A New Method for Breath Capture Inside a Space Suit Helmet

This project investigates methods to capture an astronaut's exhaled carbon dioxide (CO₂) before it becomes diluted with the high volumetric oxygen flow present within a space suit. Typical expired breath contains CO₂ partial pressures (pCO₂) in the range of 20-35 mm Hg (.0226-.046 atm). This research investigates methods to capture the concentrated CO₂ gas stream prior to its dilution with the low pCO₂ ventilation flow. Specifically this research is looking at potential designs for a collection cup for use inside the space suit helmet.

The collection cup concept is not the same as a breathing mask typical of that worn by firefighters and pilots. It is well known that most members of the astronaut corps view a mask as a serious deficiency in any space suit helmet design. Instead, the collection cup is a non-contact device that will be designed using a detailed Computational Fluid Dynamic (CFD) analysis of the ventilation flow environment within the helmet. The CFD code, Fluent, provides modeling of the various gas species (CO₂, water vapor, and oxygen (O₂)) as they pass through a helmet. This same model will be used to numerically evaluate several different collection cup designs for this same CO₂ segregation effort. A new test rig will be built to test the results of the CFD analyses and validate the collection cup designs. This paper outlines the initial results and future plans of this work.