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Mars Ep. 11: Returning the First Martians

Season 1Episode 281Mar 24, 2023

Experts from NASA’s Mars Architecture Team gather to discuss the mechanics of returning the first astronauts from the surface of Mars back home to Earth. HWHAP Episode 281.

Houston We Have a Podcast: Ep. 281: Mars Ep. 11: Returning the First Martians

Houston We Have a Podcast: Ep. 281: Mars Ep. 11: Returning the First Martians

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 281, experts from NASA’s Mars Architecture Team gather to discuss the mechanics of returning the first astronauts from the surface of Mars back home to Earth. This is the final episode in a reboot of our series about a human mission to Mars. This episode was recorded on February 8, 2021.

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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 281, “Returning the First Martians.” I’m Gary Jordan, and I’ll be your host today. On this podcast we bring in the experts, scientists, engineers, and astronauts, all to let you know what’s going on in the world of human spaceflight. We’re continuing with a reboot of our series that outlines a human mission to and from the Red Planet. The eleventh and final episode discusses the mechanics of returning the first astronauts from the surface of Mars back home to Earth. This episode was recorded on February 8, 2021. Let’s get started.

(Transition to original episode)

So today, we’re wrapping up the series by talking about the end of the journey. At this point in a human mission, astronauts have used their spacesuits, they’ve collected some rocks and they packed their bags. Now they’re ready to get back to Planet Earth. Launching from the surface of another planet is an element of a Mars mission that will be wholly new, and the piece that will be truly breaking new ground. So the unique piece here is an ascent vehicle that will need to be pre-positioned on Mars, ready for liftoff way in advance, and launch flawlessly without ground support that we’re used to here for Earthly launches. To help dive deep into this area, we’re bringing in four – yes, four — experts. First is Tara Polsgrove: she has a degree in aerospace engineering from Georgia Tech and a master’s degree in systems engineering from the University of Alabama; she currently serves as the lead systems engineer with the Human Landing System program, part of the Artemis program, but before that she was in a leadership role on the Mars architecture team. We also have Dr. Tom Percy, who holds a Ph.D. in aerospace systems engineering from the University of Alabama and a master’s degree in aerospace engineering from Georgia Tech and a bachelor’s degree in mechanical engineering from Rochester Institute of Technology. Tom currently serves as the integrated performance lead for the Human Landing Systems program, part of Artemis, but before that he led ascent vehicle development for the Mars architecture team. We also have Dr. Doug Trent returning to the podcast — we met him on Episode 174, “Sticking the Landing on Mars.” He’s part of the Mars architecture team’s entry, descent, landing and ascent, EDLA, lead. He’s filling the roles that Tara and Tom held previously. And to help us wrap this series up we are bringing back Michelle Rucker, the lead of NASA’s human Mars architecture team, and we, of course, met her during Episode 142, “Preparing for Mars,” which helped us to sort of kick off this entire series. So here we go, returning the first Martians back to Planet Earth, with Tara, Tom, Doug, and Michelle. Enjoy.

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Host: Tara, Tom, Doug, and Michelle; what a great list of guests that we have to talk about this super-interesting topic, “Returning the First Martians.” This is a, this is a very interesting part of the, of the mission to Mars. You know, if we’re talking about a human mission to Mars, I think this is something that I don’t think a lot of people have explored, and I know I have a ton of questions about. And so, Michelle, in particular, I know you helped us to put together a list of experts. I am very excited to talk to all of you today. But Michelle, I think it’s very, very appropriate that you are joining us today as well. You helped us to kick off the series, and now you’re helping to wrap it all up, the whole, the whole mission to Mars. So, thanks for coming on, Michelle, it’s great to have you back.

Michelle Rucker: Hey, Gary. I am super-excited to be back with three of my favorite rocket scientists today. So first, I’d like to introduce you to Tara Polsgrove. She and I first worked together under the Constellation program. She was the integrated performance lead, I was the test and verification lead for the Altair lunar lander. So when Constellation wound down, Tara and I took what we learned about landers and ascent vehicles and we moved over to the Mars study group, and she led the entry, descent, and landing team over there. And we were joined by Dr. Tom Percy, who became our Mars Ascent Vehicle, or MAV — we call it the MAV — team lead. And about two years ago Tom and Tara were recruited back to the Moon for the Artemis program’s Human Landing System, what we call the HLS program. And so, to backfill when they jumped over to the Moon, Dr. Doug Trent joined us. And you met Doug on Episode 174, the Mars Lander podcast, where he, he talked about some of the descent work. And today we’re going to be talking about the ascent side of the round trip.

Host: Yeah, and it’s interesting because it sounds like we’re talking about the ascent side of the roundtrip, right, but we’re, we’re pulling in some folks from the Artemis world here into this discussion. I guess there’s a little bit of relation there too.

Michelle Rucker: Yeah. So, so Tom and Tara are playing hooky on the Moon, and they’re going to come on a little play date for Mars today. Full disclosure, I talked to their boss the other day, and, Lisa Watson-Morgan, who’s the manager for the HLS program, and she, she likes for them to engage with us because this whole Moon to Mars thing, it’s important to make sure both sides understand what the other is doing. And we try to take advantage of as much commonality as we can.

Host: Great. And I know ahead of this, Michelle, you referred to this as, or the MAV, Mars Ascent Vehicle, as sort of the crown jewel architecture of ascent, and so Tara Polsgrove, I’m going to pass it over to you to sort of add some context there. But first we want to hear a little bit more about you. This is the first time coming on Houston We Have a Podcast. So welcome, tell us a little about yourself and your work.

