Is it simpler to build a better space toilet, or to build a ship with centrifugal gravity and use a regular toilet?

ethan_smith 4 hours ago | parent | next [-]

The centrifugal gravity approach requires a massive structure - you need something like 200+ meter radius to keep rotation rates low enough that Coriolis effects don't make people nauseous (which would create a whole different toilet problem). Building a better space toilet is orders of magnitude cheaper and lighter than spinning up a habitat.

	▲	teraflop 3 hours ago \| parent [-]
		SpinCalc is a useful simple tool for looking at the tradeoffs of centrifugal artificial gravity: https://www.artificial-gravity.com/sw/SpinCalc/

▲

yshamrei 5 hours ago | parent | prev | next [-]

There are two issues:

- To build a centrifuge in space of sufficient size, you need to solve the problem of delivering a large amount of materials to orbit, because it has to be hundreds of meters in diameter at least.

- Such a centrifuge will create a gyroscopic effect, and the station will quickly become very difficult to control.

	▲	VorpalWay 2 hours ago \| parent \| next [-]
		Couldn't you have two centrifuges next to each other spinning in opposite directions, cancelling most of the effect out? I believe some helicopters work like that, with two sets of rotors on longer troop transport helis. A few even have two sets on top of each other. And many planes have the props on opposite wings rotate in opposite directions.
	▲	idlewords 2 hours ago \| parent \| prev [-]
		You can try it with small capsules and tethers, but it's still a pain.

▲

chinabot 4 hours ago | parent | prev | next [-]

If people are going to live in space for any period of time then they are going to need gravity so long term, yes.

	▲	__patchbit__ 3 hours ago \| parent [-]
		Scale up the nautilus body plan to a 200m radius shell and contain spindrive artificial gravity for collecting pellets.

▲

shoxidizer 3 hours ago | parent | prev | next [-]

This does sound absurd at first, but how much gravity is really needed for collection? Is there any value in just a few hundredths of earth gravity?

	▲	idlewords 9 minutes ago \| parent \| next [-]
		It's not an absurd question. The threshold value is the one that breaks surface tension and effectively pulls waste away from the body. It will be more than a few hundredths g but less than 1g. Unfortunately we have basically no data on the effects of partial gravity, in this context or any other. We can try flying partial-gravity parabolas in aircraft and simulate a Martian toilet the same way they tested the design for Skylab; I don't think this experiment has been done.
	▲	kelnos 3 hours ago \| parent \| prev [-]
		The article mentions that on Mars, with 0.38x Earth gravity, there will still be challenges, so I expect you need a significant fraction of 1g for the problems to go away.

▲

oersted 2 hours ago | parent | prev | next [-]

Ah a fellow Hail Mary fan :)

▲

giantrobot 4 hours ago | parent | prev | next [-]

Even with centrifugal "gravity" the toilets need to be designed for the worst case scenario (no "gravity"). Even if you could use a "regular" toilet the system needs to sequester and process the septic waste. That precludes even using the likes of an airplane toilet.

It's a significant amount of engineering effort, testing, feedback, and iteration to build effective life support systems for manned spaceflight. Long duration spaceflight is orders of magnitude more difficult.

Toilets are systems that can incapacitate or even kill the crew if they malfunction. In a low or microgravity environment aerosolized septic material can get in astronauts' eyes or lungs. It can also seep into electronics or other ship systems causing malfunctions. Even just clean water spraying into the cabin could be dangerous in microgravity.

▲

TylerE 5 hours ago | parent | prev [-]

You wouldn’t want to use a regular toilet even if you could, given how tight water margins are. Urine you can reclaim, feces not so much.

	▲	amluto 5 hours ago \| parent [-]
		Vacuum flush toilets are common on airplanes, trains, and ships and use a lot less water than a conventional toilet.