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 269, find out about the NASA research into preventing decompression sickness for astronauts who will walk on the Moon in future Artemis missions. This episode was recorded on October 24, 2022.
Transcript
Pat Ryan (Host): Houston, we have a podcast! Welcome to the official podcast of the NASA Johnson Space Center, Episode 269, “Locked In, Pressure Low.” I’m Pat Ryan. On this podcast we talk with scientists, engineers, astronauts, and other folks about their part in America’s space exploration program, and today we’re going to learn about plans to prevent future astronauts on the Moon and Mars from suffering from “the bends.” Our puny human bodies need to breathe air, and our normal air is about 78% nitrogen and 21% oxygen, and some other stuff. Under less than normal atmospheric pressure, nitrogen can dissolve out of your blood and form bubbles inside your body. It’s called decompression sickness, and having those bubbles inside your body can lead potentially to any number of painful conditions of your joints, lungs, heart, skin, or brain. The reduced pressure situations that can lead to this condition include scuba diving or high-altitude events or being an astronaut walking in space or on the surface of the Moon or Mars. Over the dozens and dozens of years that men and women have been walking in space, we’ve developed protocols to prevent this from happening. Well, today scientists and engineers are focused on learning how to prevent it from happening in the particular atmospheric pressure regimens we will encounter when astronauts will walk on the Moon and on Mars. This summer a group of volunteers spent two weeks locked inside a big metal tube here at the Johnson Space Center in Houston as part of the Exploration Atmosphere Prebreathe Validation. They’re working to gather data to help develop methods to ensure that future planetary spacewalks can be conducted more safely. Dr. Alex Garbino is the principal investigator of this experiment. He has a bachelor’s degree in physics from the University of Houston, and he graduated on the International Health track and the Space Medicine track from the Baylor College of Medicine — that’s doctorates in medicine and in translational biology and molecular medicine. He also earned a master’s of public health from the University of Texas Medical Branch in their aerospace medicine residency program, and he’s an emergency room physician in Houston, as well as an EVA (extravehicular activity) scientist at the Johnson Space Center. Also, with us today is one of the test volunteers. In his day job, Jeff Watters works in the Crew and Thermal Systems division of the Engineering Directorate at NASA JSC and is assigned as the Spacesuit Subsystem Manager for the Commercial Crew Program. He has a bachelor’s in mechanical engineering from the University of Wyoming, and a master’s in aerospace engineering with a bioastronautics focus from the University of Colorado Boulder. In his career he has worked on the design of five different spacesuits, most recently the xEMU, the Exploration Extravehicular Mobility Unit being developed to take us back to the Moon. Getting set for the next moonwalks: here we go.
[Music]
Host: I started off today’s episode with kind of a layman’s explanation of decompression sickness, just to catch people’s attention, but now I’ve got some experts here and I’ll defer to them to make clear what this condition is and why it poses a threat, so that we all have that background as we, as we talk about these recent tests. Alex Garbino, if I could get you to start us on this topic and explain what decompression sickness is and what causes it?
Alex Garbino: Absolutely, and thanks for having me. So, decompression sickness is, simply put, nitrogen that is dissolved in our body that as we decrease the pressure, as we do when we go up in altitude and or decrease the pressures we do in the spacesuit, that nitrogen comes out. Very similar to when you open a soda bottle, and the bubbles form and start coming out.
Host: Yeah.
Alex Garbino: Nitrogen is almost 80% of what’s in the air that we breathe. And as we go up in altitude all that nitrogen, it doesn’t do anything physiologically but it is dissolved in our tissues. And when it comes out, if it comes out too quickly, it can form a lot of bubbles. And those bubbles can sometimes cause what we call decompression sickness, which can be anything as mild as joint pain, aching, almost like a sore knee or ankle, to some pretty severe symptoms, even looking like a stroke or strong pulmonary issues, severe pulmonary symptoms.
Host: Right. Now, I explained to people that you are a medical doctor as well as a, as a, an EVA engineer. Tell, tell me about your education and, and your professional background that got you interested in research like this?
Alex Garbino: Oh, absolutely. So my background is actually started on the physics side in undergrad, and then the, I decided it was a little bit too abstract for me. So I switched to what’s called a medical scientist training program. It’s an NIH (National Institutes of Health) program that teaches basically M.D./Ph.D., so we sort of hop back and forth between graduate school in biological sciences and medical school. And after completing that at Baylor College of Medicine here in Houston, I completed an emergency medicine residency, also at Ben Taub [Hospital] in Houston. And then I joined the NASA UTMB residency program, which basically rotates us through several NASA and DOD (Department of Defense) and commercial space environments where we rotate and learn how business is done in the field. And after that I joined the H-3PO (Human Physiology, Performance, Protection & Operations) lab, which is, basically the EVA physiology lab, as most people know it, and we study not only decompression sickness but also, fatigue, injury, thermal loads, and stresses, all focused during EVA, so extracurricular activities or spacewalks.