Tara Polsgrove: Yeah, thanks, Gary. So as Michelle mentioned, I’m the lead systems engineer for NASA’s Human Landing System program. We’re excited to land the first woman and the next man on the surface of the Moon. But I also have had a great experience working with Michelle on Mars missions. And so, there really is a lot of similarities or commonality between the two systems. And so hopefully we can talk a little bit more about that today.

Host: Yeah, and so when we’re talking about this, you know, the ascent part of a human mission to Mars, diving into that idea of it being sort of the crown jewel of the entire human mission to Mars architecture, can you tell us a little bit about why it’s such an important piece of this puzzle?

Tara Polsgrove: The special thing about the MAV is it really drives the rest of the human Mars architecture, or that system of vehicles that are needed to make this mission happen. We really can’t break it into pieces and assemble it on Mars. We have to deliver it in one piece. And it’s the biggest item that we deliver to Mars, so it drives the size that the landers will need. For every kilogram of growth that we have in the ascent vehicle, we’ll then ripple back and make the landers bigger, which ripple back again to make the Earth-to-Mars transportation systems bigger. All of that must fit within the Earth launch vehicle capabilities and our payload fairings, so it really that, that vehicle affects all of the other vehicles in the chain back to Earth. Another aspect that makes the Mars ascent vehicle unique is that in our current concepts, we’d like to pre-deploy the MAV to Mars so that we know that it’s landed safely and it’s healthy before we ever commit the crew to a landing. That means it may have to sit for a long time on the surface before it’s used. It may be many months to get to Mars, and then months or years on the surface of Mars, waiting for the crew to arrive and complete their mission before liftoff. And then when the crew are ready for liftoff, we have to have high reliability and high confidence that that vehicle is going to be ready to go when they need it. And lifting off of Mars has never been done before. We have done it six times on the lunar surface with our Apollo missions, but we haven’t lifted off from Mars before, so it’s exciting challenge, I look forward to the day that we can do it.

Host: Exciting challenge indeed. It’s driving a lot of the designs of other elements of a mission to Mars. And, you know, it’s got to sit there, and when you want it to work it’s got to work perfectly, and the thing that it’s got to do perfectly is something you’ve never done before. [Laughter] So that is, that is quite the challenge, Tara. You got to have a great team to, to kind of bring it all together.

Tara Polsgrove: Absolutely. And I’ve been very fortunate to work with some amazing people over the last several years, so I’m confident that we can pull it off.

Host: Yeah. An, another one of those people, I guess, that is working on this, this idea is Tom Percy. Tom Percy, this is your first time on the podcast as well; welcome. Tell us a little about yourself and your contribution to, to the ascent vehicle.

Tom Percy: Sure, yeah. Thanks for having me, this is really exciting. So, I’ve been working with the Human Landing System program for about a year-and-a-half now, two years, and I’m currently the integrated performance lead for the program so I work pretty closely with Tara on our lunar landers. But before that I was part of the Mars team looking at Mars architectures, got to spend a lot of time looking at Mars landers and the Mars ascent vehicle. So that was kind of interesting to see how it all kind of relates to each other and how what we learn at the Moon can apply to what we’re doing for Mars.

Host: And so, what are those high-level kind of comparisons? If we’re thinking about, you know, I think a lot of us are familiar with, for example, the Apollo lander — you know, we saw Neil Armstrong and Buzz Aldrin ride that to the very surface of the Moon in Apollo 11 more than 50 years ago. So comparing that and then to some of the architecture that we’re seeing for, for using that on a different planet and some of our efforts for the Moon.

Tom Percy: Sure. So, the, the ascent vehicle in general has a really interesting kind of family tree. So, you mentioned Apollo, that was, of course, the first time we used the system like this. The LEM (Lunar Excursion Module) ascent module carried two astronauts to the surface of the Moon. It wasn’t particularly large, it was only about three foot by six foot by eight foot, and the astronauts lived and worked out of that for their entire stay on the surface. In Apollo 11, we didn’t even spend a full day on the Moon, and Neil and Buzz only did one two-and-a-half-hour EVA (extravehicular activity). But by the time we got to Apollo 17, Gene Cernan and Harrison Schmitt stayed on the Moon for three days and did three seven-hour EVAs. And back in those days, we staged all of our missions from low lunar orbit. So, the Command Module pilot would stay behind in the Command Module in a circular orbit about 110 kilometers off the surface of the Moon. And so it took about four hours to get from the surface back to lunar orbit and redock with the Command Module. Artemis is going to be a little different than that for a bunch of reasons. One of the biggest ones is that the cabin is going to be bigger. Big thing driving that is the fact that we plan to live in it for a lot longer. And we’re going to spend about eight total days, and six days on the surface, living and working out of this Artemis ascent cabin. We’re going to do more EVAs, up to five. And while we are going to start off the Artemis program with two crew going to the lunar surface, we expect to evolve that to carry four crew. Now, by the time we get to four crew they’ll be living and working out of a more permanent surface hab[itat], but they’ll still be using the HLS to get to the surface and get back to orbit. Now, the other big thing that’s different about us and Apollo is the parking orbit. We’ve selected something called a near-rectilinear halo orbit, which is a very elliptical orbit over the poles of the Moon. It really kind of balances our need to access deep space with our need to access the lunar surface, but it’s significantly larger than the orbit that we used for Apollo. And so, while it took our Apollo astronauts about four hours to get back to orbit from the lunar surface, it’s going to take our Artemis crew about a full day to travel between the surface and orbit. And so because of that, they’re going to have to live in this cabin both in a zero genvironment and a 1/6 g environment, which is much different than what we had done with, with Apollo. And the bigger orbit also means that our ascent vehicle is going to do a lot more work than the Apollo LEM had to do. We’re going to do twice as many propulsion burns, we’re going to do about 50% more work to get back to orbit. And all of that translates into a bigger vehicle. Now the nice thing about that is a lot of the characteristics of the Artemis mission profile, like the bigger orbits, the bigger crew, the extra work that we have to do to get back to orbit, are all kind of in alignment with what we expect for a Mars ascent vehicle. We are looking at large parking orbits around Mars, and the Mars ascent vehicle will have to do even more work than the Artemis vehicle will to get back to orbit, but that typically means that that vehicle is going to be staged. And the second stage of the Mars ascent vehicle will do about the same amount of work as the Artemis ascent vehicle. Mars has twice the gravity of the Moon, that’s going to drive the amount of work that it has to do. The Mars crew will also be living in their MAV cabin for a, a decent amount of time in zero gravity, which means it has to function in both a gravity field and the zero-gravity environment. And all of that means that what we do with our lunar ascent system will give us a lot of opportunity to learn and apply those lessons to a MAV.

