Pavel Vinogradov set the age record for spacewalking Friday while outside the ISS with fellow cosmonaut Roman Romanenko, SpaceFlightNow.com reported.
The two flight engineers spent more than 6 1/2 hours outside the space station installing an experiment package, mission control officials said Saturday.
Vinogradov's record-setting spacewalk wasn't flawless, however. He lost control of a 6 1/2-pound panel from one experiment, SpaceFlightNow.com said. The piece floated away and was lost.
Experts at the Johnson Space Center in Houston said the panel's trajectory likely would take it out of the space station's path on future orbits and it eventually would burn up in the atmosphere.
The task was supposed to take 6 hours but ran longer because of an equipment failure, RIA Novosti reported.
The experiment will involve the study of plasma waves and the effect of space weather on Earth's ionosphere.