Wikipedia
Ratsat, or DemoSat, was a 165-kilogram (363-pound) non-functional boilerplate spacecraft used as a mass simulator on the fourth flight of the Falcon 1 rocket.
Ratsat was carried to orbit on the first successful orbital launch of any privately funded and developed, liquid-propelled carrier rocket, the SpaceX Falcon 1.
The launch, identified as Falcon 1 Flight 4, was conducted by SpaceX, and also marked the first time the Falcon 1 rocket successfully achieved orbit, after three consecutive failures on the three previous launch attempts.
Ratsat remained bolted to the second stage of the carrier rocket after reaching low Earth orbit. It has a hexagonal prism shape, 1.5 m (5 ft) long. SpaceX co-founder Elon Musk estimates that Ratsat will remain in orbit for between five and ten years before burning up in the atmosphere.