4 ms·

You could do the "spinning drum" kind of 1G gravity, and save fuel that way.

rootusrootus 5y ago
You still need something like the 1G acceleration, though, for the travel part. If you want it to happen within a single human lifespan.
Johnny555 5y ago
Without the 1G of acceleration, you're limiting how far you can go in a single generation. At 0.1g, that 1000 light year trip would take 90 years (to those on the ship). The beauty of 1G is that it provides normal gravity and you can go great distances in a human lifespan. Of course a 2G trip will get you there in half the time, but it's harder for humans to live at 2G. Though maybe the time to the destination is not a problem if you don't mind a generational ship where generations of humans live (and die) on the journey. It doesn't matter to those on earth, since the trip will still take over 1000 years in their timeframe, so whether it's 1015 years, 1100 years or 2000 years probably doesn't really matter to them.
- ClumsyPilot 5y ago
  "The beauty of 1G is that it provides normal gravity and you can go great distances in a human lifespan." It like unicorns - beatifull and entirely fancifull. Fusion or fission cant do it, even a ship with pure antimatter drive cannot accelerate like that for decades We will have hibernation before we have practical antimatter, and lets you travel intersteller without wasting enegy
  - AnimalMuppet 5y ago
    > even a ship with pure antimatter drive cannot accelerate like that for decades Sure it can. You just need a decently-sized asteroid and an equally-sized antimatter asteroid for fuel, and you can do it for decades, even with the price you pay early to accelerate the fuel you will use later.
    - ClumsyPilot 5y ago
      What are you trying to do with an asteroid, and why does it need to be decently sized? Neither is relevant. You calculate mass fraction, i.e. for a ship to get to orbit using kerosene, the ship must be 97% made of fuel my mass. If you have an antimatter ship, if you can produce, store, and 100% efficiently use antimatter and carry nothing else as your reaction mass and don't have issues with waste heat or radiation, your ship will need to be over 90% fuel by mass to maintain 1G acceleration for years.
      - AnimalMuppet 5y ago
        > What are you trying to do with an asteroid, and why does it need to be decently sized? Neither is relevant. I'm using the asteroid for mass, to react with the antimatter. So, yeah, it's relevant. > If you have an antimatter ship, if you can produce, store, and 100% efficiently use antimatter and carry nothing else as your reaction mass and don't have issues with waste heat or radiation, your ship will need to be over 90% fuel by mass to maintain 1G acceleration for years. Yup. And it's exponential - if the non-fuel mass is 10% to be able to do 10 years, then to do 20 years, the non-fuel mass can only be 1%, and for 30 years it can only be 0.1%. That's why you need the asteroid.
        ClumsyPilot 5y ago
        Taking antimatter fuel out of your carefully designed, failsafe magnetic containment tanks and putting it into a highly-volatile asteroid of doom (attached with what? Antimatter-immune rope that can pull a billion tonns at 1G?) does not mean the rocket equasion gives you a free pass. Its still the same formula, nothing has changed. Its combined weight of your ship and it's asteroids. All you are saying is "you need a big fuel tank"
        AnimalMuppet 5y ago
        I'm saying approximately how big a fuel tank you need to refute your "you can't do it for decades" statement.
- iso1210 5y ago
  If you could somehow accelerate at 1G indefinitely you can get anywhere in the universe in a human lifespan. Of course to accelerate a 1000 ton spaceship you'd need about 4 quadrillion tons of fuel.
gorgoiler 5y ago
The 1G in this case is the acceleration towards your target star system at 10m/s^2 until you are half way, then decelerating at the same rate until you arrive. The fact that this also produces liveable conditions is just a nice side effect of a 1G ship.
- AnimalMuppet 5y ago
  But does that get you to the Orion Nebula in 15 years? Or do you have to accelerate all the way to do that? (And then you get to wave briefly at the Nebula as it goes cruising by at a significant fraction of the speed of light?)
  - Johnny555 5y ago
    Or do you have to accelerate all the way to do that That's what "1G" means in this concept, you're always accelerating at 1G (9.8 m/sec^2) On the first half of the trip you're accelerating toward the destination, on the second half, you're decelerating at 1G. https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...
    - AnimalMuppet 5y ago
      The graphic in that article is what I wanted. My point was that, due to the highly non-linear time cost, it takes much less time to travel from Earth to X if you accelerate the whole way, rather than accelerate half the way and decelerate the other half. I wanted to know which way gorgoiler used to compute the subjective time. And, thanks to your link, now I know.
  - numpad0 5y ago
    Subjectively in decades due to relativity by constantly accelerating, objectively in a millennia or worse. Wonder how to get around interstellar obstacles though, changing courses would be plain impossible
    - 5y ago

You still need something like the 1G acceleration, though, for the travel part. If you want it to happen within a single human lifespan.

