[@Savage][@Hank] Or by taking off the armour first. I assume that's what would usually be done if they for some reason needed to use a normal toilet. It should be noted, though, that the systems in Mk. II and higher power armour suits actually incorporate nutrient recycling facilities, so if the Marine needs to "go", there's nothing actually preventing him from doing so in a way that avoids embarrassment, amongst other appropriate verbs.