1. Controlled Environment Systems Research Facility Hypobaric Chambers for Biological Life Support Research Michael Stasiak, Cara Ann Wehkamp, Jamie Lawson, and Michael Dixon Controlled Environment Systems Research Facility Department of Environmental Biology University of Guelph

2. Controlled Environment Systems Research Facility Bioregenerative Life Support Systems  Edible Biomass Production  Carbon Dioxide Absorption  Oxygen Generation  Water Recycling  Waste Degradation CO 2 O2O2 Edible Biomass Processed Waste Gray H 2 O Pure H 2 O Inedible Biomass

3. Controlled Environment Systems Research Facility Plant Growth Structure on Mars Two options exist:  Earth atmospheric pressure - heavy and opaque  Reduced atmospheric pressure - light-weight and transparent material

4. Controlled Environment Systems Research Facility Benefits of Low Atmospheric Pressure  Need to minimize the pressure differential between the growth structure and the Martian atmosphere - simplifies the engineering requirements of the structure - decreases atmospheric leakage - reduces the amount of supplemental gas required for startup - ability to modify plant growth rates Martian Atmosphere (0.6 kPa) 10 kPa Plant Growth Structure 100 kPa

5. Controlled Environment Systems Research Facility  Mars is the best candidate for human exploration  Low pressure conditions may be advantageous to Martian habitation  Further investigation is required for the development of an atmospheric composition that allows for reduced pressure plant growth without compromising the plant production yields required for human life support Summary

6. Controlled Environment Systems Research Facility  Chamber design  Data acquisition and control  Temperature and humidity  Pressure  Carbon dioxide and oxygen  Lighting  Nutrient delivery Hypobaric chambers: design and function

7. Controlled Environment Systems Research Facility  Five full canopy plant growth chambers  1.0 x 1.8 x 2.5 m (WHD)  4500 litre volume  Growing area of 1.5 m 2  Highly closed systems with low leakage  Internal surfaces 316 stainless steel  20.5 mm laminate glass roof panels  Viton sealing rings on doors and glass  Fully automated  Capable of maintaining low pressures Hypobaric chamber design

8. Controlled Environment Systems Research Facility Condenser Heater Blower Internal Reservoir DOOR Lighting System Canopy 2.5 m 1.8 m External Hydroponics Reservoir Blower Cooling Coil 1.5 m Vacuum Nitrogen CO 2 Oxygen Gas Sampling

9. Controlled Environment Systems Research Facility Data acquisition and control  Argus Control Systems Inc.  Distributed real-time control  Stand-alone microcontroller (Motorola 68HC811) on each chamber  Proprietary RS 485 communications network  Each hypobaric chamber operates independently  All sensor readings sampled once per second  Experimental data recorded once per minute (higher speeds available)  Operator interface provided through a PC-based system access and management program (Argus for Windows)  PC component is not used for real time control - failure of the PC has no consequence on system control

10. Controlled Environment Systems Research Facility Temperature and humidity  Variable speed blower  Blower speed control coupled to pressure  Chilled water (4°C) and hot water (55°C) heat exchange coils  Cold exchange coil controlled to achieve required VPD setpoint  Hot exchange coil used to reheat cooled air to regulate final temperature setpoint  Two Honeywell 4139 T/RH sensors  Four Argus TN2 temperature sensors (2 soil, 2 heat exchange)  Tipping bucket for evapotranspiration measurement

11. Controlled Environment Systems Research Facility Temperature: Radish Days after closure Temperature (°C)

12. Controlled Environment Systems Research Facility Vapour pressure deficit: Radish Days after closure VPD (mb)

13. Controlled Environment Systems Research Facility Relative humidity: Radish Days after closure %RH

14. Controlled Environment Systems Research Facility Evapotranspiration: Radish 18 DAP Hours H 2 O Accumulation (litres)

15. Controlled Environment Systems Research Facility Pressure  Vacuum pump: Busch Vacuum  Pressure sensors: Pribusin Inc  Control Valve: Swagelok  Control range +/- 0.1 kPa  Pressure control ambient to 0.01 kPa  Systems not designed for pressurization  Leakage rate less than 1% per day

16. Controlled Environment Systems Research Facility 66 kPa 33 kPa Hours kPa System leakage

17. Controlled Environment Systems Research Facility 10 kPa 5 kPa Hours kPa System leakage

18. Controlled Environment Systems Research Facility Pressure: Radish kPa Days after closure

19. Controlled Environment Systems Research Facility Carbon dioxide and oxygen  CO 2 /O 2 analyzer: California Analytical Instruments Inc. Model 200  NDIR CO 2 and paramagnetic O 2 sensors  One analyzer per chamber  CO 2 : 0 – 6000 µmol mol -1 (+/- 15 from set point)  O 2 : 0 -100%

20. Controlled Environment Systems Research Facility Cold trap Hypobaric Chamber CO 2 /O 2 Analyzer CO 2 NC 1 Cold trap NV 2 Pump O2O2 NC 2 N2N2 NC 3 Condensate return NV 1  CO 2 /O 2 sampling system based on repressurization of hypobaric chamber air  Chamber air continuously removed by a vacuum pump (KNF Neuberger Inc)  Air is repressurized in a sampling loop controlled by a non-bleed precision pressure regulator (Parker) and needle valve (HAM-LET)  Pressure gauge (Noshok) used to monitor and manually set the sampling stream to 0.2 psi Pressure regulator/gauge

21. Controlled Environment Systems Research Facility Carbon dioxide: Radish 18 DAP Hours µmol mol -1 mmol accumulated

22. Controlled Environment Systems Research Facility Oxygen: Radish 18 DAP Hours Percent oxygen

23. Controlled Environment Systems Research Facility Lighting  six 1000 watt HPS lamps (P.L. Light Systems) per chamber  Maximum irradiation intensity at highest bench level approximately 1500 μmol m -2 s -1 PAR  Externally mounted lighting canopy cooled with chilled water heat exchanger coupled to a blower  Two LiCor PAR sensors continuously monitor irradiation  lighting schedule automated and under control of the Argus Control System.

24. Controlled Environment Systems Research Facility External Reservoir Internal Reservoir Nutrient A FM Legend: Electrical Conductivity (EC) Temperature (T) Flow Meter (FM) Normally Closed Valve (NC) Tipping Bucket (TB) Gravity Return (GR) Proportional Valve (PV) Nutrient B FM ACID FM BASE FM Chamber interior Pressure compensation GR NC1NC2NC3NC4 TB PV1 EC2T2 EC1T1 Pump pH1pH2 Condenser  NFT design  400 litre temperature controlled external stainless steel reservoir  Circulation pump (International Pump Technology Inc.) provides sufficient pressure for chamber delivery from ambient to 2 kPa  Gravity return of water  Electrical conductivity (2 - Argus Control Systems, Inc)  pH sensors (2 - Honeywell Inc.) currently non-functional – pH is manually adjusted daily  Gravity feed of acid, base, and nutrient solutions Nutrient delivery

25. Controlled Environment Systems Research Facility

26. Days after planting Electrical conductivity (mS) EC: Radish

27. Controlled Environment Systems Research Facility Nutrient delivery  Removable tray system  Pump truck to move crop to harvest lab  Quick-connect couplings for water delivery  Gravity return to external tank

28. Controlled Environment Systems Research Facility Acknowledgements