Host: Jeff, while we’re on this subject, tell me about your background and how you came to work on spacesuit stuff here at NASA?
Jeff Watters: Yeah, so my early experience was actually in rocketry and helping out design solid rocket motors. And so I had applied for a few NASA internships in my undergrad and never got them, but I was, you know, always applying on, like, the last day, like, getting it in ten minutes before the deadline. And so going into my final year, I knew I had one shot left and so I applied on the very first day. So I was probably the first person to apply. And much to my surprise, you know, two weeks later NASA’s on the phone and they’re saying, hey, do you want to come, you know, work on spacesuits at NASA Johnson Space Center? And I mean, well…
Host: Me? [Laughter]
Jeff Watters: Yeah, exactly. And there’s really only, you know, one correct answer to that. And that’s, you know, when do I start?
Host: Right.
Jeff Watters: So ended up enjoying that so much, you know, one internship turned into five and, you know, ten and a half years later I’m still working on spacesuits.
Host: Terrific. Now, we, Alex explained what, what decompression sickness is, and I’m aware that the protocols for trying to prevent decompression sickness in spacewalkers have evolved over time. Can one or both of you kind of give me the thumbnail sketch of how that effort to keep spacewalkers safe from decompression sickness have evolved over time? Alex, why don’t you give it a start.
Alex Garbino: Of course, sure. So this really started in, with the shuttle days, with the beginning of the shuttle. So if you remember, Mercury, Gemini and Apollo all had oxygen, pure oxygen atmospheres.
Host: Right.
Alex Garbino: And so, the nitrogen basically would come out of the body in the first several hours today. And so it wasn’t a concern during, like, the Apollo moonwalk, for example, that everybody refers to, but with shuttle and space station, a big part of those programs is to understand how the body changes from normal ground activities. And so we mostly have the same atmosphere as we have in Houston. So 14.7 psi (pounds per square inch) pressure, 21% oxygen, like you have at sea level. That’s important for the biological sciences because it lets us only change, you know, one thing at a time, the, the microgravity environment, without changing all of the other parameters. When we look at doing spacewalks then from the ISS and from shuttle, it means there’s a lot of nitrogen in the body, 80% of 14.7 psi is, is how we measure that as our body partial pressure. And so the previous protocols for that required anywhere from four to several hours of breathing pure oxygen or enriched oxygen. What that lets us do is get the nitrogen out of the body. So it’s not that we need more oxygen, it’s that we need less nitrogen. And so by putting more oxygen, we’re basically just subtracting nitrogen and that lets the nitrogen diffuse out of the body in a sort of calm and, and smooth fashion before we drop the pressure in the spacesuit and it all comes out of a bubble. So going back to the analogy of a soda bottle…
Host: Right.
Alex Garbino:…kind of like cracking it open and letting it hiss slowly rather than, you know, foam and burble out the top.
Host: And those procedures have changed over the course of the shuttle time and station time, too, to where these days they don’t have to do, it doesn’t take nearly as long to get ready as it did before, right?
Alex Garbino: Yeah, that’s correct. So we had a campout protocol, which involved basically sleeping in the airlock in the, in the shuttle and the space station. Then we had some four-hour pre-breathe protocols; now by fine-tuning the parameters, doing a little bit of exercise while breathing pure oxygen, we have that down to basically about two hours in what we call our In Suit Light Exercise pre-breathe protocol. That is great for space station, since, you know, it’s a whole day event and so, the, the less time we spend pre-breathing the better it is. When we talk to the Artemis, though, and the Moon landings, even two hours of pre-breathe is still too long. And so this effort is looking at getting that to under 30 minutes.
Host: Under 30 minutes. OK. Well, I was going to, I was going to say that, I’m making a presumption here to the fact that you guys are studying ways to reduce the time and make sure that it’s safe for planetary EVAs, would lead me to believe that the current protocols that you’re doing are for some reason not suitable for, for that future state. Is that true? Is what, what is it about spacewalks, moonwalks, or Mars walks, that would make that the current protocol inefficient or insufficient or, or whatever “in” it is?
