on early 1 , 1990 , during a spacewalk , alexander serebrov mk an experimental flying object that had been delivered to iss with kvant 2 . regarding u . s . astronauts , who flew untethered flights with a special equipment , the human vinogradov continues glued to the shuttle with a protective tether , since there is no space hopper to pick him up in case of an emergency .
us flight atlantis docks with the mir research center .