Soyuz 7K-OK No.1
From Spacefaring
Soyuz 7K-OK No.1 was an uncrewed spacecraft of the Soyuz programme, originally intended to perform a rendezvous maneouvre with Kosmos 133. After the Kosmos 133 mission failed, the rocket was moved to the launch pad on 12 December 1966 and scheduled to launch on 14 December 1966, 11:00 UTC. The launch was aborted when one of the boosters failed to ignite. As ground crews worked on the now grounded rocket, the launch escape system unexpectedly activated, ejecting the descent module. The exhaust of the escaping capsule started a fire, leading to explosions that destroyed the rocket, severely damaged the launch pad, and directly killing one person. Two more would be killed while cleaning up the aftermath of the disaster.