Firecons

We recently had a situation arise while battling in dust clouds.  
After nominating that certain batteries were going to fire on a
particular ship we rolled to get a weapons lock, and failed.
My opponent then declared that because the weapons had not been fired
and because their ship had 3 firecons that they could try to fire the
same batteries by attempting to get a lock on with the next firecon and
if that failed with the next one.
The rules state that firecons can be used to target multiple opponents
not the same ship multiple times.
Any Ideas??

Tks- Darryl