Congratulations, your alternate history has delayed Mars colonization by several decades.
Because of the ISS we know that stays of greater than 12 months in zero gravity have real but minor impacts on the human body. So 3-4 month trips to Mars in zero-g are feasible.
If we assume they aren't, those trips would be far more resource intensive.
We didn't learn any of that from the ISS which we didn't already know from Salyut 6 and 7, and Mir. The ISS, aka Mir 2, hasn't taught us anything new. The reason it exists is because decades ago, for a few years, manned space stations made sense for orbital reconnaissance because putting unmanned cameras in space was complicated. Salyut and MOL were born from this transient strategic necessity. Unmanned recon satellites soon became practical though, so MOL was canceled but the Soviets carried on with Salyut because if there was anything they were good at, it was continuing to make something long after anybody else would have canceled it. Even when they did get recon satellites they did it with Vostok capsules, they never stopped making those after launching Yuri Gragarin in one. They just kept on making them because they were already tooled up for it, finding new excuses to keep making the same old stuff. And so it was with Salyut, the program was obsolete for orbital reconnaissance but they were already making them so they kept at it, turning it into a national prestige program. Mir was a direct descendant of it, built around the DOS-7 module which was a Salyut module with 6 docking ports instead of the two on DOS-6. It never had a good reason for existing besides Soviet politics. (By the way, Skylab never had a good reason for existing either, just politics. NASA trying to hold onto their funding as Apollo was wound down.)
The ISS is nothing more than Mir 2, built around the DOS-8 module, it's a Salyut with American funding because this time America wanted to keep the Russian space program solvent to make it harder for Iran/etc to recruit that Soviet talent. And because NASA likes long term projects that require around the clock staffing because that's great for budgets and careers. That's why the ISS exists.
Also we aren't going to Mars. Sorry. A lot of individuals are passionate about that but at an organization level there is no drive for it. NASA likes to use the talk of it for fundraising but never makes progress on it and Congress won't ever greenlight it, and SpaceX uses it to keep their employee moral up but all they are demonstrably working towards is being the king of launching satellites. The only money to be made in space is with stuff pointed at Earth. There is no economic case for Mars colonization. It's not happening. I wish it weren't so because I'm a sci-fi junky, but it is what it is.
> We didn't learn any of that from the ISS which we didn't already know from Salyut 6 and 7, and Mir. The ISS, aka Mir 2, hasn't taught us anything new.
I doubt that. ISS served in space longer than Mir and Salyut-7 combined, I would expect it to run more experiments and get more data - especially as the equipment is more modern and experiments are planned with the benefit of knowledge of the previous works.
The amount of time the station spends in orbit isn't relevant, the amount of time a person spends in orbit for an unbroken stretch is what's relevant. Three of the top five spaceflight duration records were set on Mir, including the top two (437 days and 379 days.) Nobody even thinks of getting close to that top Mir record anymore because it is already known that it fucks people up.
> The amount of time the station spends in orbit isn't relevant,
The people on ISS were doing a multitude of scientific programs during that long time. That's important. Just like you wouldn't say that Hubble already seen everything and JWST isn't needed.
We still have no idea what long term stays in Martian or even Lunar gravity does to a human body. We don't know because we have spent the past half a century fucking around with useless zero-g space stations instead of building von Braun wheels which could easily be used to simulate those conditions. Because forget about Mars colonization, merely finding the political willpower to do something as conceptually simple as spinning in space is evidently impossible for us.
The simulation would be flawed. Von Braun wheels would have very significant Coriolis effects, so it'd be hard to distinguish whether any issues are due to reduced gravity or the Coriolis effects.
Bone density and muscle loss effects shouldn't be significantly effected by coriolis effects. Such effects may likely cause nausea in many people, but it is very likely that test subjects who can adapt to it and live comfortably during the period of study could be found.
My very rusty physics tells me that walking one way along the inside of the wheel would make you weigh less, and the other way would make you weigh more - is this what you're referring to? Would trying to work 'normally' in this kind of situation induce nausea, or make your food fall off your tray etc? It would be a shame if you went to all the effort to make a Von Braun wheel in space to simulate gravity, only to find that you had to stand still to do anything practical.
(I assume the astronauts in 2001 A Space Odyssey jogged in the direction that made themselves weigh more, to make their workout more intense.)
Coriolis forces acting on the human vestibular system can directly induce motion sickness just from turning your head. If it turns out humans cannot acclimate through long term exposure, the only remedy is to increase the wheel radius.
The Coriolis effects can be made to be mostly negligible, with a big enough wheel.
A big wheel may be too costly, but it can be replaced by either 2 identical bodies with a long link between them, or with a single body linked to a counterweight, in which case the cost would be only marginally greater than for the current spaceships.
In several decades of zero-g research, they didn't even manage to put a few mice up to see whether they could successfully reproduce without gravity. Are they afraid of the results?
It would be embarrassing if the mouse babies come out crippled, even if it doesn't immediately generalize to humans and the low-g environment of Mars.
They've successfully hatched small fish on ISS. For animals, IIRC embryos need gravity to determine heads and tails or something. We do already know. The answer is that we Earthian lives generally face great difficulty reproducing in zero-g.
I meant to say larger animals - it's been tried. Small fish and frogs were fine, but chicken eggs showed issues developing past some early stages under microgravity[1]. Therefore we know that animals significantly more complex than amphibians can not reproduce normally under zero-g.
> Twenty out of 30 eggs (nine out of ten 10-day-old eggs; 10 out of ten 7-day-old eggs; 1 out of ten 0-day-old eggs) were recovered alive after landing. The only living embryo of the 0-day-old egg died 24 days after launch, and was comparable to a 16-day-old embryo when it died. The high mortality of the 0-day-old eggs appeared to be related to the specific inner structure of the egg. The yolk (specific gravity, 1.029) would not have separated from the albumen (1.040) during space flight.
Still, trying it with mice (or other mammals) would have been worth it, because we can't rule out mammals being more robust during embryogenesis than birds. The ISS actually has still a few years left, so there would be some time left for such an experiment. Though I doubt it will happen.
> We still have no idea what long term stays in Martian or even Lunar gravity does to a human body.
We do know. The radiation kills us well before the lack of gravity does. The end.
We have to have shieldings thick and heavy as nuclear bunkers for a real space station to work, and such shielding is just way too heavy to be launched from Earth(unless e.g. we'd be okay with launching a toilet stall worth of habitable volume per Starship), so the station has to be mostly fabricated "in space", which is both technically and politically not yet feasible. There are theories that horizontal branches that may exist in natural crevices on the Lunar surface might work. Or for Mars some say we can just drill some mineshafts there and live inside. but all those options are equally sketchy in its own ways at this moment.
We're barely flying hatchbacks up to orbits and we want airport garages out there to park it. We're not hauling the whole building in the back of a Prius, not even on Earth, obviously.
What NASA, ESA, etc. had been doing is to drive up that Prius to the trailer home left in the middle of the desert, have them change lightbulbs, celebrate themselves and rotate crews. That's basically useless, but they keep repeating that useless "expeditions" because they'll have to start over from reinventing tubeless wheels if they stop paying for the gas even just for one year.
Because of the ISS we know that stays of greater than 12 months in zero gravity have real but minor impacts on the human body. So 3-4 month trips to Mars in zero-g are feasible.
If we assume they aren't, those trips would be far more resource intensive.