If you're a space geek like me you've probably had people ask you why we're "wasting money in space", and typically just like that, in the most impolite way possible.
Most people who ask this question are not talking about unmanned spaceflight. It seems that "science" is more than enough justification for just about any planetary probe, earth monitoring satellite or Mars rover, but human spaceflight is astronauts playing around on the taxpayer's dime. Because of this, I often hear NASA trying to link human spaceflight to science. We're told astronauts on the International Space Station are doing important scientific work, in particular biological study into zero-g protein crystal growth that will lead to cures for fatal diseases, or something. We're supposed to imagine astronauts with (space) test tubes and (space) microscopes floating around doing Important Work which makes the billions and billions of dollars, rubles, euros and yen that have been spent to build the station and maintain it.
This is what I call a "justification" for human spaceflight. The ISS wasn't designed and built to do protein crystal growth. If you ask NASA what human spaceflight is for you'll sooner or later get a long laundry list of "spinoffs" like this, including quite a few dubious inventions that NASA either had nothing to do with or at most provided some research funding, and many more that are very difficult to link to the human spaceflight program. Spinoffs are the ultimate justification as they are by definition not the reason why we do human spaceflight - they're searched for or simply made up after that decision has already been made to justify why human spaceflight should continue.
Around 1993 the Space Station Freedom was saved from cancellation by the Clinton administration to serve as a model of "international cooperation" between the US and Russia. The idea was that giving Russia something to do in space would keep them busy and stop their highly skilled workforce from defecting to Iran and other states to make missiles. Since then, International Cooperation (and yes, I have to use capital letters) has become more than just controlling the missile building talent of the world - today it's more about world leadership. The concept is often referred to as "soft power" and the theory goes that other countries will look to the US as a great way to run their own country because of all the great things NASA does in space. If that sounds like something someone made up on the spot, well....
Then finally, there's probably the real reason why NASA keeps doing human spaceflight: Pork. For anyone who doesn't "get" human spaceflight, the costs involved in launching the Space Shuttle or all the money that has been spent on the ISS look impossibly huge. Just in-case you're unaware, the average cost of a shuttle flight is about a billion dollars, and estimates of the total cost of the ISS over 30 years range from 35 billion dollars to 160 billion dollars, depending on who you talk to. At the time of writing this there's a fight going on at NASA over whether or not to cancel a rocket called the Ares I which has cost 9 billion dollars so far and, if it continues, will cost up to 30 billion dollars, again, depending on who you talk to. It's almost been decided that the capsule that was to go on top of the Ares I but will now be turned into a crew escape vehicle for the ISS, called the Orion CEV, will cost at least 4.5 billion dollars. It looks like a lot of money, but compared to the overall NASA budget and how many years it is stretched over, it's not really a lot.. I worked out once that the average US taxpayer pays $10/month for everything that NASA does.. but if you were the sales executive at the company that won that contract it sure would be a lot to you. And your company sure wouldn't mind paying a campaign contribution to your Congressman as a thank you for "bringing home the bacon".
But these are not acceptable answers... The truth tells us why NASA keeps doing human spaceflight but it doesn't tell us why they should be doing human spaceflight. To answer that we have to ask some of the big minds who have inspired many of us in the space community.
Carl Sagan was the undisputed best communicator the space advocacy community ever had. His series Cosmos was broadcast in 60 countries to over 500 million people. He founded the Planetary Society to continue his advocacy of astronomy and exploration. His hallmark was in expressing the overwhelming vastness of the cosmos and our insignificant role in it. In a word, Sagan's followers were in it for the "wonder". The universe is a beautiful place full of fascinating things and is available to anyone who looks up at night (assuming you live far enough away from city light pollution).
Notably, Sagan was a strong advocate of robotic exploration of the solar system. He arranged experiments and was responsible for the plaques on the Voyager probe which carried a message out of the solar system in the hope that it may one day be picked up by extraterrestrial intelligence. He strongly advocated for the SETI program too, and strongly advocated against the Space Shuttle and International Space Station. So it might seem a little strange that I would bring him up, but plenty of Sagan's followers are advocates of human spaceflight; why?
To many, Sagan's dismissal of human spaceflight became indefensible in 1993 when the crew of the Space Shuttle Endeavour mission STS-61 performed the first servicing mission of the Hubble Space Telescope. Here was the most powerful optical telescope ever built, floating in space with a flawed mirror, providing only fuzzy wonder, and then humans came along and made it good. All of a sudden the public was flooded with fantastic images of distant galaxies and other wonders of the cosmos. The human spaceflight program now had a purpose and four servicing missions later the Hubble Space Telescope is still delivering the wonder.
