Linenger joined astronaut selection Group 14 at the Johnson Space Center in August 1992. He flew on STS-64 aboard the Space Shuttle Discovery. Mission highlights included: first use of lasers for environmental research, deployment and retrieval of a solar sciencesatellite, robotic processing of semiconductors, use of an RMS-attached boom for jetthruster research, first untethered spacewalk in 10 years to test a self-rescue jetpack. In completing his first mission, Linenger logged 10 days, 22 hours, 51 minutes in space, completed 177 orbits, and traveled over 4.5 million miles. Following his first mission, in January 1995, he began training at the Gagarin Cosmonaut Training Center in Star City, Russia, in preparation for a long-duration stay aboard the Russian Space StationMir. All training was conducted using the Russian language, and consisted of learning all Mir space station systems, simulator training, Soyuz launch/return vehicle operations, and spacewalk water tank training. He also trained as chief scientist to conduct the entire United States science program, consisting of over one-hundred planned experiments in various disciplines. A sampling includes: medicine, physiology, epidemiology, metallurgy, oceanography/geology/limnology/physical science, space science, microgravity science. Linenger launched aboard U.S. Space Shuttle Atlantis on January 12, 1997, remained on board the space station with two Russian cosmonauts upon undocking of the Shuttle, and eventually returned upon a different mission of Atlantis on May 24, 1997—spending a total of 132 days, 4 hours, 1 minute in space—the longest duration flight of an American male at that time. During his stay aboard Space Station Mir, Linenger became the first American to conduct a spacewalk from a foreign space station and in a non-American made spacesuit. During the five-hour walk, he and his Russian colleague tested for the first time ever the newly designed Orlan-M Russian-built spacesuit, installed the Optical Properties Monitor and Benton dosimeter on the outer surface of the station, and retrieved for analysis on Earth numerous externally mounted material-exposure panels. The three crewmembers also performed a "flyaround" in the Soyuz spacecraft-undocking from one docking port of the station, manually flying to and redocking the capsule at a different location-thus making Linenger the first American to undock from a space station aboard two different spacecraft. While living aboard the space station, Linenger and his two Russian crewmembers faced numerous difficulties: the most severe fire ever aboard an orbiting spacecraft, failures of onboard systems, a near collision with a resupply cargo ship during a manual docking system test, loss of station electrical power, and loss of attitude control resulting in a slow, uncontrolled "tumble" through space. In spite of these challenges and added demands on their time, they still accomplished all mission goals-spacewalk, flyaround, and one-hundred percent of the planned U.S. science experiments. In completing the nearly five-month mission, Linenger logged approximately 50 million miles, more than 2,000 orbits around the Earth, and traveled at an average speed of 18,000 miles per hour. Linenger retired from NASA and the U.S. Navy in January 1998, and presently lives with his family in northern Michigan.