Dr. Hogan states that the failure of SEI was not inevitable. Mistakes were made, as the saying goes, by both NASA and the White House leadership. We face the same situation now. Returning astronauts to the Moon by 2024 is possible, but there are many more paths leading to failure than success. Looking back at SEI can help us avoid some pitfalls, and perhaps increase the odds of finding the right way forward.

Lesson 1: Minimize sticker shock

Let's be honest: anything sounds expensive when added up over thirty years. The National Parks Service, a wonderful organization that manages national parks and other monuments, is not a large part of the budget each year. Yet over the next three decades, it will spend roughly $100 billion. That's just for parks! Space exploration costs more. That doesn't mean it's expensive, but lacking context it can certainly sound expensive. The United States regularly spends much more on many other programs. The Department of Defense, for example, will spend at least $21 trillion (yes, trillion) over the same timeframe, and has grown by tens of billions of dollars over the past few years with little public debate or notice. Space is cheap, by comparison.

But that message isn't enough. NASA's infamous "90-Day Study," which outlined its exploration ambitions for SEI in a 30-year time frame, estimated the program would cost between $400 and $500 billion (or close to a trillion of today's dollars). Even though these initial studies were never formally proposed by the White House, SEI was forever laden with a politically laughable half-trillion-dollar price tag.

We don't know what augmentation the Administration will ask for next week, but the lesson from SEI is that the initial estimate will likely be the number repeated ad-infinitum by the press and thus calcified into common wisdom. As such, NASA and the White House must be judicious in presenting its initial estimate, reflecting accurately the resources necessary to achieve the goal, but limiting the time horizon to the far more reasonable (and standard) 5-year budgetary window. Projecting spending over five years is hard enough for programs that have never been attempted before, much less over thirty. Limiting projections to a 5-year window will present a more accurate estimate, both in terms of actual spending and for public debate.

A particular challenge to keep in mind is that this supplemental request for NASA will be released in the context of proposed cuts to many popular programs, including many science programs. While these cuts are unlikely to happen (thank you, Congress), the fact remains that the space program—particularly human spaceflight—will be seen as benefiting from cuts to other science efforts. There is no way to address this besides being honest about the fact that NASA's budget does not depend on cuts to other programs, and that Congress can (and should) fund science initiatives across the government.

NASA today has an additional advantage compared to the NASA of 1989: "nobody cares" about deficits right now. As George H.W. Bush assumed the presidency, there was a political consensus that deficit reduction was a top priority. The Cold War was winding down and there was an expectation of a "peace dividend" from the drawing down of defense spending. The political moment, in other words, was all wrong for proposing a major human spaceflight endeavor.

Our current political dynamics are different. There is no consensus on deficits. Despite the domestic spending cuts regularly proposed by the White House, Congress, even under Republican control, has increased government spending for the past five years. It is likely Congress will raise spending caps again. This is good, as an increase in spending caps would provide both the budgetary and political space necessary to augment NASA's budget. In other words, the best way for the Trump Administration to sustain political support for its lunar ambitions is to support (or merely accept) increases in domestic spending.

The economy is also better today than it was 30 years ago. As President Bush announced SEI, the gross domestic product (GDP) was falling and the economy was sliding into a recession. Today GDP growth is stable, perhaps increasing slightly, and unemployment is very low. As in the early 1960s, the public's positive attitude about the economy helps enable the political justification for high profile engineering and exploration investments, as voters are not worried about overall spending as a proxy for the country's economic conditions.

The combined effects of a willingness to spend money on domestic programs and the psychological benefits of a strong economy will help limit any political backlash against increasing NASA's budget. However, great care is still called for when making and presenting the cost estimates for a lunar return. SEI reminds us that there are limits to what people will accept, no matter how good the economy is.

Lesson 2: Integrate institutional priorities

When Mark Albrecht, the executive secretary of the National Space Council in 1989, approached NASA administrator Richard Truly to ask if NASA was interested in returning to the Moon and Mars, the administrator initially demurred. He worried that NASA couldn't handle the additional burden of deep space exploration while NASA was struggling through constant revisions to Space Station Freedom and working to return the Space Shuttle fleet to full strength. Though the administrator embraced the idea the following day, his initial reaction betrayed that the institutional focus of NASA was (and would remain) shuttle and station, not the Space Exploration Initiative.

NASA's 90-Day Study reflected this. It re-stated the program of record (the Shuttle and a space station programs) and layered Moon and Mars programs on top of them. This simultaneously increased the cost of SEI and enabled Congress to lop out SEI parts from the budget while preserving existing programs, which it promptly did.