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 278, entry, descent, and landing experts at NASA unfold what it will take to accomplish a successful landing for humans visiting the Red Planet. This is the eighth episode in a reboot of our series about a human mission to Mars. This episode was recorded on November 17, 2020.

Transcript

Gary Jordan (Host): Houston, we have a podcast! Welcome to the official podcast of the NASA Johnson Space Center, Episode 278, “Sticking the Landing on Mars.” I’m Gary Jordan and I’ll be introducing this episode. On this podcast we bring in the experts, scientists, engineers, and astronauts, all to let you know what is going on in the world of human spaceflight. We’re continuing with our reboot of our series that outlines a human mission to and from the Red Planet. The eighth episode unfolds the intricacies of accomplishing a successful landing for humans visiting the Red Planet. Houston We Have a Podcast host Pat Ryan had a chance to chat with the experts on this very topic. This episode was recorded on November 17, 2020. Let’s get started.

(Transition to original episode)

Pat Ryan (Host): The subject is EDL, which stands for entry, descent, and landing, not edit decision list. We have two guests. Doug Trent from NASA’s Marshall Space Flight Center in Huntsville, Alabama, is the Mars architecture team’s entry, descent and landing lead. Doug has been working on the Artemis Human Landing System program, HLS, for three years, so he’s tied in to how what we’re learning from Artemis at the Moon is feeding into the development of the systems to use on Mars. Our second guest is Alicia Dwyer Cianciolo from the NASA Langley Research Center in Hampton, Virginia. She is the deorbit descent and landing mission segment lead for the HLS and a member of the EDL team for NASA’s Space Technology Mission Directorate. Alicia has been embedded with the Mars architecture team for years and has served on several science mission directorate robotic mission teams. She actually has firsthand experience landing something on Mars: she was on console during the Mars Curiosity landing in 2012 and the Insight mission landing in 2018. On this first Friday, our eighth episode on how to get to Mars. Here we go.

[Music]

Host: In listening to the Mars Monthly series, I’ve learned so much about a number of aspects of what it takes to complete a successful trip to Mars – emphasis is on “successful.” And I’ve come to realize more clearly how hard this is going to be: how much has to go right, how much smaller is the margin of error than it is for flights closer to home. And today we’re focusing on one critical aspect: landing a spacecraft with humans on board on the planet Mars. So for both of you, and Doug if you could start us off, what makes landing on Mars so challenging?

Doug Trent:Yeah, sure. So, a lot of times you hear about the seven minutes of terror and that seven minutes of terror really refers to the rough amount of time that’s required for our vehicles to go from atmospheric entry interface, basically where the vehicle just starts to enter the Martian atmosphere, all the way to touchdown. Like everyone else, we’re basically watching the vehicle perform the landing sequence autonomously, however because it takes anywhere from five to 20 minutes to receive those signals from Mars, we typically only get information about the landing after it’s actually already physically happened on the surface of Mars. So a lot of us are really just sitting there, almost in terror, clenching our fists, hoping that the landing went as planned. You know, so, Alicia has some details that she can share on that too.

Alicia Dwyer Cianciolo:Yeah, having been able to have the opportunity to sit through two landing sequences, you, you can hold your breath for seven minutes. It is a little terrifying. But, you know, we spent about eight years for the Mars Science Laboratory designing that seven, seven minutes, with a large group across the agency and with different companies. So, you know, a lot of, a lot of design and work goes into just those seven minutes making sure that we, we get it right.

Host: And there are some terrific videos that have been made, too, to, to give us the look at what that probably is like as it’s actually happening. That, the seven minutes part of it is the amount of time it takes for the vehicle to actually make the transit through the atmosphere to the surface, is that right?

Alicia Dwyer Cianciolo: Correct.

Host: And it’s terrifying because, for you, because you have to wait or because of what the vehicle is going through in the process?

Alicia Dwyer Cianciolo:Both. So, a lot of what we, what we try to plan for is all the things that we know the vehicle will encounter. And then we try to design additional robustness and margin into all the things that we, we know we don’t know as well as the things that we don’t know we don’t know.

Host:Right.

Alicia Dwyer Cianciolo:You know, we, by the time it gets to the surface we have to make sure that, you know, we’ve accounted for all of those. And you never know until it actually happens if, if we did it. So, as many times as, you know, that we’ve sent the rovers, every time it’s a different set of scenarios and a whole different environment that you encounter. So, we never really know until we get that signal back that says, it’s landed.

Host:There’s lots of different kinds of science that are involved for you guys to figure all this out. And so one of my questions, Alicia, would be how did you get interested in this line of work in the first place? I mean, what kind of paths of your interests or education and experience brought you here?

