On December 27, 1968, Apollo 8 needed to fire its engine to leave lunar orbit and return to Earth.
If the burn was wrong, the crew would never come home.
In Mission Control, a 25-year-old mathematician named Frances Northcutt, known as Poppy, had prepared the return-to-Earth calculations.
She was the first woman to work in Mission Control in a technical role.
When the burn data came back, something was off.
The numbers didn't match the expected trajectory.
She had 4 minutes to determine whether the deviation was within tolerance or whether Apollo 8 was in danger.
She ran the calculations by hand.
They were within tolerance.
She gave the go.
The crew came home.
She later went to law school and became a prominent civil rights attorney.
When asked about her time at NASA she said:
"We were just doing our jobs. Nobody thought it was unusual except the reporters."
The people who kept the astronauts alive were largely anonymous.
Most of them were young women with slide rules.