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(CNN) -- Nichelle Nichols has spent her whole life going where no one has gone before, and at 81 she's still as sassy and straight-talking as you'd expect from an interstellar explorer.

"I don't have enough sense to keep my mouth shut," says the legendary Star Trek actor with a hearty laugh. "Whatever comes up, comes out."

"I can't help myself."

As the startlingly beautiful and fiercely intelligent Lt. Uhura on the hit 1960s TV series, Nichols was a revolutionary figure at a time when the only African-American women you saw on U.S. TV were usually playing servants.

Indeed, Star Trek was reportedly the only program Martin Luther King Jr would let his children stay up late to watch.

When Nichols was considering leaving the show to pursue a career on Broadway, King Jr personally implored her to stay, saying she was a powerful role model for black people across the country -- and the world.

"That was the greatest thing," says Nichols. "That was greater than anything else, to be told that by Dr. Martin Lurther King, because he was my leader.

"So I stayed and I never regretted it."

NASA ambassador

As the original series drew to a close at the end of the decade, a real-life space race was gathering pace -- and this time it was Nichols calling for auditions.

The United States landed a man on the moon in 1969 -- but our astronauts needn't be limited to white males, said Nichols.

"There were no women, and there were no minorities in the space program -- and that's supposed to represent the whole country?" she says, her voice rising incredulously down the phone from her home in Woodland Hills, California.

"Not in this day and age. We just absolutely cannot have that. I can't be a part of that," she said at the time.

The glamorous sci-fi celebrity was soon enlisted by NASA to recruit the country's first female and ethnic minority astronauts.

She traveled the length and breadth of the United States calling for promising astronauts to come forward -- among them was Sally Ride, the first American woman in space, and Charles Bolden, the current NASA administrator.

"As a matter of fact, Sally called me to tell me that I was the way she had heard about the space program," says Nichols.

"I was somewhat of a celebrity in their eyes. I had gone on television and in several interviews spoke of why they should get involved, and they took it up and said 'she's absolutely right.'"

The kiss

Nichols wasn't just a TV celebrity -- she was a TV revolutionary, locking lips with William Shatner in one of the small screen's first interracial kisses, in 1968.

Though at the time, she didn't quite see what all the fuss was about.

"I come from an interracial family, and so it was kind of boring for me to be talking about something I experienced every day," she says. "It was not new to me, because I lived it.

"But I realized it was new on TV, and I had the opportunity to bring it to the world."

The scene -- in which Lt. Uhura and Captain Kirk are controlled by humanoids who force them to embrace -- received a huge response from the public, largely positive.

Society today has much to learn from the crew living on board the "Enterprise" in the 23rd century, says Nichols.

"Star Trek is about the freedom to be who you are, and be respected for who you are," she says, her warm native Illinois accent raspy round the edges.

"It demands that you respect everyone else equally. It's as simple as that."

Stars in her eyes

Born in the small town of Robbins, outside Chicago, in 1932, Nichols came from a family that defied convention.

Her grandfather was a white Southerner who married a black woman, and in doing so was ostracized by his wealthy parents. Nichols' father was a factory worker who also served as town mayor.

A talented dancer and singer, Nichols started performing Chicago clubs at 14, meeting one jazz legend who would change her life forever -- Duke Ellington.

"He was the greatest name in music, black or white or any other thing," says Nichols. "Everyone at every level had the greatest respect for him."

She later toured with the successful composer, despite other people's reservations about what was expected of schoolgirls at the time.

"You went to school and it was like 'girls didn't do that.' But I was like 'c'mon.' So I just jumped on this opportunity with both feet," she says.

Enduring wonder of space

As a child, Nichols was also told that "girls weren't supposed to like science" -- not that she took much notice.

"Science is not a boy's game, it's not a girl's game. It's everyone's game. It's about where we are and where we're going," she says, and you can almost picture the serene figure of Lt. Uhura in red uniform, speaking at the controls.

"Space travel benefits us here on Earth. And we ain't stopped yet. There's more exploration to come."

It seems Star Trek's legendary communications officer has a real-life message for us all.

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