7 ms·

How much energy would that be for that trip, for a reasonably sized space ship to take care of a crew for that long? Are we talking miniature fusion drive or a

How much energy would that be for that trip, for a reasonably sized space ship to take care of a crew for that long? Are we talking miniature fusion drive or antimatter type energy density required?

Johnny555 5y ago
I haven't done the calculations (which would be hard to do without knowing how big/heavy the ship needs to be), but I'd assume it's going to need something well beyond our current technology. An aircraft carrier is powered through the water (horizontally, of course) for 25 years on nuclear power. Now imagine the power it would take to make it hover for 25 years, and that's your 1G ship.
- NortySpock 5y ago
  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.
  - 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
- aardvark179 5y ago
  Assuming perfect conversion of mass to energy you will still need a staggering amount of fuel for each kg of payload. Goggle the relativistic rocket equation and you should find a page with some figures for example scenarios.
jandrese 5y ago
If the rocket equation still applies (if a practical reactionless drive has not been invented), then you're talking about mass-of-the-galaxy size spaceships to accelerate at 1G for years on end.
- whatshisface 5y ago
  The linked paper describes a laser propulsion system by means of which no reaction mass need be stored on the spacecraft whatsoever.
  - jandrese 5y ago
    Which is impractical because you don't have a way to slow down at the end. Their big plan was to accelerate a camera up to 1/4c and have it snap pictures as it whizzes past the solar system. It's also far less than 1G acceleration. You don't get big acceleration figures like 1G from laser pumped solar sails.

How much energy would that be for that trip, for a reasonably sized space ship to take care of a crew for that long? Are we talking miniature fusion drive or antimatter type energy density required?

Johnny555 5y ago

I haven't done the calculations (which would be hard to do without knowing how big/heavy the ship needs to be), but I'd assume it's going to need something well beyond our current technology. An aircraft carrier is powered through the water (horizontally, of course) for 25 years on nuclear power. Now imagine the power it would take to make it hover for 25 years, and that's your 1G ship.

NortySpock 5y ago
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.
- 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
aardvark179 5y ago
Assuming perfect conversion of mass to energy you will still need a staggering amount of fuel for each kg of payload. Goggle the relativistic rocket equation and you should find a page with some figures for example scenarios.

jandrese 5y ago

If the rocket equation still applies (if a practical reactionless drive has not been invented), then you're talking about mass-of-the-galaxy size spaceships to accelerate at 1G for years on end.

whatshisface 5y ago
The linked paper describes a laser propulsion system by means of which no reaction mass need be stored on the spacecraft whatsoever.
- jandrese 5y ago
  Which is impractical because you don't have a way to slow down at the end. Their big plan was to accelerate a camera up to 1/4c and have it snap pictures as it whizzes past the solar system. It's also far less than 1G acceleration. You don't get big acceleration figures like 1G from laser pumped solar sails.