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Post by lucubratory on Jan 11, 2018 13:57:44 GMT
Basically what it says on the tin. Could a coilgun be a hundred metres long and still be adding velocity? Five hundred metres? Five kilometres? If there is a speed limit due to something like the activation and deactivation speed of magnetic coils, could having a longer coilgun allow you to reach that maximum speed with lower g-forces on the payload?
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Post by newageofpower on Jan 11, 2018 15:57:13 GMT
Basically what it says on the tin. Could a coilgun be a hundred metres long and still be adding velocity? Five hundred metres? Five kilometres? If there is a speed limit due to something like the activation and deactivation speed of magnetic coils, could having a longer coilgun allow you to reach that maximum speed with lower g-forces on the payload? Switching speeds could be reduced via superconductive magnets and thermal quenching, but that would lead to a fairly high reload time. I believe the max speed of a coilgun is limited to a fairly high percentage of C, but that's so far out of the realm of CDE physics we barely consider it.
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Post by Kerr on Jan 11, 2018 16:17:34 GMT
Basically what it says on the tin. Could a coilgun be a hundred metres long and still be adding velocity? Five hundred metres? Five kilometres? If there is a speed limit due to something like the activation and deactivation speed of magnetic coils, could having a longer coilgun allow you to reach that maximum speed with lower g-forces on the payload? Hello, you have an misconception that velocity is limited by activation and deactivation speed, acceleration is. The faster your projectile the longer are the gaps of your coils to have enough time to create and collapse their magnetic fields. Quenchgun get around that, they use superconducting coils that are heated up until they lose superconductivity, which results in an instant collapse of the magnetic field. You could potentially get acceleration only limited by your material strength.
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Post by lucubratory on Jan 12, 2018 11:39:31 GMT
Basically what it says on the tin. Could a coilgun be a hundred metres long and still be adding velocity? Five hundred metres? Five kilometres? If there is a speed limit due to something like the activation and deactivation speed of magnetic coils, could having a longer coilgun allow you to reach that maximum speed with lower g-forces on the payload? Hello, you have an misconception that velocity is limited by activation and deactivation speed, acceleration is. The faster your projectile the longer are the gaps of your coils to have enough time to create and collapse their magnetic fields. Quenchgun get around that, they use superconducting coils that are heated up until they lose superconductivity, which results in an instant collapse of the magnetic field. You could potentially get acceleration only limited by your material strength. Awesome, thank you and newageofpower I really appreciate it! So what you're saying is there is no speed limit set by activation and deactivation speed of the magnets, just an acceleration limit? That's really handy information, thank you. If I was theory crafting a vessel, and it was already going to be five kilometres long with a hollow central cavity because of other design factors, would there be any particular reason not to have a spinal coilgun that runs the length of the ship? I'm thinking specifically of accelerating Casaba howitzer weapons as the payloads with attitude thrusters and the ability to send and receive information, so there will probably be an upper limit of G's they could be subjected to and still perform their purpose, so I doubt quench guns will be necessary. I was thinking there may be no benefit (in terms of velocity) to having a longer coilgun past a certain point, and didn't want to add a large spinal mount unless it was actually useful; it sounds like I was misunderstanding though. So to clarify, it would be possible and useful to have a 5km long coilgun in terms of final velocity difference with the vessel in question? Also, about the material stresses, is that going to be the limiter on this sort of thing at these scales? Thanks so much to both of you for taking the time to read and respond!
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Post by Enderminion on Jan 12, 2018 13:37:54 GMT
personally if I had five km to play with, it would have a Big neutral particle beam or FEL, but yeah you could but a coil/railgun in, as long as the barrel is braced it should be fine as long as the temp jump is not too high
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Post by Kerr on Jan 12, 2018 13:52:46 GMT
Hello, you have an misconception that velocity is limited by activation and deactivation speed, acceleration is. The faster your projectile the longer are the gaps of your coils to have enough time to create and collapse their magnetic fields. Quenchgun get around that, they use superconducting coils that are heated up until they lose superconductivity, which results in an instant collapse of the magnetic field. You could potentially get acceleration only limited by your material strength. Awesome, thank you and newageofpower I really appreciate it! So what you're saying is there is no speed limit set by activation and deactivation speed of the magnets, just an acceleration limit? That's really handy information, thank you. If I was theory crafting a vessel, and it was already going to be five kilometres long with a hollow central cavity because of other design factors, would there be any particular reason not to have a spinal coilgun that runs the length of the ship? I'm thinking specifically of accelerating Casaba howitzer weapons as the payloads with attitude thrusters and the ability to send and receive information, so there will probably be an upper limit of G's they could be subjected to and still perform their purpose, so I doubt quench guns will be necessary. I was thinking there may be no benefit (in terms of velocity) to having a longer coilgun past a certain point, and didn't want to add a large spinal mount unless it was actually useful; it sounds like I was misunderstanding though. So to clarify, it would be possible and useful to have a 5km long coilgun in terms of final velocity difference with the vessel in question? Also, about the material stresses, is that going to be the limiter on this sort of thing at these scales? Thanks so much to both of you for taking the time to read and respond! You use the equation √(2da) d= distance, a=acceleration, both in meters. Then you need to calculate your acceleration limit, guided artillery rounds can survive acceleration of up to 500km/s². 70.7km/s muzzle velocity with a 5km long coilgun.