Alex Garbino: So one of the, the big things that we’ve observed in, you know, sort of the decades of testing that happened with NASA and even the, the Air Force for high-altitude flights is that your metabolic rate or your basically your physical activity during an EVA or the high-altitude exposure has a huge impact on the amount of bubbles and the risk of decompression, as in several-fold increase in magnitude of, of risk of DCS (decompression sickness)…
Host: Wow.
Alex Garbino:…when, when physically active. For shuttle and ISS, we consider those non-ambulatory EVAs; that means that we’re free-floating in microgravity in the suit, and so most of the workload comes from the upper extremities, and the legs are usually used as an anchor points, but are, are not working hard. When we switch over to planetary surfaces, when we talk about the Moon and the Mars EVAs and we’re walking around going up and down craters…
Host: Right.
Alex Garbino:…carrying heavy suits, etc., and we do have a gravity component, that becomes a much higher physiological stress metabolic load on the legs. And so those large leg muscles that can hold quite a bit of nitrogen are active, then we see a lot more nitrogen being involved. And so our current protocols would require several more hours of oxygen pre-breathe to, to meet our ISS risk.
Host: And Jeff Watters, you’ve spent years of your career developing suits, spacewalking suits; is, the spacewalking suit that will be used on the Moon or on Mars doesn’t yet exist, it’s, it’s still being developed. How does not knowing what actual suit you’re going to use impact your trying to figure out how to, to deal with decompression sickness and preventing decompression sickness?
Jeff Watters: Yeah, that’s a good question. And I mean, it really kind of comes down to the suit pressure that you’re at. It’s kind of an engineering trade off there where the higher the pressure, the harder it is to design that structure. So if you’re living at that 14.7, it takes a much more robust structure to withstand that. And if you put that in terms of a spacesuit, you know, at 8.3 psi, which is what our exploration suits are designed to start off at…
Host: OK.
Alex Garbino:…that’s already as hard as a basketball or if not harder. So it’s very difficult to withstand that, that pressure. And so ideally you want to minimize the, the pressure in your suit from a structure standpoint, but that’s the opposite of what your body needs. And so, it’s really comes down to the partial pressure of the oxygen in your suit. And so you have a tradeoff between how flammable is everything, and then also the, the load requirement for the structure and the suit.
Host: So the pressure here is a big difference for, in terms of, compared to shuttle or today on the station where the, the, the structure, the pressure in the station is close to normal pressure that we experience at sea level on Earth, but that’s not what’s planned for, for, for structures on the Moon or other planets, right?
Jeff Watters: Yeah, that’s, I think they’re still determining that. You know, the, the current spacesuit, the EMU, operates at a 4.3 pressure, and so, the space station’s at 14.7 and you have that differential there. And so really a lot of the advanced suits that we’ve been working on in the last ten years started off as what is called a zero pre-breathe suit. And so they were designed to operate at a higher pressure of 8.3 psi. So the idea there is if you’re living at a very similar pressure, you reduce that pre-breathe time to go into that suit.
Host: I see. So, and therefore, you got less time spent having to get your bodies…is part of this, and I’ve read in some of the material that was made available, that the effort here is that we’re trying to maximize spacewalking time for astronauts that are on the Moon or, or on Mars. I, I wondered if that means you are trying to, or you’re assuming that, spacewalks would last for more time than current ones do, or that astronauts would be doing many more of them than astronauts on the space station do today?
Jeff Watters: Yeah, I think it comes down to really the frequency of, at, you know, the rate at which you’re doing those EVAs. So right now, we might do an EVA, you know, a couple times in six months…
Host: Right.
Jeff Watters:…but if you’re going to the Moon you need to do lots of EVAs because you’re, be wanting to explore that. And so during this protocol we actually did five EVAs, we were doing one every other day, which is probably more than what they would do on the Moon but that’s one thing they’re really looking at here is, you know, what are the effects of doing an EVA every other day? Does the DCS risk, does it build on each other? Does it get worse over time because it really just had kind of discrete EVAs before.
Host: OK. Let, let’s talk about the, you, you brought us almost into the test chamber. Let, let’s, let’s talk about that. And Alex, can you tell me where did the Exploration Atmosphere study come from? Where, where did folks decide we need to start to look into this in more detail?
Alex Garbino: So this started really in a working group, met the exploration atmospheres working group in 2005.
Host: Wow.
Alex Garbino: And then it was reviewed back in 2012, and it adjusted a little bit. It, it become with a, it started with the Constellation program.
Host: Right.