Alicia Dwyer Cianciolo:So, one of the things that got me interested was in 1997, NASA landed the first rover, Sojourner, on the 4^th of July, and I was in college at the time trying to decide what I wanted to do after I got out of undergrad. And I started watching it. It was one of those, those first missions where you could, you know, track its progress every day on the internet. And the, the things that it would learn each day, it was like Christmas, the new, the new rocks that it would explore…

Host:Right.

Alicia Dwyer Cianciolo:…the new different places it would go, it was the first time we’d ever got to see that. And it got me interested in, hey, that would be something really fun to do. And so when I got out of undergrad, decided to go to switch from physics to engineering as a major, one of the, the programs that I looked at was The George Washington University where you could take classes at a NASA research center and work on projects like this. And here it was about five years later, I was hired into this, the same branch at the center who, who worked on delivering that mission to the surface.

Host:Outstanding. Hey, Doug, what about you? Give me a brief tour of your education and experience?

Doug Trent:Yeah, so for me, kind of like Alicia, actually, it certainly wasn’t planned, it was more just kind of walking along the path as it presented itself. So, I mean, as a child, I grew up, my parents would always put me in front of the TV to watch, you know, space shuttle launches and things like that to try and keep me interested and excited in space. But as I went through school and got into college, as I was working on my undergraduate degrees, I really didn’t have that much of an interest of getting into space: it wasn’t necessarily I didn’t have an interest as much as I didn’t really think I had the capability to do it. It wasn’t until I got my first opportunity to really get involved with space, interning at the Marshall Space Flight Center, basically doing life support systems development and testing for the space station, doing that work really showed me like, oh, wow, I can actually do this, and this is absolutely amazing work that everybody’s doing, and I really wanted to be a part of it. And so, that really kicked off the next roughly six-year journey for me going through finishing my undergraduate work in mechanical engineering, and then moving forward into my graduate studies at the Georgia Institute of Technology where I focused on systems engineering. And so basically, that focus on systems engineering is what’s really led me to where I am today, you know, supporting the Mars architecture team doing entry, descent and landing lead. So basically, taking a step back from the mechanical engineering roots that I started with, and really focusing on that big picture: you know, landing on Mars obviously takes a lot of different things happening in concert all at once to get the job done. And so, having the systems engineering background, to be able to take a step back and really look at all the components that are playing into this, just really, that background helped me get to where I am today, but also, I just have found this really strong love of, you know, looking at the really big picture instead of the nitty gritty detail. And so that’s a little bit of how I got to where I am right now.

Host:Terrific. Now, you know, most aspects of human spaceflight come with various elements of risk, when we’re trying to do something that the human body is not built to do naturally on its own. Alicia, you’ve got experience landing a vehicle on Mars, so you’re conversant with some of those risks. But I wonder, what risks are there that, you know, robotic mission are things that you can accept that you would not accept for landing a vehicle that has human beings onboard?

Alicia Dwyer Cianciolo: Yeah, it’s a very challenging problem. They are, they’re not the same. And I’m really now, just now starting to appreciate the differences for what it takes to accommodate crew onboard. But really, I want to break this down a little bit because…

Host: OK.

Alicia Dwyer Cianciolo:…you know, we have the difference between landing robotic and human missions, but there’s really understanding the way that we, we’ve landed the robotic missions, and so far, or for the past two decades, NASA has sent really two classes of missions to, robotic missions to Mars. Lander missions. And there’s the 300-kilogram landers, which is kind of Mars Pathfinder, Spirit and Opportunity, Phoenix, and Insight. And then there’s the Curiosity rover and the 2020 Perseverance rover, that are both about 900 kilograms. So, that’s a three times increase in mass. And we had to change a lot of technologies just to get, you know, just to deliver, you know, that three times more massive vehicle.

Host: More so than just tripling up whatever you had done?

Alicia Dwyer Cianciolo: Right. It doesn’t, it doesn’t just scale…

Host:OK.

Alicia Dwyer Cianciolo:…the way you would expect it to. So, through the analysis we determined that we couldn’t use the technologies like the airbags or the small retrorockets that Spirit and Opportunity used, we needed a bigger heat shield that entry, to protect it during entry. In fact we had, we built the biggest one we could fit into the buildings, right? We had this limitation. But you know, now that we’re talking about sending humans to Mars, we, we have to completely rethink those technologies. The, the parachutes aren’t big enough to deliver the large masses that we need. So, just going from the 300 kilograms up to the 900 required us to change quite a few elements in our technologies. And then thinking about, you know, what it’s going to take to deliver humans and, you know, now we’re talking maybe 20 metric tons of, of payload. We, we can’t…

Host:Wow.

