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“Houston We Have a Podcast” is the official podcast of the NASA Johnson Space Center from Houston, Texas, home for NASA’s astronauts and Mission Control Center. Listen to the brightest minds of America’s space agency – astronauts, engineers, scientists and program leaders – discuss exciting topics in engineering, science and technology, sharing their personal stories and expertise on every aspect of human spaceflight. Learn more about how the work being done will help send humans forward to the Moon and on to Mars in the Artemis program.
On Episode 188, Bill Paloski, former director of the Human Research Program at NASA’s Johnson Space Center, explores the idea of artificial gravity within a spacecraft for long-duration missions and explains how it may affect the human body from what we have learned through Earth-based studies. This episode was recorded on December 7, 2020.
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Transcript
Gary Jordan (Host): Houston, we have a podcast. Welcome to the official podcast of the NASA Johnson Space Center, Episode 188,”Artificial Gravity.” 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. Name a space movie. Almost any of them, when you see them flying through space, a lot of times they’re standing or sitting in the cockpit or bridge, not floating. There’s a mention of an artificial gravity generator that helps them to accomplish this phenomenon. The idea of using artificial gravity within a spacecraft is an intriguing one. Many say it would be a good way to keep astronauts healthy on long trips, preventing bone and muscle loss for the 18 or so months it would take in weightlessness to travel to and from Mars. The question is, do we need artificial gravity for a trip to Mars? The truth is we don’t know but we’re researching this very idea to understand it better. On this episode, we’re going to explore the effects of artificial gravity on the human body. Our guest today is one of the leading minds for understanding this concept, Dr. Bill Paloski, former director of the Human Research Program at NASA. He spent much of his career exploring the effects of artificial gravity through Earth-based studies and has published several research papers on the topic. So, let’s get right into it. Artificial gravity with Dr. Bill Paloski. Enjoy.
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Host: Dr. Bill Paloski, thank you so much for coming on Houston We Have A Podcast today.
Bill Paloski: Well, thanks for inviting me. This is always a lot of fun to do.
Host: And a very interesting topic, too. Right. Artificial gravity. In terms of what people, you know, generally ask questions about when they think about human spaceflight, artificial gravity is usually one of those questions. Everybody thinks there’s a room that you can just kind of flip a switch. A little more complicated than that. So, I’m glad that we’re diving into this with you today.
Bill Paloski:Yup.
Host: I wanted to start, though, to understand artificial gravity and understand mainly what we’re going to be talking about today is the effects of artificial gravity on the human body. I want to set some context for what it takes for a person to dive into this field. Starting with a little bit of your background, it says you had a lot of training in mechanical and biomedical engineering.
Bill Paloski: That’s correct. Yes. I have an undergraduate degree in mechanical engineering and then I went to graduate school, got a master’s degree and PhD in biomedical engineering, which at that time was and at that institution was mostly electrical and systems engineering coupled with systems physiology. So that was kind of the starting point for what I did. And then after that, I spent some time working in a trauma research center and we were doing multisystem studies on people who have multiple trauma and what that means is people who are in bad accidents. We were trying to understand a sequence of organ systems failures after big accidents like that over a period of time. So that was my first introduction to looking at all the systems of the body at the same time. And if you’re going to do artificial gravity research, you need to look at all the organs that are affected and not just some of them.
Host: Oh, interesting. So that provided a nice base for you to understand artificial gravity.
Bill Paloski: Yes. A good base and for all the stuff we do in Human Research Program today but also in space physiology in general because space affects a lot of things at the same time and artificial gravity would try to undo some of those affects all at the same time. And so, you can’t just look at one organ, you have to look at all the organs.
Host: So, what point of your career did you — you said you were working with critical care medicine, you were working on the understanding of different organs within the human body. At what point did maybe your curiosity spark for space physiology?
