Browsing by Author "Nakazono, Barry"
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Item CO2 removal system for Manned Mission beyond LEO using deep space radiators and solar heaters(46th International Conference on Environmental Systems, 2016-07-10) Paredes Garcia, Jordi; Nakazono, Barry; Voecks, Gerald; Jones, Jack; Jan, Darrell; Hogan, JohnThe current spacecraft technology to remove CO2 generated in manned missions uses mostly zeolite filters, which break down relatively easy; this has caused multiple problems over the last decades. The current solution has been to replace the defective components sending replacements form Earth, but this is only viable for missions close to Earth, e.g. ISS. Once humans require longer duration missions without Earth access, highly reliable CO2 capture needs to be implemented. There is no current technology that captures CO2 levels for long duration missions. Gaseous CO2 can be captured cryogenically, and the different solidification temperatures between water, carbon dioxide, nitrogen and oxygen become the key parameters of this system. It is important to note that human generated organic contaminants freeze at higher temperature than CO2. These contaminants will be captured prior to CO2 solidification. The medical community has determined that 5000 ppm in volume of CO2 is the maximum allowed concentration within an 8 hour working period for humans. Generally levels are required to be below 600 ppm. Every astronaut generates around 1Kg CO2 / day which needs to be removed from the cabin air continuously. This system consists of staged Two-Phase Heat Exchangers (NTR: 49561), to selectively solidify water, trace contaminants and carbon dioxide. Deep space radiators provide the required cooling power, and solar heaters deliver the necessary heat to evaporate all the solidified species, during the system cycles. This is why, for missions beyond LEO, that no power is required. The energy requirements are passively collected from space. (Only a small amount of power is needed for control valves and electronics).Item Thermal Design and Validation of the Mars 2020 Gas Dust Removal Tool (gDRT)(49th International Conference on Environmental Systems, 2019-07-07) Farias, Edgardo; Jens, Elizabeth; Nakazono, Barry; Kempenaar, Jason; Novak, KeithAs part of the science goals for the planned Mars 2020 mission, two instruments, PIXL and SHERLOC, intend to study the fine scale make up rocks, minerals, organic molecules, and potential biosignatures. These two instruments are planned to be used on smooth surfaces that are free of dust and other particles. Such surfaces are prepared by using a drill with an abrading bit; residual dust and particles are then removed using a compressed gas system—the Gas Dust Removal Tool (gDRT). The gDRT stores nitrogen gas in a supply tank. When ready for use the gDRT transfers some gas to a plenum tank via redundant supply valves. A run valve then releases the plenum tank gas through a nozzle onto the abraded surface. Early in the design process a risk was identified that the valves could potentially leak below the manufacture’s rated temperature of -20C. To mitigate this risk a parallel path was implemented: 1) try to qualify the valves to -135C and quantify leak rates at low temperature, and 2) implement the capability of survival heating in case qualification efforts are unsuccessful. Thermal design for the survival heating emphasized the need to minimize energy. The valve assembly is mounted to the gDRT baseplate via G10 isolators, and is fully enclosed in an SLI shield that provides a dual function of blocking forced convection and creating a CO2 gas gap for insulation. Two patch heaters on the valve assembly are thermostatically controlled to a setpoint of -65C to -73C. This setpoint was selected as a tradeoff between survival energy and leaking risk. Thermal testing of gDRT is scheduled for January 2019. This testing will validate the thermal design and enable thermal model correlation in order to provide more accurate survival energy predictions.