Marginal at best. The Space Shuttle lofted 833 astronauts at a cost of $209 billion [1]. In 2013, NASA was paying Russia $70 million per astronaut for a Soyuz lift [2]. That comes to $58 billion in 2013 dollars. That leaves $151+ billion, ignoring inflation, to justify everything else the Shuttle did. $150+ billion is 10x SpaceX's lifetime capital expenditures. (It's about what NASA expects it will cost to put humans on Mars.)
At first, the Space Shuttle (conceived as a shuttle to an American space station, the latter never built) was an expensive way to low-earth orbit. After the ISS, the Space Shuttle became an expensive way to the ISS. It pioneered virtually nothing and nowhere and was better at nothing than any other craft.
It was not worthless. But for the cost we could have achieved vastly more. Opportunity cost is real; the Space Shuttle set spaceflight back at least a generation.
It's not fun to trash these programs. But over time, I've realized it's necessary. We cannot correct failures we refuse to recognize. The Space Shuttle's dismal ROI was a motivating factor behind the Bush administration's support of COTS [3]. Without that programme, SpaceX wouldn't be what it is today.
The Space Shuttle was remarkably well designed for orbital bombing missions, which is the only reason the Soviets felt compelled to build the Buran to reproduce its capabilities.
Should have, but didn't. At least not for manned spaceflight. We learned how to keep humans alive in space way back with the Gemini project. A long-duration orbital sojourn could have been had for the cost of the ISS. At the end of the day, I struggle to think of a single big thing we can do post-ISS that we couldn't without.
It may not make headlines, but the knowledge we have gained about long-duration human health in space from ISS is utterly beyond price. For all its problems, that alone makes ISS worth it.
> the knowledge we have gained about long-duration human health in space from ISS is utterly beyond price
The knowledge was valuable, but not priceless. The same data could have been gathered, many times over, with long-duration multi-member orbital missions. We could have probably gotten an interplanetary flight in, too. The staggering cost of the ISS crowded out a lot of good science.
There is no way we could have achieved a similar volume of data without ISS. With ISS we get six astronaut-years of data every single year, and it’s got at least another decade in it, barring political stupidity.
The argument could be made that we could have made do with less data, perhaps. But we could not have gathered this volume even once without ISS, let alone “many times”.
> There is no way we could have achieved a similar volume of data without ISS
NASA spent 72 billion 2010 dollars on the ISS [1]. (Total cost is over $150 billion.) From Expedition 1 in 2000 through Expedition 53 in September, the ISS played host to 25,290 crew days of human occupation [2]. That comes to $2.8 million per day for NASA or over $5.9 million more generally. (Remember: this does not include the cost of getting to nor from the ISS.)
The Apollo program cost $107 billion 2016 dollars [3], or $98 million 2010 dollars [4]. (This includes the cost of the Saturn I, Saturn IB and Saturn V launch vehicles.) From Apollo 7 in 1968 through Apollo 17 in 1972, the Apollo program hosted 305 crew days of human spaceflight [5]. That comes to $3.2 million per day.
TL; DR We could have replicated the time spent on the ISS with a series of Apollo programs, using Apollo technology and Apollo-era costs, and had budget left over for a manned (probably non-landing) interplanetary mission [6].
The ISS is a boondoggle [7] on every measure except number of dollars funneled to defense contractors. It's not fun to trash these programs. (I grew up adoring the Space Shuttle and the ISs.) But over time, I've realized it's necessary. We cannot correct failures we refuse to recognize.
[6] Keep in mind the degree to which I'm putting my thumb on the scale in the ISS's favor. We're counting the Apollo program's launch costs but not the Space Shuttles. We're including, in $2.8 million per day figure, everyone's crew member hours but only NASA's costs.
[7] I am not (yet) in favor of de-orbiting the ISS. Sunk costs are sunk. Looking forward, there is probably something useful to be done with the beast.
> We could have replicated the time spent on the ISS with a series of Apollo programs
I doubt an Apollo CSM [1] could support astronauts for a full year (although Mir could [2]). It has proven very handy to have a space station within reach of resupply missions and with enough space to house some gym equipment and a whole bunch of medical equipment. You might also have trouble finding people willing to spend much time beyond the Van Allen radiation belts [3] in an Apollo era space craft [4].
Here’s an article summarizing the findings of the most headline-grabbing medical study of the ISS program, the Twins Study in which Scott Kelly spent a year in space while his brother Mark remained on Earth; both were subjected to exhaustive testing, and the article briefly covers each investigation. One that I found particularly interesting: Scott’s telomeres grew significantly longer while he was in space!
Most astronauts spend six months on the station, and obviously most of them don’t have a twin, but they all add data to our knowledge of how space affects humans. We have learned a lot about how to counter muscle atrophy, and we have a better understanding of how the eyes and bones are degraded by prolonged weightlessness.
NASA loves to talk about ways that space research has improved life on earth (just google it, they’ll shout it at you), but even if you could find a way to do all that other research without a crewed space station, you can’t accumulate six astronaut-years of human medical data in space every single year for decades on end unless you’ve got a place in space to put a bunch of humans for a really long time, over and over again.
To me, that is what makes ISS a human treasure. Someday we will build a more cost-effective replacement on the basis of the lessons we’ve learned, but for now it’s the best we’ve got, and it’s quite good.
Right off the top of my head the medical data from long term space exposure will be absolutely critical to any future journeys. And I'm sure that's just the tip of the iceberg when it comes to perfecting long duration systems design, technology proofing, etc.
Hopefully the proof for this assertion is not simply that the majority of the ten longest spaceflights were conducted by the USSR/Russia, and rather the most impactful information was gathered from them.
On-orbit construction, how pressurized modules hold up after two decades of space travel, long-running experiments requiring in-person management, etc.
for the amount of money spent on getting it there and maintaining it, and because we are keeping it understaffed for safety reasons, we are getting very little return on it.
SpaceX's Falcon project is the first major progress we've made in the field of human spaceflight since the Apollo program.