Is it me or do the Patton space tanks are indestructible.. My 2 frigates and 1 destroyer have been shooting one space tank for the past 10 mins and nothing is happening to the armor.. is this a bug.
No, that just means you're using the wrong weapons to defeat them
The Patton has the Armor Regeneration hull mod; that means that low-damage, rapid-fire weapons like machineguns, and weapons that don't do a lot of DPS over time, like Tac Lasers, don't work well.
To defeat opponents like that, you have to use weapons with high burst damage or high amounts of HE damage, like Melters, plasma weapons, Sluggers, Hellbores, missiles, etc. For example, one easy way to beat them in early game with any Frigate that can mount missiles is to put Harpoons on and fire at point-blank- if you've mounted Armor Analysis, it's often enough damage to blow them away.
I'm sorry if you're finding that confusing; this mod's combat is really pretty straightforward once you get used to it, but if all you look at is DPS when mounting weapons (or if you don't really bother looking at the numbers), you'll have problems with anything that uses Armor Regeneration, period; they require a different approach.
Once it starts taking damage, though, it's really easy to kill a Patton.