Railgun recoil: why Newton won’t be denied.

bomb1Over at the Human Legion website today, I’ve finished off my personal journey through the world of railgun recoil, using an old-school bomb, and a game of billiards, and a little help from my dad!

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About Tim C. Taylor

Science fiction publisher and author of the bestselling Human Legion series. I live with my wife and young family in an English village. I am currently writing full time, when I'm not roped into building Lego.
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2 Responses to Railgun recoil: why Newton won’t be denied.

  1. timctaylor says:

    Hi Will, thanks so much for taking the time to share your experience and thoughts. As a writer I can handwave away awkward details, such as the immense stress I imagine is placed on the rails by the heat and Lorentz forces trying to pull them apart, but you technology developers can’t in the real world! You must have overcome I can’t even begin to understand.

    You’re right, of course, about recoil effects on ships, whether on water or in vacuum. They’re too massive for weapon recoil to shift them much. I imagine if a ship launches a railgun barrage while it’s trying to keeping a laser beam on a narrow target 10,000 miles away, then it might throw the beam off target. A space soldier firing a handheld railgun might have more to worry about, especially if he or she is in space.

    I share your skepticism about railgun use in space. I’m keeping it as secondary weapon for slow or stationary targets. Strafing and bombardment, really. The technology constraints in my fictional future world allow for a maximum speed of about 0.5c, and it takes months of thrusting to reach that. So we’re barely faster than a crawling worm compared with Star Trek, but even at these speeds, space combat is deeply problematic with vessels engaging at huge distances or flashing past each other in scant seconds.

    Thanks again for sharing your experience.
    Tim

  2. Will O'Neil says:

    Hi, Tim. I’ve had a good deal of involvement in railgun technology development, as well as the technology of other advanced weapons, and have an observation or two to make that may be of interest.

    First of all the dramatic plasma you see in the images of the Dahlgren tests is simply the result of air heated by the compression shocks of a projectile traveling at 2.5 km/s. Nothing so dramatic would be seen in space.

    You’re perfectly right about recoil forces, but it needs to be kept in proportion. A ship large enough to support a crew for extended missions can scarcely have a mass of less than 1 Mg, while a railgun projectile probably will not exceed 10 kg. Hence if the projectile is accelerated to velocity v by a ship-mounted railgun then the ship will be accelerated to a velocity of -v/100,000. So if v = 10,000 m/s the recoil-imparted velocity will be -0.1 m/s.

    I’m pretty skeptical regarding the practical value of railguns in space. There are limits on v that can be increased by technology but not transcended altogether. I’d certainly be very surprised if velocities of 100 km/s can ever be reached by practical weapons. But even this, impressive as it would be, does not amount to much on interplanetary scales. I’m inclined to think that particle-beam weapons or high-energy lasers would see more space use, despite all their problems and limitations in terms of terminal effects.

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