From Earth orbit to the Moon and Mars, explore the world of human spaceflight with NASA each week on the official podcast of the Johnson Space Center in Houston, Texas. Listen to in-depth conversations with the astronauts, scientists and engineers who make it possible.
On Episode 231, Kevin Takada discusses advancements and upcoming technology demonstrations for the next generation oxygen generation system for human spaceflight. This episode was recorded on January 21, 2022.
Transcript
Gary Jordan (Host): Houston, we have a podcast! Welcome to the official podcast of the NASA Johnson Space Center, Episode 231, “Advanced Oxygen Generation.” I’m Gary Jordan, and I’ll be your host today. On this podcast, we bring in the experts, scientists, engineers, astronauts, all to let you know what’s going on in the world of human spaceflight. When it comes to living and working in space, one of the critical systems to help make that happen is a reliable way to generate breathable air. On the space station, the Oxygen Generation System, or Oxygen Generation Assembly called the OGA, has been doing a fantastic job for 14 years. Running a system like this for that long offers fantastic insight into how to make it better, and better is what’s needed to go farther. Today we’re going to be discussing more about the Oxygen Generation System and the next generation system, or an Advanced Oxygen Generation Assembly, AOGA, that would be used for Artemis missions to the Moon and beyond, and tested in low-Earth orbit, of course. We’re going to be bringing in Kevin Takada, systems engineer for the space station’s Oxygen Generation Assembly at NASA’s Marshall Space Flight Center in Alabama. He’s the right guy to talk to about this topic, with a bachelor’s degree in electrical engineering and a master’s in engineering management, and of course 20 years of experience working on life support systems. Kevin is in the weeds on analyzing the Oxygen Generation System and coming up with proposed upgrades. There are a number of them, and we go through some of those, including an effort that Kevin is leading to test one of these upgrades on the International Space Station very soon, specifically, a new hydrogen sensor. Don’t worry, Kevin describes why this is important. So take a deep breath because we’re about to dive deep into regenerative life support. Enjoy.
[Music]
Host: Kevin Takada, thanks so much for coming on Houston We Have A Podcast today.
Kevin Takada: Thank you. Thanks for inviting me onto your show.
Host: What a cool topic. We have explained a little bit about just the overall Environmental Control and Life Support Systems, but I’m excited to go this deep, especially with you. I think you have a very interesting background. As a systems engineer, I think the way I would think about it is a systems engineer is very specific to looking at one particular part that sort of contributes to the grander system that is the International Space Station. I hope I’m describing that well, but instead of me doing it, Kevin, why don’t we just first go to you to describe what is a system engineer? And what is your job?
Kevin Takada: Sure, so I’m a systems engineer for the ISS Oxygen Generation Assembly, or the OGA. So I’m part of the team that monitors the OGA operation. The OGA operates 24 hours a day, seven days a week, so it’s continuously sending down data, and we’re continuously looking at the data. We’re analyzing that data in real time, looking at historical data, looking for trending to see if there’s any type of impending failure. Overall, the OGA has been very reliable, but a couple times a year it does throw us a couple curveballs, so sometimes on a Sunday night at 11 o’clock or midnight we have a meeting to discuss what’s going on with the OGA, what are our plans to recover from a failure, and we’ve got the pressure on because the clock is ticking, we got to get the OGA back up, up and operational. And if there is a problem, we’ve got to do troubleshooting, we’ve got to write crew procedures and help the crew figure out what’s wrong with the OGA and get it back up and running. On the flip side, I’m responsible for operating the OGA that’s here on the ground. So we have a duplicate oxygen generator here in our lab, and so we use that to duplicate any type of failures we see, test out new hardware, test out new ways of operating the system, and our OGA testbed here on the ground operates 24/7 as well. And then finally, I do lead some research on emerging technologies for oxygen generation. You have to remember the OGA was designed 20 years ago, so the industry has moved on and done things a little better, so trying to keep up with the latest technology innovations in oxygen generation.
