Some type of huge shield is possible, although it would have to be truly gargantuan to resist very high speed projectiles or close-range nuclear detonations. Perhaps something planetary-based might be possible. I haven't given this area a lot of thought so far.
So I was thinking about this and I thought of two different types of shield to protect against kinetic (and possibly other?) defenses.
These were my goals for the defense:
- Provide some sort of defense that would protect slow things that can't dodge (planets, moons, shipyards) from instant and unstoppable death in a universe where an average ship (like the Daring) does enough damage on impact to match the explosion of every single one of the nuclear weapons currently on earth going off simultaneously. One thousand times...
- Not make such shields invulnerable (especially for shipyards, orbital habitats, or anything smaller).
- Have some sort of plausible-ish handwavium explanation, hopefully.
So what we want is something that protects against higher energy/velocity impacts more than those of smaller impacts. We want to make a planet relatively safe from genocide asteroid strikes, but not safe from a low-yield planetary bombardment. If this shield is knocked out by a low-yield planetary bombardment from orbit, and the planet is then genocided by an asteroid attack, that's ok. There was some sort of orbit battle that you lost, and the planet was destroyed, totally different from a small invisible object moving at relativistic speeds killing you out of nowhere.
And if a hidden foe is still sniping you from the outskirts of the solar system between the Uber shield taking the high energy hits, and your normal shield and armor of the PDCs taking the lower yield hits, hopefully you'll at least have time to look or the attacker, or evacuate, or something before the kill strike. Anything that feels a little more fair to the player.
Not only must it be more effective at blocking the higher energy strikes, but it should also take less damage from the higher energy strikes. It has to be handwaved as transmitting that energy somewhere else, if an asteroid causes the shield a million times more damage than a shell it's still the best weapon, and we are trying to de-incentivise those genocidal weapons.
Idea 1:
The best way to avoid taking damage from being hit by something is to not be hit by something. Now these things we're worried about can't dodge, and the faster the projectile is going the further out you need to be to deflect it... How about you just don't get hit by it. Instead of deflecting it spatially deflect it into hyperspace. It'll pop out of space when it hits your shield, and pop back into space on the other side of the shield.
Mechanics: The shield senses the warped spatial time of relativistic movement. Maybe it starts out at a 20% chance at warping things moving 1% of c (3000 km/s) and goes up from there, I don't know. The total energy each deflection takes is proportional to the amount of time the object needs to be warped times it's mass, ie the faster the object the less time it needs to be warped and the cheaper warping it is, but you can't just send a bunch of bb bullets either.
This shield could be an installation like the Planetary Observatories, one that is very expensive and takes a lot of personnel to run, so you can't just spam them on defensive outposts everywhere. Maybe they protect orbiting shipyards and orbital habitats, but not orbiting ships, or maybe there is also a (very very large, possibly less effective) component one so you can put it on Orbital Habitats, and you could add the same thing to shipyards somehow.
There could be some research lines for them "Warp Chance", "Warp Power per Second", "Recharge Speed", and "Capacitor Size per Facility" to increase the likelihood of blocking attacks and decrease the energy cost of doing so.
I need to do a little more math to vet whether my second idea may work.