"When the U.S First Landed on the moon, How close were the Soviets?"

 Yep this was another Quora question and I shamelessly clipped it because it had infoo I never heard of before and I thought it was pretty neat.

Seventeen days before Apollo 11 landed, a loose metal fragment brought down a 3,000-ton Soviet moon rocket. It triggered one of the largest non-nuclear explosions in history.

This catastrophic failure on July 3, 1969, was the decisive blow to a secret crewed program that had made significant progress. The Soviet Union possessed much of the necessary spacecraft hardware for a human landing. They had designed the Soyuz 7K-LOK orbiter and constructed their own lunar lander, the Lunniy Korabl (LK). Unlike the two-person American Lunar Module, the LK was designed to carry a single cosmonaut to the surface. This hardware was not just theoretical; the Soviets had already built engineering models and flight units, eventually launching uncrewed LK landers into Earth orbit to verify the vehicle's systems.

An engineering test unit of the Soviet LK lunar lander, built in 1968, which was designed to carry a single cosmonaut to the lunar surface. Photo by Andrew Gray is licensed under CC BY-SA 3.0.

The bottleneck was the launch vehicle required to leave Earth orbit. To match the American Saturn V, Soviet engineers built the N1 rocket. While the Saturn V relied on five large engines on its first stage, the N1 used a ring of 30 smaller engines firing simultaneously. The plumbing required to synchronize and feed fuel to 30 engines created immense complexity. Lacking the budget for a ground test facility capable of firing the entire first stage at once, the Soviets were forced to test the complete system during live launches.

The first N1 rocket had already exploded 68 seconds into its flight in February 1969. During the second attempt in July, the loose fragment was ingested by an oxygen pump mere seconds after liftoff, automatically shutting down the engines. The fully fueled rocket fell back onto the pad, destroying the launch complex and ending any realistic chance of a crewed landing. "Here are the details of the N1 Rocket"

Still desperate to beat the Americans, the Soviets made one final play: a robotic sample return probe. On July 21, 1969, while Neil Armstrong and Buzz Aldrin were still on the Moon, the Luna 15 probe crashed into a mountain just 500 miles away, definitively concluding the space race.