Alex Garbino: If you remember back from the…
Host: I do. [Laughter]
Alex Garbino:…almost 15 years ago. And the idea was we don’t want to bring this suit pressure up so high that it makes a suit, you know, unusable. Basically, it makes it too stiff. So instead, what we do is try to decrease the pressure we’re starting with. So if we use sort of a, a pressure equivalent [of] 14-7, where we start it at sea level, the suit pressure is about the equivalent of being at 30,000 feet. Think of it as being at the top of Mount Everest.
Host: OK.
Alex Garbino: Now, we can’t jump straight to Mount Everest. And so, what we do is that we live at the equivalent of about 15,000 feet for several days before we go up. So the same way you would stage at base camp on Everest before going to the top, what we do is that we stage or live at this intermediate atmosphere, we call it exploration atmosphere, which is at 8.2 psi, about 15,000 feet equivalent. Of course, because that’s very high-altitude we run into the risk of hypoxia so we increase the oxygen level and we go from 21% to 34% oxygen. And that lets us combat the, the risk of hypoxia, high-altitude sickness, basically. And so by, by getting halfway there, we let most of that nitrogen come down, and so we can then pop up higher, you know, to the equivalent of 30,000 feet in pressure, down to the 4.3 of the suit and get to work quickly.
Host: And that sounds to me like your strategy here is to spend some time ahead, at the beginning of this process, letting people more slowly adapt to it, so that they don’t have to spend a lot of time at any given day to start that adaptation. Is that correct?
Alex Garbino: That’s correct. And we’ve done that a little bit, actually, in the shuttle and early ISS days with what was called a campout protocol…
Host: Right.
Alex Garbino:…where astronauts would sleep at 10.2 psi, which is about 10,000 feet, again with extra oxygen to, to combat the effect of the hypoxia. But that was for short durations, you know, 12 hours or so versus here, what we want to, to do with Exploration Atmosphere is basically set the habitat or rover environment that the astronauts are living in during periods of high EVA activities so they’re basically, sleeping, waking, and working at this pressure for the whole duration of the EVA stint. So for Artemis III, that would be basically the, the part in which they are on the lunar surface operations, and for future operations that would be, you know, whenever they’re planning to do lots of EVAs.
Host: So anytime they would go to the surface to, to get prepared for the moonwalks that they, that they’re, that’s the whole reason they’re going there in the first place.
Alex Garbino: Exactly. So they would be living, eating, sleeping in this reduced pressure, high-oxygen environment day in and day out while doing the EVAs as needed during this period. And then when they, you know, depart the Moon or, or finish with EVA operations, they could then go back to higher pressure.
Host: So for the test session that happened a couple of months ago, what were your goals? What, what were you, what, what did you go in there trying to determine? What data were you looking for?
Alex Garbino: So we have models that we use. So the same way a scuba diver…
Host: Well, Jeff’s a model. [Laughter]
Alex Garbino: Exactly. So we have, you know, same way you’re a diver with a dive computer will, you know, they will tell them how quickly they can go up and if they have to stop for decompression stops, etc. We have similar models for altitude exposures, but models are models, right, and so, we ran the models, we ran them, you know, this way, that way, and every which way we could. And from that we optimized the, both the, the living and the EVA pressures and then decided what is a minimum pre-breathe that we could get away with, and that was about 20 minutes for this chamber test. And so we tested that protocol with the human volunteers so that we could say, you know, does it really match what models say? So we find out before we go to the Moon whether the models are right or not. And adjust accordingly.
Host: Did science find out if your beliefs were true?
Alex Garbino: Exactly.
Host: Was this the first time, is this the first time you put people in the chamber?
Alex Garbino: This is the first time people were in the chamber at low pressure since this, my understanding is correct it’s actually since the SMEAT, the Skylab Medical Experiment Altitude Test in the 70s, in the early 70s. So this facility was used for testing of Gemini and cap, and Apollo capsules, then it was used for Skylab, and then it was not used for altitude testing until this year, basically when we did these, these tests. It was used for some ISS ECLSS (environmental control and life support system) system, so life support system tests, but those of course were at 14-7 psi. So this is the first time in, yeah, 40-50 years.
Host: And it did, those didn’t, those didn’t put people in the chamber. That was hardware.
Alex Garbino: They had some with hardware, some with people, but there wasn’t at a low pressure.
Host: Ah, OK. I see the distinction.
Alex Garbino: It was a sealed environment, but not a, a low-pressure environment.
Host: Jeff, why did you volunteer for this? Well, actually, first question is, did you volunteer for this?
