Development of small-scale hypobaric plant chambers

A system of three small-scale hypobaric plant chambers was designed and built to simulate a Mars greenhouse environment and evaluate effects of this environment on evapotranspiration of radish plants. A glass bell jar was sealed atop aluminum bases designed to house a heater, fans, humidifier, and wiring. A data acquisition and control program was developed to control pressure, air temperature, relative humidity, and carbon dioxide concentration as well as monitor leaf temperature and plant weight. The system was successful as demonstrated by the average standard deviations from the set points during performance tests (set points in parentheses): pressure, 0.2 kPa (12 kPa); CO₂ concentration, 235 ppm (9000 ppm); air temperature, 0.17 °C; (24 °C); and relative humidity, 1.03% (70%).