Complex sentence: Because the Explorers was built for construction and exploration purposes these ship have very few defenses for a ship of its immense size only having 4 pulse cannons, 4 particle beam arrays, and squadrons of Starfuries.
Split into simpler sentences: Because the Explorers were built for construction and exploration purposes, they have very few defenses for a ship its size. Explorer-class vessels have 4 pulse cannons, 4 particle beam arrays, and squadrons of Starfuries.