In this historical photo from the U.S. space agency in January of 1966, simulated Van Allen Belts are generated by a plasma thruster in tank #5 Electric Propulsion Laboratory at the Lewis Research Center, Cleveland Ohio, now John H. Glenn Research Center at Lewis Field.
The Van Allen Belts are two donut-shaped regions around Earth packed with energetic electrons that can be harmful to spacecraft. The belts are named for James van Allen, who discovered them. Van Allen researched various topics and published his last scientific paper, about the risk of asteroids hitting Earth, just before his death at 91 in 2006.
Each weekday, SPACE.com looks back at the history of spaceflight through photos (archive).