O2 Generation and CO2 Scrubbing

Using electrolysis to extract oxygen from a water reservoir for supplying breathable oxygen to the helmet's atmosphere in a space suit is a theoretically viable concept.

1. Electrolysis Process: Electrolysis involves applying an electrical current to water to split it into its constituent elements, hydrogen and oxygen. The reaction is as follows:

   
   

   2 H2O(l) -> 2 H2(g) + O2(g)

   
   
   
   

   This means that from every two molecules of water, one molecule of oxygen and two molecules of hydrogen are produced.

2. Energy Requirements: Electrolysis requires a substantial amount of electrical energy. The suit's power source, such as a lithium-ion battery, would need to be capable of supplying this energy efficiently.

3. Oxygen Production Rate: The rate at which oxygen needs to be produced depends on the astronaut's oxygen consumption rate, which varies based on activity level but is generally around 0.8 to 1.4 liters per minute at rest. The electrolysis system would need to be designed to meet or exceed this rate to ensure a sufficient supply of oxygen.

4. Management of Hydrogen: Hydrogen produced during electrolysis would need to be safely managed. Hydrogen is highly flammable, so careful containment and possible venting into space would be necessary.

5. Water Reservoir: A 20-liter water reservoir would provide a significant amount of raw material for electrolysis. Considering that each liter of water can produce about 111.1 grams of oxygen, this could sustain an astronaut for an extended period.

6. System Integration: The electrolysis system would need to be integrated with other life-support systems in the suit, ensuring that oxygen is delivered to the helmet at the correct pressure and humidity levels.

CO2 Scrubbing would be done using Sabatier reaction:

It's theoretically possible to scrub the waste CO2 exhaled by the user and react it with the waste H2 (hydrogen) produced from electrolysis to create methane (CH4). This process involves a chemical reaction known as the Sabatier reaction, which is a method of carbon capture and hydrogenation of carbon dioxide.

The Sabatier reaction can be represented by the following chemical equation:

CO2​+4H2​ -> CH4​+2H2​O

In this reaction:

• CO2 (carbon dioxide) is the waste product from human respiration.

• H2 (hydrogen) is the byproduct from the electrolysis of water.

• CH4 (methane) is the output, along with water (H2O).

The key aspects of implementing this process in a space suit environment would include:

1. CO2 Scrubbing: Efficient removal of CO2 from the helmet's atmosphere is essential. This is typically done using chemical scrubbers in current space suits.

2. Catalyst: The Sabatier reaction requires a catalyst, typically nickel or ruthenium, to proceed at a practical rate and temperature.

3. Temperature and Pressure Conditions: The reaction generally occurs at elevated temperatures and pressures, which would require suitable equipment that can handle these conditions within the safety constraints of a space suit.

4. Use or Storage of Methane: The methane produced serves 2 functions. In both cases it is expelled from the suit. 1st, as a total loss energy extraction system, using heat exchangers excess temperature is extracted from the water circulating inside the suit, the methane is simply released into vacuum to wick away heat. 2nd, same scenario, however stored for longer periods and can be used as either cold gas for small attitude adjustment, or combined with O2 produced by the suit to act as proper reaction mass for significantly higher delta.

5. Energy Requirements and System Complexity: Implementing this process would increase the energy demands and complexity of the life support system. The suit's power supply would need to accommodate these additional requirements.