This composite photo of Mars was created from more than 100 images from Viking orbiters in the 1970s. (NASA/AP)

As we celebrate the extraordinary life and accomplishments of President George H.W. Bush, we should also recall some of his aspirations that remain unfulfilled a quarter-century after his presidency.

During his White House run, Bush had been criticized for lacking vision. But on July 20, 1989, in a speech commemorating the 20th anniversary of the Apollo moon landing, he set out to confound that perception by announcing a bold new human spaceflight initiative that would send American astronauts to Mars.

The initiative faltered, but reinvigorating it would be a fitting tribute to his legacy at a moment when the nation could use a dream to unite around.

Bush himself had played a small role during the first century of air flight. As one of the youngest pilots in the Navy during World War II, he flew 58 combat missions, survived being shot down and earned the Distinguished Flying Cross. He came to understand the perils inherent in our aerospace efforts during this formative period, but he also recognized the advantages that our dominance in this sphere provided.

Two decades later, when he was elected to represent Houston in Congress at the height of the moon race, he became an important supporter of NASA. As vice president, he reengaged with the space program in the aftermath of the Challenger explosion, arguing that “the greatest tribute we can pay to the … brave crew and their families is … to rededicate ourselves to America’s leadership in space.”

As president, Bush tried to set a sweeping new course for the space program. “Within one lifetime,” the president reminded Americans, “the human race traveled from the dunes of Kitty Hawk to the dust of another world. Apollo is a monument to our nation’s unparalleled ability to respond swiftly and successfully to a clearly stated challenge and to America’s willingness to take great risks for great rewards. We had a challenge. We set a goal. And we achieved it. . . . In 1961 it took a crisis — the space race — to speed things up. Today we don’t have a crisis; we have an opportunity.”

To seize this opportunity, Bush proposed a long-range, continuing commitment that included a space station, a trip back to the moon and, eventually, a crewed mission to Mars.

The new president was offering NASA, which at the time lacked a clear mission for its human spaceflight program, a lifeline, guaranteeing his support for an assertive Space Exploration Initiative (SEI). But the fiscal realities of the late 1980s, when budget deficits had exploded, required the organization to think in a new way.

NASA, however, wasn’t up to the job. Rather than thinking innovatively and offering new ideas for reaching the moon and Mars, the agency simply recycled concepts that had been dominant within the space program since its earliest days. Its plan included the construction of a substantial in-orbit infrastructure, where massive spacecraft for lunar and Mars exploration would be assembled before departing for their final destinations. Each alternative pathway identified by a study team required enormous capital expenditures. Over a 30-year implementation period, this initiative would have cost more than $500 billion. This would have required more than doubling the agency’s budget.

The tone-deafness of NASA’s plan shocked the National Space Council. NSC Executive Secretary Mark Albrecht called it “the biggest ‘F’ flunk, you could ever get in government. . . . It was just so fabulously unaffordable, it showed no imagination.” The report quickly turned Capitol Hill against the space agency, with one key congressional aide stating that SEI was dead on arrival.

Tragically for those who yearned for a long-range plan to explore Mars, the policy window that had briefly opened quickly closed. Major foreign policy developments — the fall of the Berlin Wall and Operation Desert Storm — left Bush with little time to resurrect his dreams of sending humans to Mars.

Yet in some respects, these dreams did not die as SEI faded away. The dramatic failure of the initiative spurred reform within the space program, which began with Bush’s appointment of Dan Goldin as NASA administrator. Goldin forced the space agency to accept that it had to live within its means, introducing a level of political pragmatism that had never been part of NASA’s organizational culture.

This provided room for innovative ideas to be taken seriously.

During the 1990s, as NASA focused on building the International Space Station, long-term mission planners considered approaches like Mars Direct, which called for a direct flight from Earth to the Martian surface and back. Critically, the proposal envisioned chemically manufacturing rocket fuel using Mars’s atmosphere. This eliminated the need to build a space station for in-orbit assembly of enormous spacecraft. As a result, Mars Direct was estimated to cost $50 billion to $100 billion, spread over a decade or two. It also offered the distinct advantage of allowing astronauts to explore the planetary surface for more than 500 days. (SEI had been pegged at 30 days.)

Fifteen years after the failure of SEI, and in the wake of the disaster with the shuttle Columbia, President George W. Bush took another critical step toward reinvigorating his father’s vision. Bush eliminated the shuttle program, which had essentially marooned astronauts in Earth orbit because it proved incapable of supporting deep-space missions. This freed up resources for the development of a heavy-lift launch vehicle capable of sending cargo and crew into deep space.

In 2010, President Barack Obama announced the development of a Space Launch System that would support exploration of the moon and Mars. The initial version of this launcher is scheduled to launch in 2020, with crewed missions to the surface of the Red Planet potentially achievable by the mid-2030s.

Today, nearly three decades after SEI was announced, we have made incredible advances in what we know about Mars, but this has been accomplished solely by robotic explorers. The Sojourner, Spirit, Opportunity and Curiosity rovers have all been smashing successes, and the recent landing of the InSight mission less than two weeks ago thrilled most Americans. But we have yet to adopt a program that can take the next giant leap for humankind that George H.W. Bush envisioned.

The failure of SEI offers important guidelines for policymakers looking to implement Bush’s vision. First, the White House must provide NASA with clear written guidance regarding the fiscal constraints to consider when formulating any long-term plan. Second, consulting with Congress is essential to generating sufficient legislative support.

Finally, and perhaps most importantly, a competition of ideas that includes the entire space policy community, including government contractors, universities, think tanks and national laboratories, must guide the initiative. This would guarantee that decision-makers would be presented with a robust suite of technical alternatives for human spaceflight programs. Selecting the best possible technical approach for crewed deep-space exploration is critical, but SEI revealed that this cannot be the only consideration. Proposals must reflect the political and fiscal realities that bound what is possible if they hope to win the necessarily political and public support.

In 1990, President Bush urged his fellow Americans “to step forth with the will that the moment requires. Don’t postpone greatness. History tells us what happens to nations that forget how to dream. The American people want us in space. So, let us continue the dream for our students, for ourselves, and for all humankind.” At a time of domestic feuding and rising international tensions, perhaps such an undertaking is just what is needed to inspire and unite us as we face the challenges of the 21st century.