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Post by Enderminion on Jan 12, 2018 14:03:34 GMT
with solid slugs I can get ten times that in only 200 meters
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Post by Kerr on Jan 12, 2018 14:09:58 GMT
with solid slugs I can get ten times that in only 200 meters 4c/s²
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Post by jtyotjotjipaefvj on Jan 12, 2018 14:37:59 GMT
with solid slugs I can get ten times that in only 200 meters 4c/s² Would that be enough force to start breaking down molecular bonds? It sounds like it should be.
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Post by matterbeam on Jan 12, 2018 14:43:01 GMT
Would that be enough force to start breaking down molecular bonds? It sounds like it should be. Look at the yield strength of the projectile's material. High yield strength to mass ratio allows for the greatest accelerations. If you really want to know how fast a coilgun can go... we have examples of relativistic electromagnetic 'guns': they're called particle accelerators and they reach speeds that are basically one m/s away from light-speed.
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Post by Enderminion on Jan 12, 2018 15:13:37 GMT
with solid slugs I can get ten times that in only 200 meters 4c/s² 6.76c/s^2, ten times is a rough estimate, it's really 807km/s muzzle
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Post by lucubratory on Jan 12, 2018 21:26:21 GMT
personally if I had five km to play with, it would have a Big neutral particle beam or FEL, but yeah you could but a coil/railgun in, as long as the barrel is braced it should be fine as long as the temp jump is not too high I thought about doing free electron lasers, specifically trying for x-ray free electron lasers, but I'm limited by how little I know. I thought the length increased the energy which increases the wavelength, but assumed you wouldn't be able to increase the length if you were trying to stay within a specific wavelength (like x-rays so you can focus them with x-ray diffraction crystals). Can you increase the energy of the beam without pushing the wavelength past what can be focused, and would doing that increase the length? This ship and the setting was going to have free electron lasers anyway, so it'll be a realism concern if I've chosen to add a coilgun spitting Casaba howitzers when x-ray free electron lasers would have served better.
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Post by bigbombr on Jan 13, 2018 7:49:20 GMT
...I thought the length increased the energy which increases the wavelength, but assumed you wouldn't be able to increase the length if you were trying to stay within a specific wavelength (like x-rays so you can focus them with x-ray diffraction crystals). Can you increase the energy of the beam without pushing the wavelength past what can be focused, and would doing that increase the length? This ship and the setting was going to have free electron lasers anyway, so it'll be a realism concern if I've chosen to add a coilgun spitting Casaba howitzers when x-ray free electron lasers would have served better. Increasing the length increases the top speed of your electron beam, which increases the energy of each electron, which means they'll emit a higher energy photon, which have a shorter wavelength. Increasing beam power is done simply by accelerating a larger number of electrons (meaning more photons) or accelerating electrons to a higher velocity (which increases the energy per photon).
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Post by lucubratory on Jan 13, 2018 8:55:49 GMT
...I thought the length increased the energy which increases the wavelength, but assumed you wouldn't be able to increase the length if you were trying to stay within a specific wavelength (like x-rays so you can focus them with x-ray diffraction crystals). Can you increase the energy of the beam without pushing the wavelength past what can be focused, and would doing that increase the length? This ship and the setting was going to have free electron lasers anyway, so it'll be a realism concern if I've chosen to add a coilgun spitting Casaba howitzers when x-ray free electron lasers would have served better. Increasing the length increases the top speed of your electron beam, which increases the energy of each electron, which means they'll emit a higher energy photon, which have a shorter wavelength. Increasing beam power is done simply by accelerating a larger number of electrons (meaning more photons) or accelerating electrons to a higher velocity (which increases the energy per photon). So there will be a specific length at which a FEL produces an x-ray laser, and to make the beam more powerful it needs to draw more power to push more electrons? Would that result in the accelerator/wiggler/whatever the long bit is being noticeably thicker if you're increasing the power significantly? There's so little information on free electron lasers that I've been able to find...
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Post by Kerr on Jan 13, 2018 8:58:09 GMT
personally if I had five km to play with, it would have a Big neutral particle beam or FEL, but yeah you could but a coil/railgun in, as long as the barrel is braced it should be fine as long as the temp jump is not too high I thought about doing free electron lasers, specifically trying for x-ray free electron lasers, but I'm limited by how little I know. I thought the length increased the energy which increases the wavelength, but assumed you wouldn't be able to increase the length if you were trying to stay within a specific wavelength (like x-rays so you can focus them with x-ray diffraction crystals). Can you increase the energy of the beam without pushing the wavelength past what can be focused, and would doing that increase the length? This ship and the setting was going to have free electron lasers anyway, so it'll be a realism concern if I've chosen to add a coilgun spitting Casaba howitzers when x-ray free electron lasers would have served better. The science of FEL's can be made rather easy if you just accept the ground concept, which is usually enough to understand it. Length equals to electron acceleration, so a longer FEL would be able to produce shorter wavelength. A 500m long FEL could produce 1.24 KeV electron with are more or less equal to 1nm hard x-rays. The limit of crystal diffraction is 30KeV, or 0.4 angström (0.04nm). So a few kilometers of FEL could be worthwhile, but the advantages diminish. As you get dozens light seconds of range from lenses a single meter in radius.
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