Host: Wow, that’s a lot, Tom. And it’s all of that I mean, in just a short amount of time, you just got me so excited for, for lifting off from the lunar surface because it would be a really good idea that the whole mission profile on what it should look like and some of the operations needed to learn how to do it on Mars. And I think one of the things that’s going through my head right now, just having that general concept of how Artemis would work and pulling from what we learn there, I wonder, you know, because I’m thinking about, you call it ascent, you can maybe even call it launch ,from, from the Moon. You know, you are ascending from the surface to, to a lunar orbit when you’re talking about Artemis. Now, I wonder, you know, is, if you’re thinking about Mars, it sounds like a lot of it is going to be pulled from Artemis for a Mars mission. But I wonder, I wonder when you’re talking about launching, thinking about the ground systems and the support and the atmosphere, you know, that we have to deal with on Earth, I wonder if some of the considerations for how we do Earthly launches might be mixed into those, what we learn on Artemis, to eventually come up with what ultimately will be used as an ascent profile on, on Mars. So, so what I’m asking, essentially, is it a little bit of both? You know, a little bit of Artemis, a little bit of Earth, and then you learn, you put that with the environment of Mars to, to come up with the right profile.

Tom Percy: Absolutely, absolutely. They definitely are like launch vehicles. And we’ll learn, we’ll take what we’ve learned from launching on Earth and what we’ve learned launching from the surface of the Moon, all of that goes together to, to build the MAV, but the environments are different. We kind of catch a break at Mars because the atmosphere is so thin. So we’re not beholden to the same kind of aerodynamics that we have on an Earth launch. But certainly, things like staging a vehicle and those sorts of things are things that are common between an Earth launch and a Mars launch for sure.

Host: Very, very interesting, Tom. Now, Doug Trent, you are also joining us, but returning to the podcast, so, so welcome back. And if you, if you don’t mind sharing a little bit about what your contributions to, with, well, I guess, before you were talking about sticking the landing on Mars, so what are your contributions to actually returning, you know, lifting off and ascending from the surface of Mars?

Doug Trent: Yeah, thanks. It’s great to be back. I had a great time last time, and I’m still looking forward to this whole conversation we’re having here. But so, like you said, part of my role is on the entry, descent, landing, and important to this part, ascent lead for the Mars architecture team. So obviously, the last episode I was on I was filling that role of entry, descent, landing, getting to the surface of Mars, and now, I’m here talking about getting the crew back off the surface of Mars and getting back home. And so, just again, really excited to be here and talk about that with you guys.

Host: So, what’s your role, Doug? Is yours, I think you have something to do with sample return, is that kind of your primary, primary concern for when you’re finally going to liftoff from Mars making sure that they’re taking some good stuff with them?

Doug Trent: So actually, sample return is another mission that NASA has that we’re working on right now. I’m not as involved with it, however, it does have a lot of crossover, things that we can learn basically for human Mars ascent vehicle. So, for the sample return mission, basically, for those that might not be familiar with it, it’s a series, it’s basically a campaign of missions very similar to what we have for the human Mars campaign, where it kind of starts with the Mars 2020 Rover, Perseverance, that’s actually be landing in a few days. Basically, it’s delivering some hardware, some tube collectors, and things like this, basically bring and collect some sample that will then eventually be transported to another vehicle that has an ascent vehicle component to it, which will then deliver those samples to orbit, and then eventually returning back to Earth. So, it has a lot of similarities that we can learn not just for the MAV but in terms of the entire Mars campaign for humans in terms of having all of these interworking moving components. So, for instance, when it comes to the Mars ascent vehicle for sample return, what we can learn for human MAV, you’ve got the component of this vehicle that has to be pre-integrated with its basically launch pad, the lander that it gets delivered to Mars on, prior to, you know, we can’t do that or have humans there on Mars to help put this thing together and integrate it with launch vehicle, it’s all got to be done here on Earth and then delivered to Mars in one package, like Tara was saying earlier. So, that obviously is something that Mars sample return is going to have to work with that we as well will be able to hopefully learn from. Another component of the sample return ascent vehicle that we can learn from is they are going to be basically collecting these samples from the surface and then bringing them to the ascent vehicle and putting them on as a payload to then send to orbit. In the human architecture we have a lot of ground systems and components that will be basically interacting with the MAV and the lander when it does arrive. So, you know, we might need to either hook up power systems that were already delivered on a previous mission to basically provide, you know, power for the MAV while it sits on Mars waiting for the crew arrival. You might also have things like power transfer to basically fuel the MAV up on the surface, if that’s what the architecture calls for, or basically producing propellant on the surface if that’s how the architecture looks, you know, there’s a lot of different inner workings. And then finally, too, the sample return ascent vehicle, once it lifts off from the surface of Mars and goes through its operations to get into orbit, it has to do a rendezvous with an Earth orbit return vehicle that’s already in place in orbit. Again, that’s very similar to what we’re going to have to do with the crew where the ascent vehicle’s basically getting from Mars surface into orbit, and then it’s delivering the crew to the Earth return, the Earth in-space transportation vehicle that will ultimately take the crew safely back to Earth. So again, there’s a lot of similarities there that we’ll have opportunity to learn for, from the sample return mission that’s coming up.

