Because of the program's classified status, and for propaganda value, announcements of the outcomes of missions were delayed until success was certain, and failures were sometimes kept secret. Ultimately, as a result of Mikhail Gorbachev's policy of "glasnost" in the 1980s, many facts about the space program were declassified. Notable setbacks included the deaths of Korolev, Vladimir Komarov (in the Soyuz 1 crash), and the Soyuz 11 crew between 1966 and 1971, and development failure of the N-1 rocket (1968–1974) intended to power a crewed lunar landing, which exploded shortly after lift-off on four uncrewed tests.