Host: Very critical role, Kevin, just overall. I mean, every part of that, that you described, it’s not, this system is not one that you can really forget about, right? I mean, to your point, if something’s wrong with the system, you guys have to be on top of it because it is critical. The oxygen generation is literally providing life support. It is, it is keeping our astronauts safe and healthy aboard the station. So, so it’s that critical mix. It’s very interesting. I wasn’t expecting that when you were, when you were about to describe what a system engineer does. It sounds a very good mix of operational, and then also the actual engineering aspect. You’re always looking for the latest technologies and looking to progress.
Kevin Takada: Exactly. Exactly, yes.
Host: Very good. So let’s talk about, you know, we talk about this being a critical system to keeping the astronauts, you know, alive, safe, healthy on board the station. It’s essential. It’s what makes human spaceflight possible, but it’s part of a larger system, right? So you got oxygen generation, and I know there are some parts of this system, this assembly, that feeds into others. So can you give us an overall perspective of the regenerative life support system on board the International Space Station, and then where this assembly, the Oxygen Generation Assembly fits in?
Kevin Takada: OK, yeah. So the regenerative life support system, basically, recycles a lot of your waste products that get generated by the astronauts, so mainly it’s wastewater and carbon dioxide. Typically, you think you’d want to throw those things away, but if you can recycle those you can generate potable water and oxygen. So for example, a key part of the wastewater is urine, so we collect all of the urine that’s generated aboard space station, and we recycle all of that. So if you take the urine, you process that through our Urine Processor Assembly, we can reclaim about 87% of the water that’s in the urine, make that into potable water for drinking or for generating oxygen. And then if you look at the carbon dioxide, think of that as a waste product, but if you collect that and react that with hydrogen that’s coming from our OGA, then you can actually create water using a process called the Sabatier process.
Host: So it’s a partially closed loop, then it sounds like.
Kevin Takada: Right, yes.
Host: What you’re trying to do is you limit the waste products, limit the products you got to, you know, necessarily throw overboard. You’re recycling, you’re maximizing the efficiency of keeping it as closed a loop as possible.
Kevin Takada: Correct. It’s not completely a closed loop, but we’re trying to get there.
Host: Right.
Kevin Takada: Correct.
Host: OK, OK. Now I know, you know, when it comes to the environment of the space station, we’re talking oxygen generation, and we’ll get into electrolysis and just how that actually works, but let’s — back up to the environment of the space station itself, because it’s not just oxygen, right? It is a mixed environment with nitrogen, so how does the oxygen generation fold into supplying the space station with nitrogen and a mix of air that we can typically see here on Earth?
Kevin Takada: Sure. So we want to keep the ISS cabin atmosphere about what it is like here on Earth, so that’s a pressure of about 14.7 psia (pounds per square inch absolute), and an oxygen concentration somewhere around 21% oxygen. That’s a really comfortable environment for the crew. So each crew member requires about two pounds per day of oxygen. That’s how much they breathe in and consume per day. So the oxygen generator, we need to replenish that oxygen that gets consumed and provide that to the ISS cabin, to replenish that oxygen that gets consumed.
Host: OK, and so that – is a, that’s part of the regenerative process, and I suppose the nitrogen tanks, as far as I’m aware, it’s not, you’re not generating nitrogen, they are being shipped up on cargo vehicles and in tanks and then just supplied to the space station that way, and that’s and I guess they’re mixed in two separate, they’re mixed in separate areas but ultimately it all mixes together in the station cabin. Is that how that works?
Kevin Takada: That’s correct. Right.
Host: OK. Very good. Let’s get into oxygen generation then. This particular system, this is your, this is your expertise. What — let’s start big picture. What exactly is the Oxygen Generation Assembly?
Kevin Takada: OK, so the OGA takes in potable water from our Water Processor Assembly, and it electrolyzes that water to generate pure oxygen and pure hydrogen. And you may be familiar with this process. In some chemistry lab experiments you can fill a beaker full of water, flow some electrical current through that, and you can generate hydrogen and oxygen that way. We do it in a similar process as well, using something called a cell stack, which is a series of 28 cells, and each cell is a, you can think of as a compartment which has a very thin membrane in the middle of it, and hydrogen gets generated on one side of the membrane, and oxygen gets generated on the other side of that membrane. And the oxygen that gets generated gets sent out directly to the cabin, and then the hydrogen that gets generated either we dump that overboard, or if our Sabatier system is in place we send that over to our Sabatier system to react that with CO2 to generate more water.
