On February 1, 1990, during a spacewalk, Alexander Serebrov dons an experimental flying armchair that had been delivered to Mir with Kvant 2. Unlike U.S. astronauts, who flew untethered flights with a similar device, the Soviet cosmonaut remains attached to the station with a safety tether, since there is no space shuttle to pick him up in case of an emergency.
They could not risk going out untethered with no shuttle to save them

There was no shuttle in case of emergency
( z1 possible :polarity - :ARG1 ( z2 risk :ARG0 ( z3 they ) :ARG1 ( z4 go-out :ARG0 z3 :manner ( z5 tethered :polarity - ) :accompanier ( z6 shuttle :polarity - :ARG0-of ( z7 save :ARG1 z3 ) ) ) ) )