Reducing the allowable concentration of carbon dioxide (CO2) in spacecraft is a critical need for NASA. The system now used on the International Space Station (ISS) is the carbon dioxide removal assembly (CDRA). While it has performed well on the ISS, managers have concluded that using the device to reach the new ppCO2 limit of 2.0 mm Hg is not practical and a new method is needed.
In this project, Reaction Systems, Inc. and the University of Colorado will develop a new, membrane-based system to maintain ppCO2 at no higher than 2.0 mm Hg. The system utilizes the recent advances made in supported liquid membranes (SLMs) to achieve the high CO2 permeance and selectivity needed to make this approach practical. Performance data obtained with a Reaction Systems’ SLM was used to produce a conceptual system design that indicates an SLM system can maintain CO2 at 2.0 mm Hg and still meet size and power limits. A membrane system operates under steady-state conditions, and therefore pumps and heaters can be sized to operate at peak efficiencies, which maximizes lifetimes and minimize power requirements.
Although the conceptual design of the SLM-based system proposed here is very promising, some of the data used to generate the design were obtained under conditions somewhat different from those that would be encountered in an application. Thus, the objectives of this Phase I STTR project are to acquire performance data for these components under representative conditions and then perform a thorough system optimization study using state-of-the-art software to identify the most efficient operating conditions for all components.
Reaction Systems has been developing SLMs for CO2 control for over seven years and our partner in this project, Professor James Nabity, in the Snead Aerospace Engineering Sciences Department at the University of Colorado in Boulder, has nearly 15 years of experience developing ECLSS technologies for space habitats and spacesuits.
The immediate application of this technology is the use of a steady state system to control of CO2 in a spacecraft cabin to reach the ppCO2 limit of 2.0 mm Hg. A system that operates under steady state conditions allows all components to be sized to operate under peak efficiency conditions and eliminates the need to store and compress CO2 as it can be fed continuously into the O2 recovery system. This SLM technology could also be used in a simple, reliable system to control CO2 in a spacesuit.
This technology could also find use in capturing CO2, a known greenhouse gas, from power plants. Atmospheric CO2 has increased from 280 ppm to over 400 ppm over the last 60 years and there is evidence that the CO2 atmospheric concentration is now affecting the world’s climate. NOAA reports that the top 10 years of average surface temperatures have occurred in the last 12 years and Scientific American reports that 2016 was the hottest year on record and 2017 was the third hottest.