Ranger 3 is the shuttle like space probe used by Buck Rogers for his five month exploration of the solar system. Ranger 3 was the designation of the long range space probe that Buck Rogers was selected to fly on a six month exploration of the Solar System in 1987.
Unfortunatly, an unforseen mishap froze Ranger 3's life support systems, resulting in Captain Rogers being placed in a form of cryogenic suspension, while sending the ship away from it's assigned flightpath, only to return to the vacinity of Earth in 2491, where it was intercepted by the Draconian flagship. Following the revival of Captain Rogers, the Draconians placed a tracking device aboard Ranger 3, thus allowing them to chart a parth through Earth's defense shield when the probe was escorted to Earth by a flight of Earth Directorate Starfighters.
During it's mission to locate missing Earth colonies, the Searcher used a shuttle design which appeared to be based on Ranger 3. Compared to the original, the new craft was missing its tail-fin, and had it's wings reconfigured, with the ends swept upwards. In addition, the interior was configured to hold passengers and/or cargo.
In the narration intro Buck's spacecraft is called "Ranger 3". But the Ranger series spacecraft were unmanned lunar landers, and the National Aeronautics and Space Administration never repeats project names to avoid confusion. However, it is entirely possible that the lunar spacecraft were operated under a different designation in the Buck Rogers Universe.
Also in 1987 there were no Shuttle missions due to space shuttle Challenger exploding and being destroyed on January 28, 1986. The next time there was a shuttle mission was on September 29, 1988 with space shuttle Discovery.