Psi Combat
From Alpha Centauri Wiki
Some units (alien creatures such as Mind Worms and units equipped with the Psi Attack weapon or Psi Defense armor) can engage in PSI COMBAT. In Psi Combat, weapon and armor strengths are ignored, and the attacker is given a 3 to 2 advantage on land (1 to 1 for sea and air combat). Extra hit points from higher reactors are also negated, though this is not shown correctly on the combat odds window. MORALE level becomes quite important in Psi Combat.
PLANET rating also effects attackers psi combat at +/- 10% per point.
