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It has been found that micro-gravity adversely affects blood flow to the human eye. How will this problem be treated on flights to Mars, for instance? Rotating spacecraft, perhaps?

Martin Schröder
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Daniel Starr
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  • Glasses, if any ... there are much severe affects on the human body muscular dystrophy, bone loss, psychological effects, etc. Basically it is assumed: Homo Sapience is able to handle it long enough for a trip to mars (and maybe back). – CallMeTom Jun 26 '20 at 06:07
  • @CallMeTom Most of negative effects of microgravity have a serious impact only after return to full gravity, and don't impair 0-g operations. The eyesight deterioration is different than the rest in that it impairs astronauts while in space. – SF. Jun 30 '20 at 15:04
  • Certain people have been on the ISS for more than a year, and a flight to (or from) Mars lasts half a year. So there's no urgent need to create artificial gravity on Mars flights, and Venus comes even closer. Another question is whether effects like eyesight deterioration would also occur in the lower gravity of Mars, but we simply dunno. – LoveForChrist Jul 03 '20 at 16:12
  • @LoveForChrist: Mars gravity is about 1/3 of Earth. We have a pretty good idea of impact of 0g on health and reasonable understanding about >1g but for anything in between 0 and 1 exclusive - the longest periods are of order of minutes. We absolutely don't know if 1/3g will be enough. – SF. Jul 07 '20 at 12:26
  • @SF. Martian gravity is about 3.72 m/s² or about 0.38g which is far from "a third g" but otherwise you're right. One could test the effects of low gravity on the Moon or on a rotating space station generating 0.38g. – LoveForChrist Jul 07 '20 at 12:40
  • @LoveForChrist it's arguable if 3.72 is"far" from 3.26, and then it's entirely moot because we don't know about long-term health impact of either. Tests on the Moon would require a base that can survive Lunar night (or located very specifically on one of the polar mountain tops; and it would be testing 1.62m/s^2 which is far from 3.72) and there are no viable plans for a rotating space station currently, at least none on realistically obtainable budget. – SF. Jul 07 '20 at 13:03
  • @SF. The Artemis moon base is to be built on the south pole where the lunar day can be very long. It doesn't matter whether 3.26 (1/3 g would rather be 3.27), 3.72 or 1.625 m/s², it are lower gravities whose effects on humans should be tested instead of only circulating in LEO since the end of the Apollo missions. – LoveForChrist Jul 07 '20 at 13:29
  • @LoveForChrist For now no mission to Moon is planned for more than 60 days. – SF. Jul 07 '20 at 14:15
  • @SF. That's enough. Apollo 17 was a record of 3 days on the Moon which doesn't show us trustworthy results of the effects of low gravity. – LoveForChrist Jul 07 '20 at 16:35
  • I was most interested in flight times to Mars which can be quite long. – Daniel Starr Jul 08 '20 at 17:39
  • This article "https://phys.org/news/2018-09-vision-problems-space-astronauts-kind.html" talks about microgravity and the human eye. It's not so much about the gravity on Mars, it's about the lack of gravity during the flight to Mars. – Daniel Starr Jul 16 '20 at 16:11

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Rotating for now seems to be the only viable option for artificial gravity, and alternative is keeping a constant acceleration of g halfway through the journey, and reversing it to slow down with g on the other half, which unfortunately requires a lot of fuel.

And there are a lot of effects the different gravity has on the human body, which also won't end after the trip is done, since Mars' gravity is also smaller than Earth, there is no telling just how much our physiology would be affected in the long term!

For more on that see:

uhoh
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UrasGungorPhys
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    it's not known that a full g is required, but any constant acceleration is prohibitive. –  Jun 26 '20 at 08:46
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    "Requires a lot of fuel" vastly understates the problem. It's totally intractable with any engine technology we can build in the foreseeable future. – ikrase Jun 26 '20 at 09:41