At risk of crassness - human lives are pretty cheap and there are plenty of people willing to take the hit for a chance to be in space for an extended timeframe. Meanwhile building something with enough spin and shielding is a huge ask
There are not classified shuttle equivalents launching, not sure what you are talking about there. The X37 has the capability to land, but it is not manned and is tiny compared to the shuttle.
>research that couldn't be done with automation
I'd think there is room for both. Automation makes sense, but don't think the versatility of meatbags is entirely there yet.
A bigger problem is lack of expertise. Astronauts are not specialist in whatever is the topic of the current experiment. You need probably like 5 years of training (assume the second half of the undergraduate degree, and perhaps the first half of the PhD). So experiments must be fully automated except for a button to turn they on and off.
You can send up a lot of less versatile bots for the price of one meatbag.
"0.33g mitigates muscle atrophy while 0.67g preserves muscle function and myofiber type composition in mice during spaceflight"
https://pmc.ncbi.nlm.nih.gov/articles/PMC12985678/
Obviously, we know that the gravity of Earth is sufficient.
But the results make probable that two thirds of the gravity of Earth might be enough, while the gravity of Mars may create some problems and the gravity of the Moon is very likely to be insufficient, so the time spent on the Moon must be limited, though not so much as on the ISS.
I agree with the previous poster that any spaceship designed for carrying humans to Mars or even farther must be designed to spin and anyone who accepts to go on something else is stupid.
Making a spinning spaceship may be cheap if dual bodies or one body and a counterweight are used. It is likely that the safest solution would be to have 2 identical spacecraft, which could also be used independently but which could be coupled with cables to spin around the common center of mass at a distance big enough to create enough gravity at a low rotation speed.
The problem is not the price but the fact that nobody has tested how difficult is to control such a configuration (avoiding oscillations and instabilities) and how difficult is to solve problems like docking in a manner that does not waste energy (i.e. without changing the rotation speed of the more massive spinning spacecraft, which can be done by having 1 or more docking ports on the rotation axis, like on the hub of a wheel; in the case when the rotating spacecraft would be made with 2 bodies or a body and a counterweight that would be linked with cables, one could have the equivalent of an elevator for transporting crew and equipment from the docking port to the main body or bodies).
But someone must build and test such a spacecraft, otherwise we will never learn how to do it right and which are the real problems that are hard to predict in a simulation.
Forgive my ignorance on the topic, but surely "same as earth" would be the starting point? With everything less being a trade-off that is suboptimal