There was the possibility that a powerful enough laser could reach further into the atmosphere, perhaps as deep as altitude if it was bright enough. In this case, there would be so many X-ray photons all the air between the battle station and the target missiles would be completely ionized and there would still be enough X-rays left over to destroy the missile. This process, known as "bleaching", would require an extremely bright laser, more than ten billion times brighter than the original Excalibur system.