IRDT-1

First flight of the Fregat upper stage, the restartable block that would go on to anchor Soyuz missions for decades. The demonstration also carried IRDT, a European-Russian inflatable heat shield meant to cushion a payload's return through the atmosphere. The shield's second inflation stage failed to deploy fully, so the capsule hit the ground hard near Orenburg, but it survived reentry and was recovered, validating the basic concept.