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Post by shiolle on Oct 4, 2017 16:13:27 GMT
Not sure about the momentum thing. The ship might not be "shot out" of "hyperspace" due to the drive folding space around it. All FTL drives are basically magitec as far as we know so you can posit anything you want. However, it has nothing to do with being shot out or anything. An object is moving before the jump, and it is no longer moving after the jump. Its impulse vanishes as if its inertia was zero. As for efficiency, I'm looking for a ship that can get some decent (14.5?) Delta-V with only 50 or even 20 percent of its mass being reaction mass. Ridiculous, I know... 14.5 km/s? As far as torchships go, this is a relatively modest requirement and you have a number of options. Let's say you want 30% of your ships as fuel (as some kind of middle ground). That means you need a drive with 40 km/s of exhaust velocity. A ship with a wet mass of 5000 tons (3500 tons dry mass) using this drive will need 49 MN of thrust to accelerate at 1 g, which means that at 100% efficiency it will require 1 TW of power. That doesn't mean you need a reactor with that much power. Most engines, like NTRs and combustion rockets generate required amount of power on their own. Only electric drives require a separate power source. That does mean however that if your drive is 90% efficient (which is ridiculously good) you will need to radiate 100 GW of waste heat. You can play with numbers here if you want. Orange fields are for input, bold black fields are calculated. To change anything you will have to copy the spreadsheet from the file menu. If you look at this page, there are a number of drives that satisfy the efficiency requirements: orion, NSWR, some kind of dual-mode fusion. I also recommend you look at other dual-mode engines too. They are very useful in that they can give you both high delta-V and high specific impulse (in different modes) without your thrust power threatening to burn nearby planets.
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Post by The Astronomer on Oct 4, 2017 18:10:26 GMT
Not sure about the momentum thing. The ship might not be "shot out" of "hyperspace" due to the drive folding space around it. All FTL drives are basically magitec as far as we know so you can posit anything you want. However, it has nothing to do with being shot out or anything. An object is moving before the jump, and it is no longer moving after the jump. Its impulse vanishes as if its inertia was zero. As for efficiency, I'm looking for a ship that can get some decent (14.5?) Delta-V with only 50 or even 20 percent of its mass being reaction mass. Ridiculous, I know... 14.5 km/s? As far as torchships go, this is a relatively modest requirement and you have a number of options. Let's say you want 30% of your ships as fuel (as some kind of middle ground). That means you need a drive with 40 km/s of exhaust velocity. A ship with a wet mass of 5000 tons (3500 tons dry mass) using this drive will need 49 MN of thrust to accelerate at 1 g, which means that at 100% efficiency it will require 1 TW of power. That doesn't mean you need a reactor with that much power. Most engines, like NTRs and combustion rockets generate required amount of power on their own. Only electric drives require a separate power source. That does mean however that if your drive is 90% efficient (which is ridiculously good) you will need to radiate 100 GW of waste heat. You can play with numbers here if you want. Orange fields are for input, bold black fields are calculated. To change anything you will have to copy the spreadsheet from the file menu. If you look at this page, there are a number of drives that satisfy the efficiency requirements: orion, NSWR, some kind of dual-mode fusion. I also recommend you look at other dual-mode engines too. They are very useful in that they can give you both high delta-V and high specific impulse (in different modes) without your thrust power threatening to burn nearby planets. 1. Not moving, relative to what?
