You want to make all your ships indestructible? Why?
Anyway, you could bump up the HpMax values in universetacticstacticstypes.ini for the classes you use, but that would also increase the HP of all hostile human ships. You could also edit each mission file in universemissionsepisodes to include the following code snippet:
	RULE event SceneInit
	:action
		GetMachine("GodMode"):ChangeState(default, 0);
	:end
	END
	
	MACHINE "GodMode"
	
		STATE default
			
			RULE event Tick
			:action
				SelectEx((s.ship | s.wreck) & s.race=#race_player,
					s.this:damage := 0;
				);
			:end
			END
			
			TICK 0.1
			
		END
		
	END
Or better yet, save that snipped as a seperate file in the same folder as "godmode.inc" and just insert [code=orange]#include "godmode.inc"[/color] in each mission file after its SceneInit event.
This script would try to keep all player ships at maximum health. It would only fail, if you encounter an enemy weapon capable to destroy your in one shot.