year for each person is not a future fusion reactor level. 😀
I’m guessing you probably go faster than 0.9C after six months, given that the difference is 1 year.
Your statement makes things sound a bit confusing.
To clarify, if you are inside the ship, 152 years will pass.
Edit: Nevermind. Time travel is stupid.
No, the people in the ship will experience less time then 152 years. Relativity tells us the faster an observer is moving, the slower it moves through time.