Nope.
Okay, in Starmada X you design weapons that fit onto a vessel. Range, accuracy, damage and special modifiers. The first three are pretty obvious. Special modifiers are modifications to a weapon that more accurately meets what you think such a weapon should look like. For example, if you wanted a weapon that killed a lot of crew, you would use the option "Extra Crew Casualties". If, however, you wanted a weapon that fires more rapidly at short range than at long range, you would use the option "Range-Based Rate of Fire".
"Ignores PDS" is a special modifier, and thus modifies the space unit requirement of such a weapon. Thus if a weapon was 24 SUs in size, but you wanted it to ignore PDS, the weapons new SU cost would be 48.
Is that reasonably clear?