Bill Paloski: Well, I was working at Boston University as a junior faculty member, had a research appointment at MIT in fluid mechanics and was doing pulmonary gas exchange and cardiovascular physiology work. And one of my students came back from being away after he had graduated with a master’s degree and came back and he said, you know, “you ought to look at NASA. Did you ever think about working at NASA?” And I kind of looked at him and said “no, I never really did.” And he said, “well, they’re looking for people like you at NASA. So maybe you’d be interested in sending a resume down.” So, I did, and I got hired here in the neurosciences laboratory. And I worked for probably six or seven years on a very robust, one of the largest experiments that had ever been done before, the MVI experiments, Microgravity Vestibular Investigations. And in that, my job was to design and build a rotating chair to test the vestibular system in space. And so, we had a rotating device in space and to be able to understand the effects of spaceflight on the inner ear and how your balance system works. And during that time, Mill Reschke who was the head of the laboratory, still is, became sort of a new mentor for me and he taught me a lot about neurosciences and about space physiology. And we flew the experiment successfully on IML1 and STS-42, so it was 1991 or ’92. It was a long time ago. And soon after that, I was asked to become a civil servant and when I did, I said sure, I’ll be happy to do that and to join the neuro lab. And about three weeks after I joined the civil service, I got a call from Headquarters who said, you know, we need an expert on artificial gravity and you’re it. Learn about artificial gravity. And that was my introduction.
Host:And that’s how that came up.
Bill Paloski:That was my introduction.
Host: Wow. So, a lot of that research, you were just understanding what happens to the human body that you were doing prior to this. You were just understanding what happens to the human body. Now you have to add this element of artificial gravity, I guess. Let’s start there. Help us explain that. What is — If I say, you know, what is artificial gravity, what are those things that we are concerned about, focused on, interested in when it comes to introducing this field, artificial gravity to human spaceflight?
Bill Paloski: Yes. So, you know, one of the things that’s obvious about going into space is that there’s generally no gravity or what we call microgravity. It’s very low. And for long periods of time people are exposed to this low gravity state and the question is, well we’re used to gravity. What happens to the body if you don’t have gravity? And indeed, this problem has been thought about for a very long time. The first person to think about artificial gravity to offset what effects might happen is a guy called Konstantin Tsiolkovsky who is considered the father of the Russian space program. But he thought about the problems of people in space for a long time and he actually designed the first or had a concept for the first rotating vehicle. There have been others since then but the whole concept is that we can use centrifugal force instead of gravity. And Einstein showed long ago that his equivalence theorem says that gravity and acceleration are identical, right. So by using accelerations, centrifugal acceleration or centrifugal force, then we can generate something that’s a gravity equivalent and perhaps if we could spin the whole vehicle at the right rate that we could provide a gravity equivalent and people would be protected and then we wouldn’t have any adaptation to that environment.
Host: So, OK, so it sounds like there is already some history with adding artificial gravity as a consideration for human spaceflight. We have a lot of research in microgravity now. We have a decent understanding of what happens to the human body, still investigating, of course. But with this in mind, thinking just that there has been this concept or concepts for generating an artificial gravity field, let’s start with what is the case for introducing artificial gravity to human spaceflight? Why would we do it?
Bill Paloski: Well, it’s a very interesting question and is one that’s been around since Tsiolkovsky, right. And the thought is that people wouldn’t do very well in microgravity without gravity. And from an evolutionary perspective, we’ve had 1 g, one Earth gravity on this planet for the entire epic of evolution of all animal life on Earth and plant life. And we have, ourselves, taken advantage of all the adaptations that other animals have had along the way to be able to offset gravity. So we have cardiovascular system that can pump blood against a g load and against a hydrostatic load, so from your heart all the way down to your feet and be able to perfuse your muscles and nerves in the lower limbs and your bones and also from your heart to your head at the same time where there’s another load. We have muscles that help us move around in this environment. We have bones that provide the structure, the mechanical structure to allow us to stand up and lie down. And then we have a nervous system that can sense gravity and know the orientation of gravity and help us to decide which muscles to turn on at which time so that we can take the kinds of movements that we want to take. So, everybody recognized that long ago, and they thought well, without gravity, all those things could go kaput and we don’t know what’s going to happen to the person. So even at the dawn of the space age, Wernher von Braun, who was building the rockets to send people in space, started thinking about how are we going to create artificial gravity. And so, he had a gravity wheel that was a very big spinning thing. And if you remember the movie “2001: A Space Odyssey,” in the early part of that movie there was a space hotel that people were in. It was huge. It was a kilometer across.
Host: Very massive.