Host: OK. So, that’s more of the robotic mission, I see, for sample return. Definitely good stuff, Doug. Thank you again for joining us. I’m excited. A little bit later, we’re going to dive into the details of ascent versus descent. And I know you had a lot to share for Sticking the Landing on Mars whenever we did that podcasts so I’ll be excited to explore that component of, of this as well. Now, Tom, I want to go back to you, you did a really good job of kind of laying out just a lot of elements, even the operations really, of what’s needed for an ascent vehicle, making a lot of good comparisons to, to the Moon, particularly with Apollo, and then soon with Artemis. I want to kind of take a step back and get a kind of a grander picture from what you described though, Tom, and just talk about the bare necessities, right? So, if you’re talking about designing an ascent vehicle, what are, what is the basic things you have to have on this vehicle for it to be successful?

Tom Percy: Sure. So, you know, the basic function of the ascent vehicle is to fly the crew and our science samples off the surface of wherever it is we’re exploring. We can’t bring all of our scientists with us, so bringing samples back is a pretty important part of that. And with Artemis we’re planning on bringing at least 80 kilograms of samples back with us on every flight. But it, it essentially boils down to the ascent vehicle has to have all of the same functions as a typical crew launch vehicle here on Earth, like you alluded to before, but that includes not only the multistage rocket but also the crew capsule on top. We have to provide a habitable environment for our crew to live in and work in. But we also have to have the rocket part to be able to get them back into orbit. So, the ascent vehicle’s going to lift off the surface of Moon or Mars, just like any Earth launch vehicle. They have to have the propulsion system, they have to have a guidance, navigation and control system, and all the basic components of a rocket. But then the crew cabin is where the crew is going to spend all their time. They’re going to, they’re going to live and work there, that’s going to be their cockpit, their galley, their sleeping quarters, their washroom, their science lab. And if we use the, the ascent vehicle for habitation on the surface, it may even serve as an airlock to support extravehicular activities, or EVAs. And so, this vehicle has to be able to regulate temperatures, protect the crew from radiation and the vacuum of space, provide an atmosphere to breathe, and all the other functions that help keep a crew alive. And it has to work in two different gravity environments, especially for our Artemis mission where the crew is going to spend, you know, about a day on the way down, and a day on the way back up in zero gravity where they can float around just like, say, the way the Orion crew capsule was designed. They also have to be able to live and work out of it on the Moon where the gravity is, you know, 1/6 Earth’s gravity, but there are things that you can take advantage of the gravity to make certain subsystems function, like circulating air and it’ll be easier to do sleeping because you’ll be able to, you know, use a hammock. But other systems kind of have that zero-gravity feature that makes it a little more challenging to design on things like a potty and a crew hygiene system and those sorts of things. And so, we have to be able to live in both worlds. You can’t hang your sleeping bag off the wall like they do on the space station and expect to be able to use it on the surface of the Moon. You can’t put switches and storage units high up in a cabin where, when they’re on the surface of the Moon, the astronauts are going to be standing on the floor. And so, you have to worry about functionality and layout in a way that makes it compatible with both the zero g and the low-gravity environment at the same time. So that makes it a pretty complex system to try to try to figure out, even though the functions are pretty straightforward.

Host: Super interesting, just thinking about all the different phases of flight. Doug, kind of adding on to that, taking everything that Tom just described, when you’re thinking about Mars specifically, right, is it copy-paste from what Tom just described or are there requirements specifically when you have to talk about going to the surface of Mars?

Doug Trent: So, it is nearly copy-paste; the functional requirements are almost identical. So, all the things that Tom just said apply here as well. There are a couple of key differences that the MAV for Mars is going to have to accommodate. One is, like Tara had mentioned at the start of the episode, we’ve got an atmosphere on Mars that we have to contend with. So, again, it’s not very thick, so it’s basically just enough there to cause problems, and we have to consider it, but it’s not too much of a burden in terms of the propulsion systems. So that is one key difference that we have on Mars that we’re going to have to work with, work around. The other component that we have that is a big difference actually is planetary protection requirements. So basically, we’ve never been to Mars, so there’s a lot of, you know, debate that goes along in the medical community and science community in general in terms of planetary protection, not, or making sure that we don’t bring any contaminants from Mars back to Earth. And so, because of that, there’s a lot of consideration that has to go into design of the MAV that we might not see on some of the lunar counterparts. So for example, one of the things that we’re looking at is the option of using this pressurized transfer tunnel between the pressurized rover that the crews living and operating out of on the surface to get into the MAV, instead of going out and doing an EVA because going out and doing EVA, you know, you get a bunch of Martian dust and potentially other contaminants that could get on your suit, and then if you get in a MAV now the contamination is in the MAV and you can take it all the way back to Earth as it could, you know, piggy tail it’s way all the way back. And so, we want to try and avoid those kinds of potential contamination and hazard. And so, taking into account those things like a pressurized tunnel, to make sure that we, you know, abide by these planetary protection protocols, is going to be certainly an additional challenge that the Mars ascent vehicle is going to work with. The other thing obviously, is also, we have samples that we want to bring back from the Mars surface. It’s one of the big reasons that we want to go is to bring back some potential scientific samples. And these samples are going to, again, have to abide by similar protocols and protections to make sure we don’t get contamination, but also, you know, we’re going to have to accommodate those payloads in terms of getting them back up into orbit. How big they are, you know: if they’re a long core sample of Martian material, we’re going to have to fit that into the trunk, per se, in some way. Well, if it’s going to need to be maintained in an environment that’s very similar to Mars so it doesn’t degrade over time on its trip back to Earth, we’re going to have to provide power and thermal control and things like that to make sure that the sample maintains pristine condition all the way back to Earth. So, these are some additional design challenges that we’re going to have to face with the MAV. But in all, it is still very similar to the Artemis program. So that is something that we are looking forward to be able to learn from and build off of.

