A Moon-Toilet

This is my submission for NASA’s Lunar Loo Challenge 2020, with the problem statement, “Design a space-toilet concept for the Artemis moon-lander, that allows astronauts to urinate and defecate in both microgravity and lunar gravity.” Additionally, the concepts had to abide by various design, physics, electronics, and chemical constraints, with a technical-readiness level of 3-5.

Competition Details

I named it **“Loo-Nar”** —a compact space-toilet concept with features that make going to the toilet effortless, clean, and safe, for the astronauts in the Artemis moon-landers. The following sections explain each feature in detail:
Seating Guide using Haptic Sensing
Since the bowls on all compact space toilets are much smaller than usual to save space, sitting/aiming correctly is challenging for astronauts.
To make this effortless and perfect everytime, the LooNar has a Seating Guidance System using haptic guidance:

**Sensing**: Arrays of infrared proximity sensors near the bowl to determine the exact position of the astronaut’s bottom.
**Guidance**: 4 haptic vibrators are embedded in the toilet seat to guide the astronauts to center themselves on the toilet seat—by making them shift themselves in four directions: up, down, left, and right to center themselves.

Here’s a low resolution mini-prototype to demonstrate the concept:

2. Physics of Waste Guidance

In the absence of gravity, the waste released into the toilet must be actively guided in because it doesn’t fall into the toilet naturally.

The Loo-Nar has air jets across the inner rim of the toilet bowl, blowing air onto the inner surface. The bowl is designed to have a gradually curving surface as well. Two physical phenomena created by these jets help in waste guidance:

**Coandă effect:** the tendency of a fluid jet to stay attached to a convex surface. Hence all the air blown by the jets follows the bowl’s surface and goes into the toilet pipe, taking any waste that touches the surface
**Bernoulli effect:** When the speed of a moving fluid increases, the pressure within the fluid decreases. Hence, the air jets on the sides create low air pressure neat the surface and the inlet pipe due to the Bernoulli effect, which also aids in directing waste downwards.

3. Waste-Trapping using Surface

The waste collection bags are designed to keep the sludge securely contained inside them at all times, making use of the surface tension of water. Each bag can accommodate the waste from two crew members for a whole day. This is how they do it:

**Using Water Surface Tension to trap waste**
Due to the high surface tension of water, solids and liquids that come in contact with it, stick to it in the absence of larger external forces like gravity. The waste collection bags make use of this principle to secure the waste inside.
The bag is coated with hydrophobic film on all the inner sides except for the bottom, where it is intended to be trapped.
A cellulose (hydrophilic) sheet is stuck to the bottom.
A tiny layer of water-based liquid is filled in, that only sticks to cellulose sheet.

The bag is sealed to the waste-inlet of the toilet bowl and the gas-exhaust using elastic bands.
As the solids and liquids keeps coming in through the toilet throughout the day, it keeps sticking to the bottom layer of liquid, and the sludge keeps growing upwards

4. Odor control: air filtering

**Fan**

The other end of the waste bag is connected to the gas exhaust port, which has a low-power fan always running to pressuring the air to pass through its filters.

**Filters**

The exhaust has two filters: an active carbon filter to block odorous gases like Hydrogen Sulphide, and a graphene membrane to block flammable gases like methane, that is generated by human waste.

5. Waste Stabilization: Active Enzymes

The bacteria in the faecal matter, urine, and vomit, are broken down throughout the day by organic active enzymes; this ensures that the gas producing bacteria are not kept alive for long, and the entire sludge is completely stabilized and odor-free when kept in storage.

These enzymes stored in a tank inside, are pumped and sprayed on the sludge throughout the day, through an atomizing nozzle inside the gas exhaust.

6. Sanitation

After every use, the toilet is flushed with an anti-bacterial liquid, to make sure that the toilet bowl is sanitized for the next use. This liquid is stored in another tank inside, and pumped through the nozzles embedded in the toilet seat.

7. Waste Storage

Inside the Loo-Nar, the bag rests on a removable tray, that supports its from all sides as the sludge keeps increasing.

When the day ends, the openings are sealed with the plastic sealers that come attached to the bag, and the tray is taken out.

The tray has a lid which opens outwards, which helps the astronauts easily slide this into the “poop cabinet”, to store the sludge securely until it is time to dispose it.

8. Structural Frame

The toilet seat of the Loo-Nar, along with all its components, rest on a 6061 aluminium alloy structure. This structure makes it easily withstand the weight of astronauts by distributing the stress, while keeping the overall weight low.

When a 132 KG (290 lbs) astronaut puts their entire weight on the toilet seat in the lunar gravity, the structure only gets displaced by a maximum distance of 2.5 millimetre.

9. Raisable Toilet Bowl for Men

For men to stand and urinate, the toilet bowl can be lifted up and bent towards their direction.

The flexible pipe is made of polyurethane; when the astronaut raises the toilet bowl, it allows him to bend and adjust the bowl so that he can aim properly. The push-lock mechanism at the end of the pipe prevents it from sliding back in unless pushed back in with force.