NASA landed the first person on the moon's surface on July 20, 1969, half a century ago this year. The monumental achievement saw astronauts Neil Armstrong, Michael Collins and Buzz Aldrin successfully fly to the moon, land and return to Earth. The moon landing was hailed as the greatest achievement of the 20th century, but the Apollo program was far from smooth from start to finish. Most importantly, the crew of Apollo 1 – the first piloted Apollo mission – died in a tragic cabin fire during a rehearsal startup.
And many astronauts who flew into space under the banner of NASA risked their lives every time they hit the Earth.
Professor Craig Underwood of the University of Surrey Space Center spoke to Express.co.uk about the incredible courage and determination of NASA astronauts.
Most NASA crews in Gemini, Mercury, and Apollo programs have experience in aviation, military, and experimental aircraft test flights.
Because of this, astronauts were spacecraft in the field of space flight, who could safely watch death in the face every day.
READ MORE: Amazing photos reveal Neil Armstrong in the last days before launch
NASA Landing Landing: Neil Armstrong Comes Near to Death in Multiple Cases
NASA landing: Astronauts were nearly stranded on the edge of space in an X-15 rocket plane
Prof. Underwood said: "They worked in a way we couldn't think of today about the risks that were taken.
"Test pilots died at a huge rate in the 1960s, not only in the US but also in the UK.
"We are absolutely terrifying today, but they were prepared to take those risks and push forward."
Commander Armstrong was a naval aviator in the Korean War before joining NASA and was a test pilot for an X-15 experimental rocket.
READ MORE: Neil Armstrong's biggest regret for space race revealed
The future commander of Apollo 11 first cheated on death in 1951, when his Panther jet fighter was struck over Korea by enemy fire.
Test pilots died at a huge rate in the 1960s
Then, in 1957, he flew a Bell X-1B pilot plane, which crashed when his landing gear failed to move properly and disintegrate.
Just a few years later in 1962, while flying an X-15 rocket propulsion at the edge of space, the aircraft descended or "ballooned" into the Earth's atmosphere, almost standing Armstrong in space.
Fortunately, the astronaut's famous steel nerves kicked in and allowed him to draw a trajectory that pulled him back to earth.
READ MORE: How UK-Based Technology Will Find Water and Put Man on the Moon by 2050
Prof. Underwood said: “The X-15 was a huge aircraft exploring the limits of knowledge, flying hypersonically.
"So they were all extremely brave people. Of course, we lost three astronauts in the fire of Apollo 1 and ironically, it was a terrestrial test.
"It was an awakening and, although tragic, it was an important lesson and they processed it and made it a much safer craft."
But the experiences of Commander Armstrong's near death were not over.
Moon landing line: A detailed look back at the Apollo 11 moon landing
NASA Landing Landing: A moon landing exercise nearly killed an astronaut in 1968
In 1966, during the Gemini 8 mission, a critical malfunction of the spacecraft's throttles threw astronaut and fellow pilot David Scott into a near-deadly rotation over Earth.
Commander Armstrong stabilized the spacecraft and terminated the mission, but came dangerously close to exiting the G-forces exerted by the rotation.
Then, in 1969, just a year before it flew to the moon, a training incident with a Lunar Landing Vehicle (LLTV) nearly killed Commander Armstrong in the crash.
Fortunately, the pilot cut himself off from a vehicle falling from a jet engine before it spectacularly exploded into a ball of flame.
The final brush of death appeared during the Moon's landing itself, when the Apollo 11's "Eagle" lunar module was ejected to a course strewn with rocks on the moon.
In the event of alarms and on-board computers inundated with navigation data, Commander Armstrong had to direct the Eagle to a clear landing spot.
The astronaut safely touched the Moonlight Sea of Tranquility with less than 30 seconds of fuel remaining.
The nail biting of the nail ended with Armstrong humming to NASA's mission control office to say, "Houston, peace base here. The eagle has landed. "
In total, there were 18 deaths of US astronauts and Russian astronauts killed in space flight, except for space flight activities such as the tragic Apollo 11 crash.