Bill Paloski: Right. And people went to space and they lived in this hotel and they could walk around and do the things that they want. There were some issues with that, technical issues, but other than the cost, it seemed like the right way to go. So, we really thought before we started sending humans in space that we would probably need artificial gravity. And there was a whole bunch of scientists that were brought together in the ’50s to think about how we would do it, but the urgency of trying to get people in space with the space race pushed us into capsules and going into space said “hey, wait a second. People can live for this long, so let’s forget about artificial gravity for a while until we have to go for a long time.” And then at the end of the ’60s when we were going to start doing Skylab and other longer-duration-type missions, they brought the community together again. We didn’t need it for Mercury or even for Apollo but surely, we’re going to need it when we have longer missions. And once again, there was no funding for it. We went and did the experiments that we went and sent to people. And we didn’t need it so we could go for a longer period of time. And the Russians were doing it on Salyut station and then on their Mir station. We started doing it on the shuttle. And we kept thinking each time that we take the next step deeper into space we’re going to need artificial gravity. Well, the fact is that it’s perceived to be very expensive to build and to have a rotating vehicle. And so, we’ve developed other countermeasures for antigravity systems, what we call antigravity systems, and mostly it’s exercises what we do on the ground. So if you do resistive exercise and aerobic exercise, you can maintain the bones, the muscles, and the cardiovascular system through the space station era that we’re in now pretty well through six-month missions and even in the few subjects that we’ve done up until one year, we’re able to protect it with just exercise. So, the question becomes, again now we’re going to go to Mars, so let’s get the community together and that was part of the call for me in the ’90s. It was “hey, pretty soon we’re going to go station and we’re going to go to Mars.” And there was a big challenge there about whether we’re going to go to Mars first or build a station and the station won out. But the whole idea was get the community together and start thinking about what we would need to do and how we would need to do it. During that period, I ran two international artificial gravity workshops, one in 1999 which was the first one that they asked me to do to try and put together a global plan for how we would do these studies and what studies needed to be done. And then the second one that came about in the early teens and again, I was away from NASA and working at the University of Houston and I got a call from the person that was in my current job saying “hey, there’s this new thing that’s come up, this thing called [Space-Associated Neuro-Ocular Syndrome] SANS which is a visual problem that seems to be related to fluid shifts to the head because gravity is not pulling blood down to the feet and it’s causing some problems in astronauts. Would you think about doing artificial gravity again? This might be a real no kidding reason for having artificial gravity.” So, we pulled together another one of these meetings and talked about what to do. And since ’99, there have been a lot of studies on the ground for how to do artificial gravity, not really, very many in space for reasons that we’ll get in to, I think, later in the talk.
Host: I want to dive a little bit deeper into understanding, I think you gave a great overview of, I think, why gravity is good for the human body. You know, we have a lot of understanding on the different systems and how they’re affected by a 1 g environment because that’s what we’re in right now. That’s how we’re recording this podcast is in 1 g. You talked about potential vision problems, you talked about mitigating some of the effects of spaceflight through exercise on the International Space Station. Let’s explore a deeper overview of exactly what’s happening to the human body in microgravity and again readdressing this case, because of these things are happening to humans in microgravity, the reason why artificial gravity is something we want to research and understand.
Bill Paloski: So, in space, there are a number of things that we know are affected by the loss of gravity or by microgravity, and those happen with those systems that we know are affected by gravity. So, we lose bone mass, bone mineral density. We lose muscle mass. We lose some of our cardiovascular function but it’s actually hard to measure until people come back to Earth and then we start seeing that there’s a change there. And then we lose orientation, space orientation and our ability to walk and move around. We ambulate in a different way in space. The thought is again that by using artificial gravity we could offset all those affects. By having some kind of the g level, maybe 1 g, maybe less, we don’t know exactly what the right g level is, and maybe a rotating station and maybe not, maybe part of the station rotating or maybe just rotating the people inside the station for part of the day. Realize that the gravity effect is predominately when we’re upright with respect to the Earth. So, it’s when you’re standing up or sitting as you and I are right now. And about a third of the day most people are lying flat and so they’re not getting those same kinds of effects of gravity on Earth. So, maybe you only need to provide stimulus for two-thirds of the time, which is what we get on Earth and if you’re a couch potato, a lot less than that, right. So, the question becomes how much gravity and for how long a period of time?
Host: Interesting. OK, so really yes, a summary of what we’ve just talked about is gravity is good and by introducing gravity to spaceflight, a lot of these things that we need countermeasures for such as you talked about bone loss, muscle loss, right now that mitigation strategy, that countermeasure is exercise, a combination of aerobic and resistive. That countermeasure perhaps needs to be replaced or reduced with the introduction of artificial gravity because gravity then becomes the countermeasure. Is that sort of — am I interpreting that right?
