In 2001, NASA engineer Michael Ewert developed and patented a unique solar-powered vapor-compression refrigeration system that operates without batteries or external power of any kind. The system, which is powered by a photovoltaic panel and custom-designed electronic controls, could be used not only for long-duration space missions but also to build more environmentally friendly refrigeration systems here on Earth. Currently, Ewert is the Deputy Project Manager for NASA’s Exploration Life Support Project, which is developing new technologies needed to sustain human life on long-duration space exploration missions.
NASA Tech Briefs: What is the Exploration Life Support Project, and what does NASA hope to accomplish with it?
Michael Ewert: Exploration Life Support – or ELS – is one of about two-dozen technology development projects that NASA has to develop the new technologies needed for future human exploration missions. For ELS in particular, our goal is to create the technology that will help keep the crews alive during long duration missions without relying so much on resupply from Earth. On space shuttle the missions are fairly short and on the International Space Station they have the ability to resupply fairly frequently, but for going to Mars or other long missions, that won’t be the case.
NTB: One of the Exploration Life Support Project’s stated objectives is to develop new technologies that are efficient with respect to resource requirements such as mass, power, heat reaction, volume, crew time, consumables, etc. Can you give us some examples of the types of projects the group is working on in these areas?
Ewert: One example is that the space shuttle uses lithium hydroxide canisters to extract carbon dioxide from the atmosphere after the crew breathes it out. We’re developing an amine swing-bed technology that can be regenerated by exposing the bed to the vacuum of space intermittently. That way we won’t have to throw away any lithium hydroxide canisters.
Space station also has some regenerable processors for both air and water, but they take quite a bit of power, so our Exploration Life Support Project is working on several options for both air and water to help reduce the power consumption for an enclosed life support system.
NTB: Two of the primary areas of research your group has been involved with are water recovery and waste management. These are obviously crucial to the future of long duration manned spaceflight, or the establishment of a lunar outpost. What kind of progress has been made to date in these areas?
Ewert: We have extensively tested three wastewater distillation technologies recently and are in the process of determining which performed the best for the kinds of wastewater streams we expect to see in future missions. Part of the research is figuring out how the process will handle the wastewater streams with things like toothpaste or shaving cream that does not go into the wastewater system currently. We learned that the toothpaste being used was just not being tolerated well, so we had to research and find another toothpaste to use that can be processed in the processor.
Beyond that we’re developing or evaluating several technologies for water recovery from the brine that is left over after the distillation process. Even after the primary processor distills the water, there’s still a concentrated salt solution that has a fair amount of water left in it, so we’re trying to recover that last little bit of water from the brine.
For solid waste we’ve evaluated a variety of technologies working with our colleagues at Ames Research Center and with several SBIR companies. One exciting one is a plastic melt compactor, which heats and compresses mixed trash, melts the plastic in the trash, and extracts the water at the same time, so you’re left with a stable plastic disk, kind of like a hockey puck, and the volume of the original trash is reduced by about a factor of ten. It also helps deal with the smell that could be created by microbes in the trash.
NTB: Could the water recovery technology your group is developing, which involves converting urine and other types of wastewater into clean, potable drinking water, someday be applied to places here on Earth where clean drinking water is in short supply?
Ewert: Well, the applications and conditions are very different in space and in remote areas on Earth, but the principles are the same, so yes, there are many parts of the work that we do that could help out on Earth as well. In fact, several members of our team have been involved with efforts outside of NASA, such as Engineers Without Borders.
NTB: Do you envision any other potential commercial applications for the technology your group is developing?
Ewert: I’m sure there are many. One that comes to mind is what we call a lightweight contingency water treatment system that can take seawater, or even urine, and make it into potable water.
NTB: What impact do you think President Obama’s proposed cancellation of the Constellation program will have on the Exploration Life Support Project?
Ewert: Well, I don’t want to speculate too much on that, but there’s still a big emphasis on research and development within NASA, and specifically in closed-loop life support, so we believe we’ll have lots of good work to do, and that we’re already doing. No matter how we explore space in the future, if we do it with humans their basic life support needs will be the same, so we have that knowledge and we plan to be ready to support those kinds of missions.
NTB: Before becoming the Exploration Life Support Group’s Deputy Project Manager in 2007, you led their Systems Modeling and Analysis Group for a number of years. Tell us about that position and some of the tools you used to model proposed life support system designs.
Ewert: That was an interesting experience. We generally tried to help guide the technology projects by doing systems analysis and searching for the best technologies to develop. We developed one spreadsheet tool called the Advanced Life Support Sizing Analysis Tool, or ALSSAT, which allowed us to rapidly evaluate many different technology options for different proposed mission scenarios. It actually does mass balances and calculates mass, power, and volume of the life support system hardware based on mission requirements.
We also used industry standard software to perform more detailed dynamic analysis. Another thing we developed was a document called the Baseline Values and Assumptions Document that has been widely used by researchers both inside and outside of NASA. It kind of helps fill in the blanks for some of the conditions and requirements that future technologies will see so that the technology developers know those parameters before the actual programs have developed their detailed requirements.
NTB: About 10 years ago you invented a solar-powered vapor compression refrigerator system that operates without batteries or external power. Tell us about that invention and how it works.
Ewert: Well, I was working on thermal technology development at the time, and we actually integrated 3 types of cooling system with solar photovoltaic panels. They were a thermoelectric cooler, a Stirling cooler, and a vapor compression cooler. The vapor compression unit turned out to have the best commercialization potential since that cooling technology is already widely used on Earth. The novel thing that a colleague named David Bergeron and I did was to integrate the vapor compression cooling system with the solar panels and an ice thermal storage system using a new algorithm programmed into a microcontroller that allowed the compressor to run at variable speeds, depending on the amount of sunshine available, and to store the cold, if you will, as an ice block for periods of time when the sun is not shining.
NTB: You’re also involved with a company that has licensed the technology from NASA and is commercializing it, correct? How’s that going?
Ewert: NASA has spoken with several companies interested in the technology and one license agreement has already been signed. That company is working first on a battery-free vaccine solar refrigerator. There are other applications as well, for self-sufficient refrigerated shipping containers, for example, or maybe vending machines that are off-grid, or ice makers, that could come out of this, so I think the commercialization is going well.
NTB: What would you say have been some of the biggest technical challenges to achieving more widespread commercialization and use of solar energy?
Ewert: Well, cost and the intermittency of the solar resource are always challenges with solar energy, so I believe that smart integration of the technology is the key. For example, if you can make use of the existing insulated cabinet of a refrigerator and just improve that, as we did with the solar refrigerator, and run an existing compressor in a way that maximizes the capture of solar energy, and look at the system as a whole, then I think you have the best chance of a successful product.
Another place I see this happening is with building-integrated solar energy systems. I think a renewable energy future is coming, and I think NASA is kind of helping make that possible.
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