A former astronaut for NASA finally revealed a secret he’s been keeping regarding the agency’s Apollo 15 mission to the Moon. According to the astronaut, a design flaw of NASA’s Apollo Command Module freaked him out.

Former astronaut Alfred Worden served as the command module pilot for NASA’s Apollo 15 mission, which was launched on July 26, 1971. It was the fourth mission of the Apollo program to land on the Moon.

As the command module pilot, Worden stayed in lunar orbit while the other astronauts David Scott and James Irwin explored the Moon’s surface. While inside the command module, Worden noted that he experienced a technical design flaw that startled him during the mission.

According to Worden, the three seats inside the command module were mounted on top of swiveled shock absorbers. When he started the spacecraft in order to orbit the Moon, the vibration from the engines caused his seat to suddenly turn away from the module’s control panel.

“When I fired the engine to circularize, and I forget how many feet per second I had to add, instead of looking at the instrument panel I was suddenly looking out the left window,” he said according to Express. “Because when I ignited the engine, that couch because of Newton went like this and now I’m looking out the side window.”

“You talk about freaked out,” he added. “I was really freaked because I could not reach a single control.”

Fortunately for Worden and his crewmates, the command module’s computer systems still functioned perfectly, allowing him to return to the control panel. Despite the mishap, the former astronaut said that he was still able to carry out all of his responsibilities as the mission’s command module pilot.

Worden noted that he’s been keeping his terrifying experience aboard the command module a secret ever since Apollo 15’s launch. Since he’s no longer part of NASA, he said he can no longer be reprimanded by the agency for revealing details about the command module.

“I never told anyone that, only 45 years later I dare and even try to mention that,” he said. “They can’t do anything to me now.”

Astronaut David Scott sits in the lunar roving vehicle during the Apollo 15 mission in 1971. NASA