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Post by samchiu2000 on Sept 19, 2017 9:53:23 GMT
Well iirc the us navy didn't say to the 1000 or 400 shots are fired under full power mode. iirc? If I recall correctly.
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Post by matterbeam on Sept 19, 2017 13:36:44 GMT
Fgdfgfthgr: There is a way to reduce friction and skin effect losses to near zero. Instead of running a current through the projectile between the armatures, you create a plasma behind the projectile and run the current through it instead. The plasma can survive higher currents and temperatures with no friction or skin effects. The plasma pushes against the projectile to accelerate it. ieeexplore.ieee.org/document/209811/?reload=true
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Post by Kerr on Sept 19, 2017 15:57:12 GMT
Fgdfgfthgr : There is a way to reduce friction and skin effect losses to near zero. Instead of running a current through the projectile between the armatures, you create a plasma behind the projectile and run the current through it instead. The plasma can survive higher currents and temperatures with no friction or skin effects. The plasma pushes against the projectile to accelerate it. ieeexplore.ieee.org/document/209811/?reload=true Wouldn't this count as an plasma sabot?
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Post by newageofpower on Sept 21, 2017 22:26:42 GMT
Fgdfgfthgr : There is a way to reduce friction and skin effect losses to near zero. Instead of running a current through the projectile between the armatures, you create a plasma behind the projectile and run the current through it instead. The plasma can survive higher currents and temperatures with no friction or skin effects. The plasma pushes against the projectile to accelerate it. ieeexplore.ieee.org/document/209811/?reload=true There is, of course, the consequence of thermal ablation via exposure to the plasma. But in a hypervelocity weapon that should be orders of magnitude less than physical friction from contact railguns. Say, let me know if you're interested in more internet arguments, matterbeam.
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Post by matterbeam on Sept 22, 2017 0:01:41 GMT
There is, of course, the consequence of thermal ablation via exposure to the plasma. But in a hypervelocity weapon that should be orders of magnitude less than physical friction from contact railguns. Say, let me know if you're interested in more internet arguments, matterbeam. Thinking more about the concept, we might conceive of a variant where the railgun armatures are replaced with thin carbon wires and the projectile is equipped with a solid propellant sabot like lithium. Instead of relying on the Lorentz force, an electrical arc can run through the propellant block and vaporize it. Like an arcjet without any on-board power requirements and using the excellent conductivity of plasma, you can push the propellant gasses produced to stupid temperatures and achieve high velocities before the wire length run out. Since the wires do not have to handle any forces on the wires themselves, you can make them very thin and very long, to the point where we can consider them as wire-powered rocket projectiles. For further consideration! I love these 'internet arguments'. I created my toughsf blog simply to provide topics for discussion in attempt to recreate some of the discussions on Rocketpunk Manifesto and sfconsim-l, both of which are pretty much dead right now.
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Post by omnipotentvoid on Sept 22, 2017 7:18:15 GMT
Does anyone know how much of a problem friction is with molecularly perfect manufacturing? As far as I'm aware, friction between most solids depends mostly on surface structure. With most of that gone, I'd imagine that there would be relatively little friction between rails and armature. Also, most of my 10km long 1%c guns have an acceleration time of less than 10ms. Any plasma hot enough to do significant damage to the projectile in that time will destroy the rails. Not to mention that the dynamics and thus heat transfer properties of plasma with a few dozen GA flowing through it differ significantly from just plain plasma of the temperature (im not really sure how, but I'm pretty sure more heat would be transferred into the rails than the armature).
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Post by matterbeam on Sept 22, 2017 13:20:21 GMT
Does anyone know how much of a problem friction is with molecularly perfect manufacturing? As far as I'm aware, friction between most solids depends mostly on surface structure. With most of that gone, I'd imagine that there would be relatively little friction between rails and armature. Also, most of my 10km long 1%c guns have an acceleration time of less than 10ms. Any plasma hot enough to do significant damage to the projectile in that time will destroy the rails. Not to mention that the dynamics and thus heat transfer properties of plasma with a few dozen GA flowing through it differ significantly from just plain plasma of the temperature (im not really sure how, but I'm pretty sure more heat would be transferred into the rails than the armature). As I understand it, friction is caused by temporary bonds forming at the molecular interface between surfaces. They are created very quickly and breaking them takes force and energy, which is converted into heat. Molecularly perfect surfaces would have near zero roughness and less contact area between the surfaces... but not zero. At above-zero temperatures, molecules in a solid vibrate and flex, creating temporary roughness. You can only reduce the microscopic surface area down to the macroscopic surface area, and two 'perfect' surfaces will touch along all points. Put these together, and you'll always have some friction. At railgun velocities, temperatures rise quickly and cause more temporary roughness and so on.