Alicia Dwyer Cianciolo:…right, even the things that we wanted, that we designed and upgraded for the Curiosity and Perseverance rovers, you know, now we can’t use the parachutes, we can’t use the retro rockets, we need something different. And so we’re looking at what it would take to do that. And it’s a whole bunch of different technologies, like, inflatable structures and, but they still have to fit into launch vehicles. So now, when you add crew we can’t have things like I mentioned, the parachutes: when it deploys it results at a very high g load on the vehicle, so like up to nine or 10 gs, which crew doesn’t want to have to experience. So, we’re looking at ways to redesign the entry guidances, and entry vehicle path through the atmosphere to reduce those gs to something that the crew can survive, plus it’s also a little bit much, much more comfortable ride on the way in. So, it’s those kinds of things that we have to take into account, especially when you have crew on, crew onboard.

Host: I didn’t realize that the difference would be quite so big: you went from like 900 kilograms to 20-metric tons. But in both cases you’re trying to land a payload safely, it’s just that one of them has living people onboard, the other one it has a robotic payload. Is, is there a, a significant kind of difference in how you work out those risks or is it a completely different set of calculation?

Alicia Dwyer Cianciolo:Well, one of the other primary differences is that with all the robotic missions that we’ve tried to land, they, several of them have been ballistic. So, which means, you know, we don’t control them on entry. And so we land where you land and that usually requires very large, flat rock-free areas, so hundreds of kilometers in diameter. And so we don’t get to pick exactly where it lands. For Curiosity we, and then for Perseverance, we will be able to, or we were able to steer it. Much, the first time we had a guided entry for those vehicles. And we were able to reduce that hundred-kilometer diameter footprint on the surface, you know, where we, it could have landed down to about ten kilometers in diameter. So the difference for when we add crew onboard is that now the crew isn’t going to want to walk very far to get their stuff, and what the architecture setup is that we deliver all of the vehicle, all the crew logistics, their supplies and their ascent vehicle and everything, before they ever get there. So, they know it’s safe on the, on the surface.

Host:So, now you have a, you have a matter of trying to target the landing of your human crew close to their supplies, which you’ve sent on ahead.

Alicia Dwyer Cianciolo: Right, exactly. And they don’t want to walk very far to get there. So now instead of landing in ellipses where we think, you know, we can get there within ten kilometers in diameter, we’re now talking about landing in something that’s one kilometer in diameter. And even the way that the technologies that allow us to do that, we’re actually still developing. They’re the precision landing sensors, where you have to put them, when they have to turn on so that we can actually see, you know, where you’re trying to go and where you’re targeting on the surface.

Host:Now, I understand that the actual spacecraft that’s going to land people on Mars has not yet been designed. Doug, is it possible to give me a sense of how big or how heavy you think that vehicle is going to be? Or compare to what’s already been landed on Mars?

Doug Trent:Yeah, absolutely. So, I noticed that a lot of what you were saying before, you know, you were shocked a little bit about how much mass that we’re saying it might cost. And a lot of that comes from the fact that humans tend to be pretty needy payloads, there’s a lot of stuff that they need to be able to survive in the environment base on Mars. Things like life support systems, you need water to drink, you need food to eat.

Host:Right.

Doug Trent: You need someplace to live and sleep and work out of, and so all these things come together to really increase the amount of mass that we really got to deliver to Mars compared to what we would need for a robot which, you know, typically doesn’t need those things.

Host: Right.

Doug Trent:So, Alicia kind of alluded at it. Previous payloads landed on Mars, you know, we’ve had a couple hundred kilograms with a lot of our rovers. And recently we’ve been, you know, putting down rovers that are upwards of one metric ton. But basically, a lot of our current study suggests that human class landers are going to require a capability to land roughly 20 times that, so on the order of 20, 25 metric tons per lander, onto the lunar surface. And…

Host: So, it’s…

Doug Trent:…these missions actually are going to, I was going to, well…

Host:What I was going to say, is that a similar number for the first vehicle that’s coming delivering supplies as well as the one that’s got the actual people in it?

Doug Trent:That’s correct.

Host:OK.

Doug Trent:So, each Mars mission, right now that we look at, we’re typically looking at around three 20-ton landers to do the mission. So, you’d have two landers delivering cargo before you land the third one with crew, and even that third crew lander is going to have some additional cargo on it.

Host:Right, right.

Doug Trent: So typically, when we’re looking at these three-lander architectures, the first one is going to land things like maybe your surface power systems, potentially some additional propellant for your ascent vehicle, that will actually take the crew off the surface. And then the second lander is, right now, typically designated for that actual ascent vehicle, because, you know, typically, we like to bring our humans back home after a mission.