Jeff Watters: Yeah, I definitely volunteered. I don’t think NASA would want hostages in there. [Laughter]
Alex Garbino: Jeff, don’t get me into trouble here.
Jeff Watters: Yeah, no, I definitely volunteered. And I remember telling my dad that, you know, I had volunteered for this study, and you know, there was going to be eight of us living in this metal tube for two weeks. And he kind of looked at me and gave me this crazy face, like, why would you do that? And I started explaining, you know, I was like, you know, we’re validating the atmosphere for going back to the Moon. I mean, essentially, we’re baselining the entire lunar mission profile. And that was just so cool to me that, you know, like when we go back to the Moon, I think it’s just so awesome to have been, you know, a small part of that.
Host: And what, when you agreed to go, what had you been told about how long it was going to be, what you were going to have to do, who were you going to be with? I mean, all those normal kind of questions I think people would, would want some answers to before they put their hand up and said, yeah, I’ll go.
Jeff Watters: Right. Yeah. So they gave us a really long, maybe 20 page informed consent: all the risks, all the different studies they’re going to do, all the…you know, fluid and all the things they’re going to take. And you’re looking at this, you’re like, wow, this seems like a lot. And I applied just thinking, you know, it was like, oh, I probably won’t get selected. And I was still kind of wishy-washy and it wasn’t until I actually like saw the, the habitat and I saw this thing and I was like, that’s cool. Like, put me in coach, I’m ready.
Host: Describe it, but what, what was it that you saw that, that, that sucked you in?
Jeff Watters: Yeah. I honestly like walking into the chamber, it feels like you’re walking into a, like a space habitat. And I had done some space habitat design in grad school, and it was nothing to this fidelity. And just seeing how well it was constructed and it’s all built into this altitude chamber. And just really got me excited thinking about this, because when you’re in there it, it feels like you’re in a different place. It doesn’t seem like you’re just in a, in the high bay in Building 7.
Host: Right. Can you tell us what it looked like? You know, how wide and how tall, and how cushy were the chairs and, you know, whatever. What was, what was it like?
Jeff Watters: Yeah, not much was cushy in there. So imagine like a, a tube about 20 feet in diameter, so about the size of your living room. We had three stories in there. Our first floor was where we did all our EVA, our spacewalk; there was different metabolic simulations in there so that we could work out and get a similar load to what they would be doing in space. We also had an exercise bike in there where we do VO2 testing. And then on our second floor was kind of our living quarters. We had eight pretty cramped bunks stacked on top of each other, and two bathrooms. We did have a toilet; it was a no-flush toilet, and so one of our favorite hobbies I think was a favorite hobby of many astronauts and that’s fixing the toilet because it broke every other time. And then the third floor was kind of our galley. We had a big table up there where we would eat, have crew time up there. We had a TV up there and we would, you know, have our meetings up there and people would try to work in there. Didn’t have a lot of head space. I know on the third floor I continually had to duck so I didn’t hit my head on a, a fire sprinkler. So it was a little cramped in there, but you get used to it and you learn where to put your head and not put your head.
Host: Sure. What about the, the people that you were ended up in there with, because you didn’t know them before you went in, right?
Jeff Watters: No, a lot of these guys I had met, you know, maybe a few weeks, maybe, some even a few days beforehand. But I, I really wish they were here today because the, the crew was just awesome. You know, everyone in there was so hardworking and cooperative and it was really just a cool experience being with these like-minded people where it wasn’t a competitive environment. It wasn’t, you know, it’s, we’re all on the same team here. And to me that was one of the coolest things was the, the camaraderie that we came out with because we all had this shared experience of going through this together and that’s kind of a bond that you can’t really recreate elsewhere. And so, it was very diverse background of, I mean, rock star candidates, you know, in there. And it was just really fun to go through it with them.
Host: Alex, where did you find these volunteers? What, what kind of people came forward that you had to choose from? What, what and what kinds of things did you tell them you were going to have them do while they were in this test?
Alex Garbino: Yeah, so we got people mostly from on NASA, on site NASA. The recruitment period was actually during COVID, so although initially the idea was to have it open to volunteers from anywhere, because of COVID restrictions we ended up limiting to people that were already, you know, approved to be on site. And we basically just needed people who met certain, you know, criteria, which is basically sort of the same age range, etc., as our astronaut population.
Host: OK.
