As the first person to walk on the moon, he is a man whose name will be remembered for generations to come. But one of the other well-known things about Neil Armstrong is that he hardly ever gives interviews.

It was therefore something of a coup for Alex Malley, chief executive of Certified Practicing Accountants of Australia, to secure almost an hour of Armstrong's time to discuss the astronaut's trip to the moon.

In the illuminating conversation posted online on the CPA Australia website, Armstrong revealed how he thought his mission, Apollo 11, only had a 50% chance of landing safely on the moon's surface and said it was "sad" that the current US government's ambitions for Nasa were so reduced compared with the achievements of the 1960s.

"Nasa has been one of the most successful public investments in motivating students to do well and achieve all they can achieve," said Armstrong. "It's sad that we are turning the programme in a direction where it will reduce the amount of motivation and stimulation it provides to young people."

As a child, Armstrong said he had "become fascinated with the world of flight, as an elementary school student, and determined that, somehow, I wanted to be involved in that."

He served as a fighter pilot in the Korean war and was working as a test pilot when President John F Kennedy issued his challenge to the country's scientists to land on the moon. "We choose to go the moon and these other things," said Kennedy to an audience at Rice University in 1962, "not because they are easy but because they are hard, because that goal will serve to organise the best of our energies and skills, because that challenge is one that we're willing to accept, one we are unwilling to postpone and one we intend to win."

At the time, the US had only managed to send Alan Sheppard 100 miles above the surface of the Earth for 20 minutes. "Now the president was challenging us to go to the moon," said Armstrong. "The gap between a 20 minutes up and down flight and going to the moon was something almost beyond belief, technically."

Over the course of the following decade, each Apollo mission was used to test different parts of the propulsion, navigation and communication technology required on a journey to the moon.

"A month before the launch of Apollo 11, we decided we were confident enough we could try and attempt on a descent to the surface," said Armstrong. "I thought we had a 90% chance of getting back safely to Earth on that flight but only a 50-50 chance of making a landing on that first attempt. There are so many unknowns on that descent from lunar orbit down to the surface that had not been demonstrated yet by testing and there was a big chance that there was something in there we didn't understand properly and we had to abort and come back to Earth without landing."

When Armstrong and Buzz Aldrin made their descent aboard the Eagle to the moon's surface, the on-board computer had intended to put them down on the side of a large crater with steep slopes littered with huge boulders. "Not a good place to land at all," said Armstrong. "I took it over manually and flew it like a helicopter out to the west direction, took it to a smoother area without so many rocks and found a level area and was able to get it down there before we ran out of fuel. There was something like 20 seconds of fuel left."

Once the astronauts had reached the surface and he had muttered his immortal line, "one small step for a man, one giant leap for mankind", Armstrong said there was too much work to do to spend too long meditating or reflecting on where he was.

In the years since his legendary mission, Armstrong has watched Nasa's position and ambitions erode. "I'm substantially concerned about the policy directions of the space agency, which are directed by the administration," he said. "We have a situation in the states where the White House and the Congress are at odds over what the future direction should be and they're playing a game and Nasa is the shuttlecock they're hitting back and forth as both sides try to get Nasa on the proper path."

So how did Malley, who was clearly in awe of Armstrong during the interview, manage to land his exclusive? "I know something not a lot of people know about Neil Armstrong – his dad was an auditor," he said. "For people who are leaders or aspire to be leaders, listening to Neil Armstrong is far better than doing any educational MBA programme that exists in the world today."