Satguns - railgun on a satellite with evasive capabilities
So, railgun cold war coming up: http://www.popsci.com/an-electromagnetic-arms-race-has-begun-china-is-making-railguns-too
And I imagine that the powers that be will be less shy about using these cheaper, non-mass-destruction weapons, as opposed to expensive ICBMs-that-go-big-boom.
So in my story, preparing for that probable first strike, that would be aimed at taking out the adversary's railguns, the US would like to protect its railguns by placing them on small satellites in orbit. The purpose of this is to enable complete evasion (dodging) of incoming railgun shots (incoming from Earth's surface). Also, I really really want a super cool Satgun that can shock the bad guys by "stepping aside" from their supposedly unstoppable attack.
However, the requirements for an effective railgun on a satellite seem to come in direct conflict with the evasive capabilities. I'm not going to ask for hard science here, because I realize this may be quite beyond our current tech level. So sci-fi it is! The story can be set at any point between 2020 and 2100.
My question is: How would the US build a Satellite that can both use its own railgun and evade railgun shots coming from the Earth's surface?
Clarifications:
Despite what the link/s above may suggest, I'm not set on China being the adversary in the story, and I'm only thinking about the US because they seem to have the most advanced tech in this field, and therefore the greatest chance of pulling a Satgun off.
The railguns (both on Satguns and on Earth) are your everyday easygoing 32MJ guns such as the ones that the US Navy currently tells us about: http://www.popularmechanics.com/military/research/news/a27455/us-navy-railgun-more-powerful/
The slugs are not guided, they just fly up/down real quick.
My Satguns need to be:
1. For the purpose of evasion:
2. 477
As small as can be
3. Highly maneuverable (depends on whether we can detect an incoming slug very early on)
4. Capable of receiving warning on an incoming slug on time for a successful evasive maneuver (actual sensors don't have to be on board, but the data about a specific slug headed towards a specific satellite needs to reach the satellite on time)
5. For containing and using their railgun:
6. Big enough to contain the railgun/s and energy supply (The smallest thing that I can think of that'll give enough juice is a nuclear reactor)
7. Big enough for ammo storage - at least a hundred slugs (since you can't easily replenish depleted ammo in space)
8. Handle recoil (I've read some cool ideas about using recoil energy rather than absorbing it)
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o BOOM ! ! ! 898