Host:Right.

Doug Trent:And so, we have a full lander, typically dedicated to that vehicle that does that process to get them back off the surface of Mars. And then finally, the third one, once we’ve got everything in place, all the cargo, the landers, we’ve got, you know, our ascent vehicle, we’ve got a check out from it from Mars, it says it’s ready to go, it can come off the surface with the crew, then we’ll send our crew out and actually land them on the surface of Mars with, again, another one of those 20-tons landers.

Host:Does the increased size or maybe the shape of the vehicle or something, does that make a difference in how, in the degree of difficulty it is to, to land it softly, if we can say it that way?

Doug Trent: It does. So again, like Alicia was saying, you know, some of the previous technologies that were used for landing some of those robotic rovers, like, airbags were basically, you know, they just go on a ballistic trajectory, they kind of bounce around and roll around on the surface and they land where they land, not terribly precise. If we’re going to be landing multiple landers in a small area so that they don’t have to walk terribly far to get it, obviously that takes some different technology as well. As, like she said, the parachutes tend to induce some pretty significant loads on the vehicles during decent, those are so high that we really can’t subject astronauts to those levels, and so we’ve got to come up with new technologies and new methods to basically land these kinds of payloads on Mars to support that. So currently the designs that we use, what we’re looking at is basically employing two key technologies to really help us scale these landers up to this new delivery mass that we need. So, the first technology that we employ is a Hypersonic Inflatable Aerodynamic Decelerator, HIAD for short is typically what we call it. And basically what it is, is it allows us to get a much larger diameter to do our initial entry deceleration in the launch vehicle constraints that we have. So basically, you know, we’re fixed on diameter based on the launch vehicle that we fly on, maybe, in some cases, it might be an 8.4-meter SLS (Space Launch System) fairing…

Host: But you’re talking about the diameter of the vehicle itself, the part of it that is going to be leading the way through the atmosphere?

Doug Trent:Correct. But actually, what we’ll do is we’ll inflate large toroidal type sections of the vehicle that kind of come out and deploy to get a vehicle diameter that’s much larger than the primary structure of the vehicle, upwards of 16 meters. And so that’s going to give us the surface area, basically, to slow down initially when we start impacting the atmosphere, and that’ll help slow it down not as fast, so we don’t induce those huge loads that we would see via a traditional parachute.

Host:You mean you’re going to ease on the brake? You mean you’re going to ease on the brake…

Doug Trent:Right, exactly.

Host:…instead of slamming it.

Doug Trent:Ease on the brake. Got to be nice to our human payload.

Host:Right, OK.

Doug Trent:The second component, obviously is going to be, we don’t want to rely on just an inflatable airbag approach where we bounce on the surface and roll around because it’s just not going to be a very conducive way of landing sensitive payloads but also humans. And so, the second component is basically a supersonic retro propulsion technology. And basically what that’s going to do is once we’ve extracted as much energy as we can by using the thin atmosphere that does exist on Mars to slow the vehicle down, we’re going to have to do a little bit more to make sure that we get that soft touchdown, similar to like what we had in the Apollo days with a, you know, a soft touchdown in the lunar lander on the lunar surface.

Host:Right.

Doug Trent:And so basically, what we have is this supersonic retro propulsion component of the landing system that will basically perform the last little bit of propulsive work to basically get that very soft touchdown on the surface.

Host: Neat. Alicia, are there other technologies that, that you guys are trying to incorporate into this that you didn’t have for the robotic landers?

Alicia Dwyer Cianciolo:Absolutely. In order to meet our precision landing constraints, you know, so that the crew doesn’t have to walk so far — we can deliver them without, you know, running into any other pre-deployed assets…

Host:Right.

Alicia Dwyer Cianciolo:…what we will use are a whole bunch of sensors, and right now we’re studying whether we can keep those sensors onboard the entry vehicle or if we need to preplace beacons on the surface or in orbit. But essentially, what these sensors will do is tell us where we’re at and how fast we’re going as we’re flying in, into the landing site. So, we have what we call terrain relative navigation sensors, which are cameras that we take images of the surface as we’re coming in and compare those to onboard surface, onboard maps of the terrain to, to tell us exactly where we are and how fast we’re going. We also have, as we approach the landing site, we have a navigational Doppler lidar, which will tell us, again, our velocity and altitude and how, our range, how far away we are from the site. And then, as we get really close we, we’re anticipating and right now advancing technologies so that we can have a, a lidar that will take an image of the surface right where we want to land and tell us where the rocks and the hazards are so that we can basically avoid them with the hazard detection sensor. And while none of these have flown on any of our vehicles yet, this, Perseverance will be the first mission to, to demonstrate using the terrain relative nav[igation] system.

