Aliens, steel egg

Someone on Earth knew about the aliens. Someone battled them, and survived. Before Ripley, there was a first encounter. Aliens and humans have fought before! When a human spaceship discovers a vast egg-shaped vessel in Saturn's orbit, the crew powers in to investigate. Thinking the ship might contain usable metal for Earth, they force their way aboard. Three teams split up to explore the ship. Already the aliens have awoken. The first of all the battles unfolds.