Scott Kelly, a veteran of the International Space Station, will return for an experimental year-long stay aboard the orbital outpost in 2015, a test run for future missions to the moon, asteroids and Mars.
Scott Kelly last flew in 2011 and will be paired with Russian cosmonaut Mikhail Kornienko for a 12-month assignment on board the International Space Station beginning in early 2015.
"Life on the space station is pretty routine, you know. In the morning you wake up, you are at work, when you go to sleep you are also at work. So imagine being in your office a whole year and you never get to leave," said Kelly.
Cosmonaut Mikhail Kornienko served as a flight engineer aboard the station in 2010.
Only four people have lived off-planet for a year or longer, all Russians who served aboard the now-defunct Mir space station. The single longest stay in space was a 438-day mission in 1994-1995 by cosmonaut Valery Polyakov, a physician.
The current U.S. record for a long-duration flight is held by former International Space Station commander Michael Lopez-Alegria, who spent 215 days in orbit between September 2006 and April 2007. Most stints on the station, a $100 billion, permanently staffed laboratory that orbits about 250 miles above Earth, have lasted no more than six months.
With the retirement of the space shuttles last year and the completion of the U.S. construction of the $100 billion station, NASA is working on a new space transportation system that can fly astronauts to the moon, asteroids and other destinations in deep space.
The goal is to send a crew to Mars in the mid-2030s.
The year-long station missions are intended to collect medical data and to test protocols for countering some of the adverse impacts of long-duration spaceflight, including bone and muscle loss, risks to eyesight and reproductive systems and changes in the immune and cardiovascular systems.
Kelly and Kornienko are scheduled to begin a two-year training program early next year.