Host: So the membrane serves as a way to separate those two things, the idea being, that’s the goal of the electrolysis process is you don’t want hydrogen intermixed with oxygen. It helps with the separation.
Kevin Takada: Exactly.
Host: Is that sort of the purpose? OK.
Kevin Takada: Exactly. It helps with the separation, and it also is integral to the actual electrolysis process.
Host: OK, where you’re actually sending the electrical current. I understand.
Kevin Takada: That’s correct, yes.
Host: Now, it’s not the only way of generating oxygen on station, right? There’s also — we have our Russian partners who have their own system.
Kevin Takada: That’s correct, yes. So they have an oxygen generator as well. It operates somewhat similar to ours. They typically can support three crew members with their oxygen generator, so our Mission Control works with our Russian counterparts to balance the two systems. Depending on how many crew members are on board, we have to generate more oxygen or if crew members leave then we can dial down our oxygen production, so there’s a coordination between the two systems.
Host: OK. Good, good. Yeah, so you’re not, you’re not introducing too much air, you’re always maintaining the, the mix that you ultimately want.
Kevin Takada: Correct.
Host: OK, I’m definitely understanding. I want to go back to the hydrogen for a second, because I think this is going to feed, this sort of background is going to feed in nicely to some of the stuff you’re working on for next generation. The hydrogen sensors that are on board the Oxygen Generation System, there are, what, what exactly do they do and how and how does that work? Actually, you know what? Before we get there, let’s talk about what exactly they’re doing and why it’s important to have sensors that, that detect hydrogen in the presence of, on the oxygen side of the membrane.
Kevin Takada: Sure. So before we send the oxygen out into the cabin, we analyze the oxygen content. It should be pure 100% oxygen with a little bit of humidity mixed in, but we don’t want any hydrogen in that oxygen because that would be a flammable, combustible mixture, which would be dangerous. So our hydrogen sensors are analyzing that oxygen, and if it detects really any amount of hydrogen we want to shut down the system because something’s wrong, but we have a setpoint of about 1% hydrogen. If there’s 1% or greater detected of hydrogen, we immediately shut down the system; the software automatically shuts down the OGA. And so, what you need to remember is if there’s 4% or greater of hydrogen, that’s where you have a flammable mixture, and the higher your concentration the more dangerous that is, so we want to stay well below the 4% and even below the 1%. So as long as it’s not detecting any hydrogen, we go ahead and send out, all that oxygen out into the cabin.
Host: Understood. It’s a — you have that that margin there to protect the crew. Now when it, when it shuts down, right? That’s like we were saying in the very beginning of this conversation, this is a very critical system, so it’s not something that can be, I’m assuming, right, it can’t be shut down for a long time, so what are the steps that you and your team are working through in such an event, which I don’t think has happened, by the way, I don’t think an event has occurred, but what are the steps?
Kevin Takada: Yeah, so we’ve had to shut down the OGA at various times to do maintenance.
Host: Oh OK.
Kevin Takada: We do —
Host: Maintenance
Kevin Takada: — you know, change out our hydrogen sensors, about every seven months. We do have occasional failures that we have to have the crew go in and swap out equipment. So we’re down sometimes for a period of a day or two or three. We don’t like to be down, but sometimes we are, so when we know that we’re going to be down we ask our Russian counterparts to be sure that their oxygen system is working. There’s also stored oxygen on board, and there’s also stored oxygen that’s launched during every launch, bring up stored oxygen that can be released into the cabin. So, there are some backups and contingencies that help us out.
Host: Very, very important. So the system itself, you mentioned in the very beginning that it is, you know, I think you — the number you had mentioned was it was designed 20 years ago, so things have certainly progressed. Looking back at the history of the OGA itself, and just what it has accomplished, what has it shown over, because that’s a lot of years of operation, looking back at the OGA, that and some of the details there that help us to inform the next part of our topic, which is, you know, what we’re going to improve?