Alex Garbino: And then we walked through a very detailed consent process to explain to them exactly what they were going to be doing during the chamber, what tests we were doing. Although the, the main focus of the test is a test for decompression risk, because we are living in this high-altitude environment we also had during the off-EVA days we actually had a very busy science schedule where we were making sure people could adapt to this environment and live in this environment without any, any issues. So we had cognitive tests, exercise tests, etc.
Host: Oh, that’s other science besides the decompression sickness studying science. So you had something for them to do.
Alex Garbino: Yes. And what we need to do is not only say, you know, whether our pre-breathe protocol works, but also the environment that they’re living in that we said, you know, we’re living at this 15,000 feet altitude equivalent with 34% oxygen is actually, you know, an atmosphere you can live in, work and thrive and not be the equivalent of being, you know, living up in the mountains with any headaches or anything like that. So we need to verify that; was also a great opportunity to test some of the food systems that were planned for Artemis. And so we had the NASA food lab provide the, the food options for the, the 11-day test as well.
Host: Can you give me a, a, a, an idea of what the timeline was like over this 11 days and, and, and the various, the pressures to which you submitted the volunteers?
Alex Garbino: Absolutely. So we started sea level, right? So 14-7 psi, 21% oxygen. We then did a three-hour oxygen pre-breathe, basically to jumpstart the process and then lower the chamber down to the 8.2 psi, 34% oxygen atmosphere. So basically we took the chamber to the equivalent of 15,000 feet. We then stayed there for 48 hours to let the body equilibrate to this new pressure, let all the, the nitrogen, you know, that takes a little bit longer to diffuse out of the body to fully diffuse out.
Host: It squeezed out the last of it.
Alex Garbino: Exactly, make sure that we were really living at this environment and not just dropped in. And then after that we did an EVA, which lasted about six hours, and that was down at 4.3 psi, so about 30,000 feet equivalent. And then we would come back and have a one off-day to basically recover, reset everything, reset the nitrogen in the body, and then do that again. And then again and again and again. So for five cycles of EVAs, so 11 days total.
Host: When you say you “did” an EVA, what, what were the, the, the crew inside the, the chamber actually doing? Were you getting in spacesuits, for instance, or what were you doing to do an EVA?
Alex Garbino: Right, so the way we simulated an EVA was the actual, the whole chamber pressure dropped to 4.3, so the, the pressure of the, of the suit. And then they had the, several EVA simulation tasks. So they would go, all the subjects would go up and down steps, do some cycle ergometer – basically pedaling with your arms – do some fine motor skill tasks. And then also, we would measure for decompression stress by looking at bubbles in the bloodstream, both with ultrasound and with a Doppler, to get a measure of the, the degree of decompression stress that we were provoking.
Host: So that’s real, that’s real-time monitoring then?
Alex Garbino: Correct.
Host: Wow.
Alex Garbino: So we had six subjects, six crew members that were doing the tasks and we had two Doppler tasks that were either using a Doppler or an ultrasound machine, the same you would use to look at a baby during a pregnancy…
Host: OK.
Alex Garbino:…to look in the blood vessels and look for bubbles because we can actually see and monitor those bubbles, with ultrasound and with Doppler, circulating in the bloodstream. Although those are not directly correlated, there’s a close association between the number and the amount of bubbles we see in the bloodstream and the risk of decompression illness.
Host: So it’s a, a warning sign if nothing else.
Alex Garbino: Correct.
Host: And what, what, so you’re really doing a spacewalk with all of the crew members at one time, not just a couple as we know a spacewalk today, because they were all inside the habitat that was reduced to down to 4.3 for everybody. Yeah. And, and what kind of spacewalk did other tasks and, and I, I guess I’m just pushing to find out a little more; what, what did, what, what kind of spacewalk task did you do, Jeff?
Jeff Watters: Well, we all went through the same, like kind of rotating circuit, and so you’d kind of start off and you’d have, for example, like a high step, where you’d be stepping on a 12-inch box for five minutes, and then you would move over to another station where you would maybe do something like repair a satellite. Then you had maybe go to the next station where you’d do a weight transfer where you’re just moving weights around, kind of simulating picking up rocks or something like that. And then every 15 minutes we would lay on a cot and they would either do Doppler or ultrasound monitoring on us to try to see if there’s any bubble formulation. And then there was another circuit that was very similar to the first one, and so I was really going through the, this circuit of eight, eight places over and over and over again for six hours.
Host: [Laughter] OK. But, but that was to do work, to force any nitrogen that might still be in your blood to, to come out and see if, and see if there was, I guess, I take it?
