A few weeks before the Apollo 11 moon landing, the Soviets attempted the second unmanned launch of their own lunar launch vehicle, the N1. This occurred at pad 110R (also called 110/38) of the Baikonur Cosmodrome. Although slightly shorter than the American Saturn V, the N1 had much more thrust and specific impulse in all of its stages.
The first 10 seconds of the launch seemed normal. Telemetry indicated all 30 (wow!) of the first stage engines within normal parameters. However, the LO$_2$ turbopump for engine #8 had exploded a quarter-second before liftoff, for reasons that were never completely determined. This initial explosion apparently severed supply lines to other engines, starting on-board fires.
At T+10.5 and an altitude of 100 m, pieces began falling off the tail section, and the on-board computer started shutting down failing engines. By T+12 and an altitude of about 200 m, all but one engine was shut down. The remaining engine (#18) began to pitch the massive rocket to almost 45°. The N1 fell back onto the launchpad due to lack of thrust.
The explosion was equivalent to 1000 tons of TNT, making it one of the largest non-nuclear explosions in human history. Pad 110R was completely destroyed. The blast shattered windows as far as 40 km away. A giant red mushroom cloud and the roar of the blast could be seen and heard from the Leninsk residential area 35 km away. Pieces of debris fell as far as 10 km. Only about 15% of the kerosene on-board actually detonated; much of the remaining fuel rained down in small unburned droplets.
On a positive note, the emergency escape system fired automatically, and carried the unmanned crew capsule to a safe landing.
I can find sources claiming the pad was "rebuilt", but no evidence of an actual launch. Buran/Energia was launched from pad 110L. Was pad 110R ever used again for a launch?
Source: http://www.russianspaceweb.com/n1_5l.html
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