My good colleague Neil deGrasse Tyson has been getting a lot of attention recently for his passionate argument, repeated in forums ranging from his recent book to countless media appearances and March 7 testimony to the U.S. Senate, that “after we stopped going to the Moon, we stopped dreaming about tomorrow.” Tyson suggests doubling the NASA budget, portraying the space agency as a “major force of nature like none other” and the “most powerful agency” advancing “the dreams of a nation.” He is a very shrewd person, and likely recognizes that such a dramatic budget increase is not in the cards; he is following the proven strategy of asking for a lot in hope of getting a little. But will even that happen? I have my doubts.

Tyson is most certainly correct in saying that the end of Apollo marked a turning point in U.S. space ambitions. Faced with a 1969 proposal to continue trips to the Moon during the 1970s and to send initial expeditions to Mars in the 1980s, President Richard Nixon demurred, announcing in March 1970, that “space expenditures must take their proper place within a rigorous system of national priorities. 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 important to us.”

Making space activity “normal and regular,” as that has been defined by the workings of the American political process over the past 40-plus years, resulted in a space effort that kept humans close to their home planet, carrying out valuable but not very inspirational work. It has been robotic missions in planetary exploration and astrophysics that have produced exciting scientific results and publicly captivating images. The “dream” motivating most members of Congress who have lent their support to NASA’s programs seems to have been primarily high-quality jobs in their districts. Several presidents have spelled out new visions for America’s space program, but then have not fought for the political support to make those visions real.

I wonder whether space exploration has ever really been, as Tyson suggests, a central element of “the dreams of a nation,” closely linked to American aspirations for a better tomorrow. Or was the idea that space activity is an essential part of the U.S. future rather the temporarily powerful legacy of a relatively small group of advocates, most notably Wernher von Braun and Walt Disney, who in the 1950s shaped a romantic vision of what lay ahead in space?

In his thoughtful book “Space and the American Imagination,” Howard McCurdy suggests that “during the 1950s space advocates worked hard to promote their dreams. They convinced the public that space travel was something real and desirable.” Sending people into the solar system, these advocates argued, “provided an opportunity to continue the practices that had spurred invention and innovation and made America great.”

The vision of these advocates became part of the popular culture of the time and laid the foundation for public acceptance of President John F. Kennedy’s 1961 decision, driven almost exclusively by Cold War concerns, to send Americans to the Moon. Absent its link to that decision, it is a fair question whether the dream of space travel would have persisted as long as it has.

Space advocates built on the geopolitical rationale for Apollo, suggesting that it would produce immense payoffs in terms of innovations relevant to the American economy and quality of life. Whether or not they have appeared in the years since, those payoffs were not visible to Nixon and his associates as they decided to rapidly reduce the NASA budget from its Apollo peak. The advocacy argument of the 1950s for a vigorous space effort had by the end of Apollo lost its potency, and efforts since 1970 to revive it have not found widespread political or public acceptance. The usual reason given by the space community is “if only they understood” (whoever “they” are) the multiple benefits flowing from the space program, there would be greater support for space. The alternative explanation, that the arguments have been heard, evaluated and largely rejected, is seldom discussed by the true believers.

Perhaps the problem is that the wrong arguments have been made. Former NASA Administrator Mike Griffin, in a 2007 speech, distinguished between “acceptable reasons” for space exploration — such as scientific discovery, economic benefits and national security — and what he believed were the “real reasons” — competitiveness, curiosity and monument building. Now Tyson is combining both the “acceptable” and the “real” reasons in his advocacy. He asks both “How much would you pay to ‘launch’ our economy?” and “How much would you pay for the universe?” Perhaps by appealing to both the rational and emotional aspects of the case for space, Tyson can stir up enough public and political support to make a difference.

I wish I were more optimistic that this could happen, but working close to the center of policymaking in Washington is sobering. Three years ago, the Augustine Committee titled its October 2009 report “Seeking a Human Spaceflight Program Worthy of a Great Nation.” I doubt that the compromised program that NASA is currently pursuing, not only in human spaceflight but also in robotic space science, can be characterized as “worthy of a great nation.”

After the failure of President Barack Obama’s 2010 initiatives to reshape the way NASA goes about its business, the most probable prospect for at least the next few years is some version of the current program with its political support driven primarily by the desire to preserve jobs, contracts and scientific communities, operating indefinitely on a flat and inadequate budget. This will result in a NASA little changed from the space shuttle/international space station status quo. This suboptimum effort will still produce significant benefits for the country, just not the excellence that could be achieved by the kind of better-formulated and better-supported program, carried out by a revitalized space agency, that Tyson is advocating. It will not achieve the impact he seeks, transforming “the country from a sullen, dispirited nation, weary of economic struggle, to one where it has reclaimed its 20th century birthright to dream of tomorrow.”

Neil deGrasse Tyson is following in the distinguished path of such articulate space advocates as Tom Paine, Gerard O’Neill and Carl Sagan. As McCurdy observes, “Expectations invariably fail, but the underlying vision rarely dies. Rather, people update the vision. The dream moves on.” As the current custodian of the space dream, Tyson deserves widespread support as he defines and advocates that dream in ways that might make a difference. Even so, and unfortunately, he may still be in pursuit of an illusion, not a feasible reality.

John M. Logsdon is professor emeritus of political science and international affairs at George Washington University’s Elliott School of International Affairs and founder of the university’s Space Policy Institute.

John M. Logsdon is the founder and former director of the Space Policy Institute at the George Washington University’s Elliott School of International Affairs, where he remains professor emeritus. His book “After Apollo? Richard Nixon and the American...