Using fancloth to simulate gravity

Question

Whilst pondering on forms of artificial gravity that do not involve rotation, I have returned to the idea originally proposed in this question: Could fans be used to simulate gravity?

One of the main problems is the constant noise; an issue that seemed insurmountable until I discovered the concept of fancloth, originally proposed by J. Storrs hall. The idea is of thousands or even millions of microscopic fans, so densely packed that they resemble a continuous material. Storrs proposed this be used in aircraft, but I propose using a layer of fancloth covering the roof of a spacecraft to simulate gravity on the occupants. It would presumably be less noisy save for a faint hum, and if they were powerful enough then there would be no “whoosh” of air trying to flow back up.

Aside from the fact that the internal organs of the occupants would experience no gravity, (unless the fans were ludicrously powerful) and that objects under tables/furniture would be shielded and experience zero G, are there any major problems with this idea?

Answer 1

Impractical

Note that is does not matter whether the air movement is being generated by some fictional "fancloth" or by a small number of really big fans, the entire idea of having artificial gravity based on air movement has a number of significant problems.

1. Solid horizontal surfaces will create horizontal air movements. If a big fan or fans are blowing straight down onto a solid floor then the air will hit the floor and then... go sideways. Ditto for tables, kitchen benches and any other surface that is intended to support people or objects. In order for this to have any chance of working, all horizontal or horizontal-ish surfaces must be mostly open gridwork so the air can continue on "downwards" to wherever it is collected to be channelled back up to the "top" of the affected area. Otherwise the horizontal forces will knock things over sideways. So open gridwork for all horizontal surfaces is essential before the other consequences can even be considered. (Unfortunately, solid horizontal surfaces are needed for some purposes such as chopping boards in a kitchen. As will be seen, this is a relatively minor problem due to the other issues.)

2. "Weight" is proportional to surface area rather than mass. This is the big one. A person standing with their arms by their sides will have roughly the same aerodynamic cross-section as a piece of A4 or A3 paper. Which means that either a person is only experiencing the force required to keep 5-10 g of paper down or the paper is experiencing the force required to keep a 50-100 kg person on the ground. The former means that the person is effectively floating, the latter means that a piece of paper will get shredded through the open gridwork required by point 1. It also means that as soon as a person lies down they suddenly get many times "heavier" and are plastered against the ground, unable to move, as if they had found themselves on a 5G (or more) world.

3. Noise. The air speed required to make a person feel that they are experiencing a full 1G or even something close to it will be at least 80 km/hr or much more (200 km/hr is typical freefall speed, which is where airspeed force and gravity force are equal), depending on what body weight/body orientation the wind is optimised to simulate 1G for. Which means that everyone will be perpetually living in a very noisy environment where they need to shout to even attempt to be heard over the wind.

4. Convection. This is good news for keeping computers cool but bad news for everything else - convection currents will be frantically cooling everything off. Hot drinks, food etc will get cold very quickly, except that they will be blow away by the hurricane-strength wind before it matters.

5. Other stuff. Clothing will need to be strong enough to avoid wardrobe malfuctions. Eyes will be perpetually drying out such that constant wearing of goggles would be essential. Skin would be blasted and also dehydrated. Hairstyles... I don't see any point in continuing here - this is not an environment humans can live in for sustained periods.

Edit: Almost forgot the energy requirements for such a system. Friction will make the flowing air slow down, so energy will need to keep being put into the system to keep the air flowing at high speed. However much "stuff" is being affected by the gravity-simulating airflow, the energy requirement will be roughly the same as constantly propelling an equal amount of drag-inducing "stuff" through the air using propellers.

Answer 2

YOU WOULD ALSO NEED SUCTION GRIDS ON HORISONTAL SURFACES

If you just blow air down from above, it would deflect from floors, tables and other horisontal surfaces, leading to rather turbulent conditions. This can be prevented by having suction grids on horisontal surfaces, sucking air in as rapidly as it is blown down from above. This would create a stable air flow from above to below. Having a grid above suction vents will prevent feet and objects getting stuck too hard to floors and tables.

To generate a pull/push similar to a standard gravity, the air flow needs to be very strong - compare to the "anti-gravity" attractions at fairs, where you get to 'fly' short distances wearing a flight suit above an air pump. Clothes and hair would flap incessantly, and the constant strong draft could cause pneomonia. Paper thumb-tacked to boards would quickly be blown off or torn apart. However, to just create a sense of up and down with a light flow - enough to let you walk gingerly on floors - could be feasible. But it would not fool your inner ear and be of little help countering deterioration of muscles, heart and bones.