The Derelict is the informal designation for the spacecraft discovered on the Acheron LV-426 moon. In 2122 an unknown warning signal broadcast from the Derelict summoned the Weyland-Yutani commercial hauler USCSS Nostromo to the Acheron moon. The Derelict is believed to have crashed on Acheron several millennia prior to the arrival of the Nostromo. The port prong on The Derelict measure 161.6 meters in length and the starboard prong 174.3 meters. The craft is 116.6 meters wide and 61.0 meters wide between the starboard and port prongs. According to official historical records The Derelict was thought to be destroyed in 2179 when the atmospheric processor on the Acheron moon entered meltdown, but it somehow survived and was later explored by a Colonial Marines squad.
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The Derelict is a large, asymmetrical, wishbone-shaped craft, with a thickened central section between two horns, which bend upwards. It has numerous tunnels that go off to many places. It has three large openings near ground level between two horns, leading into the ship's interior. It is through one of these openings that three of the Nostromo crew members (Captain Dallas, Navigator Lambert, and Executive Officer Kane) entered the ship. The interior of the Derelict resembled more a living organism than a spacegoing vessel, with skeletal walls, circular gangways and steep passages.
One interesting aspect of the ship is that exactly what part of the ship seen by the Nostromo's crew goes completely unexplained. It would seem to be the bow, or front, because the exterior of the ship looks almost like the stern (back-end) of a ship that has hit the ground and buried its nose in the dirt.
The Space Jockey remains in his pilot seat, as seen in Aliens: Colonial Marines.