Bill Paloski: Yes, it could be that gravity could become the countermeasure but most of our crew members and most active individuals exercise anyway, so they’re going to exercise part of the time. Now maybe they don’t have to exercise as much in space if they have gravity too. But in order to maintain fitness, aerobic fitness and muscular strength at their preflight levels, they’re probably still going to have to do exercise. It won’t be gravity alone, but gravity could help.
Host: OK. Now let’s switch gears for just a second and we talked about some of the ways that gravity is good and the introduction and the case for having artificial gravity for deep space missions. You’ve already alluded to some of the complications of designing a system. You mentioned and previewed the idea of a very large structure. I remember “2001: A Space Odyssey.” That hotel was massive. I remember those long, those big hallways, right. They were nice and wide. I was like, wow, that would be nice for a spacecraft. So considering some of those engineering challenges, if this is something that was very important, to mitigate some of the things that you were talking about, some of the things that are happening to the human body, what are some of those challenges for designing that system?
Bill Paloski: So yes, designing the system is really the biggest challenge and what the system needs to look like. We know that we need gravity. Well, we know that people need gravity and it’s really for when they come back to Earth or to a different environment because our system — sorry, I’m going off on a tangent. Our systems are plastic and what that means is that they adapt, and they adapt to the loading that they’re given and that’s a feature, not a bug. So when you go to zero gand you spend a lot of time in zero g, you become a zero g individual and you don’t need the bone strength or the muscle strength or the cardiovascular activities and you need a different kind of guidance system, inertial guidance system. And all these systems adapt to make that perfect. The real problem is when you come back to Earth or when you go back to another g environment and all the sudden you need the old systems and you don’t have them. So when we talk about it being a problem, it’s not really a problem for the system, it means we have a really, really robust system, set of systems in our body to adapt to almost anything but if you expect to be able to operate normally when you come back to Earth or when you go to a planet, then you have to be able to protect those things.
Host: That makes so much sense. I think — it’s been described to me that the human body is just an ultimate efficiency machine, right. So, if you’re in the microgravity environment, as you’re saying, your body recognizes that it needs to turn off that sense of motion. I think it’s called intra-vestibular system, if I’m not mistaken.
Bill Paloski: The neurovestibular system, yes.
Host: That neurovestibular system, yes, it shuts that’s off, so up and down. It’s adjusting to there is no up and down. There’s just microgravity. Bone and muscles, you don’t need that as much. So yes, as you were saying, I mean it’s being efficient for the zero-gravity environment, not very efficient for when you land again.
Bill Paloski: Yes, exactly. So, the most obvious way to provide gravity is to rotate the vehicle and that’s what the big minds a century ago and a half a century ago thought about but that’s very costly. And so, the engineers have been thinking about other ways to do it. And indeed, there were two designs that were commissioned at NASA that I’m aware of back in the aughts and around 2005 plus or minus a little bit. One out of JSC by a guy named Kent Joosten and he designed a very interesting vehicle that was a very long stick-like vehicle about 100 meters across with a nuclear reactor on one end and a crew compartment on the other end that would spin and bring people all the way to Mars and back. And about the same time another guy called Stan Borowski at Glenn Research Center was working on nuclear thermal rockets and he designed one that could itself open up and turn into a like a baton, I think, that Joosten calls it, his, a baton and would be able to spin with the crew on one end and the power system, the propulsion system on the other end. And those things were feasible in terms of mass power, volume. They had some issues that the engineering community didn’t like. The maintenance of those things was really challenging, especially external maintenance. If you had to do an EVA, there were some questions about if you had to stop the rotation to do an EVA and then turn it back on. There were issues with guidance, navigation and control because of a spinning target on some place out there. And there were some other engineering challenges that made it so that it probably wasn’t the highest priority way to go about doing things. A second approach is to rotate part of the vehicle. In fiction, if you remember “2001: A Space Odyssey,” the deep space vehicle, I think was called Discovery, had a part of it that rotated but the rest of it was stationary. So, you may recall the scene where the crew member comes down a hallway and then goes through a hatch and climbs down a ladder and gets to the thing. Well, remember, I think I told you that ω2r is the