From Longman Dictionary of Contemporary Englishblast off phrasal verbTTSif a spacecraft blasts off, it leaves the ground → blast-off → blast→ See Verb table
Examples from the Corpus
blast off• The space shuttle is set to blast off on a nine-day mission tomorrow at 4:18 a.m.• Minutes after blast-off the rocket exploded.blast-offˈblast-off noun [uncountable] TTSthe moment when a spacecraft leaves the ground Ten seconds to blast-off. → blast off at blast2 