As I write this, it is 50 years to the moment after the Lunar Module Eagle ascended from the surface of the Moon, carrying a victorious Neil Armstrong and Buzz Aldrin up to their rendezvous with crewmate Mike Collins in the Command Module Columbia. Although I am too young to have personal memories of this event, I’ve been following the mission on its 50th anniversary through the web site Apollo in Real Time. It’s been exciting, and I, like many others involved in the space industry, have been driven introspective.

Why did we send Apollo 11 to the Moon, and why should we keep sending people to explore space?

The first question is all about geopolitics. The United States sent Apollo 11 to land on the Moon because the country wanted a very public way to demonstrate the superiority of its technical capabilities over the Soviet Union. The deep political worry at the time was that the USSR would not only beat the US to the Moon, but that they would emplace weapons there that the US could not counter-target — messing up the strike and counter-strike strategies underlying the insanity of mutually assured destruction. So, the US also decided to conduct its lunar landing in a way that would establish a specific set of norms for space exploration activities: We do this on behalf of all the people of Earth. We are here for science and knowledge. We show the world everything we do, as we do it. We come in peace, for all mankind. Apollo 11 literally left a model of an olive branch on the Moon.

But now the race is long over, and the norms established are taken for granted (if we remember them). Why continue? I find this a difficult question for me to answer — partly because I don’t believe several of the common arguments to be very compelling. Those arguments are science, spinoff technology, and inspiration.

Science is the easiest to dispense: our robotic probes reach across the Solar System, relaying extensive data back to scientists on Earth. The time, effort, and expense of sending a human mission to, say, Mars, absolutely dwarfs the cost of a robotic science mission. As an example, a recent report estimated the cost of a 2037 Mars mission as $120 billion (not including some other significant developments like a precursor lunar landing); the NASA Science Mission Directorate puts a cost cap of about $600 million on Discovery-class missions like the InSight lander, meaning we could send 200 robotic missions for the cost of one human mission. We would have to make sure that the science output of a human mission is at least 200 times better than the science of a robotic mission, and I’m not sure that’s a case one can make. Likewise, while space exploration, and human spaceflight in particular, has produced a great deal of technology that we now use on Earth in engineering, science, medicine, and daily life — those “spin-off technologies” are, almost by definition, ancillary benefits of a development program that had a different objective. This isn’t a bad thing (and NASA investment is far better at spinning off technology than, say, military investment)…but if we as a society have the goal of getting those technologies, we would just fund their development in the first place, rather than hoping that useful spin-offs come out of another program.

It seems to me like inspirational power is the most common reason cited to continue human spaceflight activities. Here, for example, is the current NASA administrator on Twitter:

Whenever someone tells me that the United States needs to inspire more students to study scientific and engineering fields, I want to ask them: What comes after this great inspiration? When a student says that NASA activities make them want to study math and science — are we, as a nation, going to invest in a technical education system to support their ambitions? Because, right now, we do not; those students are left hanging with the means already at their family’s disposal. And then suppose that these inspired students do get a degree in science or engineering: what do they do with it? Supposedly there has been a “STEM shortage” for years, but I do not see it materializing in a shower of job offers for recent graduates. Where are the university science departments desperate to fill vacant professorships? Where is the bipartisan call to expand the civil services of NASA, NOAA, NSF, CDC, and other national scientific agencies? Where are the private research and development organizations with a backlog of open lab positions to fill? Where are the engineering firm recruiters waiting eagerly outside the doors of college engineering buildings? Our lack of national investment in technology, research, and development belies our stated goals. And, in the vacuum, our previously inspired students are off to Google and Facebook to tweak the algorithms for selling users’ private data to advertisers.

My engineer’s brain struggles with the fact that I can come up with other rationales for human spaceflight, but they seem somehow squishier than the arguments above — the ones I don’t find very resonant after a little thought. After all, the arguments I described so far seem quantifiable: number of undergraduate degrees awarded in STEM fields. Number of scientific papers written by human spaceflight researchers. Number of commercialized technologies. Maybe the solution is to look at the problem with something other than an engineer’s brain.

I think the purpose of human spaceflight should be to expand human life out into the Solar System.

I also think that the reason we don’t often hear this statement articulated is that spaceflight proponents (especially NASA staff) don’t believe this argument will resonate with the public, but I believe they are wrong about that.

People get invested with spaceflight when the engineers, scientists, and astronauts involved connect spaceflight with human experience. Look at Neil Armstrong’s contemplative words as he took his first steps on the Moon. Look at Chris Hadfield singing “Space Oddity” aboard his own tin can. Look at the engineers at JPL whooping as a robot touches down on Mars. And look at the way these things catch the public eye, in a way that a purely technical accomplishment does not. Human experience has a value all its own — despite seeing the pictures and reading about the scientific results, I still want to ask the surviving Apollo astronauts, what was it like?! No, really, what was it like, on the Moon? I think it is worth having people living and working in space, for the sake of connecting the awesome experience of our cosmos to our humanity, and for creating an enduring example of what humans can achieve when we pull together and decide to build something.

Ultimately, I want to see permanent human habitation in space and on other planets. Beyond the romantic notions, there are some simple economic drivers that ought to push us in that direction. Any economic model that assumes growth, on a finite planet, is going to run into trouble eventually — and considering some of the anticipated resource shortages connected to the climate crisis, that point may come sooner than we think. (For another thing, with the world’s most powerful militaries blindly chasing “capabilities” in a way that brings us ever closer to nuclear war, I’d feel a lot more comfortable for the future of humanity if some of us were outside their reach.) No place that we’ve yet discovered will be as amenable to human life as the Earth, even in the face of climate crisis or asteroid impact, but that fact does not mean that we won’t eventually need to have humans off the Earth’s surface.

Now, if that’s really the winning justification for human spaceflight — having humans living in space and developing a culture that connects back to people on Earth — then that implies some changes to NASA’s objectives. Instead of having astronauts “learn to live and work in space,” NASA ought to get people actually living and working in space. This brings to light another reason why we may not see human habitation put forward as the reason for human spaceflight: I am asking for a major, concerted effort on NASA’s part; one that emphasizes long-term approaches to human spaceflight and spacecraft at the expense of the Apollo short-term race approach. We should be looking at regular launches to low Earth orbit, major development effort on in-situ resource utilization, designing and building large habitats that are amenable to long-term human life and work, and allowing a great deal of autonomy to the people in space. But, just as it’s nearly impossible for the US government to close unneeded military bases, it’s proven impossible to reorient NASA from the same kinds of work that has been done at each NASA field center for decades, going all the way back to the 1960s.

Which brings us, of course, to the reason why no humans have set foot on the Moon since the Apollo program: politicians like to have NASA, but they don’t like the implications of having NASA do things. Having NASA do things requires allocation (and re-allocation) of resources. They’ve tried to have it both ways, for decades, by splitting the difference. And we’re left trying to justify the space program as it is, with unconvincing arguments, instead of having a rationale behind the total human spaceflight endeavor and building a space program to satisfy that rationale.

Having a resonant driving force behind human spaceflight could help NASA maintain consistent direction in the decades to come. Do I have the winning argument? I really don’t know. But one thing’s for sure: the arguments we’ve been using so far aren’t working very well, if holding human spaceflight to steady progress is the goal.