Some time in 2122, a warning signal being broadcast from the derelict was detected by Weyland-Yutani and the commercial hauler USCSS Nostromo was subsequently sent to investigate, without the knowledge of its crew. The ship was believed to have crashed on LV-426 several millennia prior to the arrival of the Nostromo.
The derelict was thought to have been destroyed in 2179 when the Atmosphere Processing Plant at the nearby colony of Hadley's Hope exploded, but it in fact survived the blast and was later home to an extensive Weyland-Yutani research camp, known as the Origin Facility.
The derelict is a large, asymmetrical, wishbone-shaped craft, with a thickened central section between two horns. The port prong measures 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 prongs appear to bend upwards, although this could be an effect of the way the craft is lying on the moon's surface. On one side, near ground level, the ship has three large openings. It is through one of these openings that the Nostromo crew members Arthur Dallas, Joan Lambert and Gilbert Kane entered the ship as part of their investigation. The exact nature of the openings is unclear, although Kane theorized that they were in fact airlocks, possibly left open following some kind of emergency evacuation from the ship.
The interior of the derelict resembles more a living organism than a spacegoing vessel, with walls and vaulted ceilings seemingly made of bone, and many organic shapes and structures in its passageways. Indeed, Kane additionally suggested that the ship may have been a biological construct, "grown" rather than built by the race that created it. During their exploration, theNostromo crew surveyed only one small part of the vessel, including the cockpit, as well as a cavernous cargo hold beneath. However, later studies found the ship contained numerous very large internal compartments and numerous cargo bays. [Source: wikia]
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