This caused more Sagan followers to reassess their dismissal of human spaceflight. They started asking astronauts: what's it like up there? and actually waiting around for the answer. Unsurprisingly the answer is full of wonder. Frank White's famous book "The Overview Effect" describes the transcendental feeling of universal connection with the Earth and the cosmos that astronauts report after seeing the Earth from space. Today, the suborbital spaceflight market counts it as one of their deliverables, along with the wonder of zero gravity.
In short: space is awesome, let's go there.
Wernher von Braun was a German missile maker who surrendered to the US at the end of WWII and was shipped with his team to live in New Mexico to build more missiles. He was also a visionary but no-one in the military really cared about that stuff. In 1957 the Soviet Union launched the first man made satellite into space, it was called Sputnik. Although this was not anything the US couldn't do and was only a minor threat to national security, it was a major blow to "prestige". During the height of the cold war, countries around the world were looking to the Soviet Union as a model for how to run their economies. The US didn't like this and felt that as more countries went "red" the inevitability of hostilities with the Soviet Union drew closer and closer. In launching Sputnik the Soviet Union was saying to the world: we're better than the US, you can be better too, just do things our way.
The answer, of course, was for the US to launch their own satellite, an American satellite. Only problem was, the only people they had available that could make it happen were Germans. Soon after, the Soviet Union started launching dogs and then humans into space. The US was way behind.
Fundamentally, the problem was that the US didn't have enough people studying Science, Technology, Engineering and Mathematics (or STEM for short). Without increased STEM education the US would become a backwater. But if kids don't want to enroll in STEM classes, what can you do? You can't force them. That'd be something the Soviet Union would do. The answer? "Inspiration".
Project Apollo soon followed and if you ask just about anyone at NASA or in the aerospace community, you will discover that they were very inspired by Apollo. Today, the younger generation will tell you that they were inspired by the awesome sight of a Space Shuttle launch, or they went to Space Camp when they were a kid. The point is, inspiring these kids to enroll in STEM education pushes forward not just space technology but all technology. It's like the spinoffs argument but even more indirect - not only can NASA take credit for inventions they threw some research dollars at, they can also take credit for anything where the inventor was inspired to STEM education by spaceflight. And what's more, all these STEM educated people are important for the National Security, so human spaceflight is important for National Security. See how it works?
Wernher von Braun's dream was to fly humans to Mars. The Mars Society is the embodiment of the dream, and is fueled by the promise of inspiration. Getting to Mars is a Grand Challenge and will require Technological Progress of the Apollo kind, so we can expect lots and lots of inspiration.
Gerard K. O'Neill was a Princeton University physics professor who had applied to be an astronaut but washed out. Following the Apollo Moon landings, public perception of human spaceflight as a pointless endeavor with no payoff was at an all time high, and other contemporary events (like the Vietnam War) had begun to shatter the belief that Technological Progress was a necessarily positive force in the world.
Nevertheless, O'Neill proposed that humans may one-day live and work in space. He assigned engineering tasks on the subject to students and gave lectures around the country. O'Neill saw Space Colonization as the solution to many of the "major problems" of the world that were haunting the nightmares of people who wrongfully believed they could predict the future. In 1972 a book was released which summarized the findings of these alarmists and was widely read in the scientific community. It was called "The Limits To Growth". After arguing in the scientific literature and going on speaking tours for years, O'Neill released his own popular book "The High Frontier".
The consequences of a rapidly growing world population and finite resources was widely accepted fact in the 70s. The affluence of the US would decline as the other nations of the world caught up. For their growing populations they would want coal, and gold and iron and oil.. especially oil. The oil shortage of the 70s was seen as proof. There wouldn't be enough to go around and everyone would have to go without. Everyone believed it. O'Neill believed it. People still believe it today. It's all so hopeless.
O'Neill's answer was eloquent: who says we've only got the one world? The Moon, which the US has just got done conquering, is rich in iron, aluminum, silicon and oxygen. We could go live there! But being a good scientist, and professor, O'Neill famously asked his brightest students: "Is the surface of a planet really the right place for an expanding technological civilization?" (Notice the word "expanding").
We all live at the bottom of a well.. a gravity well. The Space Shuttle is so big, and the Saturn V was so much bigger, because our gravity well is so deep that we need to spend 90% of the vehicles mass in fuel just to get the little tiny crew bit into orbit. The Earth's gravity well is so deep that, it is said, once you're in orbit you're halfway to anywhere in the solar system. So, if you've just spent all this fuel (not to mention pain, sweat, tears and astronaut blood) to get out of a gravity well, why should you be so eager to dive back into another one?
