Why spacecraft protection stops short of naval armor

Can spacecraft be armored against small debris and satellites?

They can carry light shielding against micrometeoroids, but current launch and mass limits make protection against large or high-velocity impacts impractical.

Space vehicles already carry passive protection against very small debris and micrometeoroids. This is armour under the broad definition offered here, although it provides protection only within a limited impact scale. It does not make a spacecraft resistant to a sufficiently massive object striking at high relative velocity. Naval levels of structural mass would also create severe launch problems with current rockets. Existing protection against small particles therefore qualifies the initial rejection of spacecraft armour.