How many centuries from now is Star Ship Polaris set in, BTW?
Depending on how distant in the future we're talking about here, shields might not be as unrealistic as you might think. Last I've heard, NASA and the Air Force has been into research to make energy shields a real thing.
Though to be honest, for the next few centuries, we'll probably only have shields capable of deflecting interstellar debris, radiation, and maybe light forms of directed energy (which are just more forms of radiation). Deflecting dedicated weapons systems will be much harder to develop, and I'd imagine that ships might depend on polarized hull plating to augment their defenses, and that is if they use anything else in combat at all.