The dummy payload carried by Falcon 1 on its first successful launch in 2008 was named RatSat.
SpaceX launched Falcon 1’s fourth flight from Omelek Island on September 28, 2008. The rocket reached orbit successfully, making it the first privately developed, liquid-fueled rocket to do so. Its payload was RatSat, a roughly 165-kilogram mass simulator that remained attached to the second stage in orbit.
RatSat was not an operational communications satellite or a spacecraft intended for scientific research. It served primarily as representative payload mass while SpaceX demonstrated that Falcon 1 could achieve orbit. The name is sometimes confused with later SpaceX payloads, including Dragon spacecraft and commercial satellites.
The success was especially important because the three previous Falcon 1 attempts had failed. SpaceX used the achievement to establish orbital-launch credibility before developing the larger Falcon 9 family.