Johnny555 5y ago

Without the 1G of acceleration, you're limiting how far you can go in a single generation. At 0.1g, that 1000 light year trip would take 90 years (to those on the ship). The beauty of 1G is that it provides normal gravity and you can go great distances in a human lifespan. Of course a 2G trip will get you there in half the time, but it's harder for humans to live at 2G. Though maybe the time to the destination is not a problem if you don't mind a generational ship where generations of humans live (and die) on the journey. It doesn't matter to those on earth, since the trip will still take over 1000 years in their timeframe, so whether it's 1015 years, 1100 years or 2000 years probably doesn't really matter to them.

ClumsyPilot 5y ago
"The beauty of 1G is that it provides normal gravity and you can go great distances in a human lifespan." It like unicorns - beatifull and entirely fancifull. Fusion or fission cant do it, even a ship with pure antimatter drive cannot accelerate like that for decades We will have hibernation before we have practical antimatter, and lets you travel intersteller without wasting enegy
- AnimalMuppet 5y ago
  > even a ship with pure antimatter drive cannot accelerate like that for decades Sure it can. You just need a decently-sized asteroid and an equally-sized antimatter asteroid for fuel, and you can do it for decades, even with the price you pay early to accelerate the fuel you will use later.
  - ClumsyPilot 5y ago
    What are you trying to do with an asteroid, and why does it need to be decently sized? Neither is relevant. You calculate mass fraction, i.e. for a ship to get to orbit using kerosene, the ship must be 97% made of fuel my mass. If you have an antimatter ship, if you can produce, store, and 100% efficiently use antimatter and carry nothing else as your reaction mass and don't have issues with waste heat or radiation, your ship will need to be over 90% fuel by mass to maintain 1G acceleration for years.
    - AnimalMuppet 5y ago
      > What are you trying to do with an asteroid, and why does it need to be decently sized? Neither is relevant. I'm using the asteroid for mass, to react with the antimatter. So, yeah, it's relevant. > If you have an antimatter ship, if you can produce, store, and 100% efficiently use antimatter and carry nothing else as your reaction mass and don't have issues with waste heat or radiation, your ship will need to be over 90% fuel by mass to maintain 1G acceleration for years. Yup. And it's exponential - if the non-fuel mass is 10% to be able to do 10 years, then to do 20 years, the non-fuel mass can only be 1%, and for 30 years it can only be 0.1%. That's why you need the asteroid.
      - ClumsyPilot 5y ago
        Taking antimatter fuel out of your carefully designed, failsafe magnetic containment tanks and putting it into a highly-volatile asteroid of doom (attached with what? Antimatter-immune rope that can pull a billion tonns at 1G?) does not mean the rocket equasion gives you a free pass. Its still the same formula, nothing has changed. Its combined weight of your ship and it's asteroids. All you are saying is "you need a big fuel tank"
        AnimalMuppet 5y ago
        I'm saying approximately how big a fuel tank you need to refute your "you can't do it for decades" statement.
iso1210 5y ago
If you could somehow accelerate at 1G indefinitely you can get anywhere in the universe in a human lifespan. Of course to accelerate a 1000 ton spaceship you'd need about 4 quadrillion tons of fuel.

gorgoiler 5y ago

The 1G in this case is the acceleration towards your target star system at 10m/s^2 until you are half way, then decelerating at the same rate until you arrive. The fact that this also produces liveable conditions is just a nice side effect of a 1G ship.

AnimalMuppet 5y ago
But does that get you to the Orion Nebula in 15 years? Or do you have to accelerate all the way to do that? (And then you get to wave briefly at the Nebula as it goes cruising by at a significant fraction of the speed of light?)
- Johnny555 5y ago
  Or do you have to accelerate all the way to do that That's what "1G" means in this concept, you're always accelerating at 1G (9.8 m/sec^2) On the first half of the trip you're accelerating toward the destination, on the second half, you're decelerating at 1G. https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...
  - AnimalMuppet 5y ago
    The graphic in that article is what I wanted. My point was that, due to the highly non-linear time cost, it takes much less time to travel from Earth to X if you accelerate the whole way, rather than accelerate half the way and decelerate the other half. I wanted to know which way gorgoiler used to compute the subjective time. And, thanks to your link, now I know.
- numpad0 5y ago
  Subjectively in decades due to relativity by constantly accelerating, objectively in a millennia or worse. Wonder how to get around interstellar obstacles though, changing courses would be plain impossible
  - 5y ago