Thioaptamer Diagnostic System

This Phase I project Summary will be formatted as a series of summary statements, with additional comments. The summary statements are intended to focus on the most significant findings and discoveries – things that the project team knows now, but we didn’t know at the beginning of the project. 1) Direct Contact Between Gases is an ECLS System enabling capability. The Phase 1 project focused on CO2 capture, using direct contact of gases and liquids to facilitate the kinetics of solubility based absorption. At the beginning of the project, we were thinking about the CO2 capture application, but we were not thinking about ECLS system level impacts. In the course of the phase 1 effort, we realized that many fundamental unit processes in biological and chemical systems (absorption, evaporation, transpiration, distillation, condensation) need direct contact between a gas phase system and a liquid phase system. Capillary technology that enables gas absorption into a liquid helps all ECLS processes that involve gas absorption – it also enables evaporation, transpiration, distillation, and condensation. Fluid management capability is more broadly applicable than we had originally thought. 2) CO2 capture using liquid sorbents in microgravity is feasible. The phase I project set out to assess feasibility of the CO2 capture application. Liquid pumping rates are sufficient, high viscosity is tolerable, contact area is sufficient, flow distribution networks are initially large, but there are design paths to reduce system size. It is feasible to use direct gas/liquid contact for CO2 capture, and with the right designs and sufficient development, these systems promise to be smaller, more power efficient, and more reliable that current systems. 3) There are other ways to contact gases and liquids – but thin film capillary techniques are new, exciting, and have amazing potential. As a result of this phase I project, we are able to put thin film contactors in context with other fluid management systems. Once placed in context, the power and significance of thin film contact becomes apparent. Two existing methods of gas/fluid management are membrane contactors, and wet spray reactors. Membrane contactors have nearly perfect liquid containment, but unacceptably slow kinetics. Wet spray contactors have great kinetics, but no gas/liquid containment. In the balance between kinetics and containment, thin film contactors are in the “goldilocks zone” – they have sufficient kinetics and sufficient control. This is new and potentially powerful. 4) ECLS system reliability is the key to exploration missions – the key to reliability is having system attributes that favor reliability Slow moving, gently sweeping, uniform rate, ambient temperature, ambient pressure systems are more likely operate reliability than systems that involve vacuum systems, high temperatures, hazardous chemicals, and transient operating conditions. If mission planners place a priority on system reliability, ECLS system developers should focus on processes that have the attributes of reliability. 5) The processes with favorable reliability attributes tend to be biological. Biological systems tend to be ambient temperature, ambient pressure, free of hazardous chemicals, operate at a steady rate, and have the attributes of reliable systems. If Mission Planners want a reliable ECLS systems, then ECLS system developers should increase the technical maturity of biological systems. Biological wastewater processes can credibly achieve >98% recovery of water from wastewater. Biological algae based systems can credibly achieve >75% oxygen from CO2. 6) The single greatest impact on launch mass of an ECLS system is water. The best way to enable biological water processing is to develop a capillary based method of urine capture that doesn’t use pretreat chemicals. The ISS potty uses a rotary phase separator that needs strong pretreat chemicals to prevent biofouling and clogging caused by precipitate build up. These pre-treat chemicals, by design, are intended to kill all microorganisms. Rotary phase separators and biological wastewater systems are essentially incompatible. The most enabling thing a fluid mechanics expert can to is to capture urine without the use of pretreat chemicals. This is one of the central technical tasks of the Phase II proposal, the project team has already developed and patented capillary methods of capturing urine in a potty environment. Forward work would involve testing the long term effectiveness of frequent rinsing and occasional system dry out, heat sterilization. 7) There is good, promising, forward design and development work – but no fundamental “show stoppers” – to develop a thin film liquid sorbent CO2 capture system. Thin film fluid management starts with several constraints – everything in contact with the air is at the same pressure, and fluids generally move because of a pressure gradient. Thin film fluid flow must rely on capillary gradient, with is a slow and relatively feeble process. The practical limits of fluid movement is just a few centimeters. Phase I identified that a CO2 capture system needs a traditional closed pipe pumping system to deliver liquids through thousands of ports across a broad area in order to have sufficient contact area. Phase I fluid sizing calculations (shown in detail in this report) show that the pumping and manifold system will likely be bigger and weigh more than the capillary surface. Phase I efforts also show that there are lots of design ideas to make this new system smaller and more effective. It is feasible to make a thin film system. 8) The most capable Ionic Liquids are not presently feasible, but other chemically active liquids can be used to make an effective thin film CO2 capture device. Dr. Brennecke and the Notre Dame group were key members of the Phase I team, and they are not on the Phase II proposal team. They did nothing wrong, this group is awesome. Two of Dr. Brennecke’s students developed candidate ILs with properties that best matched NASA’s needs. The candidate IL had amazing capacity (41% by weight) and low regeneration temperatures (significant cyclic performance with regeneration temperatures as low as 60C). But the IL was not stable, after a few tests it produced a strong odor – indicating chemical breakdown. This has several implications: The first is that Phase I feasibility study results indicate that IL based systems with 40% cyclic capacity are not likely. But that doesn’t mean that CO2 capture using liquids isn’t feasible. There are other ionic liquids and commercially available amines that have good stability, low vapor pressure, and capacity in the 10-15% range. These kinds of systems would represent significant improvements, but not transformative ones. The Brennecke group’s top priority is doing fundamental development work on ILs. NASA needs fundamental development work to occur, but not as part of a NIAC feasibility study. Dr. David Klaus at CU has an NSTRF sponsored doctoral student who is studying ILs for NASA ECLS applications. Jordan Holquist is relatively less interested in doing fundamental chemical development and relatively more interested in considering the use of ILs for NASA ECLS applications. Dr. Klaus and Jordan Holquist will lead IL efforts in the NIAC Phase II proposal, because they are a better fit. But look for future proposals with collaborations between JSC, University of Colorado, and Notre Dame in the area of technology development of ionic liquids. Anything with the potential of achieving 40% capacity and regeneration temperatures below the boiling point of water needs to be further developed. 9) The C9 reduced gravity flight showed feasibility – and taught us about flow instability issues. The C9 reduced gravity aircraft test campaign was an incredible experience. The ability to see films develop, cavitation to occur, and systems recover from cavitation was monumentally helpful. But the real benefit of the test campaign was to gain a deeper understanding and appreciation of fluid management – especially fluid management with multiple pumps. There is a difference between knowing the data and having an understanding. C9 results are shown in greater detail later in the report. 10) Capillary fluid management has ECLS system wide implications. We started the Phase I effort thinking about test articles and CO2 capture subsystems. We finished the Phase I effort thinking about a system level ECLS design with thermal management, air revitalization, and water recovery systems. It is exciting to think about things at a system level, and it is invigorating to plan collaborations with researchers that I’ve never collaborated with before.