Vostok 4
The Soviet Union launches Vostok 4 with Pavel Popovich aboard, while Andrian Nikolayev orbits overhead in Vostok 3. The two vehicles pass within four miles of one another, but with no precision maneuvering, rendezvous or docking equipment, there’s little practical engineering value in the tandem space flight, other than to prove that ground controllers can handle two simultaneous flights. Popovich returns to Earth after nearly three days.