Kevin Takada: Sure. So, overall, the, the OGA has been quite reliable. It’s generated over 23,000 pounds of oxygen for the crew to breathe, but we have had some, some issues that we’ve worked through. So early on, back in the early ’90s, we did do a lot of development work, just to figure out what works, what configuration is good, what configuration is bad, how did we want to design the system? And then in the early 2000s, we actually designed the system and built the hardware, and then tested it out extensively on the ground. And then in 2006 we launched the OGA on a space shuttle mission, and installed it on the space station and then we had a brief checkout period. And then around 2007, that’s when it actually became operational, and we began operating it on a regular basis, and it’s been operating 24/7, essentially, since then. So currently, we’re managing a couple issues with OGA. We can still do that, you know, it’s still operational, but we’re keeping close tabs on some issues. Right now what we’re dealing with is, we have a little bit of a low water pressure going into the cell stack. It’s a little bit lower than we like to have, but we’re still able to operate the system, so we’re looking at that. We actually are flying down a failed unit that failed last year that had a similar type of issue, so we’ll get some more insight once we get that in our hands and understand exactly what’s going on there. We have currently also an issue with our nitrogen purge system. It seems to have developed a small leak. We can live with it, but eventually we’re going to want to change it out if it gets any worse. And luckily, we’ve got a spare on board to swap that out if and when we decide to do that. We’ve had some past issues with some of our hydrogen sensors, which I think we’ll get into later. And then we’ve had some issues with some sensors and valves and so forth that we’ve had to work around and to continue to operate. So, overall, it’s very reliable, but we’ve had some issues that we need to manage.
Host: You know, and just to that point, you know, it’s been operating for 14 years, that’s certainly a long time. All these issues, certainly the idea being that you have your eye on them, but that, you know, these are manageable. You’re looking at solutions, and that’s what I want to get into next is this idea of the Oxygen Generation System, running for that long, it has to provide you and your team such a good insight into what it takes to run a life support system for a long period of time, which is the ultimate goal, right? And if we’re thinking about Moon, Mars and beyond, you have to have a reliable system, so that’s where this idea of an Advanced Oxygen Generation System comes in, and I know you and your team are working on that. And I think a lot of the ideas behind what a concept of an advanced system would look like is addressing some of those concerns and increasing reliability. So, so can you give us an understanding of what you’re looking at to make, you know, that you and your team are proposing that would go into an advanced, more reliable system?
Kevin Takada: OK, so yeah. So as you mentioned, we’re looking at taking the existing OGA design and making that more reliable and more maintainable. So, if you’re going to use this for a deep space mission, that’s a three-year mission, where help is very far away, the crew is going to have to get much more involved in the maintenance and repair of the system. So currently, the crew, when there’s an issue they swap out these black boxes — we call them orbital replacement units. There’s a whole bunch of components inside of them. They don’t dig inside there to try to fix the exact component that’s failed, so they swap out these orbital replacement units, send it back to the ground, we repair it and ship it back up. But in the future they’re going to have to dig deep, get down into the nuts and bolts, figure out exactly which valve or sensor or wire has failed, and go in there and do that repair. So we’re trying to make it more maintainable and easier for the crew to get into. So, we’re redesigning some of our enclosures that go around the cell stack so that the crew can go in there and do the maintenance where they don’t do that right now. And then in addition, some of our components, like I mentioned, maybe we can make those more reliable, especially the cell stack. Looking back on some of the failed cell stacks, taking those apart, we see where the membrane is not quite in the condition we want it to be, it gets a little thin over the years. So we’ve got some ideas on how to use a more reliable membrane that’ll last hopefully longer than about the five-year lifetime that we’re seeing with these cell stacks. We want to increase that even longer. And some of the valves and sensors, we think we can make those more reliable, to last even longer than what we’ve been seeing.
Host: You know, the reliability, the, the idea that something can last longer, and then what I found interesting was, I didn’t even think about it, but it makes a lot of sense: if you have a regular — in order to maintain a system, if you have regular shipments to and from, you know, literally bringing sensors back down to the ground and shipping them back up, and that’s part of regular maintenance, the idea to make, you know, cancel that out altogether and have the maintenance be done on board, because the idea being on a on a trip to Mars you don’t have that luxury, you can’t just ship new parts anytime you want, you got to have the parts there or you got to be able to go in and change out the parts. And so is the idea to implement this, or parts of these on the International Space Station first? And I think this will lead into the next part of our conversation, but I think that’s the idea, right? You’re not going to just put it on a Mars or Moon mission, you want to you want to try it out on the space station first.
