Bulgarian cosmonaut (astronaut) who became the first Bulgarian in space.

Ivanov graduated from the Bulgarian air force academy at Dolna in 1964 and served as an instructor at the academy before becoming a squadron commander of fighter aircraft in Bulgaria's air force in 1967. In 1978 he was selected to participate in the Soviet Union's Intercosmos program. An unusual circumstance of his selection was that the Soviet government required him to change his surname from Kakalov to Ivanov, owing to the obscene connotations of the word “Kakalov” in Russian.

In the Intercosmos program, non-Soviet cosmonauts flew alongside experienced Soviet crews on routine missions in order to demonstrate solidarity with states sympathetic to the Soviet Union. Ivanov's Soyuz 33 mission, however, diverged sharply from routine. Soyuz 33 was launched as planned on April 10, 1979, but while approaching space station Salyut 6, the craft suffered engine failure. The crew's only chance of survival depended on manually igniting a reserve engine that possibly had been damaged during the malfunction. After a day spent in orbit, commander Nikolay Rukavishnikov succeeded in igniting the engine, and the Soyuz touched down 180 km (112 miles) outside its landing area.

Despite the failure of the mission, Ivanov was named a Hero of the Soviet Union and awarded the Order of Lenin, the Soviet Union's highest civilian honour. He returned to military service in Bulgaria, earned a doctorate in aerospace engineering, and was elected to the National Assembly, where he participated in the creation of Bulgaria's first democratic constitution in 1991. He also became managing director of Air Sofia, a Bulgarian air cargo company.