Elon Musk's plan to send two paying tourists on a trip around the moon in 2018 will be 50 years after the flight of Apollo 8, the first time human beings left Earth and travelled to another world. Both flights are the most daring of their times.

The Apollo Moon Program was a turning point in 1968. After years of difficult work designing and building the world's largest rocket, the setback of a fire that claimed the lives of three astronauts during a test on the launch pad, a lunar lander that was behind schedule and not ready to fly, it was beginning to look like the goal of meeting President Kennedy's deadline of landing on the moon by the end of the decade would not be reached. And the Russians were still ahead in the space race.

But thanks to a bold decision to leapfrog the schedule and make the first manned flight of the new rocket a journey around the moon, the entire program was given the boost it needed to ultimately achieve Kennedy's dream.

Apollo 8

Commander Colonel Frank Borman leads the way as he, Command Module Pilot Captain James A Lovell Jr., and Lunar Module Pilot Major William A. Anders head to the launch pad for humanity’s maiden voyage around the moon and its first aboard the Saturn V vehicle, developed by NASA’s Marshall Space Flight Center in Huntsville, Ala. (NASA)

Apollo 8 was not supposed to go to the moon. The program called for a step-by-step process where all the technology for the moon landing would first be tested in Earth orbit before heading out for the real thing. The brand new Saturn V rocket had only flown in unmanned tests, and the lunar landing module was still under construction. So rather than wait, an incredibly daring decision was made to send three astronauts all the way to the moon on their very first flight and test everything except the lander. That decision, and the flight itself, are considered by many historians to be the riskiest decision in the history of spaceflight. No human had ever been that far from Earth, and all the technology was new.

A photo like no other

When Frank Borman, Jim Lovell and Bill Anders orbited the moon in December 1968, they came upon a sight no human eyes had ever beheld, the sight of the whole Earth rising above the lunar horizon. I had the fortune to meet Bill Anders who took the first Earthrise picture, and his comment about it was, "That was not on our agenda! We were there to photograph the landing sites on the moon."  But thanks to that serendipitous picture, humanity saw itself for the first time as a small, exquisitely beautiful blue ball floating in a vast blackness, a single living organism floating through a hostile universe.

To top it off, on Christmas Eve, while still orbiting the moon, the crew of Apollo 8 read from the book of Genesis, ending with, "...good night, good luck, a Merry Christmas, and God bless all of you — all of you on the good Earth."

That dramatic mission came at a time of great political turmoil in the United States. Students were protesting against an unpopular war in Vietnam, which was claiming thousands of American lives. Senator Robert Kennedy and Martin Luther King Jr. had been assassinated and civil unrest was rampant. Apollo 8 was credited with saving 1968 from becoming one of the worst years in American history.

Musk's vision

Now, half a century later, Musk wants to take a giant leap forward with a new rocket and a similar trip around the moon during a time of political unrest, although one not quite as violent as 50 years ago. Musk also has a slight advantage over his predecessors in that his new heavy lift rocket is not entirely new.

Falcon Heavy, is actually three Falcon 9 rockets strapped together to make one giant booster. The Falcon 9 has a proven track record with many trips to space, delivering cargo to the International Space Station and launching satellites into orbit. The Heavy is scheduled to make its first unmanned test flight later this year. The Dragon capsule that will carry the space tourists will also be flown to the space station to prove its worth.

SpaceX Crew Dragon

The SpaceX unveil event of Crew Dragon, the next generation spacecraft designed to carry astronauts to Earth orbit and beyond. The spacecraft will be capable of carrying up to seven crewmembers, landing propulsively almost anywhere on Earth, and refueling and flying again for rapid reusability. As a modern, 21st century manned spacecraft, Crew Dragon will revolutionize access to space. (SpaceX)

This new flight will not orbit the moon like Apollo 8. Instead it will fly very close to the lunar surface, for a spectacular photo op, then use the gravity of the moon to slingshot itself back to Earth on a so-called, free-return trajectory. This is what the stricken Apollo 13 mission used to return to Earth when an explosion crippled the spacecraft. The whole tourist trip should take about six or seven days.

If this flight succeeds, it could provide a huge boost to deep space exploration and the push to get people to Mars.

It is kind of sad that this mission comes half a century after the first flight to the moon. No one has been back there since 1972 because all efforts went into the space shuttle and building the International Space Station, which are amazing achievements, but neither able leave Earth orbit. NASA is building a new heavy lift rocket called the Space Launch System that will be even more powerful, but it is hugely expensive and will only fly once every couple of years.

Musk could go to the moon much sooner and far cheaper, showing that the private sector can take care of local spaceflight, leaving NASA to explore more daring probes farther into space.

After the Apollo 8 mission and the following moon landings, it looked like we were on our way to the stars. We've been sidetracked for a while; now it's time for another giant leap.