The Butterfly Effect From Hell: 7 Smallest Errors With Largest Ripple Effects
Mars climate research were ruined because the calculations were in inches
The team that built jet engines for Mars climate research didn’t even think to use the metric system in their calculations and didn’t inform NASA everything was in inches. You can imagine how wrong everything went when they started to build it.

Two planes were destroyed in mid air because their windows were square
The De Havilland Comet was a real masterpiece of a plane. In 1954 2 Comets literally blew up in the sky, taking 54 lives. All that because the square windows were experiencing metal fatigue at their corners. This is why the modern planes all have round windows.

One loose screw that destroyed a space rocket
“To the moon!” said the Russians. “Not a chance!” – said the loose screw.
In 1969 the Soviets launched one of their most expensive space rockets. It survived less than a minute because of one little, tiny, itsy-bitsy screw that got sucked into the fuel pump and BOOM! RIP, Russian space program.

One missing dash cost NASA $80,000,000
In 1962 NASA launched their first interplanetary space probe aimed at Venus. Unfortunately, one tiny line, a silly typo that completely changed its course. NASA had to abort the mission after the first 5 minutes, making it one of the most expensive mistakes in the history of space exploration.