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Post by Kerr on Oct 4, 2017 18:16:01 GMT
"I like the Lagrange point idea, however there are interesting considerations: Can you jump directly to, say, Moon L1 from Alpha Centauri? What happens to conservation of momentum when you jump between solar systems? Nearby stars are usually moving at 20 - 100 km/s relative to each other. Theoretically for most types of jump-like FTL this velocity shouldn't magically cancel out (conservation of momentum). If you can do the former and momentum is conserved, you can use this speed to your advantage. Just select your destination so that your velocity after the jump points into the general direction of your target. That means there are certain windows of opportunity where you can gain the most advantage out of your relative speed. That also means all interstellar ships in this universe need to have at least a few dozen km/s of delta-v to be of any use. That also means that certain systems, like Barnard's star would be harder to get to even if they are closer to home. Still, could you please clarify how efficient you want your drives to be?" Yep. Jump from L1 to Alpha Centauri with a travel time of two or three days. Not sure about the momentum thing. The ship might not be "shot out" of "hyperspace" due to the drive folding space around it. As for efficiency, I'm looking for a ship that can get some decent (14.5?) Delta-V with only 50 or even 20 percent of its mass being reaction mass. Ridiculous, I know... L1 to Alpha Centauri in 2-3 days? I hope that means time dilation and not just brute speed, if it is the later you have to deal with time travelling.
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Post by shiolle on Oct 4, 2017 20:50:01 GMT
1. Not moving, relative to what? Relative to the destination Lagrange point.
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Post by srbrant on Oct 8, 2017 3:07:19 GMT
"I like the Lagrange point idea, however there are interesting considerations: Can you jump directly to, say, Moon L1 from Alpha Centauri? What happens to conservation of momentum when you jump between solar systems? Nearby stars are usually moving at 20 - 100 km/s relative to each other. Theoretically for most types of jump-like FTL this velocity shouldn't magically cancel out (conservation of momentum). If you can do the former and momentum is conserved, you can use this speed to your advantage. Just select your destination so that your velocity after the jump points into the general direction of your target. That means there are certain windows of opportunity where you can gain the most advantage out of your relative speed. That also means all interstellar ships in this universe need to have at least a few dozen km/s of delta-v to be of any use. That also means that certain systems, like Barnard's star would be harder to get to even if they are closer to home. Still, could you please clarify how efficient you want your drives to be?" Yep. Jump from L1 to Alpha Centauri with a travel time of two or three days. Not sure about the momentum thing. The ship might not be "shot out" of "hyperspace" due to the drive folding space around it. As for efficiency, I'm looking for a ship that can get some decent (14.5?) Delta-V with only 50 or even 20 percent of its mass being reaction mass. Ridiculous, I know... L1 to Alpha Centauri in 2-3 days? I hope that means time dilation and not just brute speed, if it is the later you have to deal with time travelling. Relax, it's time-dilation. All warp cores are carefully designed so that the travel time within hyperspace is synced with the passage of time in real space by default. (For example, 15 hours in hyperspace means 15 hours have passed in the rest of the world.)
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Post by The Astronomer on Oct 8, 2017 3:09:18 GMT
L1 to Alpha Centauri in 2-3 days? I hope that means time dilation and not just brute speed, if it is the later you have to deal with time travelling. Relax, it's time-dilation. All warp cores are carefully designed so that the travel time within hyperspace is synced with the passage of time in real space by default. (For example, 15 hours in hyperspace means 15 hours have passed in the rest of the world.) It looks like it's contradicting itself.
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Post by srbrant on Oct 8, 2017 3:17:39 GMT
Relax, it's time-dilation. All warp cores are carefully designed so that the travel time within hyperspace is synced with the passage of time in real space by default. (For example, 15 hours in hyperspace means 15 hours have passed in the rest of the world.) It looks like it's contradicting itself. Oh dear...
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Post by The Astronomer on Oct 8, 2017 3:32:19 GMT
It looks like it's contradicting itself. Oh dear... Example of time dilationAt .8c, every 36 minutes on your ship equals an hour on Earth. If your handwavium hyperspace's time rate is synced with the real space, a trip to AlphCen (4.3 ly) at .8c in real space would take 5.375 years according to a person on a still frame and would still take 5.375 years if you travel in hyperspace according to a person on a still frame, but it'd take 3.225 years according to your ship. The only thing that will help is the lack of obstacles, possibly.