Jeff Watters: Yeah. And so all our workloads were actually kind of designed for us to give us a kind of more realistic, what you’d be doing on a spacewalk. So they purposely had some tasks where you were kneeling down, they wanted to check that out. A lot of the tasks focused on lower body movements, because as we go to a planetary environment most of the work would be done with lower body and that’s where the biggest decompression sickness concern was.
Host: It’s also, as Alex mentioned earlier, it’s the biggest difference between future spacewalks and current spacewalks, that current astronauts on spacewalks don’t walk. Did you find it entertaining or enjoyable for, to do these faux-spacewalking tasks?
Jeff Watters: You know, that was one of the most challenging things is, it was pretty, you know, it’s fatiguing physically because you’re basically working out at a, a medium rate for six hours. It’s very doable. The hardest part was maybe mentally, like keeping your head in the game, making sure you’re doing the right thing.
Host: Wow. Yeah.
Jeff Watters: And so, the first one or two EVAs, I think we just kind of did it in, not in silence but it was just, you know, us just working and you can’t really talk to your crewmates. So we have open comm[unication]s that we can talk to the test team, but you’re kind of talking to everyone, so there’s not a lot of communication. And then, eventually, they brought in, they started playing songs for us. And so, that was really cool because we, you know, we made a playlist, like a crew playlist, and they start playing that. And we have some of the test team come on, on. We had DJ Crumbles, who would tell us jokes, and you know, even like our medical doctor had, was a great, great storyteller. And so they really did a great job of keeping us entertained. So I, I remember being a little bored on the, you know, the first one or two and then, it was just really fun kind of, you kind of just, it’s almost like being in a, like a radio show live, you know, listening to that.
Host: Wow. It’ll be fun.
Jeff Watters: Yeah.
Host: What did you do when you weren’t pretending to do a spacewalk?
Jeff Watters: Well, there wasn’t a lot of time to be bored. I was definitely never bored. So in our off days we did a lot of science activities to really characterize some of the physiological and cognitive adaptations to that environment. And so, that included things like cognition testing, visual acuity, VO2 max testing…well, VO2 testing. And you know, we, we definitely had down times and so a lot of the, the crew mates tried to stay up to work as much as they could. And so, really an important thing here is it’s not an isolation study, so we had a tablet connected to the NASA network. We could have email, we could stay in touch with our coworkers for, you know, via Microsoft Teams, things like that.
Host: Yeah. You weren’t pretending that you were out in deep space somewhere?
Jeff Watters: No. So physiologically it was, but you know…
Host: You weren’t beyond regular communications with Earth.
Jeff Watters: Right. And so, you know, it looked like we would have, you know, we had free time built into the schedule, but you were, it seemed like we’re always doing, you know, you had chamber operations and you had to do transfer locks, you know, had to fix the toilet. And so some of the crew, you know, we’d like to watch Netflix in our downtime, I would sometimes listen to music. One of the favorite pastimes with some people would be kind of doing a video chat with family. And so that was really cool seeing, you know, people’s kids and they’d be doing like a live tour in there and just seeing how excited the kids were to see that and like, this is where we’re do, you know, this is where we sleep, this is our toilet, kind of thing. Yeah. So.
Host: Nice. Now, Alex, you mentioned a few minutes ago about using ultrasound and, and Doppler to, to gather data from the test subjects. Were there other ways that you were able to gather data or, or just simply observation of what they were doing that was, was part of your data gathering?
Alex Garbino: So not during the EVAs, they were doing the EVAs they had the task to follow.
Host: Otherwise then, were there, were there, when you were just keeping track of them in between EVAs from day to day that was also part of the, of the test?
Alex Garbino: Right. So during the non-EVA days, there was a series of other tests that we did. Blood draws, we did food surveys, we did cognitive battery testing the same as we do for astronauts on the space station. And we did some metabolic tests by pedaling on a, on a bicycle, exercise bicycle, to see how things were going.
Host: Cool. Now, you talked about how you got the, the subjects into the test; what did you have to do especially to, to get them out, to get them back to Houston ground pressure?
Alex Garbino: So that took about 30 minutes, that was actually a relatively straightforward process. Adding pressure is the, the easy part. So returning to site level was just a matter of letting the chamber come, repressurize all the way back to site level. And then, after medical exam our crew were able to exit the chamber and go home.
Host: Everybody left; you didn’t have a party?
Alex Garbino: We did, we did have a, a dinner party. It was late in the evening, around 8 p.m., so everybody had a party but then wanted to go home, see their family.
Host: I bet. This was two months, three months ago now that, that this happened; do you have any early characterization of what you may have learned from the test?