Host: Cool.

Alicia Dwyer Cianciolo:So yeah, we’re testing these things now, so that we can expand on them and help for future, help the future missions.

Doug Trent:I obviously am closely tied in with the Human Landing System that NASA is currently working as well, and so our HLS partners are currently developing lunar lander systems as part of the Artemis program to land humans back on the Moon. Now, obviously, we like to try and invest in technologies that can be applicable in other places, and this is definitely these landing sensors and these precision landing systems is something that, you know, if we’re going to build up a sustainable lunar presence, being able to land multiple payloads, again, in a very tight area together, so that they don’t have to walk far to go get their payloads on the lunar surface, that kind of technology is very directly applicable to here on Mars. And so we actually have a lot of commercial partners currently developing lunar landers that are going to employ these kinds of technologies that will be directly applicable to, you know, future Mars missions too. So, it’s definitely a great partnership that we have with commercial industry. It’s something that not just NASA is doing all on our own, we definitely have support from you know, companies like SpaceX, you got Blue Origin, Dynetics all developing landers right now under the Human Landing System program to help further these technologies along with us.

Host:And it only makes sense to make the best use of all the knowledge that you have.

Doug Trent:Absolutely.

Host: The one thing, in the things that you’ve described, there was one thing I was kind of listening for, and I didn’t hear, how do you – and especially with the human landers, and you’ve talked about the reasons why you want to land it fairly close to all the supplies that have been sent ahead, but — so, how do you steer that thing in order to get to that smaller target area? If you’ve got a large enough ship to be carrying the human crew of, we don’t know how many yet, plus whatever supplies you’re bringing along, moving at that kind of speed, how do you, do you steer it to head it toward the site you’ve identified?

Doug Trent: Right, so it’s definitely a lot of planning ahead of time, before we go and actually initiate any kind of descent. Obviously, there’s always going to be a little bit of uncertainty in terms of how exactly do my engines fire, do they fire for the exact amount of time that I, you know, have commanded to do so? And so those are going to introduce some errors. But you know, making sure that, you know, we have technologies and, and components in place that can basically execute the command as we tell them to do so, so that we get nearly as close to what we predict. Now, obviously, like I said, there’s variations and so we do have secondary, basically reaction control systems; it’s basically a second propulsion system on the vehicle that basically will provide control of the vehicle during these key descent maneuvers. So both during the aerodynamic deceleration, but also during the final retro propulsion. The second propulsion system helps orient the vehicle as it’s doing these maneuvers to make sure that we stay on track as we go in for our final descent and landing. And all of this is getting informed and happening in concert with these precision landing technologies, all of the, the optical observations that you know, cameras are taking pictures of, we’ve got maps of Mars that are pre-loaded onto the vehicle so that what it’s seeing and what it expects to see it can try and line those up. And all this is happening in concert to make sure that we get those very precise landings that we need to really execute these missions.

Host:And so, it seems, sounds to me, like the biggest part of that steering is to be aimed properly when you launch, at the right place and at the right time.

Doug Trent:Absolutely.

Host:There have been 10 — if I’ve got that right – there’ve been 10 successful landings of payloads on Mars from Earth…I don’t know how many from other planets, but eight by the United States, two by the Soviet Union back in the ’70s. Alicia, how valuable is the data from those uncrewed robotic missions, how, of successfully landing on Mars, how valuable is that data in helping you develop the current EDL plans?

Alicia Dwyer Cianciolo:It’s very important: what it’s helped us do is provided 10 trajectories, paths through the atmosphere that tells us what the atmosphere is like at each of the different altitudes that we passed through. Now, granted, those are for a specific time, season, location, so they, they’re a very limited data set. But for, in some regions of the atmosphere it’s all the data that we have. What makes them even more valuable is that missions like Opportunity and Spirit and Curiosity, they’ve been on the surface at a location where we know exactly where they’re at, for years. And most, the rovers that are there all carry a science package that allows them to measure the density, temperature and pressures at the surface. And that really informs our, some of our atmosphere models so that we can, the orbiting spacecraft will be able to correlate data with that. It provides, so there’s two spacecrafts right now, Mars Odyssey and [Mars] Reconnaissance Orbiter, two U.S. spacecraft, and then there’s the Mars Express, the European one, that are taking data of the upper atmosphere all the time.

Host:OK.

