NOTE: This involves editing a game file. Make a backup before proceeding.
Ok, find the config.cfg file in the Bethesda SoftworksStar Trek Legacy directory and open it with a text editor.
Find the line that says cfg_SPPlayerDamageModifier and set its value to 0.00, then save the file.
When you start the game, your ships won't take damage in campaign mode.
More damage to enemy ships:
Note: This involves editing a file, create a backup copy before proceeding.
Find the file Config.cfg in the Bethesda SoftworksStar Trek Legacy file directory. Open the file with a text editor such as Notepad.
Find the line SPAIDamageModifier and change the number to whatever you want it to be like 100.0. In Campaign, enemy ships will take more damage than usual.
Thanks to Revolution Readers Geary and bixbilby!