on may 1 , 1990 , during a spacewalk , alexander serebrov dons an experimented riding wheel that had been delivered to mir with kvant 2 . lacking u . s . astronauts , who flown untethered flights with a similar mechanism , the soviet cosmonaut remains attached to the station with a safety tether , meaning there is no space shuttle to pick him up in case of an emergency .
US shuttle Atlantis docks with the Mir space station.