- NASA astronaut Peggy Whitson has spent 665 days in space, more time than any other US astronaut.
- Scott Kelly, who spent almost a year on the ISS as part of a study that also involved his twin brother, has logged a total of 520 days in space.
- Here are the 15 US astronauts that have spent the most time off of Earth.
Astronauts can be sent to space for a variety of reasons, ranging from conducting research on the International Space Station (ISS) to studying the effects of space travel on the human body. Some missions are brief trips into orbit lasting 10 to 15 days, while others can last months.
Overall, Russian cosmonauts have spent the most time in space – they hold the top eight spots in global rankings of days logged in space. But American astronauts have racked up an impressive amount of time in zero gravity, too.
Here are the 15 US astronauts that have spent the most time in space.
Andrew Feustel — 226 days
- Sergei Karpukhin/Reuters
Feustel became an astronaut in 2000. He helped refurbish the Hubble telescope in 2009, and commanded the ISS on Expeditions 55 and 56 in 2018.
Daniel Bursch — 227 days
Bursch flew on four space missions between 1991 and his retirement in 2005.
Rick Mastracchio — 228 days
Mastracchio was selected to be an astronaut in 1996 and flew to space as a mission specialist on four missions that involved preparing the ISS for the arrival of permanent crews and making crucial repairs to the orbiting laboratory.
Leroy Chiao — 229 days
Chiao went on four space missions and was the commander of Expedition 10 on the space station. He retired from NASA in 2005 after 15 years.
Carl Walz — 231 days
After four space shuttle missions and one ISS expedition, Walz retired in 2008.
Timothy Kopra — 244 days
- Shamil Zhumatov/Reuters
Since being selected as an astronaut in 2000, Kopra has worked as a flight engineer on Expedition 46 to the space station, and as commander of Expedition 47.
Michael Lopez-Alegria — 257 days
- Brian Cleary/AFP/Getty Images
Lopez-Alegria joined NASA in 1992. He went to space on four missions and served as the commander of the ISS during Expedition 14 in 2006. He retired in 2012.
Joseph Acaba — 306 days
- Shamil Zhumatov/Reuters
Since joining NASA in 2004, Acaba has been to space three times. He has twice he served as the flight engineer on Expeditions to the space station.
Sunita Williams — 322 days
- Sergei Remezov/Reuters
Williams joined NASA in 1998 and has flown on two space missions. She is currently preparing for her third: the second crewed test flight of Boeing’s CST-100 Starliner spaceship. Williams was known as the woman who’d completed the most spacewalks until Peggy Whitson surpassed her record.
Donald Pettit — 370 days
- Matt Stroshane/Getty Images
Pettit became an astronaut in 1996. He lived on the ISS for five-and-a-half months and six-and-a-half months on two separate expeditions. He also operated the station’s robotic arm during spacewalks.
Michael Foale — 375 days
Edward Michael (Mike) Fincke — 381 days
Mike Fincke joined NASA as an astronaut in 1996 and has completed three space missions, on which he served as a science officer, flight engineer, mission specialist, and commander of the ISS. He’s now training for first crewed flight test of Boeing’s CST-100 Starliner spacecraft.
Scott Kelly — 520 days, including a nearly year-long stint on the ISS for a study that involved his twin brother Mark
Scott Kelly joined NASA in 1996 along with his twin brother Mark. In addition to his other missions, Kelly spent almost a year on the ISS as part of a study about how the human body reacts to long durations of time in space. For that study, Mark Kelly remained on Earth for purposes of comparison. Scott retired from NASA in 2016, and Mark Kelly is now running for a senate seat in Arizona.
Jeffrey Williams — 534 days
- NASA Handout/Reuters
Williams was selected as an astronaut in 1996. He worked as a flight engineer on several expeditions and commanded the ISS for the first time in 2009. He broke the record for the amount of time spent in space in 2016 and held it until 2018.
Peggy Whitson has spent more time in space than any other US astronaut: 665 days.
Whitson started as a researcher at NASA in the 1980s. She went on to become an astronaut, and Whitson visited the International Space Station for the first time in 2002.
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