Best/Realistic Way to Acclimate Astronauts to Zero G

Question

I'm trying to provide a somewhat realistic explanation of how astronauts were able to overcome the harmful physiological effects of prolonged zero G exposure. As of 2017, issues include: bone/calcium loss (presumably permanent), muscle atrophy, cardio-vascular atrophy and the list goes on to include a few similar health problems.

In my story, the exact date of present day is uncertain, but the reader knows its the future. I simply want address what happened in the interim. I have two ideas so far:

1. accelerated evolution/genetic engineering, where, assuming a sufficiently advanced lab, the gene for adapting to zero G is turned off. This way astronauts can have normal bone and muscle activity as if under normal gravity and 1 atmosphere of pressure, ect.

2. Medication, a pharmaceutical 'miracle' drug is administered once a day to reverse the adverse effects.

However I don't want to go too far on the Believable <---> Miracle continuum. Are there any more realistic but still suitable ways to acclimate to zero G?

Zero G Tasks: ship maintenance (internal/external), some parts of the ship don't have artificial gravity. Field science, planets or asteroids having very little gravity.

Duration: Indefinitely, career astronauts on long voyages.

Answer 1

There plenty of issues with long term Zero G habitation. I don't think one thing will credibly fix that in your story. You'd have to go with a combination of things. For example have drugs that reduce some of the effects.

But combine this with manditory centrifuge sessions like centrifuge tanks as sleeping units. Your astronauts will be forced to undergo daily centrifuge sessions to offset the adaption to Zero G.

Further as we already do a regime of exercise, preferably in a centrifuge. Gotta keep those heart muscles working. Thinner blood itself can probably be offset by drugs of some sort.

While drugs might certainly help, as will 'perfect genetic samples' Gattica style, you will still need to strain the muscles and bones. So some form of exercise and centrifuge or other artificial gravity will remain.

Another thing that might work are an exoskeletal suit. But instead of aiding the wearer it holds him back. Forcing him to excert himself. Can probably be merged with a regular uniform for use in the pressurized part of the ship. Perhaps a breathing slot to attach to oxygen ports around the ship in case of a leak etc.

This page might have some inspiration for you.

Answer 2

On the matter of bone loss: there is a great NASA article on this, which essentially states that in space you will excrete 250mg of calcium more than you intake per day. Which means that as long as you have a diet that includes sufficiant calcium supplements you should be fine.

You mentioned cardio vascular atrohpy, but this is rarely an issue for astronauts, UK astronaught Tim Peak was on the ISS for 186 days, during which he ran a marathon, the ISS is well coped to ensure astronauts keep exercising so that when they return to Earth they have enough muscle to stand up and walk around.

Worth noting: the most time spent in space in a single mission is 437 days and there were no major health issues, other than some to do with muscle tone, but that happens for all space missions.

edit: on the matter of eyesight issues:

from NASA again: "Comparing the blood analysis with nutritional assessments revealed that crew members experiencing vision changes had consistently lower folate levels and higher levels of metabolites. The comparison suggests the vision changes may be due in part to what's called a "dependent one-carbon metabolic pathway" change." Also worth noting that this only happens for about 25% of astronauts, so if you basically give your potential life long astronauts say a 1 year test, to screen out anyone for whom eyesight could be an issue they you're sorted, beyond that more tests are being done, it could be a dietry problem but nothing is concrete.

TL;DR:
You don't really need to equip your astronauts unless they plan on staying there for somewhere in the region of decades, at which point the existing reseasrch doesn't help you in suggesting potential problems.