Alicia Dwyer Cianciolo:And so that we can correlate some of that data to the, with the surface measurements, and then it can inform our, our model development and our, that we use for the design of the future missions. So, there’s some regions of the atmosphere where we just don’t have any, any data, and that’s, you know, we, we use that to inform future mission planning as well as future mission design. What, what kinds of missions could we send, whether it’s flying ones — so there’s a helicopter that’s going to be flying on Mars 2020 — that’ll give us a new opportunity to look at different atmosphere in different regions that we haven’t been able to at this point.

Host:And you’re talking about meteorological conditions. The one that I know anything about is dust storms, we hear about dust storms on Mars a lot. What kind of challenge do you face if it’s time to land on Mars and there’s a big dust storm going on?

Alicia Dwyer Cianciolo:Well, until recently, we said we won’t land if we’re in orbit. [Laughter]

Host: We’ll wait. [Laughter]

Alicia Dwyer Cianciolo:We’ll try to wait it out, right? And so, for most of the year it is not global dust storm season and so that would be a reasonable assumption to make. There are times when you do get those, those global storms that do take months to decay. But what we, what we’ve planned for so far is that you could stay in orbit and wait. The problem is, really, it creates a level of uncertainty that we just haven’t been able to, to understand and measure, because just the atmosphere on a, on a clear day is, it has uncertainty in it and variability that we have to plan for. Adding in the additional complexity of a dust storm, which essentially what it does is it, it, it heats up the atmosphere so that all the density is at the higher altitudes, and there’s lower density near the surface. So, it just makes, you know, most of our models aren’t set up to, to capture the full variability that that could entail, we don’t have a lot of measurements during that. So, it’s really just as an uncertainty in the mission design and planning that we would like to avoid. The other challenge is that, and some of the global storms where you just can’t see the surface, it does make using those precision landing sensors a challenge. So, there are lots of things that we would like to avoid with that. The other challenge is that with our capability in our data that we have so far, we can, we can forecast weather on the surface of Mars for about a day; that’s about how good we can predict ahead. So, it would be OK if we were in a, say, a one sol, one day of Mars orbit around it, and only took 11 hours to get once we deorbit from that, from that to get to the surface it would take 11 hours, we think we’d have a pretty good estimate of what the weather at the surface would be; where if we decided to be in a larger orbit, say a five sol or an orbit that takes five Mars days to go around, it would take a two and a half day, days to, to get from, you know, once you deorbit that to the surface it would take two and a half days. Well, since we can’t predict out that far, that also adds an additional uncertainty.

Host:Right.

Alicia Dwyer Cianciolo:We’re trying to identify what, what information we would need to improve those prediction models so that, you know, would enable that kind of prediction capability for those types of missions. But right now, we would like to say, we’d like to avoid landing in a dust storm. But if we had to, then we’d have to add additional robustness to the system in the way of extra propellant, or, you know, we’d have to, we’d have to…

Host:To be able to wait.

Alicia Dwyer Cianciolo:Right.

Host:Yeah. One important part, got to be an important part of the consideration for this, has to be the location on the surface, like where on Mars do we want to land? Doug, can, can you give me an idea of what are the characteristics of a good landing site, or a perfect landing site?

Doug Trent:Yeah, so choosing a landing site is actually quite complex of a task. There’s a lot of factors that go into play. For the robotic landers, the previous Mars missions, there’s really always been a very clear science objective that’s been defined in partnership with, you know, lots of NASA scientists. However, when landing humans on Mars, there’s some other considerations that come into play. Obviously, we want to do science and things like that, but one of the largest things that has to be defined is, you know, what are we going to do when we get there? Are we going there because we want to do human exploration? And so, in that case, we might be landing in one spot, want to do some scientific exploration in that area and then land in a completely different area on the planet to do science exploration somewhere else. That’s one way. Another one might be, if I’m hoping to develop a longer-term human presence, maybe a Mars colony perhaps, the latter, so that Mars colony is going to require a site rich in raw resources which can be refined to use and utilized for further developing the colony. So, things like ice, so that we have water to develop, and we can convert that into air to breathe. You might need, you know, a site rich in specific minerals and things like that, that I can refine into resources to actually build structures and things like that. So outside of these questions, obviously, there’s also the performance related part of it. So, in terms of selecting the landing site, not all landing sites are the same in terms of how they impact the, the design of our vehicle. So, things like surface condition, how soft or how hard is the surface that we’re going to be physically landing on? How many rocks and boulders are there, and how far are they dispersed or how close are they together in the potential landing zone? What’s the slope, the elevation of the local terrain? Is it, you know, perfectly flat or maybe is it kind of like a little foothill that we’re landing near or maybe even on? All these play a role in the design of the actual lander itself. However, basically, landing is not the only component. So obviously, we’re here talking about how we, how do we stick the landing, but unfortunately, taking it back on a more systems perspective, landing isn’t the only component. So obviously, with our crew, like I said earlier, we want to bring them home. And so ascent is another portion of the mission, very important part of the mission to get our crew home. And unfortunately, the landing site selection and how that impacts the ascent vehicle might not be the same as how it impacts the descent system. And so, you know, for instance, in terms of the landing vehicle, I would prefer the land, the landing system at as low altitude as possible. And that’s mainly because I’ll get a more dense atmosphere, it allows me to slow down better and so I can have less propellant, basically. However, the ascent system would prefer to land on top of the highest mountain possible, because that just puts me that much closer to orbit, which then it requires less propellant. So really…

