Carbon Dioxide Measuring Systems for Manned Spacecraft.

For manned space flight to date, three types of CO2 sensors have been developed. At present, the infrared approach to CO 2 detection is considered the most reliable and sensitive system available for use in manned space flight. The problems of total pressure sensitivity can be offset electronically, ff required, on future missions; however, at present, the excellent pressure control which the environmental system supplies the spacecraft makes such refinements unnecessary for normal operations. T HE LEVEL of CO2 within the breathing atmosphere of manned spacecraft is an important parameter that provides an indication of the well-being of the astronauts, hence, affects to a marked degree the success of a mission. In the Gemini and Apollo spacecraft, as in the Mercury, the internal atmosphere is circulated through a lithium hydroxide canister to remove metabolic CO2. In order to insure that the atmosphere remains within tolerable limits, measurements of the CO2 partial pressure in the spacecraft is required. Man produces, in a spacecraft, between 2.1 and 7.4 pounds per day of CO2 depending on his activities. The amount of lithium hydroxide provided in the CO2 absorber is based upon these production rates and considers the astronaut's workload during a mission. 1 The Mercury system used 5.4 pounds of LiOH for the 33hour MA-9 mission; ~ the Gemini canister contains 81 pounds for a 14-day mission; the Apollo system utilizes CO 2 PARTIAL 7 PRESSURES (MM OF HG) 5 4 3 2 I O CO 2 BUILDUP VS TIME I FOR TOTALLY FAILED ABSORBER MERCURY SUIT SYSTEM