Complex sentence: Submarine crew members routinely operate in close proximity to stored weapons in torpedo rooms, unlike Air Force missiles where exposures are relatively brief-hence justifying the additional costs of the premium supergrade alloy used on the Navy weapon.
Split into simpler sentences: Submarine crew members routinely operate in close proximity to stored weapons in torpedo rooms, in contrast to the Air Force where exposure to warheads is relatively brief. This justified the additional costs of the premium supergrade alloy used on the Navy weapon.