A French air force colonel and two Soviet cosmonauts were blasted into orbit tonight on the first East-West space mission originally conceived as a gesture of detente.

Col. Jean-Loup Chretien became the first Westerner to take part in a Soviet space launch when a Soyuz T6 spacecraft lifted off atop a red, white and blue rocket. Soviet television showed the countdown and liftoff in a live broadcast from the Baikonur Space Center.

The three men are scheduled to spend nine days in space and dock with the orbiting space station Salyut 7. The two Soviet cosmonauts are Col. Vladimir Dhanibekov and Alexander Ivanchenkov.

The last East-West space venture was organized at the height of Soviet-American detente and involved a linkup between the Soviet Soyuz and American Apollo crafts in July 1975.

Tonight's flight, which had been approved by former French President Valery Giscard d'Estaing in 1979, in many ways symbolized the importance of detente between Moscow and Western Europe.

The Soviet authorities have taken a low-key approach to the joint mission, apparently to meet French insistence that political overtones be kept to a minimum. Instead, Soviet television emphasized the importance of the scientific cooperation between the two countries in outer space explorations.

No senior French or Soviet official was present at the Baikonur Space Center for the launch.

A moment before ignition, Chretien spoke in Russian to the television audience, uttering the French revolutionary slogan "liberty, equality and fraternity."

In a two-hour program preceding the launch, all three crewmembers made statements over television saying the flight was to symbolize friendship between the French and Soviet peoples.

The cosmonauts are scheduled to carry out various scientific experiments during their flight. One of the most important tests involves continued monitoring of the crew's organs and circulation.