equation, angular velocity squared times the radius is the equation for centrifugal force. And so, when the person is at the center of rotation, r is zero. So, the gravitational loading is zero. And the farther you get away, the higher the loading is. So, if you’re climbing down a ladder, of course, you’re getting farther away and every step your body gets heavier and becomes a bigger challenge for your muscles. But they were living and working and exercising in this environment that was spinning for eight or ten hours a day or maybe 12 hours a day and then going back to the rest of the vehicle for the rest of the time. So, it was intermittent, and it was rotating part of the vehicle. If you remember “The Martian” a couple of years ago, the Ridley Scott movie, with Matt Damon, they had a wonderful vehicle, Hermes vehicle which also had a very big rotating section that they spent a lot of time exercising and living in. That would be perfect to go in and out of there and go in and out of zero g and back and forth. Each of those things, though — then there was another design that was developed at NASA, I think at JSC, by a couple of engineers that was called the Nautilus system and the Nautilus had a stationary part and a rotating tube that was connected to the station. It never got built but it was another concept for how you might do that. So, part of rotating the vehicle or part of the vehicle saves some of the mass, power, volume but also has some of the same complexities that rotating the entire vehicle and actually there’s more moving parts. So, it adds some additional complexity as well. So, the engineers again are still not keen on that. So, finally, we come down to a solution which is what we’ve had to do on the ground for all of our ground-based studies and that is to rotate the people within the vehicle and that is to have a very short-radius centrifuge, where you can put a person on the centrifuge for a period of time, maybe an hour or two a day, maybe more. And that’s part of what our goal is in most of the ground-based studies is to figure out what’s that prescription, what’s the right prescription to be able to protect all these systems. You may couple this short-radius centrifuge within the vehicle to exercise, maybe you do exercise and rotation at the same time. Maybe you just do rotation and do your exercise separately. There are lots of different paradigms but fitting it inside the vehicle is much easier and much better. But it introduces some other problems. If you remember the ω2r equation that I brought up, now you have a vehicle that might have a radius of two meters and have a person who is two meters so at their feet is 1 g and at their head is zero g. So, across the body there are different g levels all the way up and down the body. I don’t think that’s such a bad idea after having done studies in bed-rested individuals on Earth. I think that’s feasible. I think that people can deal with that. The other issue with mainly the rotating vehicle but also in part with the rotating segment of a vehicle and it’s one that the astronauts brought up at the last meeting that we had is that you lose the third dimension of the vehicle. So, astronauts are used to being able to use the entire room and to be able to get any place that they want in the room, up and down, back and forth. And if you start moving the room around and it has a floor that it pulls you down to, then getting to the ceiling is harder. So, that’s another downside to the rotating vehicle and the rotating parts of the vehicle from an astronaut perspective.
Host: Yes, fewer things because right now, yes, they have a bunch of racks on the International Space Station. They have racks on the floor, on both of the “walls” and on the ceiling and they have access to all of them and they can adjust their orientation as necessary to best work with them. I remember one astronaut, I forget who it was, it might’ve actually been Mike Hopkins. He was telling a story of working on a rack and he just like he could not get to this one part and he called to the ground saying he was having trouble with his reach. And they said, just flip inside down because he had run this maintenance, this particular maintenance test so many times on the ground in that particular orientation and it didn’t even occur to him, oh yes, I can turn upside down. And you’re right, that’s one area you’ll lose. You’ll lose this access to something you can’t reach because you’re exposed to gravity. I guess also from an engineering perspective, you could say that you can lose having that system exist on that one side knowing that an astronaut may have some difficulty accessing it. Limiting that access might be a challenge, too. Yes. A lot of different designs that we just went over. It’s actually interesting. It’s not a single case sort of thing. There’s a lot of ideas being thrown out here. I think what I love having you here to describe, Bill, is that you’ve already alluded to these bed rest studies. If you’re thinking about what does happen to the human body in artificial gravity, these studies are some of the ones that we’ve been conducting at NASA to understand just that, what happens to human body in an artificial gravity environment? Can you talk about some of these studies, these Earth-based studies that you’ve conducted?