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Post by srbrant on Oct 8, 2017 3:58:35 GMT
Example of time dilationAt .8c, every 36 minutes on your ship equals an hour on Earth. If your handwavium hyperspace's time rate is synced with the real space, a trip to AlphCen (4.3 ly) at .8c in real space would take 5.375 years according to a person on a still frame and would still take 5.375 years if you travel in hyperspace according to a person on a still frame, but it'd take 3.225 years according to your ship. The only thing that will help is the lack of obstacles, possibly. Copied and pasted. Thanks. Back to the issue of efficiency. In CDE, I've found that drop-tanks are a godsend for travel, but that would end up with a lot of remass wasted in space and a lot more debris. Then again, Kessler syndrome in my story is already a problem. Two words: scrap asteroids. At this point, I'm afraid to say that this will have to be handwavium. Just have to make it as less wavy as possible.
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Post by Enderminion on Oct 8, 2017 4:01:12 GMT
wormholes can avoid most of these issues right? FTL and the like?
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Post by The Astronomer on Oct 8, 2017 4:08:43 GMT
Example of time dilationAt .8c, every 36 minutes on your ship equals an hour on Earth. If your handwavium hyperspace's time rate is synced with the real space, a trip to AlphCen (4.3 ly) at .8c in real space would take 5.375 years according to a person on a still frame and would still take 5.375 years if you travel in hyperspace according to a person on a still frame, but it'd take 3.225 years according to your ship. The only thing that will help is the lack of obstacles, possibly. Copied and pasted. Thanks. Back to the issue of efficiency. In CDE, I've found that drop-tanks are a godsend for travel, but that would end up with a lot of remass wasted in space and a lot more debris. Then again, Kessler syndrome in my story is already a problem. Two words: scrap asteroids. At this point, I'm afraid to say that this will have to be handwavium. Just have to make it as less wavy as possible. If you're going to handwave tech, make a kind of substance that converts into directional energy, with no waste heat problems whatsoever. It'd make the ultimate drive, if you don't fancy Alcubierre reactionless drives (the one which likes to fry/vaporize planets at your destination if you go superluminal) or EMDrives.
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Post by srbrant on Oct 8, 2017 4:35:24 GMT
Copied and pasted. Thanks. Back to the issue of efficiency. In CDE, I've found that drop-tanks are a godsend for travel, but that would end up with a lot of remass wasted in space and a lot more debris. Then again, Kessler syndrome in my story is already a problem. Two words: scrap asteroids. At this point, I'm afraid to say that this will have to be handwavium. Just have to make it as less wavy as possible. If you're going to handwave tech, make a kind of substance that converts into directional energy, with no waste heat problems whatsoever. It'd make the ultimate drive, if you don't fancy Alcubierre reactionless drives (the one which likes to fry/vaporize planets at your destination if you go superluminal) or EMDrives. No waste-heat problems sounds...not...right. Well, lemme get crackin'!
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Post by Kerr on Oct 8, 2017 6:50:12 GMT
L1 to Alpha Centauri in 2-3 days? I hope that means time dilation and not just brute speed, if it is the later you have to deal with time travelling. Relax, it's time-dilation. All warp cores are carefully designed so that the travel time within hyperspace is synced with the passage of time in real space by default. (For example, 15 hours in hyperspace means 15 hours have passed in the rest of the world.) How do your warp cores work exactly? Because within a warp bubble you are at rest, no time-dilation whatsoever. So you either travel over 4 years to Alpha Centauri from the crew's perspective or your Warp core is FTL, which means that you are time travelling.
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Post by srbrant on Oct 9, 2017 2:14:13 GMT
Relax, it's time-dilation. All warp cores are carefully designed so that the travel time within hyperspace is synced with the passage of time in real space by default. (For example, 15 hours in hyperspace means 15 hours have passed in the rest of the world.) How do your warp cores work exactly? Because within a warp bubble you are at rest, no time-dilation whatsoever. So you either travel over 4 years to Alpha Centauri from the crew's perspective or your Warp core is FTL, which means that you are time travelling. Hard to think of a non-technobabble explanation for that one, seeing how it's superluminal travel. Best I have is "transdimensional synchronization."
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