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elukka
Junior Member
Posts: 73
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Post by elukka on Sept 22, 2017 13:37:12 GMT
I'm curious about a less technical point: Would plasma armature railguns have muzzle flashes in potentially interesting colors as the plasma is ejected?
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Post by Enderminion on Sept 22, 2017 13:45:04 GMT
I'm curious about a less technical point: Would plasma armature railguns have muzzle flashes in potentially interesting colors as the plasma is ejected? most important aspect
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Post by matterbeam on Sept 22, 2017 14:16:46 GMT
I'm curious about a less technical point: Would plasma armature railguns have muzzle flashes in potentially interesting colors as the plasma is ejected? Definitely. A big burst of hot, pink-red lithium plasma would come out of the muzzle.
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Post by 𝕭𝖔𝖔𝖒𝖈𝖍𝖆𝖈𝖑𝖊 on Oct 4, 2017 3:58:42 GMT
The title is not long enough to write down all things in this topic. I need some help! There is a debate going on insider a discussion group. Someone said that the conventional railgun can never reach speed more than 7km/s because of Skin effect. And "the ships might intersect in Third cosmic speed so the speed of railgun is not important.", he said that's because Voyager One had already reached that speed. What should I do to beat her???! When I ask her why not to say her opinion on Science and Technology board, she says that she won't do it because that will only happen if the audience is not too dumb to understand what she is saying. "The railgun which shoots 7x sound speed bullets had burned over half of butt of the bullet." "Also burn the rail." "Due to the Skin Effect that creates heat on the butt of bullets, the higher the speed is, the lower the efficiency of the railgun." When we ask her where is the paper talk about the Skin effect, she says she will get it later. And she thinks even electromagnetic Light Gas Gun can't get to speed more than 11km/s. "It's nothing about AC or DC, what really caused Skin effect is the speed of your bullet." "Look at such designs for few grams bullets, how much science commonsense does he(Q-Switched) can know?" Her evidences. (http://www2.es.titech.ac.jp/j-hasegawa/research/plasma.html) PS:We assuming the railgun in CDE is not Light Gas gun or Plasma driving gun!PS2: Third cosmic speed is 16.7km/s. Because space is a vacuum? The third cosmic speed is only the speed which a craft requires to leave the solar system it doesnt make a difference on the projectiles themselves and is not even a barrier like the sound barrier
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Post by Fgdfgfthgr on Oct 4, 2017 10:07:48 GMT
Because space is a vacuum? The third cosmic speed is only the speed which a craft requires to leave the solar system it doesnt make a difference on the projectiles themselves and is not even a barrier like the sound barrier She mean the relative speed of spacecraft can reach third cosmic speed during battle.
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Post by omnipotentvoid on Oct 4, 2017 10:37:03 GMT
I've found some isues with the skin effect argument. Primarily, the skin effect occurs in high frequency AC systems. With pulse times in the range of 10s to 100s of milliseconds (effectively meaning switching on and off again during firing with a "frequency" somewhere around 100 to 10 herz) I'm not sure if the skin effect is that much of an issue. Beyond that, the skin effect is highly dependant on the geometry of the current flow. With railgun armatures shaped as they are, the skin effect may be significantly weakened.
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Post by matterbeam on Oct 4, 2017 19:34:34 GMT
I've found some isues with the skin effect argument. Primarily, the skin effect occurs in high frequency AC systems. With pulse times in the range of 10s to 100s of milliseconds (effectively meaning switching on and off again during firing with a "frequency" somewhere around 100 to 10 herz) I'm not sure if the skin effect is that much of an issue. Beyond that, the skin effect is highly dependant on the geometry of the current flow. With railgun armatures shaped as they are, the skin effect may be significantly weakened. As far as I know, railguns use direct current, not alternating current. The latter is for coilguns. Correct me if I am wrong.
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Post by bigbombr on Oct 4, 2017 20:00:16 GMT
I've found some isues with the skin effect argument. Primarily, the skin effect occurs in high frequency AC systems. With pulse times in the range of 10s to 100s of milliseconds (effectively meaning switching on and off again during firing with a "frequency" somewhere around 100 to 10 herz) I'm not sure if the skin effect is that much of an issue. Beyond that, the skin effect is highly dependant on the geometry of the current flow. With railgun armatures shaped as they are, the skin effect may be significantly weakened. As far as I know, railguns use direct current, not alternating current. The latter is for coilguns. Correct me if I am wrong. AFAIK, coilguns also use DC. But the switching of coils is so fast it might act in some ways like AC. I might be wrong though.
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