Host:But then you’d have to walk down the mountain, right? You have to walk up the mountain to get to it.

Doug Trent:Yeah, absolutely. And so, it’s just basically highlighting the fact that there’s this trade amongst the various different components so that the lander isn’t the only component in a Mars mission, there’s a lot of other things that go into place. And so, for me, an ideal landing spot would be something that’s flat, has a nice hard surface, so I don’t have to worry about my landing gear sinking into like a really dusty surface or something like that.

Host:Right.

Doug Trent: Large enough that I can land several vehicles in close proximity. So, like you said, top of a mountain, probably not a good idea. And really only a small amount of smaller rocks, so I don’t have to worry about maybe a landing gear, you know, hitting a large boulder or something like that, or maybe a larger rock that puts me in a weird tilt when I land or something like that would be not ideal. And lastly, I’d like it to be close to at least some useful resources, particularly something like water ice, that can be useful for, you know, life support, drinking and things like that.

Host:Particularly if it’s an early mission, where you’re going to have to be setting things up from scratch.

Doug Trent:Right.

Host: You don’t want to have to go far to, to get them.

Doug Trent:That’s, that’s true.

Host:I, I, I can understand as you say it that there are so many different things to, to take into account that it’s, where you want to land is not a simple answer. And, and one of the big parts of it, as you noted, is that it depends on what you want to do there. So, that’s all part of the stuff that you guys have still got work to do to figure out in the years to come. One thing we didn’t talk about, that I want to now, as we’ve considered all these elements and kind of try to synthesize it, is to flesh out the human detail for me. If we all three were strapped into the Mars vehicle and headed down for the surface, Doug, can you give me a sense of what it would look like, and sound like and feel like as we rode through the Martian atmosphere to the surface?

Doug Trent:Yeah, so unfortunately, I have not had the chance to fly on a space shuttle or maybe land on the Moon.

Host:Yeah; not yet.

Doug Trent:Yeah, not yet, maybe someday. So, it is a little bit challenging to say how it might look and sound inside the vehicle. But we can definitely make some educated assumptions or guesses on how that might look. So obviously, the design of the crew cabin is going to have a huge impact on what it physically looks like and sounds like. You know, the materials that it’s made of, how big it is, all these things are going to play a role in how that might happen. However, with the design of the current entry, descent, and landing system, there is a bit that we do know that it’s going to be similar to. Based on the design that we have right now, it’s going to be very similar to both a shuttle landing and a lunar landing; you kind of get components of both. So, this is because, you know, like I said, the initial parts were definitely entering an atmosphere, going very, very fast, and so you’ve got that component very similar to a shuttle how it reenters the Earth’s atmosphere — obviously, it’s going hypersonic and so you’re going to get plasma buildup and things like this. So, any kind of windows that you might have, you’re going to see just fireballs out the windows…

Host: Right.

Doug Trent:…similar to any kind of re-entry during Earth. So, we would expect to see similar kinds of events while landing on Mars, and, of course, the sounds that would accompany those kinds of things. However, unlike a shuttle re-entry and landing, the shuttle lands, basically, it glides down back to the surface and lands on a runway. However, like we were talking about, again, we’re going to have a hypersonic retro propulsion, supersonic retro propulsion system, where we have to basically turn on engines to do the final little bit of landing. So that’s where basically the more like a lunar landing component comes in. So obviously we’re going to have the sounds of you know, pumps spooling up to start moving propellant, you’re going to have engines igniting, all the good sounds that comes with a loud, powerful, rocket engine igniting and so, you’ll have that component as well that’s maybe a little bit different than the shuttle system. Now, the crew is going to experience acceleration similar to those experienced by the shuttle astronauts. And that’s not just random, that’s by design. We obviously have a very good understanding of the limitations of the human body under accelerations and have designed the lander and the descent profile to basically provide that environment such that it’s not too extreme for the astronauts. However, we are still working with our medical community on the finer details. So, things such as seating orientation: you know, are they going to be sitting upright like we sit in a chair here on Earth, or is it going to be, or is it going to be more of an inclined position to better accommodate the acceleration load? So, for instance, you know, we might lean them back at some kind of angle to put their back towards the vehicle so that we have a good, large surface on their body to impart some potentially higher loads. So, things like this we haven’t really nailed down yet and it’s still under study, but we’re obviously working with the various communities necessary to kind of flesh these details out.