Bill Paloski: Sure. So, after the 1999 workshop, we decided as an international community that a number of studies should be done. We put together a plan for what studies should be done. And it starts with deconditioning subjects on the ground, like they’re deconditioned in space due to lack of gravity. And the model for that is head down, tilt bed rest. So, we put somebody in bed for in general somewhere between 30 and 60 days and strict head down, tilt bed rest. They can’t pull their heads up. They can’t get out of their bed. They go to the bathroom in the bed. They eat in the bed. They do all their playing and everything in the bed. So, by being tilted down, all the fluid from the lower extremities is moving to the upper extremities and they’re not exercising their bones and muscles and so it’s been a good model. So, we started with that and we have a lot of data on bed rest studies that have been done around the world since the late ’80, early ’90s. And we said, OK, that’s the control condition. And so now let’s try doing bed rest and starting to use short-radius centrifuge and so look at the prescription. And the first one that we did was one hour per day and the glevel was about two-and-a-half-meter centrifuge. The g level was two and a half g at the feet and one gat the heart, because of this g gradient that I talked about before. And at the head was a little less than 1 g, about .6 g or something like that. So, we’re stimulating all the systems, but they were being stimulated at different levels. And in order to understand this, we had investigators from every physiological system that might be affected and indirectly. So, if you have some changes in the bone and you put more calcium in the blood, then there might be some other problems in the renal system, in the system that’s clearing calcium or maybe renal stones would start to form. So, we had people, we had 27 different experts in different areas of the body, including psychological folks who kind of look at the psychology of being spun each day and what it felt like and how to keep from being bored and that sort of thing. And we actually had a plan for studies in the U.S., Russia and Germany, three set of group study. And we ran the pilot study with everybody’s approval of the measures that we would make, and we made standard measures so that everybody could compare their data. And right after just about the end of our study, [Exploration Systems Architecture Study] ESAS came along, and the artificial gravity project got canceled. So, it turns out that [European Space Agency] ESA was interested. ESA picked up the ball and they ran some other studies they called BRAG, you know, bed rest and artificial gravity. Ours was called AG and bed rest. And they followed through with a similar set of things trying to flush out the space of knowledge for how long and what g levels and whether you have exercise or not. So, they ran a few studies that contributed to the knowledge base that we’re developing on Earth. And then in recent years, we financed through HRP a set of studies in a new facility in Germany that was joint with a ESA group and we called it AG bed rest. And this is now starting to look at AG as a countermeasure specifically for the SANS issue, the shifting of fluids to the head. We completed that about two years ago and we have another set of these coming forward starting next year in Germany again. The Europeans are going off to Toulouse where there’s another capability for that in Slovenia where there’s a third capability in doing the same sort of thing. So the worldwide community is, when possible, kind of feeling out this entire set of what sorts of things work and what sorts of things don’t work and what sorts of side effects might you have for these systems and that’s pretty much where we’ve been for the past two decades is trying to put all those together. It’s still not clear that we need to do it, but we want to do it. Now we did try to fly a centrifuge on station around 2009 or 2010. And again, it was the same international community and we put together an international proposal to do it on station. And it turns out after a lot of hemming and hawing and the U.S. was going to provide the crew and the integration, the Japanese were going to fly it and the Europeans were going to pay for the device and have it built, and flight certified. It turns out that the station really isn’t designed for that much vibration. So instead of just having a person laying there, we were going to have a person with a cycle ergometer that would spin and do the ergometer. And that much vibration was bad for the station and it was decided that you would have to have a very expensive vibration isolation system that the Europeans weren’t willing to pay for to be able to do it. So, we kind of lost the possibility of doing human centrifuge work on station at this time. We’re still looking at the possibility as we start looking at commercial carriers. There’s at least one commercial carrier that actually designed in a short-radius centrifuge to the design. And so, they are not ready to fly that yet but if there’s a need, then we might be able to do that and back away from the station. The station’s vibration isolation would still make it be something that’s in low-Earth orbit but a little bit separated from the station so we could have crews go over to it and do their work or something like that. So that’s another concept for doing human studies in low-Earth orbit. And we really need to use the station or one of the commercial providers should be able to validate everything we’ve learned on Earth because it’s going to be different in space. We know it’ll be different in space and we can get a prescription on Earth using the techniques that I talked about but until we validated it in space, we won’t know that it’s really something, you won’t want to go to Mars with that system until you validate in space.
Host: Absolutely. And low-Earth orbit would definitely a good place to do that.
Bill Paloski: Absolutely, yes.
Host: You mentioned a few, when you talked about a community, an international community, it is pretty telling on how widespread the curiosity is in this particular field. I wanted to explore a little bit deeper, you talked about all the different experts, I think you said like 27 different fields, including psychological. What are some of those other fields? What are some of the curiosities that are bringing together this community that we want to find out what happens to the human body in artificial gravity?
