During the 1950s and 1960s the USSR used dogs for sub-orbital and
orbital space flights to determine whether human spaceflight was
feasible. In this period, the Soviet Union launched missions with
passenger slots for at least 57 dogs. The number of dogs in space is
smaller, as some dogs flew more than once. Most survived; the few that
died were lost mostly through technical failures, according to the
parameters of the test. A notable exception is Laika, the first dog to
be sent into orbit, whose death was expected from the outset.