Host:One of the things that it occurs to me you’ll also, when working with the medical community, you got to consider the fact that these astronauts who are about to land have been in a weightless environment for, for many, many months now, and they may be a lot weaker than, than they were when they launched.

Doug Trent:Yeah, that’s absolutely correct. I mean, right now, the, the missions that we’re looking at, they could take months, basically, to get the astronauts to Mars. And, you know, we’ve seen from astronauts coming back from the space station all the time, you know, they’ll land wherever they land and typically we have a whole host, a whole crew of people from Earth to help them out of the vehicle and move them to, you know, whatever transport vehicle to move on after they’ve landed. That’s something we’re not going to have on Mars. And so, that deconditioned state of the astronauts when they get to Mars is certainly a very large concern that we have. Ideally, they’ll be able to get out of their chairs; the size of these landers and how tall they are, they’re likely going to have to probably crawl down a ladder or something of that sort to be able to get to other assets that might be on the surface, like a rover or other payloads or things like this. So, a lot of it right now, the approach is, well, when they land on the surface we’ll give them a certain amount of period, maybe it’s a few days or a week or so, to basically condition to that new environment, basically the Mars gravity, to hopefully give their bodies enough time to at least kind of get their walking legs back underneath them to basically execute the mission.

Alicia Dwyer Cianciolo:But that’s a good point. So, what, so that means that the, whatever they land in has to have everything that they need to live for that amount of time.

Host:Right.

Alicia Dwyer Cianciolo:And we’ve talked about being able to maybe just deliver the crew in something like an Orion capsule, or you know, something, a smaller vehicle, and then have them get out, but because of this deconditioned crew environment that they will be in, we do need to have them land in something that’s got all the things that they will need to live for that long before transferring.

Host:Right. Alicia, you’ve, you’ve already landed robotics on, on Mars before; have you thought what it’d be like the first time you can land something that’s got human beings inside of it?

Alicia Dwyer Cianciolo:You know, back when the movie “The Martian” came out, they had all these different ideas of how to, you know, as we’re designing these and we’re looking at, you know, how can we use our imaginations to figure out how all the different parts could be interchangeable, or if something did go wrong how would you, you know, address that. You know, so it’s, you know, getting out and looking for the first time at this new planet that we haven’t ever, you know, looked at with our with human eyes — we’ve done it with robotic eyes a lot of times — and try to just imagine what that would be like, I think it comes back to the engineers on also imagining, you know, what could go wrong with the systems that we’re building and how we could, you know, make sure that, they’re robust to a wider range, because we just don’t know what it’s going to be like. So that’s, that’s part of the challenge and it’s also part of the fun.

Host:Yeah, to be able to figure out how to do something that people have been thinking about doing for generations; it’s got to be a really cool job to have. Alicia and Doug, this has been terrific to hear your perspective on this. Thank you, very much, and good luck with the work.

Alicia Dwyer Cianciolo:You’re welcome.

Doug Trent:Thank you.

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Host: Hey, thanks for sticking around. I hope you’re enjoying our reboot of the Mars series. You can check out more Mars episodes that we have at NASA.gov/podcasts, make sure to click on our podcast, and we have a collection of episodes up on the left navigation, of course containing a lot of Mars episodes, but you can check out some of the other collections we have, as well as listening to any of our episodes in no particular order. There are also many other shows across the whole agency that you can check out while your there. If you want to talk to us specifically, we’re on the NASA Johnson Space Center pages of Facebook, Twitter, and Instagram. Just use the hashtag #AskNASA on your favorite platform to submit an idea for the show, maybe ask a question, just make sure to mention it’s for us at Houston we Have a Podcast. Thanks to Will Flato, Pat Ryan, Heidi Lavelle, and Belinda Pulido as well as Jaden Jennings for their part in the podcast as always. Shoutout to former podcast team members Alex Perryman, Norah Moran and Jennifer Hernandez for their help in the original episode. The episode originally aired on December 4, 2020, as Episode 174. Thanks again to Alicia Dwyer Cianciolo and Doug Trent for taking the time to come on the show. Next week, for Episode 9 in our Mars series, we chat with Paul Niles about what’s so interesting about Mars from a planetary scientist. Give us a rating and feedback on whatever platform you’re listening to us on and tell us how we did. We’ll be back next week.