Kevin Takada: Exactly. So the space station has been a great testbed for us for the OGA and all of the other systems. So eventually we want to implement an advanced OGA on the space station and run that for a period of at least three years to make sure that this advanced OGA is reliable and works like it should, so that’s the plan, yes.
Host: OK, perfect. Now, now that’s where I want to get in, because we’re going to talk about actually that test, and I think that’s really exciting. But I think a big part of that test, and you alluded to it a little bit earlier in our discussion, is the hydrogen sensors, and these are very important, right, they detect the quality of the oxygen that’s being put out so the astronauts can breathe it and make sure that it is truly safe air. And so, you mentioned that, you said we would address the issues with the hydrogen sensors later, and so let’s talk about that now. What are the current issues with the hydrogen sensor? That will help us to lead into a discussion of what we’re about to do to make them better here in the near future.
Kevin Takada: Alright. So the OGA has some existing hydrogen sensors in them, overall. They’ve worked really well, but there’s some issues we want to address if we want to go to a deep space mission. So the existing sensors, they have a very limited life of seven months, and after that time we have to have the crew go in, take it out, put a new one in, send it back to the ground, have it recalibrated and then sent back up. So we have a pipeline of eight or nine sensors that are in continual rotation, so that’s a logistics thing that we have to handle, a continuous pipeline of sensors from the space station to the ground. In addition, these sensors require special tools, and the crew has to go in and do periodic purging of these sensors to keep them in good operational shape. And we have seen a percentage of these sensors fail on orbit, unexpectedly, where they work just fine on the ground and then we stick them in and they just go off scale, and we have to disable some of these sensors. So, that’s an interesting aspect there where they were fine on the ground but when we install them on orbit, they sometimes can fail, but we are able to detect that and recover from that, but that’s an issue we have to manage. And then also they’re sensitive to nitrogen, and that’s important because for OGA we do a nitrogen purge every shutdown and startup, to be in a safe configuration to purge out any hydrogen that may have been in there, so that’s an issue.
Host: Any nitrogen that may have been in there? Is that what you mean?
Kevin Takada: Any hydrogen, yes.
Host: Oh, any hydrogen? OK.
Kevin Takada: Yes.
Host: Got it. The nitrogen pushes the hydrogen out. OK. I understand.
Kevin Takada: Yeah. And then finally, these sensors are custom-manufactured. The fleet that we have now was custom-manufactured 15 or 20 years ago, and so we only have a limited number of them, and it’s a question if we could manufacture more of these in the future.
Host: OK. So this leads perfectly into next generation. We talked about some of the issues here of the sensors, and the exciting thing is some of the things that you and your team have been working on, is thinking about that next generation, what it looks like, and you came up with a cool system called H2ST. Now, what is this system that is going to be launching here very soon?
Kevin Takada: OK. So H2ST stands for the Hydrogen Sensor Technology demonstration, and basically, it’s a little suitcase-size box that contains some replacement hydrogen sensors. These are commercially available sensors, that what we’ll do is we’ll install that on the front of our OGA rack. We’ll connect it up to the oxygen outlet port of the OGA, and so the product oxygen will actually flow through our system first. We’ll be able to analyze for any hydrogen and then that oxygen will be sent out to the cabin. So we have some valving in there to do some periodic calibrations, and we also have a flow meter in there to make sure we’re getting the proper flow, and so that’s what we’ll be doing with the H2ST. We’ll be installing that on our OGA for a period of three years. And the H2ST also will be able to send down all of the data real time so we’ll be able to continuously monitor on the ground the performance of our tech demo on orbit.
Host: OK; is the, is the experiment goals to have those hydrogen sensors work continuously for those three years, or do you have replacement parts, just, you know, just like you do the recalibration work from the ground? Is it going to be all done, is it going to be all done on orbit? What are some of the investigation, you know, procedures that you’re going to be running?
