Nagel first flew as a Mission Specialist on STS-51G, which launched from the Kennedy Space Center, Florida, on June 17, 1985. The crew aboard the Shuttle "Discovery" deployed communications satellites for Mexico (Morelos), the Arab League (Arabsat), and the United States (AT&T Telstar). They used the Remote Manipulator System (RMS) to deploy and later retrieve the SPARTAN satellite which performed 17 hours of x-ray astronomy experiments while separated from the Space Shuttle. In addition, the crew activated the Automated Directional Solidification Furnace (ADSF), six "Getaway Specials," participated in biomedical experiments, and conducted a laser tracking experiment as part of the Strategic Defense Initiative. After completing approximately 170 hours of space flight, "Discovery" landed at Edwards Air Force Base, California, on June 24, 1985.