I'm trying to work through the mechanics of hard sci-fi space combat, and I came across the Casaba Howitzer.
The basic idea is a nuclear shaped charge. The blast from a nuclear bomb is partially contained into a cone / beam of plasma which can do some serious damage, according to the numbers in the link above. For reference, a one-megaton Casaba could theoretically apply an energy of 6.7MJ/m^2 to a target 1000 km away, or vaporize half a meter of aluminum at a range of 50 km.
The first two obvious ways of applying this concept are A: Put them in a missile which gets close to the target, and detonates outside the target's point defense grid, or B: Use very large versions for long-range combat. Even if you're too far away for the blast to destroy the enemy's armor, it can still wreck havoc on exposed sensors and other delicate components, as well as contribute to overheating the target.
While the idea is cool, I don't really like its implications for my 'realistic' space combat system. However, it occurred to me that the key word in the description of the Casaba's energy delivery method is 'plasma'. The Casaba's casing is vaporized into plasma, which is hurled at the target at near-relativistic speeds; but plasma, by definition, is charged, which means you should be able to repel it with a magnetic field. I know that we're working on magnetic fields for modern spaceships, which can theoretically protect from solar radiation for a fairly minimal energy cost. How much can such a system be scaled up? Could you build a version that could effectively protect against a Casaba? How much energy would it require?
Also, shields in soft sci-fi lose integrity / require more power the more they're hit. Would a magnetic shield hit by a Casaba somehow 'lose integrity', or would it continue to function just fine as long as it's fed enough power to repel damage to the ship?