Are there any possibilities to counter the negative effects of low or micro gravity by increasing the atmospheric pressure?
Could increased atmospheric pressure act as a countermeasure for effects of microgravity?
Not all adverse effects of prolonged stay in microgravity environment, for example, it wouldn't make the slightest of difference regarding gravity gradient loss or decalcification, but it could increase atmospheric drag equally on all limbs and effectively help combat muscle atrophy. Problem is, it wouldn't be really practical, nor safe to additionally increase atmospheric pressure.
The mixture of breathable air would also have to use some other filler gas than nitrogen to prevent nitrogen narcosis, so perhaps argon that is equally inert. But regardless the filler gas used, increasing atmospheric pressure would additionally increase the load on the structure and further complicate extravehicular excursions (egress and ingress), and depending on the mixture used, might increase fire hazard.
Other, much simpler techniques with similar effects could be used instead, such as e.g. elastic compression garments, like ESA's Skinsuit, that offer resistance with the use of stretchable fabrics. They might be rather uncomfortable though, and still require strict exercise and dietary regime to help alleviate gravity gradient, body mass and blood volume loss.
$\begingroup$ What about streaming air, pushing everything to the "floor"? $\endgroup$ Jan 27, 2014 at 15:09
1$\begingroup$ @LocalFluff Well, you'd want air circulation anyway for obvious reasons, but I don't see how a strong vertical flow would do much good, you'd want a connected system, like e.g. a space wheel to take the best advantage of it. Problem with localized flow is that it creates polarized regions of both increased and decreased air pressure, and local eddies. So you might get a sufficient pressure on a macro scale, but your feet wouldn't be any firmer on the "ground", quite the contrary since you'd be dealing with compressed backflow under your feet in all directions. $\endgroup$ Jan 27, 2014 at 16:14
$\begingroup$ Yes, a connected flow in some circulation. The floor would be a wind transparent grid covering powerful sucking fans. Experiencing a hurricane, or a strong water stream, anyway feels like gravity, if it were managed to be stable. Could pressure in that sense simulate gravity usefully? Maybe instead of performing hours of exercise a day, one could sleep in a suit inside a shower cabin with a forceful stream of air or water to mitigate some microgravity health problems. $\endgroup$ Jan 27, 2014 at 16:34
1$\begingroup$ No external pressure alone would simulate gravity, all it would do is provide a more-or-less omnidirectional force. But what you're saying isn't anything more than "increasing atmospheric pressure", which is what the question is about since it doesn't specify how one is to achieve that, and it's what I was answering. In that respect, it wouldn't change anything, but it would restrict mobility and require loads of hardware. There's other problems with "wind" though, including health issues due to localized cooling of surfaces this airflow would be in contact with. It's just not a great idea. $\endgroup$ Jan 27, 2014 at 16:46