The man who has spent most of his life known as the last man to walk on the moon came close to being the first, but could have missed out entirely by a later decision to wait.

Cernan came within eight nautical miles of the lunar surface in the Apollo 10 orbit mission, the trip planned until less than six months earlier to be the first manned landing.

"Was it disappointing? At the time yes it was, but in retrospect not at all," he said from Houston on Saturday.

"One of the biggest risks I ever took at the space program was turning down an opportunity to land on the moon on Apollo 16, but in the right seat, not the [mission commander's] left seat," he said.

"My boss thought I was crazy."

With the Apollo astronauts having trained in set crews for years, he was warned there was no guarantee he would be given a mission of his own. But crews were reassigned, and on December 11, 1972, Cernan and his geologist colleague Harrison Schmitt – "we called him Dr Rocks" – stepped down into the lunar dust.

Later this month the former navy pilot captain will touch down in Australia, where he will be the main attraction in a number of Q&A sessions arranged together with screenings of the award-winning movie The Last Man on the Moon, based on his autobiography.

Cernan and Schmitt spent 75 hours parked on the moon, including 22 hours outside the spacecraft, the longest of any astronauts. The experience of being in the "science fiction world" of "God's front porch" was unbelievable, he said.

"Soon as you shut the engine down, you are experiencing a moment of the greatest silence a human being can be surrounded with," he said.

"I'm looking at mountains that are as high as the Grand Canyon is deep, there's no haze, there's no trees.

"When you look back at this planet it is a philosophical experience, and, for me at least, it was a spiritual experience, I came to the conclusion that there is absolutely a single creator of this universe because if there wasn't it just wouldn't be here."

In addition to time, the latter missions had advantages over the Apollo 11 team, such as extra wheels.

Cernan, already the second American to walk in space as part of his Gemini 9 mission, was one of six men to drive a rover on the lunar surface. He holds the speed record with a somewhat slow-sounding 22 km/h, downhill.

"That's not very fast but when you hit one of those little crater potholes or a rock, it gets your attention, let me tell you," he said.

A lighter lunar module also meant a record "payload" of 115 kilograms of moon material was brought home, about six times that of the historic 1969 landing.

Famously remembered for leaving his eldest daughter Tracy's initials, "TDC", in the dust, Cernan acknowledges the years of intense training after joining NASA in 1963 – "we were gone eight days a week" – took their toll on the astronauts' families.

"We were on a great white horse, and we neglected what was going on at home," he said.

"I would probably change a few of those very personal things that went on in my life."

Now 82 and one of just seven moonwalkers alive, Cernan, who still flys his own plane, said he hoped the film would leave a legacy of inspiring youth to take risks to achieve their goals.

"The dreamers of today are the doers of tomorrow," he said.

"We are going to go back to the moon, men and/or women are going to land on Mars."

The Last Man on the Moon screenings and Q&A sessions with Cernan will be held in Sydney on May 30, Melbourne on May 31 and Canberra on June 2. Tickets can be bought at ticketmaster.com.au or the Canberra Theatre Centre website.