Kevin Takada: We’re planning for the sensors to be operational for the full three years.
Host: Cool.
Kevin Takada: I’m not expecting any failures, but we want to characterize the performance of these sensors over those three years. How much do the sensors drift over time? How much do they lose of their accuracy? So we have an idea on the ground of how the sensors work, but we want to get them on-orbit in the microgravity environment, in the environment of the space station that may be different from what’s here on the ground. One of the key aspects is, since we’re a closed loop system, is that there are some trace contaminants that build up over time, and so those trace contaminants may affect the H2ST. We know that it has affected other systems in the past, so we want to see if our system is susceptible to these trace contaminants. And then also we’re going to have the crew, every 90 days, go in there and flow some calibration gas, which is 1% hydrogen in air, past these sensors and measure the response, because hopefully when it’s connected up to the OGA, it’ll never see any hydrogen and will always be reporting zero hydrogen. So, we want the crew to go in occasionally and do some calibration checks.
Host: OK. The way that the experiment is designed, you know, it sounds, it’s an interesting experiment, right, because it’s a mix, it sounds like, and you can correct me if I’m wrong, it sounds like it’s a mix of an experiment. You’re trying out a technology demonstration, seeing if this is something you want to, you know, verifying what you think is, could be used operationally, but it also sounds very operational, too. Is there some hybrid of using these sensors with the old sensors? How exactly, how exactly does it work operationally on the station?
Kevin Takada: Right. So we’ll be operating the H2ST in parallel with the internal hydrogen sensors that are inside the OGA. So our H2ST won’t do any control of the OGA, but the internal hydrogen sensors will. If they detect any hydrogen they will automatically shut down the OGA, but we will, all we’ll be doing is gathering data and analyzing that data on the ground.
Host: OK. When it comes to what makes a good hydrogen sensor, based on what you learned from operating the hydrogen, you know, the Oxygen Generation System and using those sensors over time, what are some of the new requirements, the new goals, that you’re — that went into the design of seeking, you know, and ultimately using this particular sensor?
Kevin Takada: OK. So the goals of the new sensor are they have to be accurate in detecting hydrogen and oxygen. They have to have a fast response time, because we want to be able to detect any hydrogen and shut down the system quickly before that hydrogen gets released out into the cabin. We want to have the ability to recalibrate these sensors by the crew and not have the need to send them back down to the ground for recalibration. We want to not have any special tools, we don’t want to have the crew to go in and do any special procedures on these sensors, And we do want these to be commercially available so they’re low cost and easily replaceable. And then finally, probably the most important is that these sensors need to operate in a pure oxygen environment, and in a high relative humidity environment — lots of humidity is in that product oxygen, close to 100%. So you could be condensing some moisture, so that’s a concern that we have to be aware of.
Host: So a lot, a lot of checkboxes there. It’s got to be, you know, you know what you’re looking for, so when you went out, how’d you, how’d you narrow it down?
Kevin Takada: OK. So a couple years ago, we did a market survey of all the hydrogen sensors out there. There’s a lot of vendors out there, 50 or more different vendors out there that are selling hydrogen sensors. So we down-selected to about seven commercial sensors that we thought would meet our needs, that were in the hydrogen range that we wanted, that had the proper flow rate and would be able to accept the humidity levels that we have. And so, we purchased these sensors and did an initial screening test, and surprisingly, six out of the seven immediately failed, and we had to rule those out. We were left with one sensor that seemed to operate very well. And so, we decided to move forward with that one sensor, and we went ahead and did two years of extensive long-term testing with that one sensor. We put it in our OGA that we have here on the ground and monitored it for a period of two years. It worked very well. And we also did some bench testing with the sensor, you know, flowed various percentages of hydrogen and oxygen through the sensors, various humidity levels, various temperatures and so forth, and put it through its paces, and it passed those tests, and so after that point, we decided to move forward with the H2ST tech demo and fly these sensors.
Host: That certainly has to be a challenge. Whenever you find something that you like, in order to test it before it can actually fly, sounds like that’s not an insignificant amount of time that you have to run in ground testing before you say it’s ready to go ahead and test even further in space. So that’s, you know, that’s certainly a long time. What was the day-to-day like in monitoring that whenever you, you know, had to had to, had to go through the ground testing?
