The United States famously landed two astronauts on the Moon on July 20, 1969. Ten more astronauts would follow over the next three years. And then that was that. On Dec. 14, 1972, astronauts Harrison Schmitt and Eugene Cernan left the Moon after three days on the lunar surface. No human has returned since.
Many of those enthusiastic about human spaceflight have fretted over this prolonged absence, chastising NASA over a perceived ineptness. But the reason we aren't on the Moon today is simple: Nothing yet justifies the expense and risk to human life.
The only reason we went to the Moon was because of the Soviet Union. The Space Race was an extension of the missile-based nuclear arms race between the Soviets and Americans that began after World War II.
"I'm not that interested in space," President John F. Kennedy told NASA Administrator James Webb two months after his famous Moon speech, as revealed in 260 hours of recordings Kennedy made in the Oval Office and publicly released in 2009. It could have been a race to the center of the Earth, for all Kennedy cared, as long as it demonstrated technological superiority over the Soviets who, in 1957, shocked the world by launching the 200-pound Sputnik satellite.
Americans would endure a decade of catch-up to the Soviets in space. The Apollo 11 was a crowning achievement, but it took an unprecedented corralling of resources. NASA had a 4.3-percent chunk of the federal budget in 1966, employed upwards of 400,000 people, and had the support of more than 20,000 industrial firms and universities — evidence of its warlike mission.
This wasn't sustainable, and President Richard Nixon understood that. "What we do in space from here on in must become a normal and regular part of our national life and must therefore be planned in conjunction with all of the other undertakings which are also important to us," Nixon told the American public in 1970, just after the successful Apollo 12 mission and a month before the ill-fated Apollo 13.
For many the space enthusiast, it nevertheless remains incomprehensible that, a half century after landing on the Moon, all we have in terms of human space exploration is six or seven astronauts in a tin-can of a space station a few miles above Earth maintaining ant colonies and doing flips for schoolchildren. No one in 1970 could have predicted such limited human presence in space in the 21st century.
Yet that's all there is until we find a reason to be in space that justifies the danger and expense. To return to the Moon and maintain a presence, two factors must come to fruition. There must be competition, either commercial or militaristic, to push us there. And there must be an economic driver that makes the venture sustainable.
A military competition is heating up. China has its own space stations (yes, plural), rockets to take humans there, and plans to establish lunar bases in the 2030s. China also has had several missions that have orbited or landed on the Moon, including a rover that operated for 31 months.
A commercial competition also is evolving. Companies have announced plans to take the public on suborbital flights (Virgin Galactic), to orbiting hotels (Bigelow Aerospace), and around the Moon (SpaceX), all likely to occur in the next decade. NASA and other space agencies will use these commercial services to take their astronauts and equipment to the Moon for far cheaper than what has been possible. This sets the stage for science bases on the Moon akin to activities in Antarctica, where scientists and support crews live for a few months to a year at a time.
Private companies will prospect the Moon in search for valuable resources, such as water for fuel (hydrogen and oxygen). If this proves profitable — still a big "if" — then we will at long last have the makings of a space-based economy. Tourism on the Moon could follow.
We won't live on the Moon and Mars just because it's awesome. Awesome isn't sustainable. We will only venture there with any sense of permanence when the activity becomes a natural extension of what we do today. Fifty years passed between when the first explorers set foot on Antarctica and when nations established permanent bases, as technology permitted. Fifty years after Apollo 11, the natural time to return to the Moon may be upon us.
Christopher Wanjek (firstname.lastname@example.org) is the author “Spacefarers: How Humans Will Settle the Moon, Mars, and Beyond,” to be published by Harvard University Press in February 2020.