Bill Paloski: Well, we have neurological experts, both neurological of the brain but also the stimulation of the muscles and the gut. So, we had those folks. We had muscle experts, and some are strength, muscle strength and endurance experts, but others are muscle physiology and how are muscles made up and do we change the kinds of fiber types in the muscles and those sorts of questions. Cardiovascular, some are interested in the vascular system and how the nervous system interacts with the vascular system. Others are interested in the heart itself. If you’re not pumping hard, will you start losing heart muscle or will the heart begin to atrophy in the physiologic terms? So yes, and we had renal experts. I don’t think we had any liver experts per se, but we had microbiology folks. I mean, we had basically every kind of expert and some where two or three deep. That’s how we got to 27.
Host: I mean, it’s just fascinating to me just how widespread and everybody’s getting together and pulling their own expertise and looking at their own expertise on this one item, artificial gravity. I find it absolutely fascinating. You also talked about a control. You know, you talked about this having your head tilted down in the bed and there was this control group and then there were some other items that you were sort of isolating. The introduction of artificial gravity, I believe, was there an introduction with or without exercise, was there something with or without lower body negative pressure? What are some of those things that you’re introducing beyond the control group of tilting down?
Bill Paloski: Right. So, the control group — and we do those in every experiment now. We use a control group that has no exposure to anything else. Another way of doing artificial gravity, which I didn’t mention, is using lower body negative pressure. And this simulates only part of gravity’s effects. it simulates the effects of bringing fluid to the lower extremities. You’re in a big vacuum chamber basically and it pulls fluid down. If you design it in the right way and also takes advantage of the loading, to load the bottoms of your feet, and the bottoms of your feet are incredibly important for understanding balance. And you may know that right after flight, crew members have a lot of disorientation, but they have trouble walking, ambulating and its coordination but it’s also not knowing how to interpret the sensors from the bottoms of their feet. They’re very important for you to be able to stand up. And so LBNP will stimulate the bottoms of the feet and will stimulate you to have to stand against this load. So, some of the musculature in the lower extremities, presumably the bones in the lower extremities, and then the cardiovascular system overall. And that requires no spinning at all. It’s just a vacuum system that you get yourself in to.
Host: Vacuum pants.
Bill Paloski: Yes. And so, we do the same thing. What we did with AGBRESA was AG and bed rest but also, we had an arm of that study that included LBNP instead of AG. So, it’s looking at, you know, what if you can’t spin anybody at all because of the constraints of the vehicle, could you still, what could you benefit from by using LBNP by itself?
Host: Now, OK, so we got some investigation in Earth-based studies that the bed rest study is proven to be very valuable in this field. You talked about the complications of low-Earth orbit and the vibration environment. Station didn’t quite get there but the potential for commercial providers. I know we’ve addressed this on this podcast actually, the five hazards of human spaceflight. One of them is altered gravity fields. And so, it comes to mind the idea that very soon we’re looking to put humans, the first woman and next man on the Moon in a sustainable way and we’re going to get research through a partial gravity environment. I’m wondering, is there any benefit to understanding how a human reacts to a partial gravity environment that maybe could be revealing for artificial gravity?
Bill Paloski: Absolutely.
Host: Oh, great.
Bill Paloski: And vice-versa. So, by looking at — we know that physiological systems don’t just turn on and off. They have some kind of threshold. And you have your thresholds tested for hearing periodically, right, and they’ll have a tone at a certain level, and they’ll make it louder and louder and it gets to the right level of loudness, you’ll hear it and you’ll push the button, right. So that there’s a threshold in hearing. There’s a threshold in almost all of our systems. And the question for what we could do on the Moon is, is the 1/6 g of the Moon above the threshold for many of the physiologic, for any or many of the physiologic systems. So, if you’re on the Moon for a long enough period of time, say six weeks or eight weeks, do you find that you don’t have any continuing loss of bone or muscle. You would expect it to stop immediately but does the exercise and the presence of that g level help with the loading across the whole body and is it above threshold? If it is, then we have a pretty good idea that when you get to 3/8 g on Mars, that’s also going to be above threshold. So, it tells us a lot about what kinds of countermeasures we might need to send to Mars, if we can find out on the Moon. So, from a biological standpoint, the basic physiologists and biologists really want to know where those thresholds are. We’re looking at some of those in rodent centrifuge on the station right now because you can spin rodents for long periods of time at a lot of different g levels and you can look at whether there are thresholds in those systems and whether you can identify them. We can’t do that right now with humans but if we had a centrifuge that we could use humans on, then we could do some spins on a vehicle periodically at Mars g, for instance, and be able to get some prediction of what kinds of protection we’ll get from Mars g alone, without all the rest of the stuff we’d have to send to be able to protect the crew members on Mars. So, I think there’s a lot of potential there, both ways the centrifuge can help us understand the thresholds but also being on the planetary surface can help us again with humans in the line of fire.