Kevin Takada: Sure. So we laid out a test plan, and first installed it in OGA and monitored its performance daily and did some periodic checks every couple of weeks, and then we also took that out and did some bench testing on it as well. We initially started looking for alternate hydrogen sensors, I would say, at least ten years ago, and then we got serious about looking for alternate hydrogen sensors, I’d say, about four or five years ago, and so it’s been a long process.
Host: Oh, I get — yeah, I bet. Absolutely. But you know, and here we are. This is going to be, you guys are targeting to go up to the space station and test this out. Now, and by this, I mean the sensor technology, and it’s going to be done in low-Earth orbit. That seems like a very, very good place to test things. From your perspective of just working with the Oxygen Generation System for, for much if not all of your career, right, it’s been running continuously for 14 years, you’ve been, you’ve been involved in the operation, and you’re thinking about advanced technologies pushing forward; why, from your perspective, is low-Earth orbit such a good place to do this kind of work, technology demonstration?
Kevin Takada: Well, it’s very good because it’s close by, for us relatively. We can return our experiment after we’ve flown it, and we can get real time data from it, and it’s the microgravity environment that we want, and it’s a very realistic environment, obviously, for us to test in, and it’s better than any ground test that we could do.
Host: No, without question. Now, you mentioned when you were considering — you know, you were, you were listing some of the issues that you’re tracking with the Oxygen Generation System after it running, that you would like to improve, and you listed a couple of improvements that you’re already thinking about for an Advanced Oxygen Generation System. The sensors just being, you know, I guess one of the first steps in trying out new things, testing new technologies. What are some of the other upgrades that you’re hoping to do in maybe the near future and hopefully test in low-Earth orbit?
Kevin Takada: Right, so for as part of the advanced OGA, it’s the cell stack. So we’re building a new cell stack, with the new design in it, with the improved membranes, and a couple other improvements within that. And so within the next couple years we want to get that new cell stack on orbit. We’re building new pressure sensors and new valves here on the ground right now, and we’re actually going through our design process of the advanced OGA right now. We’ve had our Preliminary Design Review last year. We’ve got our Critical Design Review, our CDR, coming up in March. So, we’re in the process right now of building the components of the advanced OGA that we’ll actually deploy in a couple years on ISS.
Host: Oh, that’s very exciting. I was thinking that you were going to follow the model of the sensor, right, where you’re testing components on the current system and trying out new things, but it sounds like wow, you’re well on your way for, for an entirely new system, which I guess —
Kevin Takada: Yes.
Host: — it puts together all of the different things that you’re trying to accomplish. Is that the idea?
Kevin Takada: Yeah.
Host: Ultimately — go ahead.
Kevin Takada: So we’re going to take the existing OGA that’s on ISS, and we’re going to upgrade it to the advanced OGA configuration, so it’s not going to be an entirely new system, but an upgraded system.
Host: I see. The AOGA is the plan to upgrade the current system. It’s the —
Kevin Takada: Correct.
Host: — consolidated, comprehensive plan. I understand. OK.
Kevin Takada: Correct, yeah.
Host: So it’s not a replacement of the system. Very exciting, though. Absolutely, yeah. And you’re making some great progress there. All right, one final, one final topic, because we’re on the, we’ve been talking about the Advanced Oxygen Generation System and obviously this is your expertise, generating oxygen, maintaining the systems that do so. This is not the only system that generates oxygen, and particularly for the future of human spaceflight, one of the critical components is the generation of oxygen inside a spacesuit. Now, we talked about the generation inside a spaceship, like the International Space Station, continuously regenerative, that sort of thing, but is there any involvement on your end and using your expertise to thinking about what comes next for oxygen generation in a spacesuit?
Kevin Takada: Right. So we’ve been looking at that for probably about ten years now.
Host: Oh, wow.
