1. As the H2 - 02 fuel cell reaction occurs, a corresponding transfer o f CO2 occurs from the a i r side of the matrix to the H2 side. The rate o f this transfer depends upon 'the partial pressure of CO2 in the air stream and the cell current density. Unused hydrogen exits the cell mixed with :he transferred CO2 and i s then stored or further processed i n the CO? reduction system.
2. The Bosch process takes a gas mixture of H2 and CO2. heats it to between 1460 and 1810°R (811 and 1006°K) and then passes it through a steel wool catalyst to produce carbon and water vapor. Each oass over the steel wool typically converts only
3. The Space , Station propulsion system 90-day impulse requirements are determined using two types of atmospheric models. The f i r s t i s a 2-sigma model, shown i n figure 5, which encompasses 97.5% o f the "estimated" possible atmospheres that could occur over an 11-year solar cycle. The 2-sigma atmospheric model i s used to size the tanks, thrusters, lines, etc., o f the propulsion system. The second i s a zero-sigma (or nomina;) atmospheric model, also shown i n figure 5, which encompasses 50% o f the "estimated" possible atmospheres that could occur over an 11-year solar cycle. The nominal atmospheric model i s used to determine the expected resupply schedule over the IO-year mission o f the station. Both curves show how the density fluctuate over 11-year and annual cycles. Daily and orbital fluctuations due to light and dark side variations and geomagnetic disturbances have been averaoed out. The aerodvnamic drao used n determining impulse requirements i s a f k t i o n of the coefficient o f drag, atmospheric density, velocity (squared), and the effective crus 8 sectional area o f the station. For a oiven a1titude only the atmospheric densjty changes significantly over time. The velocity (24931 ft/sec) i s the circular orbit velocity a t 270 nm altitude. The average cross sectional area of the station i s determined with the orbiter docked for 14 days of every 90-day resupply period. This results in a total effective cross sectional area of 31775 ft 2.
4. Available Specific and 90-0ay Impulses