Host: Yeah, you guys are doing such a good job of painting a picture, I’m like imagining everything you’re describing, Doug, in my head. I’m trying to get a good picture of astronauts going from, you know, wherever they are, a rover or a habitat through a transfer tunnel or however, or to an MAV, a Mars ascent vehicle. Now, Tara, help me to kind of continue to paint this picture. When you’re going over to an MAV, how should I be imagining this in terms of how its positioned? Is there, you know, is there ground infrastructure that has been put there ahead of time like a launch pad? Is it coming, you know, off of legs or whatever? Give me a sort of a sense of what that looks like, the Mars launch pad, I guess we’ll call it.

Tara Polsgrove: Yeah, for Mars, really, the lander becomes your launch pad. There’s no infrastructure there on Mars like there is here on Earth with, you know, a nice setup with access gantries and umbilicals, and a team of people helping you, right? You’re on your own. In our current concepts, the MAV sits on top of the descent and landing vehicle, so that really is your launch platform. And when we land on Mars, we may not land on level ground. Of course, we’ll avoid the steep hillsides, but even being a few degrees off will affect things and the MAV will have to be capable of tolerating things like that. We may also have a configuration where the ascent engine is firing into the descent stage. It may even be embedded in the descent stage somewhat. So, the effects of that engine and the engine plume rushing back up on the vehicle will also have to be considered and taken into account, and we will have to separate from that landing vehicle safely. Another thing that’s different, you know, on Earth, we have teams of people that walk the landing site — or, I’m sorry, walk the launch pad — to make sure that there’s no debris. They call them FOD teams, Foreign Object Debris teams, and they scour it, make sure there’s no little, tiny bit of anything that could come back up and damage the vehicle during liftoff. There’ll be none of that on Mars. So, we will have kicked up some amount of debris during landing, and then as we get ready for ascent and light those ascent engines, they’ll be kicking up debris of their own. So, we’ll need a robust system that’s capable of handling any kind of debris that comes its way and lifting off safely.

Host: A robust system, very interesting. Now I’m trying to, I’m continuing to try to imagine all of the different components here now. I’m trying to piece together just, I think one of the things is like how, how the Mars Ascent Vehicle would get there? So you’re talking about it’s got to be positioned in such a way that it’s, you know, you’re taking care of dust, you want to be positioned just right, you know, as able to kind of fix these different angles. So, you know, is there, is there certain requirements that it’s got to land like upright or vertical, or you’re just sort of still kind of exploring the different options to make sure that whatever, however it gets to the surface, that it’s going to be propped up and ready to go, you know, I guess no matter how it lands?

Tara Polsgrove: Yeah. Well, we’ve got great assets in Mars orbit that are taking pictures and surveying landing sites, so we’ll have good understanding of the landing area. And we’ll pick our landing sites so that it’s as level as it possibly can be, right? And we’ll have advanced systems on board to make sure that we’re able to land accurately in those safe areas. But, like I said, even a few degrees off is something that has to be compensated for. And so it’s just not the kind of the perfect situation that we would have on Earth.

Host: Now, Doug, one of the things I’m thinking about is, OK, so the Mars ascent vehicle lands on Mars. It has to get ready, right, to eventually take those humans back up through the Martian atmosphere and into a Martian orbit. You know, what are the considerations for fuel? Do you bring all the fuel you need with you? Do you make it on the surface through, you know, in situ research your resource utilization? Is it a mix of both? Are there considerations there when you’re thinking about the, the profile?

Doug Trent: And that, Gary is the million-dollar question. So, even in NASA we are continually debating that exact question, whether we take propellant with us or we make it when we get there? So right now, basically, we’ve been challenged to use a design for the first mission, the first human Mars mission, that utilizes minimal infrastructure build up on the surface of Mars. So, basically what that means is we don’t want to have to take a whole bunch of extra components to basically pull off that first mission. So, in situ resource utilization, unfortunately, it does require some upfront work to get going. One is you’re going to need a pretty substantial power generation scheme on the surface to be able to provide the power necessary to actually gather that, you know, resources and convert them into propellant for the mass. So that’s challenging, and then also the actual technology itself of how do you convert Martian soil or oxygen or Martian atmosphere or whatever into usable propellant. So those are some things that, you know, we want to try and avoid those upfront investments here for the first mission. And so, we’ve been challenged with basically bring all the propellant with us. And so that’s kind of the option that we’re currently working with. Now, all that said, obviously in just a few short days, we’ve got the Mars Perseverance rover, which is going to be landing on Mars and with it, it carries an experiment, the MOXIE, the Mars Oxygen in-situ Resource Utilization Experiment, which is basically going to be helping us make those first steps of how do we convert these Martian resources into usable, in this case, oxygen, which is a major component of our propellant. So, it is taking that first step in terms of helping to understand how we do that, but they, being able to ramp that up and apply a full scale to a large human mission will be challenging to do on the very first mission, and so basically our first mission is looking at basically bringing all of our propellant. Now, that does provide some challenges. Obviously, I don’t get to just remove everything from the table and make it simple by bringing my propellant. Now, if I’ve decided that I’m not going to make my propellant but I’m going to bring it, I have to find a way to deliver that propellant to the surface. If I’m not putting it in the ascent vehicle initially when I land that vehicle, which typically I’m not because that would be exorbitantly heavy to try and put on one lander, which means now I’m going to land it prepositioned somewhere else on another lander. So now I have to figure out a way to transport that fuel across the surface of Mars and then put it into my MAV before my crew arrives, things like that. So it definitely comes with its own set of challenges. And so, you know, it’s kind of a give and take that we, again, continually are looking at and studying to try and understand what would be our best option in terms of fueling the MAV in our architecture.