Kevin Takada: Yes. So currently, you know, it’s currently aboard the space station there’s no, we don’t have a way of generating high pressure oxygen for the spacesuits. So, what’s, what happens now is that high-pressure oxygen is flown up in tanks, called NORS (Nitrogen Oxygen Recharge System) tanks, and they’re flown up regularly to support the EVAs (extravehicular activity). But ultimately we’d like to be able to directly generate high-pressure oxygen right on board, to have it right there, and so we’re talking about pressures that are over 3,000 psi. So that’s what’s required to support the spacesuit. So whenever you’re talking about high-pressure oxygen, the risks go up exponentially. High-pressure oxygen is a lot more, could potentially be a lot more dangerous than ambient-pressure oxygen, so there’s a lot more to consider to building a safe system that can generate high-pressure oxygen. So there’s a couple different technologies out there that we’ve been looking at and funding over, over the years. One of them is building an OGA-type cell stack but beefing it up and changing the design a little bit so that it can actually generate high-pressure oxygen on that one side of the membrane, and it’s really surprising when you think about it: this, this very thin membrane can hold back over 3,000 psi of pressure. So we went through several years of design with the cell stack. We had some initial issues. We had an initial failure. We’ve modified the design, we think we’ve got a good design for a high-pressure cell stack that can directly generate that high-pressure oxygen that’s required. Another alternative way of generating high-pressure oxygen is connecting up a compressor to the outlet of the ISS OGA, and so this compressor could take in the ambient-pressure oxygen, compress it up to the 3,000 psi, and store that oxygen. And so, we’re doing some ground testing here to see if we can get that, that to work, hooking up a mechanical compressor to an, to an OGA system. Now there’s a lot more considerations there as well. As I mentioned, the oxygen coming out of the OGA is very humid, got lots of water content in it; for the spacesuits they want bone-dry oxygen, so we’ve got to remove all of that humidity out of the oxygen before we compress it. In addition, there’s some trace amounts of hydrogen and some other components in there; we’ve got to remove those before we compress that. And then also, we have to look at the reliability of a mechanical compressor, because historically, you know, there’s been some issues with reliability of mechanical compressor. It’s essentially a series of pistons that compress the oxygen over several different stages up to the final 3,000 psi pressure. And then some of my colleagues are looking at even different technologies as well.
Host: Very exciting stuff. Yeah, you have your hands in everything about giving an astronaut the ability to breathe in space; very, very important stuff and very exciting. Kevin, I had so much fun learning everything that you’re doing, not only, you know — it’s hats off to you and your team for maintaining such a critical system for so long, but already making big strides in thinking about the next generation, and it’s in a very exciting time as we’re continuing, you know, we’re working to continue human presence in low-Earth orbit and thinking about Artemis and beyond, and you have your hand in all of that, so appreciate you coming on Houston We Have A Podcast today and sharing all of your expertise with us. Thanks very much.
Kevin Takada: Thank you very much for having me.
[Music]
Host: Hey, thanks for sticking around. God, I learned a lot from Kevin today. He is definitely the person to talk to, and doing some very important work with his team over in Huntsville, Alabama, contributing to, every day, keeping the Oxygen Generation Assembly up and running. Very important work, and thinking about the next generation stuff. Go to NASA.gov/iss to learn more about what’s going on board of the International Space Station. You can find updates about the H2ST system. Visit ISS Research page to learn more. We actually go into depth about a number of different systems that are being tested, and we hope to provide some updates there very soon after it launches here and is ultimately installed on board the space station in, this summer is what they’re aiming for. Go to NASA.gov/podcasts to check out our podcast, Houston We Have A Podcast. You can listen to all of our episodes, the entire collection is there; you can listen to them in no particular order. There’s also a number of other shows across the agency that you can find there. If you want to talk to us specifically, we’re on the Johnson Space Center pages of Facebook, Twitter and Instagram. Just use the hashtag #AskNASA on your favorite platform to submit an idea or ask a question for the show. Make sure to mention it’s for us at Houston We Have A Podcast. This episode was recorded on January 21st, 2022. Thanks to Alex Perryman, Pat Ryan, Heidi Lavelle, Belinda Pulido, Nicole Rose, Rachel Barry and Joe Sanford. And of course, thanks again to Kevin Takada for taking the time to come on the show. Give us a rating and feedback on whatever platform you’re listening to us on and tell us what you think of our podcast. We’ll be back next week.