Learning how to keep humans in space is a quite worth the expense in my opinion. One day or another, we'll have to figure it out.
The true mission of the ISS was to serve as a jobs program for the shuttle.
The Apollo missions accomplished infinitely more--including launching Skylab--than the shuttle and ISS ever could have accomplished.
It will take some big changes to make space more habitable than Earth. If we can make a survivable enclosure in space, odds are that we can make a survivable enclosure on Earth and save the fuel costs, keeping us closer to some nifty raw materials. Massive impacts might make that unsafe,[0] but mostly we're looking at being engulfed by the sun in 5 billion years as a hard stop.
It's hard to really comprehend how much time that is. It's ten times longer than primates have been around. It's almost 1.5 times as long as all life has been around. Humanity as we know it will no longer exist at that point. If we have living descendents, they could be as unrecognizable to us as apes are to amoebas.
At that point we're just planning for "life in general" to survive, which we could accomplish by just sending probes with some spores or dormant bacteria on long voyages to distant habitable planets.
I wouldn't generally recommend procrastination, but this is probably a problem we can kick down the road a few generations. If we hit snooze for just 1/5000th of the remaining time we have, that'd give us a solid million years to up our technological game before tackling interstellar travel. At that point, the problem will probably have become either trivial or hopeless.
So ultimately, I'm not yet convinced that human survivability experiments are 1000 times as urgent as telescopes, probes, and rovers. That's what I'd be looking for to justify manned's absurd cost premium.
I was actually hoping this article would convince me otherwise, but if put up next to the top things we've learned from unmanned space experiments, I don't think it would compare very favorably. Definitely not 1000 times favorably.
I think we all yearn for the stars, and know this is the sort of thing we want to conquer, we want it to be among the great triumphs of humanity. But if we really want it, we should be smart about it. There's so much low hanging fruit we can get from unmanned. It could aid technological progress and deep understanding of the universe, leading to breakthroughs that ultimately leapfrog us past some challenges we'd meet if we just tried to bang our head against colonization today.
[0] Note that mammals have survived some crazy impacts before, probably by living underground. If we can make a survivable enclosure underground or under the ocean, that will be easier than making one and then launching it into space. Also, near earth object detection and mitigation programs are probably the best way to improve humanity's survivability given current technological capacities (ie, we can't build megastructures in space yet), and those programs compete for NASA money against humans in space too! Gradual climate change is unlikely to make Earth less habitable than Venus or Mars or space. Even if we lost most of our atmosphere and temperatures began to fluctuate by +/- 50 degrees, there'd still be advantages to building controlled structures on Earth rather than building such structures and launching them into inhospitable space. There are degrees of inhospitably, and Earth would have to become nightmarish (eg, probably engulfed by the sun) before we left.
> Do you think that advances in interstellar travel capability will appear out of thin air?
No.
It should have been obvious from my post that this is a straw man, that I'm not arguing to halt all science and wait for advancements out of thin air. I want to pursue science efficiently, because we have limited resources. Also, the time scales involved here will radically change the nature of the problem beyond our comprehension.
This 5 billion year problem you want to start tackling today changes immensely if in 1% of 1% of that time our descendants are all clouds of digitally encoded consciousness that propagate primarily through EM radiation and psychic clouds of gas. I'm not saying that change is particularly likely, but some change on that magnitude is all but certain on this time scale (ie, 1.5 times as long it took proto-bacteria to turn into apes).
Suppose cavemen suddenly had a revelation that air transportation would some day change the world. It would be foolish and dangerous if they immediately devoted their free time trying to jump as high as possible, rather than just working on fire and wheels and spears.
Ultimately fire, wheels, and spears are foundational technologies for the disciplines that made flight and rocketry possible. So even though they seem like distractions from air travel, they're actually the most efficient path to solving that problem.
This is all the more obvious for probes, telescopes, and rovers. Those are the wheels, fire, and spears of space. Those all give us incrementally more information about the very nature of the universe, the nature of other possible planets, and how to build functioning intelligent machines that can survive in hostile environments. If there's some way to bend space to our will for instantaneous interstellar travel, or some way to get highly complex machines to shepherd us among the stars, we discover it there, not by putting a guy on a treadmill in microgravity.
You made two assumptions that I would not, which make me believe we should continue to pursue manned exploration.
1) We have 5 billion years to figure this out.
There are many ways in which humanity could be wiped out on Earth, not just the death of the sun. Also I remember Elon Musk had a counterpoint to this as well that it's not a given that technology will always move forward. We need to exploit this chance while we have the capability.
2) The cost difference between a manned and unmanned mission are 1000 to 1.
That may be true for some missions, but I can't imagine that is anywhere near true for something like science missions for a station in low Earth orbit like the ISS. I would be interested in knowing what the actual cost differences are.
I. 5BY
I had a somehow longer version where I explained why I chose the 5 billion year figure. There are a lot of factors that could make life on Earth harder than it currently is, but really only a few that could make Earth less hospitable than Mars. Mars is basically just a gravity well. Maybe with usable water. An Earth worse than that is a long way off.
On the other hand, if Mars isn't enough, and we need interstellar travel, then we need either near instant travel or generational ships.
Generational ships mean we've mastered living in space without a planet. If we're sustainable in space without a planet, then orbiting destroyed Earth (for minerals) is as good as leaving it, unless the sun is expanding.
Near instant travel obviates the need for learning lessons about survival in space.
(I suppose we could get a tech that could take us to any planet in the galaxy in a FTL but five year long trip similar to sublight trips. That seems unlikely though.)
Impacts could destroy Earth. So sure, we should spend good money to look for asteroids (telescopes in space!) and learning how to divert them (with robots!). Note though, mammals somehow survived a mass extinction event from a massive asteroid before. So it'd have to be pretty big to prevent us from just making (maybe underground) shelters.
If the atmosphere or magnetic field weakened, there'd be a huge radiation hazard. Underground or undersea habitats would be more technologically feasible for us than space, though, and would provide better radiation shielding than anything we could build.
II. 1000:1 was silly.
Tech costs though, yeah. Good call. Maybe more like a factor of 10. Possibly as high as 50: http://www.tellmehowmuch.net/how-much-did-the-hubble-space-t...
http://www.businessinsider.com/mars-rover-curiosity-cost-eac...
http://www.nbcnews.com/id/14505278/ns/technology_and_science...
http://www.space.com/12166-space-shuttle-program-cost-promis...
None of these are easy to compare though. Is the Hubble platform equal to the ISS? How many shuttle launches equal one rover? I don't know. Maybe that brings them even further in line.
But if you ask me, at what exchange rate would I change unmanned tech points for manned tech points, based on the relative contributions to science from each, I think it'd be like 5:4 in favor of unmanned. Even if unmanned was more expensive, I think it's tackling some pretty interesting problems right now. I'm weird though, I know.
N.B. - Musk's point was really interesting too, thanks, kind of like "Foundation." I'm not sure where it takes me. It's like, "If humanity could develop only one more technology, what would it be?" Interstellar travel would be pretty compelling. I can think of interesting alternatives, but sure, interstellar seems like it might win.