"July 3, 1969 - Vehicle serial number 5L - At liftoff a loose bolt was ingested into a fuel pump, which failed. After detecting the inoperative fuel pump, the automatic engine control shut off 29 of 30 engines, which caused the rocket to stall. The rocket exploded 23 seconds after shutting off the engines, destroying the rocket and launch tower in the biggest explosion in the history of rocketry and also the largest manmade non-nuclear explosion ever (nearly 7 kilotons of TNT equivalent.) The destroyed complex was photographed by American satellites, disclosing that the Soviet Union was building a Moon rocket. The rescue system saved the dummy spacecraft again. After this flight, fuel filters were installed in later models."
They didn't work so well, either.
And just for fun, here is a KeyHole8 photo taken more than 40 years ago.
Verum audaces non gerunt indusia alba. - Ipsi dixit MCMLXXII