Host: Michelle, when I, when I’m hearing all these fantastic experts describe all the different kind of needs for Mars ascent vehicle, comparing it to Artemis, you know, thinking about in-situ resource utilization, thinking about the giant team it takes and a lot of great minds to, to address some of these, some of things that these guys are talking about, Michelle, are just things that I wouldn’t have thought about, I wouldn’t have thought about as like a concern. So, thinking about what it takes to sort of bring the teams together here, to think about all these different components, you know, taking, and the challenges that have to be presented, just like Doug’s describing — well, we may not want to do that, so just make sure you have a good plan for having all the fuel with you, and how are you going to do that, how are you going to solve those problems –so it takes a big team, Michelle, right?

Michelle Rucker: So, so Mars is a system engineer’s dream. Almost every piece of it, there’s not necessarily one right way to do it, there’s a lot of different options. And every single one of those options influences other pieces of the architecture. So, Mars is interesting, you can’t just look at the lander or just look at the ascent vehicle and make decisions based on just the functional requirements of that one piece of the architecture, because, of course, for example, Doug just described what you choose to do, whether you’re going to make propellant or bring propellant, that influences potentially how big your lander has to be. So, it’s, it’s really fun; it requires a lot of, as you said, a lot of different discipline experts, thermal, propulsion, power, and people that can just visualize what happens if I change this one detail over here, understanding how that ripples through the architecture. I think Tara described at the beginning of, of her discussion, trying to chase those details down, knowing what happens if I tweak this one thing, what is the flow-down impact somewhere else? So, yeah, it requires a lot of people with both detailed discipline expertise, plus being able to look across the architecture at the big picture and understand how different things affect the whole thing.

Host: Beautiful. And, and Doug, I want to take that opportunity to toss it back to you because as I mentioned earlier you, you walked us through an in an earlier podcast the entry, descent and landing phase. Now, you’re talking about ascent phase. You’re one of these people that is thinking about the different, the different elements here, at least those, those two. So, give us a good understanding of, of those two elements in particular, and how they’re related, the descent part and then ascent when it comes to a mission to Mars.

Doug Trent: Right. So like Tara said, obviously, the, the descent system for Mars in this case is actually going to be our ascent pad, basically, our launch pad for the ascent vehicle. Obviously, there’s a very tight coupling between the MAV and the lander there. Obviously that, that lander is going to have to provide a whole bunch of services for our MAV to ensure that the vehicle is ready and prepared to perform its role of getting the crew back up into orbit. So that would include, you know, power, a stable place to launch from, propellant possibly to feed up into the MAV from, you know, other surface elements and things like that. And so, there’s a lot to deal with there. Now also, there’s this coupling between the two elements in terms of the, the task that they’re having to perform in terms of, so the lander obviously has to land somewhere on the surface of Mars, where we’ve indicated, and the MAV has to basically take off from that same surface or same location back to orbit. Now, unfortunately, the design and, of these two elements kind of prefer different landing site locations. So, when we were talking about the landing system, we had mentioned that it would much prefer to land somewhere that is a lower altitude so that you have more time to slow down and perform the soft landing. That’s something that we’ve seen very frequently with robotic missions on MAV — or, I’m sorry, robotic missions on Mars — they, they much prefer to go to lower altitude locations because they’re using large parachutes and inflatable kind of deceleration — or not inflatable deceleration, but inflatable airbag-type systems — to basically come to a stop on Mars, where the MAV on the other hand, because it’s got to climb back up off the surface, got to climb out of a gravity well, the higher that that vehicle can be on a surface on Mars the better it is because it’s just got to fight less gravity to get back up off orbit. So, again, lander wants to be as low as possible, MAV wants to be as high as possible, and the two are mated together. So obviously there’s kind of some trades that go along with trying to figure out what is an ideal location. Another component that obviously is important for the MAV too is the latitude. So the latitude, basically, how far north or south I am from the equator, plays a pretty significant role in how much work the MAV has to do to get back up into orbit, where the lander is pretty insensitive in terms of the latitude that it has to land at, because it’s using the atmosphere to really take out a lot of its energy to get to a landing site. The MAV, basically, if it’s further north or south off the equator, I’m not getting the benefit of basically the rotation of the planet throwing me into orbit, so now the MAV has to do some extra work to basically make up that difference. And so, the further north I go the more work that MAV has to do. But again, coming from the system engineering component of it, like Michelle was talking about, the MAV is not the only component. And obviously, one big thing is determining landing site is what’s at that location that I’m interested in doing. So, for instance, if I’m really interested in looking for the potential of ice and what that brings along with it, typically what we’re aware of is the further north you go the more likely you are to find that ice stored up in the Martian soil and things like that. And so, obviously, again, that’s an opposing kind of challenge that we have with the MAV where the MAV wants to stay as close to the equator as possible to try and minimize how much work it has to do to get to orbit, but if we want to go looking for water we want to push as far north as we can to try and find, to basically increase the chance of finding that ice water. And so again, it’s always these trades that we’ve got to work for from a systems engineering kind of perspective for this Mars architecture.

