LOS ANGELES (Reuters) - When the filmmakers of “Mercury 13,” a new documentary about American women who trained for space flight in the 1960s, set out to chronicle their little-known story, they had no inkling how current issues involving women would come into play.

Seven members of the First Lady Astronaut Trainees, also known as the "Mercury 13", a group of women who trained to become astronauts for America's first human spaceflight program in the early 1960s, gather outside Launch Pad 39B near the Space Shuttle Discovery at NASA's Kennedy Space Center in Cape Canaveral, Florida, U.S., in this 1995 photo. (L-R) Gene Nora Jessen, Wally Funk, Jerrie Cobb, Jerri Truhill, Sarah Rutley, Myrtle Cagle and Bernice Steadman. Courtesy NASA/Handout via REUTERS

British filmmakers Heather Walsh and David Sington said the movie took on added dimensions from matters like equal pay and workplace harassment.

“We felt we were doing something that wasn’t a history piece, but it spoke to us today,” Sington said in an interview ahead of the film’s Friday release on Netflix.

The film tells the story of 13 women who passed the same rigorous testing as the Mercury Seven male astronauts in NASA’s program that first sent Americans into space between 1961 and 1963.

The women, all accomplished pilots, were tested by William Lovelace, a physician who helped develop the tests for the Mercury program. According to NASA’s website, Lovelace’s Woman in Space Program was a short-lived, privately funded project testing women pilots for astronaut fitness in the early 1960s.

Thirteen of the 25 women recruited into the program passed the punishing physical exams, which included sensory deprivation and a vertigo-inducing shot of ice water into the inner ear. But the women never made it into space.

It was not until 1983 that the first American woman astronaut, Sally Ride, achieved space slight, some 20 years after Soviet Union cosmonaut Valentina Tereshkova.

Walsh said she was “awakened” during production of the film by how relevant the struggles of past generations of women are today.

“I may have been blinkered somewhat in terms of how women are treated,” Walsh said.

The filmmakers believe the Mercury 13 women would have had a profound normalizing effect on equality around the world.

“It was just the most tragic missed opportunity,” Sington said. “In so many ways it would be a better world today if women would have walked on the moon.”