# How would a zero gravity cat litter box work?

In fiction cats are often chosen as the optimal zero/micro gravity pet. Clearly there is some rational for this, all existing answers at How do astronauts turn in space? include cats in them.

While most litter boxes on Earth use sand or some pseudo dirt substance, it seems unlikely this would be a good solution without significant gravity. It is possible to teach a cat to use toilet so a space cat using a toilet is an option. Though it looks like current space toilets use different facilities for liquids and solids so not the best option for a cat. How would a zero gravity cat toilet/litter box work?

While there have been a lot of animals in space they have all been confined, this question assumes a cat with free range of the environment like it's human companions. This question is about the mechanical/physical solution not the training issues which would be best addressed at Pets.SE

• As an owner of cats, my immediate response is "awww hell no." Let's not take cats to space without a hab centrifuge. Commented Oct 9, 2015 at 14:44
• I'm not the close vote though. I'd like to see this question work--please prove me wrong! I just don't think it is going to happen. We'll see what other users think. Commented Oct 9, 2015 at 14:46
• @JamesJenkins Do you know why the area surrounding the cat litter box stays clean here on Earth? It's not gravity, it's me developing OCD around it. :D Commented Oct 9, 2015 at 14:50
• @JamesJenkins Imagine a box with a sink large enough to take the cat's doo-doo, and air flow from above it going through it at big enough pressure so doo-doo et al. flow in that direction. Now guess where you'd find the cat next time she'd need to do her stuff. She'd be livid too! I think that if I'd want to solve this, I'd try to marry a Roomba with one of those DoD SPHERES and bless it with some Robonaut logic (and an air freshener). Commented Oct 9, 2015 at 14:56
• OK, here's an idea. Use a non-Newtonian magnetorheological fluid over an electrostatic speaker, then control its viscosity, surface tension, shape and porosity with acoustic, electrostatic and magnetic forces provided by the speaker (its mesh will have to be modified somewhat to be also ferrous which they usually wouldn't be). You'll need some proximity sensors, constant supply of power, and quite a bit of fine tuning / calibration to make it work as it should, depending on how much of solids it holds in the putty. Commented Oct 9, 2015 at 16:25

How about a non-zero-gravity litter box?

While cats have a natural inclination towards the litterbox anything unconventional requires a certain amount of training and kittens require a certain amount of training anyway--you start out with the cat in a fairly small environment that includes the litter box, once it has a good understanding that that's where to go you expand it's environment.

That means you need a station large enough you can confine the cat in the area of it's litter box for a bit--that's a pretty substantial station.

Thus lets give the cat a litter box on a squirrel cage spun to perhaps .05g--we are simply after enough to keep things from floating away. The "litter" is ferrous material encased in something that will keep it from rusting--magnets are used to keep the cat from tossing it out of the box with it's pawing.

The litter box actually comprises the whole ring although the cat only sees a small part of that, the rest of it is behind the scenes. The cleaning mechanism normally rotates very slowly relative to the litter bed, it stops if it senses a cat in the box and then resumes when the cat has been gone for a minute.

Such a system would not work for small kittens and might be unsuitable for sufficiently elderly cats--it requires a cat capable of jumping into/out of the rotating ring.

• The ring, or carousel, could have a single opening with a sensor that would start it turning when the cat entered so it would be stationary when not in use. Commented Oct 10, 2015 at 2:59
• @JoeL. I considered that but I figured it might as well clean as much as possible. Commented Oct 10, 2015 at 4:02
• I'm trying to imagine a cat jumping onto a spinning surface in zero g--doesn't sound easy. Commented Oct 12, 2015 at 14:06
• If a cat is living in zero-g I would figure it has learned how to get around. I think training in a spun section of the station would be needed--perhaps at first the cat is confined to the litter box ring. Commented Oct 13, 2015 at 1:48

It's not an optimal solution, but fitted cat-diapers might suffice, at least for short periods.

• So the astronauts would have to take turns changing them as their days routine. This might also prevent the cat from masking there territory (however it might be able to unlearn this). Commented Oct 10, 2015 at 23:15

A solution by Jack McDevitt in "The Cat's Pajamas" (2012)

used magnetic gravel and gentle suction to overcome the problems of a zero-gee environment.

This was offered as a solution to a related question by Null On SciFi.SE