There is an inherent problem with your idea: railguns with any sort of range and striking power are freaking huge! To give you an idea, here is an illustration of a *real* proposal for an orbiting railgun called "[Have Sting][1]" which was one of the various ideas floated during the research phase of the Strategic Defense Initiative in the 1980's:

[![enter image description here][2]][2]

*Have Sting with Space Shuttle orbiter to scale. Illustration by [Scott Loather][3]*

The enormous length is to provide the proper armature for the railgun itself. The cone shaped item is a small nuclear reactor to provide "hotel" power while on station and power the large tracking arrays. Actual combat power was cleverly provided by having liquid hydrogen and oxygen aboard. Several rocket engines can be seen, which allow the platform to slew around and orient to the target, but the burning H2/LOX mixture powered a large turbine as well, which provided megawatts of electricity for short bursts when firing.

Obviously Have Sting would be highly visible in orbit and easily tracked from the ground, but the railgun projectiles would be devastating at thousands of kilometres range, so theoretically the Have Sting could provide for its own self defence and fire on rockets climbing into orbit with ASAT payloads.

Now your conception is for "small" railguns in orbit. While even screws, nuts and bolts and even paint flecks can be traced from the ground, a satellite with is the size of a "[Cubesat][4]" (10×10×11.35 cm cubic units, has a mass of no more than 1.33 kilograms per unit) will be much harder to track and can be built in large numbers.

[![enter image description here][5]][5]

*1U Cubesat unit*

Now the armature will be very short and there isn't much room for capacitors, tracking systems or much else. Because of the small size and lack of consumables, micro railguns like this would have very short service lives in orbit, and may be held on the ground and launched in bundles of 10-100 at a time to be dispersed in orbit when needed.

[![enter image description here][6]][6]

*3U Cubsat. A weaponized one may have to be at least this large*

Such a railgun satellite will only be good as either an "escort" satellite for a much larger and more expensive one, firing its single shot at any unidentified satellites or space vehicles approaching, or as an "assassin", moving in with a swarm of fellow cubesats and attempting to overwhelm an enemy spaceship with a multitude of shots to kill any defending satellites and strip away any armour protection it might have. Since orbital velocity is 7 Km/s, the amount of kinetic energy that even a ball bearing sized round would have would be orders of magnitude greater than a rifle bullet. Attempting to fire and hit a target by firing against the direction of orbit means the pellet is striking with whatever velocity the railgun imparts + the 7 Km/s the enemy platform is orbiting at.

So tiny railguns that can fly in swarms *could* provide a different means of fighting a space war, but the ranges, timeframes and other factors will be extremely different than what we think of today.


  [1]: https://warisboring.com/the-death-star-that-might-have-been/
  [2]: https://i.sstatic.net/16oQv.gif
  [3]: http://up-ship.com
  [4]: https://infogalactic.com/info/CubeSat
  [5]: https://i.sstatic.net/geU7B.jpg
  [6]: https://i.sstatic.net/xVDyv.jpg