The answer is resources, which weighed heavily on everyone's mind in the 70s. If you're going to live in space, with an expanding population, you need resources and all the resources O'Neill knew about were at the bottom of gravity wells. If we don't want to go down into the well, how do we get out the water? err, I mean, resources. Another great question!
The fundamental problem with getting material out of a gravity well isn't lifting it up - the analogy to a water well kind of fails you there - it's giving the resources enough horizontal momentum that they can enter a stable orbit. On the Moon, that velocity is low enough that O'Neill figured a high speed train could achieve it. The train would be magnetically levitated about the track and the resources would be hurtled into orbit in steady stream. Then a big catcher's mitt would grab the resources and deliver them to a stable point in space where the colony was being built. When completed, the massive colony would spin to provide artificial gravity. Housing 10,000.
The colony would be economically self supporting. They could, for example, build satellites and "launch" them, but the primary market that the colony would support would be energy. Remember, to everyone in the 70s it was apparent that the world's oil supply was drying up (this is still apparent to a lot of people today). What would the cars run on when all the oil was gone? Well, electricity seems like a good bet, and there's lots and lots of free electricity available in space in the form of solar power. Beaming power from a space colony down to earth is the fundamental O'Neillian dream. The dream that provides hope.
A Modern Perspective
Carl Sagan's love and wonder for the cosmos is powerful and universal. So long as the scientific spirit of openness continues there will always be marvels for the public to enjoy. The continuing light pollution around cities, while tragic, makes the public appreciation of orbital telescopes even stronger. Human servicing of those telescopes and the sheer marvel of the Earth be it experienced on suborbital spaceflight or future orbital spaceflight will always be valuable.
Wernher von Braun's drive for Grand Challenges to inspire the next generation to continue Technological Progress is, to me, a fundamental part of modern life. There is no problem, great or small, that humanity cannot overcome with the measured application of scientific knowledge and technology.
Gerard K. O'Neill's vision, while grand and exquisite, has always felt to me to be a little too much a reaction to his times. Space Solar Power today has as much relevance to O'Neill as Communication Satellites has to von Braun.. neither are or will be manned as originally envisioned. What's more, the fundamental motivation for O'Neill's work, The Limits To Growth, has been shown to be fundamentally alarmist and, well, wrong* - even if the damage they've done to our hope is permanent, I don't think the same urgency exists today as it did in the 70s and so I'm sad to say that I think O'Neill's solution has been ruled out. So are we destined to travel down a path where Technological Progress is shunned for Conservation and Environmentalism? I hope not.
That said, Gerard K. O'Neill's vision has always had the greatest appeal to me. Over the years it has been slowly changing. The less timeless motivations have been replaced with more timeless ones. Where O'Neill would have said that the Earth is running out of resources, modern commentators prefer to estimate the vast wealth available in space and ask: as soon as it becomes economical won't someone go get it? Similarly, where O'Neill would say solar power can replace oil when it runs out, modern commentators ask: can anyone close the business case for Space Solar Power?
When you start to think like an Economic O'Neillian the vision changes completely. The fundamental motivation for human spaceflight becomes closing the business case. Does mining the Moon make good business sense? Only if there aren't cheaper resources available. In space, cheaper means less delta-v. If you or your resources are at the bottom of a gravity well then you better plan to spend a lot on delta-v. The traditionalist O'Neillian answer is to build a huge infrastructure on the Moon to get the cheapest delta-v possible (which, btw, is a consistent theme in launch hardware), but the Economic O'Neillian looks to other opportunities. The Near Earth Asteroids and Comets (or NEOs), the moons of Mars, and the asteroid belts are interesting opportunities. By choosing to live there you have all the resources you need without the delta-v penalty of getting them to the colony. Building your colony inside the asteroid/comet/Moon gives you radiation protection (the number one issue to long term colonization of space) and still allows you to spin the habitat to produce full artificial gravity (an option you just don't have if you're living on a planetary body without full Earth gravity).
The pure Economic O'Neillians are gaining traction and if they rephrase O'Neill's famous question as "where is the best place for an expanding human civilization?", the answer may end up being: "whereever you can make a living."
* brobof after screaming and yelling at me a lot, informs me that this paper clearly shows that The Limits To Growth was not wrong, and that we really are headed for the kind of global collapse that it predicts. While I'm not going to be turning into another chicken little anytime soon, I retract my comment.