Fifty years ago, on December 19, 1972, the Apollo 17 astronauts splashed down in the Pacific. They were the last humans to visit the Moon—and the last to be more than 400 miles from the Earth. Since that date, astronauts have only been in low Earth orbit. It is thus richly symbolic that NASA’s Artemis I mission had its own Pacific splashdown recently, during Apollo 17’s 50th-anniversary celebration. It was, of course, only an uncrewed test of the space agency’s new lunar craft. Humans will not fly around the Moon for two to three years. Why has it taken more than five decades to send humans back to the Moon?

It was certainly not Apollo 17 commander Eugene Cernan’s expectation when he stepped off the lunar surface for the last time on December 14, 1972. He was aware, as was everyone in the space agency, that lean times were ahead. Two years earlier, NASA had deleted Apollos 18 and 19 to save money and focus on the Space Shuttle. Congress and two presidential administrations had been cutting NASA’s budget since 1967 as the Vietnam War, poverty, urban problems, and environmental crises made the space program less and less popular. Once Neil Armstrong and Buzz Aldrin stepped on the surface in July 1969, many Americans wondered why we didn’t stop. We had beaten the Soviets and proved American technological superiority—the fundamental purpose of Project Apollo. Although the later landings yielded a huge scientific haul of samples and data, the public did not much care about lunar science’s value to understanding solar system history. It seemed like a waste of billions of dollars to voters preoccupied with other problems. Thus, Cernan knew it could be two decades before a new human lunar program would be feasible. But it was hard to believe that American astronauts wouldn’t make it back before the end of the century.

The Space Shuttle finally orbited in 1981, after thin NASA budgets and challenging new technologies caused years of delay. With a new, space enthusiast president in office, Ronald Reagan, NASA leadership set about pushing what they had always believed was the “next logical step” to a sustainable space infrastructure, a space station. The shuttle had been sold to the Nixon administration as a way to make spaceflight much cheaper (a promise never fulfilled), but it was originally supposed to be a crew and cargo transport vehicle to a permanent space base. In late 1983, Reagan approved what eventually became the International Space Station (ISS).

It fell to his successor, George H.W. Bush, to propose sending humans back to the Moon and on to Mars. Bush spoke on the steps of our Museum on July 20, 1989: the 20th anniversary of Armstrong and Aldrin’s historic first Moonwalk. But his Space Exploration Initiative was short-lived. NASA’s 90-day study produced a politically toxic estimate of half a trillion dollars to establish a Moon base and land humans on Mars. Congress quickly lost interest.

As it was, the agency was preoccupied with keeping the shuttle flying after recovering from the Challenger disaster of 1986, while advancing a space station project already years late and billions over budget. The year 1990 saw major technical embarrassments, notably the discovery that the newly launched Hubble Space Telescope had a flawed mirror. Politicians and the media attacked NASA as bloated and bureaucratic, leading to cost overruns and failures. The collapse of the Soviet Union and the end of the Cold War also undercut one of the civil space program’s key rationales. The space station came within one vote of being canceled in 1992 and was only politically safe after the Clinton administration merged it with the tottering Russian program to create the ISS in 1993-1994.  Although the Cold War’s end ushered in an era of stagnant NASA budgets, it did have the ironic effect of saving the station, based on the argument that it would keep Russian rocket engineers from working for Iran, Iraq, or North Korea. Going back to the Moon was not on the agenda.

The next attempt came after the second shuttle disaster, that of Columbia in 2003. Criticisms of NASA, beyond those specific to the accident, focused on a human space program that seemed to have little direction beyond keeping the shuttle and ISS alive. In response, President George W. Bush announced the Vision for Space Exploration in early 2004. The shuttle would be phased out once the ISS was complete. NASA would create new vehicles to go back to the Moon and on to Mars. Then, as now, the agency argued that we needed to develop at the Moon the experience and technology necessary to go to the Red Planet. NASA created the Constellation Program, which was to put Americans on the Moon by the 50th anniversary of Apollo 11—2019. But it was predicated on the shuttle program ending sooner than it did, freeing up money. Constellation was underfunded and soon fell behind schedule, producing cost overruns. President Barack Obama canceled it soon after coming into office.

That leads us to the last, and in many ways, most unusual part of the story. Constellation’s cancellation did not actually kill the human lunar program. Democratic and Republican senators, particularly those from states with NASA centers or industries tied to the human space program, banded together. They funded a giant booster and a spacecraft based on Constellation designs and shuttle technologies. Thus the Space Launch System (SLS) rocket and the Orion spacecraft emerged in the early 2010s. But they had no clear destination. Eventually, Congress directed NASA to build a small station in lunar orbit and develop the capability to land and create a Moon base. Under the Trump administration, the program got a name, Artemis (the sister of Apollo in Greek mythology), and a new objective: carry out a landing by 2024. While that date was never realistic, it put Artemis on a path that has continued under the Biden administration. After 50 years, the United States again has a sustained program to send astronauts back to the Moon.

Why for over 40 years was there no such program and why has one emerged in the last decade? The answers are rooted in money, national prestige, and space program jobs. Apollo’s success undercut the logic of a program based primarily on Cold War competition; the failure of the Soviets to send any cosmonauts to the Moon only reinforced the disinterest in more missions. In an era of cutbacks, just building a presence in low Earth orbit became NASA’s only feasible human spaceflight program. The attempts of the two Bush presidencies to change that dynamic ran into a lack of support in the public and the political class for greatly increasing the agency’s budget.

What changed after 2010? The shuttle program’s end in 2011 freed up budget money but threatened massive layoffs in NASA centers and the aerospace industry. Congress wanted to sustain jobs in key states and felt that the human spaceflight program needed a higher purpose than just keeping ISS operational. Artemis has thus continued without a broad popular mandate or clear international competition, contradicting the pattern of the previous 40 years. China is mounting a space program that now includes robotic lunar and Mars probes, a permanent space station, and ambitions to build a Moon base. Competition with a foreign power may again become a major factor in the future, helping to sustain Artemis, but has not been critical so far.

How will the American public react when astronauts go back to the Moon? Undoubtedly with excitement, just as there was in the 1960s. But what happens afterward? Will the public quickly lose interest, as it did after Apollo, and even if that happens, will it matter? Is there now a political base to keep Artemis in business at some level? Given the pattern of the last decade, I would say yes. Whatever happens, I look forward to humans once again traveling to the Moon in the next few years, whether on Artemis II or SpaceX’s Starship, both of which may fly there by 2025.

Michael J. Neufeld is a Senior Curator in the Space History Department and the lead curator of the "Destination Moon" gallery.