NASA astronaut Kayla Barron. Credit: NASANASA has assigned astronaut Kayla Barron to join three crewmates on a SpaceX Dragon spacecraft set to launch to the International Space Station in October, rounding out a four-person team after the space agency was unable to secure an agreement to add a Russian cosmonaut to the mission.Barron, a lieutenant commander in the U.S. Navy, will be launching on her first mission to space. She joins commander Raja Chari, another first-time space flier, veteran astronaut Thomas Marshburn, and rookie European Space Agency astronaut Matthias Maurer on SpaceX’s third operational Crew Dragon flight to the space station.Chari, Marshburn, Maurer, and Barron will spend about six months on the orbiting research complex, replacing the Crew-2 astronauts who arrived at the station in April.SpaceX is manufacturing a brand new reusable Crew Dragon spaceship for the Crew-3 mission, which is scheduled to launch aboard a Falcon 9 rocket Oct. 23 from pad 39A at NASA’s Kennedy Space Center in Florida.NASA has contracted with SpaceX for at least six operational crew rotation flights to the space station, following an unpiloted Crew Dragon demonstration mission to the station in 2019 and a crew test flight in 2020.The Crew-3 mission is the next SpaceX flight to carry astronauts to the space station, but SpaceX first plans to launch its first purely commercial Crew Dragon flight into orbit in September. That mission, named Inspiration4 at set to launch from Florida in September, will feature the first all-civilian crew on a three-day trip into low Earth orbit, without going to the International Space Station.About a month later, the Crew-3 mission is scheduled to blast off.NASA originally hoped to finalize an agreement with Roscosmos, the Russian space agency, to fly a Russian cosmonaut on the Crew-3 mission. But NASA officials said last month a draft of the agreement is still awaiting approval from the U.S. State Department, and time ran out to select and train a Russian cosmonaut for the mission launching in October.NASA wants to sign an in-kind agreement with Roscosmos to fly Russian cosmonauts on U.S. crew missions and continue launching U.S. astronauts on Russian Soyuz flights to the space station. The no-funds-exchanged agreement would ensure at least one U.S. astronaut and one Russian cosmonaut are always aboard the outpost to operate crucial systems on the U.S. and Russian modules.If a medical emergency or a hardware failure forced a premature ending to a space station expedition, the ISS could be left without personnel trained to oversee key parts of the complex.NASA announced Chari, Marshburn, and Maurer’s assignment to the Crew-3 mission in December. The agency confirmed Barron’s participation in the mission in a statement May 17.Barron and Chari will become the first members of NASA’s 2017 astronaut class to fly in space.The Crew-3 mission patch. Credit: NASAChari, 43, is a colonel in the Air Force. He was born in Milwaukee and raised in Cedar Falls, Iowa, before earning a bachelors degree in aeronautical engineering from the U.S. Air Force Academy and a masters degree in aeronautics and astronautics from the Massachusetts Institute of Technology.Before his selection as a NASA astronaut in 2017, Chari flew F-15E combat missions in Operation Iraqi Freedom, graduated from the U.S. Naval Test Pilot School, and served as commander of the 461st Flight Test Squadron and director of the F-35 Integrated Test Force.Marshburn, a 60-year-old medical doctor, will fly as pilot on the Crew-3 mission. He was born in Statesville, North Carolina, and graduated from Davidson College with a bachelors degree in physics and earned a masters degree in physics from the University of Virginia.Marshburn later graduated with a doctorate of medicine from Wake Forest University and masters degree in medical science from the University of Texas Medical Branch. After working as an emergency physician, Marshburn joined NASA as a flight surgeon and supported astronauts flying on the Russian Mir space station, multiple space shuttle missions, and crews on the International Space Station.NASA selected Marshburn as an astronaut in 2004, and he flew as a mission specialist aboard the space shuttle Endeavour on the STS-127 mission in July 2009. Marshburns second mission was a long-duration expedition on the International Space Station, during which he launched and landed on a Russian Soyuz spacecraft.Marshburn has logged 161 days in space on his two previous missions.European Space Agency astronaut Matthias Maurer, 51, will fly as a mission specialist on the Crew-3 mission.Maurer is from Sankt Wendel in the German state of Saarland. ESA selected Maurer to join its astronauts corps in 2015. Before becoming an astronaut, Maurer graduated with a doctorate in materials science engineering from the Institute of Materials Sciences of the Technical University in Aachen, Germany, and began working at ESA in 2010 as a crew support engineer.Barron, 33, was born in Pocatello, Idaho, but considers Richland, Washington, her hometown. She earned a bachelor’s degree in systems engineering from the U.S. Naval Academy and a master’s degree in nuclear engineering form the University of Cambridge.She qualified as a submarine warfare officer and served on three patrols on a ballistic missile submarine before her selection as a NASA astronaut candidate in 2017.Email the author.Follow Stephen Clark on Twitter: @StephenClark1.