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Elon Musk and SpaceX are planning a manned mission to Mars as early as 2029.

The mission timeline is unclear, but one proposal (page 16) from SpaceX, which uses Hohmann transfer orbits for minimum fuel requirement, is for a 919 day mission, with 224 days outbound, 458 days on Mars and 237 days return. The SpaceX site is now suggesting a 6 month journey.

Although large volumes - similar to the ISS - for crew accommodation on Starship are likely (page 13), the entire journey will be in weightlessness. In spite of vigorous physical exercise on the ISS, astronauts can take months to recover some physiological and mental functions once they returned to Earth. "The rule of thumb is for every month in space, it takes two months for the bones to recover". Astronauts experience difficulty walking immediately after return to Earth and require assistance.

I dream of them stumbling and falling over each other when they reach the surface of Mars - a whole clumsy display as the try and help each other stand and walk in the heavy suits that weigh them down, almost as much as on Earth without the suits. Great comedy but a ridiculous reality.

Is it reasonable to expect that astronauts sent to Mars, who experience 6 to 7 months of weightlessness on the journey, may not be fit to accomplish their mission objective once they arrive.

Is the SpaceX proposed mission architecture for a manned mission to Mars feasible? Or must it be modified - with great cost and delays - to included some form of artificial gravity, such as that illustrated in the movie The Martian and the book written by Andy Weir.

Hermes from The Martian

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    $\begingroup$ Short answer: Will the ships require artificial gravity? no. Would it be reasonable to add it in the long run? yes $\endgroup$
    – The Rocket fan
    Commented Apr 14 at 18:52
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    $\begingroup$ Given that we know similar durations of weightlessness aren't deadly and can be recovered from, if you were designing a mission to Mars that couldn't use artificial gravity for some reason, presumably you'd tailor the surface mission objectives to allow that to work. I think you'd have to add additional constraints for artificial gravity to be a requirement. $\endgroup$
    – Erin Anne
    Commented Apr 14 at 21:20
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    $\begingroup$ If you look at some of the related questions on the site, even making the whole trip in 1G will not leave you with astronauts in peak physical and mental condition. $\endgroup$
    – Erin Anne
    Commented Apr 15 at 4:57
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    $\begingroup$ I doubt very much that any people will be aboard a 6-7 month trip to Mars, although some of their kit might take that route. Much more likely would be half of that, or perhaps even a bit less using nuclear propulsion. It's too soon to tell. Being in deep space for such an extended period is not only gravity that is the problem but also radiation. $\endgroup$
    – Slarty
    Commented Apr 15 at 9:57
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    $\begingroup$ I think it boils down to your attitude to risk. We have some grasp on zero g risk but none on 0.38g. And zero g followed by 0.38g followed by zero g is even further into the long grass. No doubt some would give it a shot, but whether the grey suits at NASA would be prepared for such risks is another matter entirely. $\endgroup$
    – Slarty
    Commented Apr 16 at 11:27

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Micro-gravity is Probably Not a Show Stopper

I'm highly skeptical of Musk's claims at this point, especially regarding any kind of timeline, but I don't think a micro-gravity only trip to Mars is out of the question.

First Several Hours

This NIH study says, in a nutshell, that astronauts will be fairly useless for the first couple of hours after landing due to vestibular abnormalities.

But the study also notes that even after 160 days on ISS, 5 hours was long enough for isolated astronauts to perform some basic functions:

during return of Expedition 6 from the ISS, a technical malfunction caused the Soyuz spacecraft to land some 460 km away from its planned touchdown point. The 5-hour delay for arrival of the ground support team gave the crew an opportunity to open the hatch, unstrap, and egress the Soyuz spacecraft without any outside help. Performing fast, coordinated movements was not possible, and head movement provoked oscillopsia and nausea.

But with 400+ days on Mars, our future explorers can probably afford to spend a couple hours in the lander feeling sick.

Frame Challenge - Peak Condition

OP states in a comment that they expect a requirement for "peak physical & mental condition when they arrive" -- and I think that's a mistake.

With 460 days on the Martian surface, two days of doing absolutely nothing but recovering represents a loss of less than 0.5% of the mission time. That's certainly an acceptable trade off if it allows for a much cheaper ship design.

And further, "peak condition" is still probably not required for excursions to the surface. One could easily imagine a schedule of 20 minutes outside one day, followed by 30 minutes the next, etc. Such that the astronauts don't hit their full stride until weeks after they've touched down.

Time inside the lander or habitat - at low gravity and without heavy suits - could be spent analyzing samples, unpacking supplies, and doing other low impact work.

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  • $\begingroup$ And presumably surface exploration will be assisted by landers, which could have been sent on an earlier mission. In some cases the crew need only collect the samples for analysis on Starship or return to Earth. Great answer @codeMonkey.. I'm encouraged, but I still have my doubts about microgravity and other aspects. It's a high risk mission even if everything goes right with Starship. $\endgroup$
    – Galerita
    Commented Apr 15 at 15:48
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It would depend on how long the astronauts stay in space enroute to Mars, and whether those on the trip to the red planet are trained government astronauts, or civilians. Spending several months in microgravity is really no big deal for the astronauts of government space agencies, except upon landing back on Earth. When people land back on Earth after spending months in orbit, their muscles and bones have usually atrophied to the extent that walking becomes difficult or impossible for the first few hours or days. We have people and equipment on Earth to cart these astronauts away from the capsule, no such luxury will exist on Mars, thus astronauts will be on their own. No doubt artificial gravity will be advantageous in this regard, but not absolutely necessary.

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  • $\begingroup$ Why would it make a difference if an astronaut is "government" or "civilian"? It's the training and equipment on board that matters regarding the astronauts health. There's plenty of "civilian" astronauts on the ISS with long duration stays. And the reason they have difficulty in walking right after landing is the vestibular system, not their muscles. $\endgroup$
    – DarkDust
    Commented Apr 18 at 15:40

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