Alex Garbino: Yeah, so this first test with six subjects put us pretty much within the error margins of the model predictions. What we need to do is repeat the test with additional subjects that we have enough statistical power to prove, you know, our model predictions are what we expect them or not. So right now we are in the, in the right trajectory, but we need to get more subjects tested before we can be sure.
Host: Is that just like one more test or two or three? Do you need to do this test with a, a universe of hundreds of test subjects?
Alex Garbino: Ideally, one more test should be sufficient.
Host: Ah, OK.
Alex Garbino: It depends how many cases of decompression we see. So one or two more tests should get us the answer we need.
Host: And then I would assume that it takes some amount of time to study all the data to really draw conclusions, right?
Alex Garbino: Correct. And what takes a lot longer is to analyze the cognitive test data and all the other secondary measures that we’re also doing to characterize this atmosphere.
Host: And the, and just, I, I guess I missed your reference to it earlier, the cognitive test data; give me a hint of what that’s about?
Alex Garbino: Right. So for cognitive testing on the non-EVA days, we do a cognitive batteries called Cognition, and it’s the same test we use for astronauts during the, their spaceflight on the space station. We also have a docking simulator, which again tests for cognitive performance, as well as the metabolic assessments to make sure that they’re able to do the, you know, sustain the same workload that they do on Earth.
Host: So you have video games for them, is that it?
Alex Garbino: I let Jeff answer that one.
Jeff Watters: Yeah, that was actually one of my favorite parts. It was called ROBoT (Robotic On-Board Trainer) and really it was, it’s the space station trainer for the Canadarm. And, you know, this was developed to train the astronauts, but they have such a, a data collection of the normal learning curve to complete this, so we did it for about two weeks before going into the chamber and then every other day in the chamber when we weren’t doing an EVA, and then two weeks after the chamber. And so, they likely can tell that it was like, you know, we’re on a normal trajectory and then maybe we dropped or maybe there was no effect. And so, with all the detailed statistics in there, they should be able to tell whether we have a cognitive performance, pre and post, whether we, you know, follow the normal learning curve.
Host: Cool. Well, I understand that Alex is looking for additional test subjects so you can’t go again, but would you?
Jeff Watters: I’d go again. Yeah. I enjoyed it.
Host: It was fun. Alex, are you, do you already have a target about when a second test might happen?
Alex Garbino: Yes. So again, probably in the same timeframe of this year, of this coming year, in the summer, we’ll be doing another 11-day test and we’ll be doing a three-day warmup, probably in the spring as well, to get ready.
Host: Terrific. I look forward to hearing what happens then because we’re all looking forward to seeing people walk on the Moon and we’ll know now a little more about what, some of the work that had to be done in order to make that happen. Alex Garbino and Jeff Watters, thanks so much for sharing the story with us today, appreciate it.
Alex Garbino: Thank you.
Jeff Watters: Thank you.
[Music]
Host: I came to work at NASA about midway through the Space Shuttle Program, and that was when I learned about the pre-breathe protocols used before astronauts left the shuttle airlock to work out in the shuttle payload bay. The protocols changed over time as the science improved. It went from a requirement that they sleep in the airlock at reduced pressure wearing an oxygen mask the night before a spacewalk, and then spend hours in a suit breathing pure oxygen before going out for a six- or seven-hour spacewalk, while later just had the astronauts doing exercise to speed up the removal of nitrogen from their bloodstreams. The work that NASA’s scientists and engineers are doing now to develop new protocols in conjunction with the development of the spacewalking suits of the future will mean something new and wondrous for us Earthlings to watch coming up here sooner than you might think. I’ll remind you that you can go online to keep up with all things NASA at NASA.gov. In fact, you can get all the NASA news you want delivered to you every week. Just go to NASA.gov/subscribe to sign up for the NASA newsletter. You can also find the full catalog of all of our podcast episodes by going to NASA.gov/podcast and scrolling to our name, where you can also find the other exciting NASA podcasts — that’s right, where, at the same spot where you can find us, NASA.gov/podcasts; very convenient. This episode was recorded on October 24, 2022. Thanks to Will Flato, Daniel Tohill, Heidi Lavelle, Belinda Pulido, Jaden Jennings, Chelsey Ballarte and Rebecca Wickes for their help with the production. And to Alex Garbino and Jeff Watters for letting us in on this step in the research that will lead to the moonwalks, and Mars-walks, that you and I will be watching in the years to come. We’ll be back on the first Friday in January when we’re going to start a special series on Mars exploration.