Host: Bill, this is such a fascinating topic, artificial gravity. I wonder, you know, there’s already, it sounds like artificial gravity is just, you see the astronauts in zero gravity on the International Space Station. You’re not used to it, but it sounds like there’s so much we’re already looking at and there’s so much to look forward to. You got the bed rest studies. There’s a lot of curiosity when it comes to Artemis missions. I’m curious, what excites you? Continuing with this field, you said you’ve been in this field for a very long time. What’s exciting you about the future when it comes to understanding artificial gravity?
Bill Paloski: I think getting artificial gravity in space is the key from my perspective. The things we’re talking about doing on the lunar surface to be able to get at least a single point on that curve but if we could do more with humans in space and actually we’re just getting ready to start these experiments with the rodents and the Japanese where we can start looking at thresholds in zero g. You know, we had an opportunity at the very beginning of station to fly something called the centrifuge accommodation module. It was a very large rodent centrifuge that was going to be connected to the module and for some reason, budget or something else, it got canceled right at the very beginning. If we had had that, we would know so much today about the thresholds about at least in small animals about their thresholds and about interactions amongst the various systems and we could be doing these intermittent studies with rodents on station, could’ve been doing them for 20 years but that went by the wayside. So, we’re trying to catch up and everything that we can do in space gives us a whole new picture on what happens. Can we interfere with adaptation in a positive way and keep that adaptation from continuing along those directions. And we know there’s lots of ways we can change adaptation on Earth by going to the gym, for instance. You know, if you spend a lot of time in the gym, you build up muscles. You end up if you’re dieting correctly, then you’ll end up losing fat mass and get yourself in better shape and if you stop doing that, then the adaptation continues toward what the norm is. We know we can do that. The question is how well can we do it in space with the systems that we’re most concerned about protecting for when they get to Mars and there’s nobody there to help them? So those questions about how can we do this and, of course, I’ve always been fascinated from the beginning with multisystem studies where you’re looking because you look at one study by itself, something else is going on that you’re not aware of. And until you get all the right people that are talking about their system and what the impacts could be on their system, then you’re not going to do it right. And station offers us an opportunity to do multisystem studies with international people, with a lot of smart people tied together. So that’s what excites me. And I’ve kind of moved to the management side over the last seven or eight years and I’m not doing my own research but I help to drive the directions of research and help to set the stage so we can do those things and that’s the thing that’s most exciting to me about AG research these days or what the possibilities are.
Host: Unbelievable. There’s so much and it’s so widespread I think maybe than people realize. It’s not — artificial gravity is just not like a small in-house thing, right. There is an international community bringing together so many different fields, looking at all the different systems as you’re saying, trying to get a good understanding of this and there’s a lot to look forward to. Bill Paloski, I really appreciate your time coming on. This has been such a cool topic to talk about today, artificial gravity. I really appreciate you coming on today.
Bill Paloski: Well, thanks a lot for giving me the opportunity. It’s always fun to talk about things that you love.
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Host: Hey, thanks for sticking around. Really fascinating conversation we had with Dr. Bill Paloski today. I really hope that you learned something. This podcast is available at NASA.gov/podcast as well as a variety of other podcasts we have all across NASA at different space centers across the US. We, here, on Houston We Have a Podcast, have a series called “Mars Monthly” where we’re putting out Mars related episodes on a human mission to Mars on the first Fridays of every month. Consider this a bonus episode, right, artificial gravity a lot of the things that we’re understanding about it are Earth-based studies but it’s very applicable to a mission to Mars. You can check out this and other episodes of this series, “Mars Monthly” at NASA.gov/Johnson/HWHAP/mars-episodes or just search Houston We Have a Podcast, Mars Episodes. I bet you it’ll come up. You can check us out on the Johnson Space Center pages of Facebook, Twitter and Instagram. If you have a question for us, use the hashtag #AskNASA on your favorite platform to submit an idea or a question for the show. Just make sure to mention it’s for us at Houston We Have a Podcast. This episode was recorded on December 7, 2020. Thanks to Alex Perryman, Pat Ryan, Norah Moran, Belinda Pulido, Jennifer Hernandez, Michelle Rucker, and Jenny Turner. Thanks again to Dr. Bill Paloski 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 the show. We’ll be back next week.