LV-426 The Nostromo incident
Ellen Ripley worked for the Weyand Yutani corporation as a navigation officer on the commercial towing vessel Nostromo. This vessel was towing an ore refinery back to Earth when it was diverted by the corporation to planet LV-426 to investigate a distress call. The crew were attacked by an extremely dangerous Alien Xenomorph. Ripley was he sole survivor as she escaped on a shuttle after setting the Nostromo to self- destruct.

Archeon (LV-426) Hadleys Hope colony
Due to a navigational failure her shuttle was not recovered for fifty years while she remained in hyper sleep. Upon returning to Gateway station (Earth orbit) the Weyland Yutani corporation blamed her for the loss of the Nostromo and the material cost of the operation. She was working in the loading docks when contacted by the corporation because they had lost contact with the new colony on LV-426. She went back to the planet with a heavily armed colonial marine squad in the military vessel the Sulacco. Unfortunately the colony had been overrun by the Aliens, and most of the marines were killed. Ripley again survived along with Corporal Hicks, Newt the daughter of a colonist, and the badly damaged android Bishop.

Fiorina-161 (aka Fury-161)
The marine vessel The Sulacco never reached Earth as eggs left on board by the queen hatched and the facehuggers damaged the ship. The surviving crew's (inc. Ripley's) hyper sleep capsules were jettisoned in an escape vessel, and this crashed on the prison planet Fiorina-161. Again Ripley was almost the sole survivor. However the escape craft also contained a facehugger which infected a prison dog. Another massacre followed with most of the prisoners being killed in the attempt to combat the Alien. Ripley was instrumental in this fight, however she discovered that she had already been implanted with an Alien embryo. Rather than let it live she committed suicide.

USM Auriga
Two hundred years after Ripley's death scientists on the medical research ship USM Auriga cloned Ripley from her blood sample taken on Fiorina-161. They needed her in order to obtain the queen Alien she had been carrying when she died. This worked with only a minimal transfer of Alien DNA to the Ripley clone (the new Ripley had acid blood and enhanced strength). Unfortunately the Alien specimens they had managed to create escaped and killed many of the scientists and military personnel. Ripley with the help of the crew of a smuggler vessel The Betty fought the Aliens including the Queen and destroyed the USM Auriga. However the Queen had some of Ripley's DNA a gave birth to a cross breed know as the New Born. This was killed by the Ripley clone onboard The Betty.