Would it be possible to make ammunition for railguns and gauss rifles that would degrade over time either through a natural process or by the means of star radiation, so the missed shots don't endanger future space traffic? Hopefully turning into something less harmful after leaving the star system.

I was thinking about some kind of a carbon composite with enough iron mixed into it to keep the ammunition magnetic and with enough mass to keep the ammo effective. I know that carbon is tough and can be shaped, not to mention the wide variety of materials that are made from it, plastics, cellulose, diamond etc. The projectile would degrade over time, eventually crumbling to smaller, less harmful, pieces and eventually to dust. Similar to plastics, but it would have to be much faster.

Another option that came to my mind is to compress some kind of a dust mixture and use that. it could contain some kind of a charge or maybe just some volatile or unstable materials that would do the trick after a some distance.

What sort of materials do we have now that we could use so that the future railguns don't fire back at us after turning around some massive space object?

Although it would be probably rare. a galaxy wide civilizations could encounter this problem eventually. We usually try to make things last, so this would be opposite to what materials are in demand for now. But I am still curious what are our options.

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    $\begingroup$ Are you looking at "pure" railgun rounds, like a solid slug, or would you accept e.g. a round with an explosive warhead? $\endgroup$
    – Cadence
    Mar 2, 2019 at 22:25
  • $\begingroup$ I was thinking about solid rounds. explosive rounds could be made to just explode after a certain distance. which could solve the problem pretty easily, but it's not really degradable ammunition. Let's stick to solid rounds then. $\endgroup$ Mar 2, 2019 at 22:38
  • $\begingroup$ 👍Thoughtful of the consequences! I guess most projectiles would be caught by gravity well and undergo orbital decay... takes about several decades but eventually. $\endgroup$
    – user6760
    Mar 3, 2019 at 0:42
  • $\begingroup$ The likelihood of encountering a slug would be negligible, about the same risk as being hit by a micro-asteroid probably, in the vastness of space a million bus sized slugs would quickly spread over hundreds of kilometres and would over a couple days be about as densely packed as the asteroid belt $\endgroup$
    – P.Lord
    Mar 3, 2019 at 11:59
  • $\begingroup$ As long as the velocity of the railgun round is higher than the planet's escape velocity, it won't stay in orbit. If you really want to make sure, use higher velocity than the star system or even galactic escape velocity - then the probability of hitting anything before the heat death of the Universe becomes negligible. And you want high velocity anyway. $\endgroup$
    – Eth
    Mar 4, 2019 at 11:31

1 Answer 1


Make projectiles of supercold materials that thaw and sublimate away in space.

Superconducting railgun projectile.

Your projectiles are made of solid oxygen or perhaps a noble gas cooled to freezing. Superconductivity is an excellent quality for an electromagnetic weapon projectile as ohmic heating is a big problem otherwise. With no resistance to the flow of current the superconducting projectiles will not heat up as they are fired.

Until later, and that is what the OP wants. Supercold projectiles with low freezing points will sublimate readily. The lower the melting point of any object the more readily it will sublimate away as a gas. Even a steel projectile has some amount of sublimation, but projectiles which are extremely cold and with a low freezing point (e.g. a frozen noble gas, or oxygen) will more readily sublimate away as the gas due to ambient radiant heating as they fly through space.

This also will produce narrative possibilities - for example, cooling the punch with a railgun round fresh from the freezer.

  • $\begingroup$ Would the frozen gas rounds work for railguns as well? since those need to be in contact. would they have the mass to do effective damage on impact? wouldn't they just explode instead of breaching the target like standard rounds? actually that might be pretty cool. haven't thought about that. (sorry not really part of the question. i just need some clarification) :) $\endgroup$ Mar 2, 2019 at 22:51
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    $\begingroup$ It seems to me that a pure frozen gas round would be difficult for a railgun to grab and fling. It could be possible to freeze metallic shavings in the round, so that there's something to grab onto. Ordinarily, those shavings would get heated by the railgun, too, except supercondctivity for the win, maybe. I'm suggesting shavings rather than solid mass so that when the gas sublimates, the shavings will disperse rather than remaining a single remnant. Depending on what gas used, the slug could be rather explosive, too... could solid hydrogen mixed with solid oxygen work? $\endgroup$
    – Ed Grimm
    Mar 2, 2019 at 23:19
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    $\begingroup$ @NuloenTheSeeker - the original idea for the frozen gas was for a railgun. Railgun are where it's at. With extreme velocities, just about any kind of projectile will explode against the target. The kinetic energy still gets delivered. $\endgroup$
    – Willk
    Mar 3, 2019 at 16:36
  • $\begingroup$ @EdGrimm - railguns do not grab their projectiles physically. Friction of any sort is the enemy here. The energy is delivered via the Lorenz force through the projectile. The equal and opposite reaction is, as I understand, a force pushing the rails apart. $\endgroup$
    – Willk
    Mar 3, 2019 at 16:38
  • $\begingroup$ @Willk Correct. What gasses can be moved with the Lorentz force? Iron shavings are much more strongly affected by that than any gasses I know. There's a few other things that are pretty strongly affected, including anything that can be made magnetic. But all of those things that I'm aware of are solid at standard temperature and pressure. $\endgroup$
    – Ed Grimm
    Mar 3, 2019 at 21:24

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