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Post by Fgdfgfthgr on Sept 18, 2017 8:12:29 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. |
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Post by kuriosly on Sept 18, 2017 8:53:56 GMT
Imperially, the US navy only gets 2.4km/s
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Post by samchiu2000 on Sept 18, 2017 9:43:56 GMT
Interesting. What is EM light gas gun btw???  |
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Post by Fgdfgfthgr on Sept 18, 2017 9:46:22 GMT
Interesting. What is EM light gas gun btw??? He said that Light Gas can achieve that speed. But the setting is the conventional railgun. |
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Post by Enderminion on Sept 18, 2017 11:34:25 GMT
using heat-sunk rails (diamond coating), thick rails, and discarding sabots, you should be able to negate the affect, IIRC 7km/s is about the max for railgun shooting in Atmo
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Post by Kerr on Sept 18, 2017 15:56:57 GMT
In Atmosphere railguns can only achieve 6km/s, because at that speed aerodynamics start failing, just like jumping from too high into water, at some height (final velocity) the water will be as hard as stone, because the molecules can't move out the way in the short time and start compreesing, at 6km/s a decent size munition will impact with several grams of air every second, each gram yielding the energy of 4g of TNT. The munition will turn itself into a shooting star few second after launch. In vacuum the maximum velocity of a railgun varies on several factors, sabot and rail material, how much power can you put in? Do you use special ways to reduce friction? nearly frictionless solid-lubricants or plasma sabots?
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Post by Kerr on Sept 18, 2017 16:00:04 GMT
Interesting. What is EM light gas gun btw??? You inject the projectile via an light gas gun into the railgun, nice velocities, but extreme rail ablation, but I think it helps with ablation because it removes contact time and it is easier to accelerate amoving metal projectile than a slow/still projectile, at least from personal experience of building a poor man's railgun. |
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Post by Fgdfgfthgr on Sept 18, 2017 19:57:24 GMT
In Atmosphere railguns can only achieve 6km/s, because at that speed aerodynamics start failing, just like jumping from too high into water, at some height (final velocity) the water will be as hard as stone, because the molecules can't move out the way in the short time and start compreesing, at 6km/s a decent size munition will impact with several grams of air every second, each gram yielding the energy of 4g of TNT. The munition will turn itself into a shooting star few second after launch. In vacuum the maximum velocity of a railgun varies on several factors, sabot and rail material, how much power can you put in? Do you use special ways to reduce friction? nearly frictionless solid-lubricants or plasma sabots? She does not say any special ways to reduce fiction or something like that...But "The railgun will never go over 7km/s no matter how much current goes through it. That's the limit of Electricity of human right now." |
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Post by Kerr on Sept 18, 2017 20:42:04 GMT
In Atmosphere railguns can only achieve 6km/s, because at that speed aerodynamics start failing, just like jumping from too high into water, at some height (final velocity) the water will be as hard as stone, because the molecules can't move out the way in the short time and start compreesing, at 6km/s a decent size munition will impact with several grams of air every second, each gram yielding the energy of 4g of TNT. The munition will turn itself into a shooting star few second after launch. In vacuum the maximum velocity of a railgun varies on several factors, sabot and rail material, how much power can you put in? Do you use special ways to reduce friction? nearly frictionless solid-lubricants or plasma sabots? She does not say any special ways to reduce fiction or something like that...But "The railgun will never go over 7km/s no matter how much current goes through it. That's the limit of Electricity of human right now." Actually, what does she mean with railgun? her specific definition, because current tech railguns could create dozens of km/s velocities, if the barrel is just long enough. Alright, I think she means the velocity-skin effect. "Also burn the rail." The Navy expects 1000 shots to be fired from the barrel, "current" reports suggest that the navy railgun can launch 400 shots with the same rail www.acq.osd.mil/chieftechnologist/publications/docs/FY2015_TestimonyONR_KlunderUSNM_20140326.pdfRailguns as presented in CDE COULD exist, they just require some extensive engineering and materials. |
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Post by thorneel on Sept 18, 2017 21:50:02 GMT
