I WAS SORT OF WRONG LOL. OOPS
THANK YOU @silosene LMAOOOO I totally forgot about Rocky's space being hermetically sealed, mainly because i mixed up atmospheric pressure with gravity like a total grade schooler (I was thinking of the fuel migrating scene during the Taumoeba incident where the intense changes in gravity was putting belt to ass on both Grace and Rocky.) In hindsight idk why it didn't click for me because eridians die if the atmospheric pressure goes anywhere below 19 atm.
Reviewing some canon information
How gravity in space works for eridians from Andy Weir's document.
The Hail Mary's programmed so that its acceleration and deceleration created a gravity 1.5 times of that on Earth during it's journey from Earth to Tau Ceti, so we're assuming it's the same during Grace and Rocky's journey.
Hail Mary's Gravity: 1.5 g
So here are the main sub-saharan animals in the room to address:
1. I sometimes confused gravity with atmospheric pressure. oops
2. Other than the major incidents, the atmospheric pressure of Rocky's space is perfectly normal.
3. The Hail Mary isn't usually under microgravity! On it's journey to Erid, it's at 1.5g, so heavier for Grace and lower for Rocky.
Water has a different boiling point under different atmosphereic pressure, so due to long-term exposure to the much lower atmospheric pressure of the hail mary (and 0 pressure for space in general), it's the circulatory systems that go out of whack. The atmospheric pressure in Rocky's space is normal most of the time so there's not much to worry about on this aspect.
Eridians have 5 hearts, each near the major joint of the leg. They not only pump blood along the limbs, but metals that alternate through the body to create a steady electrical charge (energy) for the micromuscles.
Rocky's hearts are the actual organs that are weakening. they're used to pumping the heavy mercury under Erid's intense atmospheric pressure gravity, so they are definitely affected by the gravitational difference in space and on the Hail Mary.
When the hearts weaken, so does the blood flow that maintains the energy required to power the micromuscles, which control the blood flow, which is required for heating water for expanding vescicles.
It should be noted that there's a big difference between the heart adjusting to pumping mercury under microgravity vs. 0.75 the gravity it's used to. So the hearts would not weaken as much, but it will still weaken.
So all in all the results are more or less the same? Right answer wrong equation situation happening over here. I could've just skipped over explaining the Hydraulic System, but at least we have a deeper understanding as to how eridian bodies work.
Rocky requires gravity for his entire eating process, which lasts at least 3 hours. There are big problems if the Hail Mary was in microgravity, but it isn't. It's just in a lower gravity than Rocky's used to on Erid. Short term there shouldn't be any problem, but there would be repercussions to 4+ years of incision and healing of the abdomen fissure under lesser gravity.
Grace and Rocky could have averted this problem if they turned on the centrifuge to 2.03 g every time Rocky ate, but it's such a tedious and energy consuming process that they probably wouldn't bother. I don't think Rocky would've noticed the difference in gravity affecting their eating anyways, and if he did he wouldn't be willing to subject Grace to more Situations(even more gravity) than strictly necessary. It's only obvious in zero g because, well, no gravity.
The result is a weaker immune system and a struggle to kill deadly pathogens from his biosphere. Ergo Rocky's immunocompromised, ergo major problems with his digestive system. By the time Rocky actually feels this backlash, which is maybe a couple months until arrival to threeworld, I think he would just power through the pain. Between Grace and Rocky at least one of the two has to be as stable as possible.
Weak hearts (perhaps not as bad as atrophy) due to long-term exposure to lower gravity.
Rocky's regimen is still mainly cardiovascular exercises, reacclimatizing the hearts to gravitational pressure on Erid.
On top of this, due to lower gravity Rocky's ability to open and heal his ventral seal has weakened. That's right folks, Rocky has major tummy aches now.
More or less the same result, just different road as to how we got here. But I'm also finding new and interesting repercussions for Rocky as I figure my way through these hypothetical situations.
Bonus tangent here bc ADHD and also i'm too lazy to make a separate post about it
Went on a dive about the state change of liquids in space and found some interesting stuff. Liquids boils differently in microgravity, in a way that it actually takes much much MUCH more heat for it to actually evaporate. (Bt this point my brain has decided to stop processing any more scientific concepts so apologies for the innaccuracies. a multitude, i'm sure)
From what I gather there is no bouyancy and natural convection, so instead of the air bubbles rising into vapor, it just condenses in the center into one large bubble. The evaporation rate in zero-g is much slower, in the way that the boiling point is the same, but water actually enters a super-heated state instead of evaporating.
Not sure exactly how it will affect the expansion of the muscles, but my verdict is A Not Good Time. Best guess is the super heated water boils against the vessel walls so there's still expansion, but gas expanding and water expanding is pretty different isn't it? The water probably chafes against the vesicles, slowly wearing away at it (brought to you by that one magic school bus episode on water erosion.)
Despite what Weir says about zero-g having less severe problems on eridians, in this case all I would argue that it it would suck more, not less; lots of problems with heat distribution, from overheating killing worker cells to the strain required from the hearts for muscles muscle to body/ vent regulation and whatnot. But this is such a pedantic detail for how Eridians fundamentally function on the Blip-A, and the Hail Mary's journey to Erid isn't even under microgravity anyways, so we can just treat this tangent as a fun(Loud Incorrect Buzzer) thought experiment. Or maybe this is another reason the Eridian crew died off so quickly, the effects of radiations exacerbated by heat irregularity.