Host: Now, Tom, I’m going to do to you what I did to Doug earlier in the podcast and talk about copy-paste, right? So now, let’s shift over to the Moon for a second. Take all the things that Doug was saying about latitude and elevation, all these different considerations, copy-paste that to the Moon: do you have to have the same considerations, because, you know, for, for the Moon you’re talking about, Doug was talking about interesting areas in the northern parts of Mars, right, so you got the permanently shadowed regions of the Moon, does, does it change whenever you have to change that latitude whenever you’re thinking specifically about operations for Artemis on the Moon?

Tom Percy: Sure. So, there are the same kinds of coupled considerations that a change systems engineering kind of approach applies for our Artemis lander. How we land affects how we’re able to come back and those sorts of things. But how it plays out on the Moon is a little different than how it plays out on Mars. So, Doug mentioned that the landers at Mars want to land at low elevations because they want more atmosphere to use to slow down; we don’t have an atmosphere on the Moon and so we’re not using an atmosphere to slow down, and there isn’t a lot of elevation variation on the Moon. So, those kinds of things don’t come into play. But the, the kinds of places that we want to go on the Moon can be similar to what we want to do at Mars. So we’ve already kind of picked our general landing area — we’re going to the South Pole of the Moon. And that gives us a good general area, but the surface features drive a lot of how we select our landing sites. So, like Tara mentioned before, you kind of want to find level ground to land on; you want to try to avoid big hazards, ridges, craters, steep slopes, or big rocks, things that are going to make it difficult for you to land, and potentially kind of push you off, off angle and make it more difficult to ascend. But we also want to look for things, like, how to maintain good communication links to Earth. So if we’re landing at the South Pole of the Moon, the Earth is going to be relatively low on the horizon and surface features may block our communication. So we have to think about over time, how is our communications link with Earth going to be affected by the things around us. And we also have to worry about lighting. There’s no atmosphere on the Moon so there’s no light scattering and the polar landing sites mean that the Sun is going to stay relatively low on the horizon as well. And so that means that it’s going to cast really long shadows, from features like crater rims and rocks and those sorts of things. And that makes it kind of disorienting if people are trying to land the vehicle manually or even for some of our advanced systems that are going to be helping us try to land safely. And we also don’t want to be caught in a shadow during the time that our crew was supposed to be there working. They don’t really want a EVA in complete darkness, and it gets very cold in complete darkness and so we have to consider lighting. But at the end of the day, we also want to be searching for that good science, just like Mars is. And so, we’re going to be wanting to try to get close to those permanently-shadowed regions on the Moon. That’s, if there’s water there that’s where it’s going to be, that’s where we’re going to find it. From a science standpoint, from a long-term habitability standpoint, we don’t want to be too far away from those things. And then from a launch and return and orbital standpoint, we, we do kind of take advantage of this particular parking orbit that we picked at the Moon, this Near Rectilinear Halo Orbit, because it goes over the poles and because we’re landing on the poles, we’re not as concerned about latitude and how it drives the amount of work that the ascent system is going to have to do to get us back into orbit because those things stay relatively the same over time. And so we’re able to spend a little more time looking for that just right spot on the Moon that’s close to the permanently-shadowed regions and safe enough that we can make a good landing and still maintain good communications and good lighting conditions for the work that we have to do there.

Host: Now, Tara, I’m going to toss it over to you for a second because some of this is making me think, you know, we’re talking about all these cool places we want to land and then eventually, you know, lift off. But I think one thing we haven’t truly explored is talking about doing this on another planet and comparing it to how we do it on Earth, because when we launched from Earth we have ground systems, we have a lot of people that are working and preparing for, for different launches. We have all this support, people running around, doing different jobs, getting us ready. That all goes away when you have to think about launching, and developing a launch pad and everything, from the Moon and Mars. So, the considerations there when you know that when you’re getting ready to perform this mission, that you’re not going to have the people there to help you do some of this work.

Tara Polsgrove: So, one of the things that the ground crew is doing when you see a launch from Earth, they’re monitoring the vehicle from a dozen different camera angles or more, and they’re also watching every sensor measurement that’s coming from the vehicle. They’ve got a hardline data connection to the launch vehicle almost up to the point of launch. And they’re just looking at loads and loads of data. There are teams across the country that are looking at all this information to catch any problems early, to look at the trending, just to make sure that everything is in tip top shape and ready for launch. When you’re launching from another planet, you don’t have quite the same support. You have data from all those sensors, but it’s telemetered back to Earth and so it’s likely at a slightly lower bandwidth. So, you pick and choose the sensor measurements that you really care about that are really important to you preparing for launch and identifying issues. And then a lot of the rest of it is automated, so that the crew doesn’t have quite so many readings to look through. And then on Mars there would be a significant time lag. It’s a 40-minute round trip communication. So, you’re not going to be getting the same kind of go/no goes from your ground crew on Mars; really, the crew is going to have to be able to determine that for themselves with the data that they’ve got in front of them and with those additional automation.

Host: Now, Tara, I want to stick with you for, for a second here because we’re talking about, you know, we’ve talked about ascent a couple of times, but what I’d like to do is just capture the operations as if we were performing this mission, as if we were ascending. Tara, let’s stick with you for the Moon. Take us through step by step. I think Tom did it a little bit earlier, but really, a detailed all the way from ascent on the Moon to splashdown and recovery on Earth, what that mission profile would look like for, I guess, the final, the final parts of an Artemis mission returning to the, to Earth?