In Atmosphere railguns can only achieve 6km/s, because at that speed aerodynamics start failing, just like jumping from too high into water, at some height (final velocity) the water will be as hard as stone, because the molecules can't move out the way in the short time and start compreesing, at 6km/s a decent size munition will impact with several grams of air every second, each gram yielding the energy of 4g of TNT. The munition will turn itself into a shooting star few second after launch. In vacuum the maximum velocity of a railgun varies on several factors, sabot and rail material, how much power can you put in? Do you use special ways to reduce friction? nearly frictionless solid-lubricants or plasma sabots? Assuming that I have a ridiculous R&D budget and don't care about operational costs or not wasting taxpayer money (you can call me the... Heptagon), would scramjet projectiles work? |
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Post by n2maniac on Sept 19, 2017 4:16:52 GMT
Honestly, not understanding a few of the terms: "Third cosmic speed" - I have no idea what this is, do you have a link to something talking about it? "Skin effect" - This comes to mind for me, is that what is being talked about? en.wikipedia.org/wiki/Skin_effectIf so, a projectile could be made with a shallow enough depth that this is mitigated, since the I2t absorbable in the butt of the projectile is independent of how deep the projectile is, as is the impulse applied (F*t ~ I2t). If the presumption is that the projectile reaches 7km/s by ablating a large fraction of its mass, I would be curious to read the paper claiming it (mostly because I am curious how they set the bounds of the problem). If I had to guess, skin effect is not accounted for in CDE (anyone, please correct me if I am wrong). |
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Post by Fgdfgfthgr on Sept 19, 2017 6:46:38 GMT
Honestly, not understanding a few of the terms: "Third cosmic speed" - I have no idea what this is, do you have a link to something talking about it? "Skin effect" - This comes to mind for me, is that what is being talked about? en.wikipedia.org/wiki/Skin_effectIf so, a projectile could be made with a shallow enough depth that this is mitigated, since the I2t absorbable in the butt of the projectile is independent of how deep the projectile is, as is the impulse applied (F*t ~ I2t). If the presumption is that the projectile reaches 7km/s by ablating a large fraction of its mass, I would be curious to read the paper claiming it (mostly because I am curious how they set the bounds of the problem). If I had to guess, skin effect is not accounted for in CDE (anyone, please correct me if I am wrong). Third cosmic speed mean 16.7km/s. I think she means the velocity-skin effect. |
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Post by Fgdfgfthgr on Sept 19, 2017 7:56:41 GMT
She does not say any special ways to reduce fiction or something like that...But "The railgun will never go over 7km/s no matter how much current goes through it. That's the limit of Electricity of human right now." Actually, what does she mean with railgun? her specific definition, because current tech railguns could create dozens of km/s velocities, if the barrel is just long enough. Alright, I think she means the velocity-skin effect. "Also burn the rail." The Navy expects 1000 shots to be fired from the barrel, "current" reports suggest that the navy railgun can launch 400 shots with the same rail www.acq.osd.mil/chieftechnologist/publications/docs/FY2015_TestimonyONR_KlunderUSNM_20140326.pdfRailguns as presented in CDE COULD exist, they just require some extensive engineering and materials. She said that 400 shots absolutely not enough., evne the Yamato's 460mm cannon can shot 200. |
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Post by samchiu2000 on Sept 19, 2017 9:04:22 GMT
Actually, what does she mean with railgun? her specific definition, because current tech railguns could create dozens of km/s velocities, if the barrel is just long enough. Alright, I think she means the velocity-skin effect. "Also burn the rail." The Navy expects 1000 shots to be fired from the barrel, "current" reports suggest that the navy railgun can launch 400 shots with the same rail www.acq.osd.mil/chieftechnologist/publications/docs/FY2015_TestimonyONR_KlunderUSNM_20140326.pdfRailguns as presented in CDE COULD exist, they just require some extensive engineering and materials. She said that 400 shots absolutely not enough., evne the Yamato's 460mm cannon can shot 200. Well iirc the us navy didn't say to the 1000 or 400 shots are fired under full power mode. |
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Post by Fgdfgfthgr on Sept 19, 2017 9:12:27 GMT
She said that 400 shots absolutely not enough., evne the Yamato's 460mm cannon can shot 200. Well iirc the us navy didn't say to the 1000 or 400 shots are fired under full power mode. iirc? |
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