The release of a long-awaited National Academy of Sciences report on the state and future of the US space program has triggered wide-reaching commentary on what it means to be space-faring. For hundreds of billions of dollars spent over the next 20 years, the report suggests, NASA could get humans (reasonably safely) to Mars. Along the way would be other missions beyond low-Earth orbit; perhaps to asteroids, Lagrange points, and the Moon. In short, it would create a new infrastructure for space exploration that reaches much farther than anything before.
Except there has been quick criticism pointing out that there is a bit of a 'business as usual' approach to all this. Many pundits would like far more emphasis on fast robotic exploration, and more radically styled human exploration and settlement off-world. There are also grumblings about how this seems to repeat a 'touch and go' approach from the Apollo era, with little to say about the longer term motivation - why humans (or the US) should be doing this, and what happens after we've set foot on a world like Mars.
Although some of these points are valid, in many ways it's wholly unfair to chide the nearly 300-page report for its focus. The task was to present the best 'horizon goal' for human space exploration, and to figure out what it would take to do this in a steady and realistic fashion - choosing between three pathways of varying cost, timing, and risk that are technically truly feasible and sustainable. Mars is that horizon.
It's also worth pointing out that the proposal doesn't ignore commercial space efforts (such as SpaceX), and includes them in its considerations (although perhaps not as much as some would like). It does also debate the possibilities of more international cooperation, and essentially says that NASA needs to change its overall approach.
As always, the greatest challenge really begins on Earth, with the vagaries of policy and politics. What's laid out in the report is doable, what's not clear is whether anyone will want to do it. And the authors are under no illusions about that. They even state that no one rationale, be it practical or purely aspirational - from economic and technological gain, to scientific and national status - can easily justify this scale of effort for these particular goals (although one notes this is focused on the US effort). But taken altogether it begins to make sense, if there's a solid plan, and if we believe that learning just how far humans can go and what we might discover is important enough.
How much would this cost? Well, increase NASA's human spaceflight budget by 5% a year (it's presently about 45% of NASA's roughly $18.5B annual budget) and you could do this with some confidence. If you did that for 20 years from today you'd be spending about $22B annually by 2034 on human spaceflight. It's a lot, but in today's dollars it's barely 0.15% of US GDP.
And that's pretty much where I'm going to leave it. The debate will continue, people will chime in. Many will balk at the cost, or even the idea of focusing attention on such off-world activities when we 'have so many problems here'. Politicians will posture, and will likely serve no useful purpose. NASA may change it's methods, and may or may not get the support it deserves.
We certainly do have problems here, but almost all of them are to do with the glass ceiling hanging over our species - our finite world and our growing numbers. We're in a rut, and we haven't figured out how we can survive for the long term without going back to pre-industrial populations and lifestyles. Personally I think that the effort to go off-world offers a glimmer of hope, a way to get out of that rut. It's not just science, it's about human exploration and discovery, two vital assets throughout our history, and hopefully our future too.