Tara Polsgrove: Sure, yeah. At liftoff, the vehicle ascends to a low lunar orbit, which is around 100 kilometers circular or about 60 miles off the surface of the Moon. And there you wait until you get the, just the right alignment to ascend to a higher orbit. So, Orion and our Gateway orbiting platform will be in a higher orbit called NRHO, near rectilinear halo orbit. We like to keep those in that higher orbit, it’s very stable, it’s easy to sit in those high orbits for long periods of time with minimal delta V (velocity) or minimal effort needed to maintain those orbits, so it’s perfect for an orbiting platform. So, the ascent vehicle will go up and rendezvous with either Orion or Gateway. The crew will transfer out of the ascent vehicle into Orion to go home. It’ll be carrying all of their lunar samples and equipment with them. So there’ll be a period of a day or so where they’re just transferring and getting things ready for the trip back to Earth. Then Orion will, will head home and take the crew to Earth while the ascent vehicle is either refurbished for a future mission or discarded.

Host: Very cool. Now, Doug, take that profile and we’ll move it over to Mars. So what, what is the mission profile from ascending from the surface of Mars, all the way back home to Earth?

Doug Trent: Yeah, sure. So, again, there’s a whole bunch of similarities here that we can learn from the Artemis program for Mars. So starting at the surface, obviously, you got the crew getting ready for launch, getting in specific suits that they’re going to ride up to orbit in. They’ve got to prepare the vehicle, any last little checks that they’ve got to do before obviously hitting the go button and doing the powered ascent. So, basically, you’ll have powered ascent. Now, obviously, once the vehicle gets into its initial parking orbit, again, similar to the Artemis program how they’re going into an initial lunar parking orbit, we also are going to go into an initial Mars parking orbit. And that just gives us an opportunity to make sure the first leg of our mission went well, all of our systems check out, we can do some potential guidance-navigation check outs and things like that, make sure we’ve got the right positions and velocities, before we move on to the next part of the mission. And so that would be basically performing the various propulsive activities necessary to get to, in this case, we’re going for the in-space transportation vehicle that will ultimately take the crew back to Earth. And again, that’s very similar to at least the sustain phase for Artemis program in that, you know, we’ve got to get the crew from the surface up to this orbiting vehicle that’s in this highly elliptical orbit around the planetary body that we’re coming from, and so, again, there’s a lot that we can learn from Artemis that’s doing that kind of operation to get ready for Mars.

Host: Very cool. Now, Michelle, I’m thinking about just a snapshot of what we’ve talked about so far in this entire “Mars Monthly” series, starting with our discussion with you about kind of preparing for, for the whole mission start to finish. And now we’ve taken deep dives into every intricate aspect at least — well, maybe not every but a lot of them, that’s for sure – of, of what it’s going to take to actually send humans to Mars and return them safely to Earth. Thinking about just a snapshot of this whole series, any final thoughts of just, of just thinking about everything we’ve talked about so far over this multi-episode near year-long endeavor?

Michelle Rucker: Yeah. It’s been a year since we started this podcast series right, right before pandemic world hit us. So this has been a lot of fun. What, what I like about the podcast series is that Mars can seem really overwhelming, because there’s just so many challenges. So, the podcast let us approach mission design the same way our system engineers do it. We, we break the whole thing down into bite-sized chunks. And then our subject matter experts, and you’ve gotten to meet quite a few of them over the last year, they get to work solving each of these individual challenges. And then our system engineers knit those solutions together. So we really appreciate the opportunity to tell our stories. Each story is really important and contributes to the whole end-to-end mission design. And I’m proud of the podcast series. I get an email from a student who listened to an earlier episode recently, and he said that what he liked about the podcast was we simplify all the individual difficulties. And these are his words, “in a way where each issue seems complex but solvable, instead of just complex and otherworldly.” And that is exactly what we do. We try to break these things down into little chunks and then solve them one by one, but because each chunk affects all the others then we have to knit them together and make sure that the end-to-end mission flows. So, there’s one thing that we hope the listeners have taken away from the podcast series is that although getting humans to Mars and back is a really big job, virtually the entire history of human spaceflight — everything we’ve done in our robotic programs, everything that we’re doing on the International Space Station, and everything that we’ll be doing in the Artemis program — has been a step on the path to Mars.

Host: Michelle, this has been truly fascinating, really, to be a part of this and you’re right, I did get to meet a lot of cool people and talk just in depth about things that have just been so revealing and just so fascinating to me. And I thank you so much for helping me to put this together. It’s taken a lot of work and like you said, it’s been almost a year that we’ve been, we’ve been doing this and working together. So, this has really been truly a fascinating endeavor and I thank you. And to Tara and to Tom and Doug, thank you so much for coming on, and going into so much detail on this final part of a human mission to Mars, returning from the Martian surface back to Earth. So, all four of you, I very much appreciate your time today. Thank you so much.

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Host: Hey, thanks for sticking around. That’s it for our Mars series. I really hope you enjoyed. You can, of course, check out more of our episodes of Houston We Have a Podcast at NASA.gov/podcasts. On the left navigation you’ll see a bunch of collections of different kinds of episodes: we have Artemis collection, we have an astronauts collection, Mars collection. Check out any of them if you’re interested in some of those topics. While you’re there at NASA.gov/podcasts, check out some of the other great shows we have at NASA. If you want to talk to us specifically at Houston We Have a Podcast, go to 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, just make sure to mention it’s for Houston We Have a Podcast. Thanks to Will Flato, Pat Ryan, Heidi Lavelle, Belinda Pulido, and 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. This episode originally aired March 5, 2021, as Episode 185. Thanks again to Tara Polsgrove, Tom Percy, Doug Trent, and Michelle Rucker for taking the time to come on the show. I hope you enjoyed us bringing this series back into your feed. Let us know your thoughts in comments and ratings on whatever platform you’re listening to us on. That’ll do it for the Mars series reboot. We’ll be back next week with your regular programming. Thanks for tuning in.