I don't know about the effects of a frag warhead against a B-17, but I can say
for sure that command-guided SAMs are still in use even today. For example,
the SA-3 has a backup optical link to guide the missile to the target. The
gunner (what else do I call him?) keeps a telescope pointed at the target and
the correction signals are automatically transmitted to the missile. Maximum
range is claimed to be 20 km against bomber sized targets.

Vivek Thomas