“Houston We Have a Podcast” is the official podcast of the NASA Johnson Space Center, the home of human spaceflight, stationed in Houston, Texas. We bring space right to you! On this podcast, you’ll learn from some of the brightest minds of America’s space agency as they discuss topics in engineering, science, technology and more. You’ll hear firsthand from astronauts what it’s like to launch atop a rocket, live in space and re-enter the Earth’s atmosphere. And you’ll listen in to the more human side of space as our guests tell stories of behind-the-scenes moments never heard before.

Episode 53 showcases Dr. Stan Love, NASA astronaut and all-around smart guy, who flew to the International Space Station in 2008 and has worked on a number of flight analog programs to understand how to conduct deep-space missions. Love explores the challenges that will need to be tackled to make a mission to Mars successful. This episode was recorded on May 18, 2018.

Transcript

Pat Ryan: Houston, we have a podcast. Welcome to the first episode of the second year of the official podcast of the NASA Johnson Space Center. This is episode 53; Mars is hard, here’s why. I’m Pat Ryan, your introducer this week. Gary Jordan comes up in just a moment. This is where we bring NASA’s scientists, engineers, astronauts, and other experts to talk about the stuff you want to know about human spaceflight. This week’s guest covers a few of those boxes. Dr. Stan Love, bachelor’s degree in physics, masters and PhD in astronomy, was selected as a NASA astronaut in 1998 and flew to the International Space Station in 2008 on the space shuttle mission that delivered and installed the European Space Agency’s Columbus Laboratory Module. Stan spent more than 15 hours outside the station on two spacewalks on that mission. He also operated the robotic arms on the station and the shuttle Atlantis.

Since then, he’s worked in a number of flight analog programs on land and underwater programs that are figuring out the nuts and bolts of how to make deep-space missions work as planned. So, he understands better than most why sending human people to Mars will be really hard to pull off, but not impossible. And he talked with Gary about the details of that earlier this year. So, as they say, let’s jump right ahead to Gary’s talk with Dr. Stan Love. Enjoy.

Episode 53 showcases Dr. Stan Love, a NASA astronaut, who flew to the International Space Station in 2008 on the space shuttle mission that delivered and installed the European Space Agency’s Columbus Laboratory Module. Stan has worked in a number of flight analog programs on land and underwater programs that are figuring out the nuts and bolts of how to make deep-space missions work as planned. He understands better than most why sending human people to Mars will be really hard.

[ Music ]

Host:Houston, we have a podcast.

[ Music ]

Gary Jordan (Host): All right, Stan, thank you so much for coming today and talking about why Mars is hard.

Stan Love:My pleasure.

Host:So, this is — this is a kind of a continuation of — this was the talk that you gave a while back and it was — and I — my compliments to you. It was wonderfully, wonderfully engaging and you sort of spelled out in various different areas as to the why Mars is hard. And you kind of sectioned it off in a way that is super understandable really. It was a good presentation.

Stan Love:Thank you.

Host:So, if you wanted to, I mean since you’re here, let’s go through that step by step. And you kind of categorized it into several different things. I guess the first thing we can start with is the one that said that’s pretty obvious is distance. Mars and Earth are pretty far apart.

Stan Love:Yes, they are. So, the Moon is pretty far away. It’s a planet-sized object and you look at it in the sky and you can blot it out with your thumb, okay? So, it’s pretty far away.

Host:Yeah.

Stan Love:Mars is a world sized object and it’s a dot, okay? You don’t even see a disc.

Host:Right.

Stan Love:And it’s a dot that most people can’t go out and even point to at night. I mean it is — it is bright among stars and it is kind of reddish but 99.9% of the population, if you took them outdoors and said point at Mars, they would be — yeah, I got no clue.

Host:Yeah. Yeah.

Stan Love:So, take something Earth-sized and remove it so that it’s a dot, that’s how far away we’re talking. The simple terms that I like to use is the International Space Station orbits the Earth about 250 miles up, okay, pretty close, just sort of above the atmosphere. The Moon at 250,000 miles is about 1,000 times further into space than the space station. So, space station is well known to us, you know, there’s a lot of people alive now who were never alive when there wasn’t people living in space, right?

Host:That’s right.

Stan Love:For 20 years now, we’ve had people living in space continuously on the space station and we’re used to cargo ships coming and going and crews launching and landing and that has become — I’m not going to say boring, but at least a frequent.

Host:Yeah.

Stan Love:Not routine, but frequent. We managed to send six crews to the Moon 40 years ago when we had a 10 times larger share of the federal budget to work with and nobody’s been back since. And part of that is because the Moon, at 250,000 miles, is 1,000 times further into space than the space station, 1,000 times, so that’s the difference between two steps and a mile. That’s the difference between walking a mile and going to Europe, okay? So, space station is, you know, I drive down to the gas station. The Moon is, I’m going to Europe, okay?

Host:Wow.

Stan Love:Mars, at its furthest, is on the order of 250 million miles away from the Earth, or 1,000 times further into space than the Moon or a million times further into space than the space station. So, as one step, so 3,000 miles.

Host:Oh, my gosh.

Stan Love:So, Mars is a long ways off.

Host:Yes.

Stan Love:It is, again, think of the Earth and remove it so far that it’s a dot. Think of a million times further in space than the space station. Think of the difference between walking across your living room and walking to Tibet.

Host:So, there’s a lot of considerations to think about why that is difficult. One, it’s going to take us longer to get there.

Stan Love:Yeah.

Host:And in space, that’s a huge consideration because that means you have to have stuff that works long enough and well enough that is going to — and reliably enough that when you get there, you’ll still be alive.

Stan Love:That is absolutely true and that’s not just your life-support equipment though, it’s everything on board that spacecraft. You have to make sure you have the supplies for that kind of thing. Think about what you pack for a weekend trip. Think about your pack if you were going to some place that didn’t have modern conveniences and we’re going for a week, and now think that’s going to be a three-year round-trip to Mars and I get — there are no stores. There is no place to get anything. I have to bring everything I need and oh, by the way, I’m in an environment that will kill me in about three minutes the whole time, out there and back, and would render me unconscious in seven seconds, so I don’t even have three minutes to do stuff.

Host:Yeah, you got to — you got to — it’s like taking a road trip, planning everything ahead of time and oh, by the way, you’re not allowed to stop.

Stan Love:That’s right, no stopping.

Host:So, yeah, that’s — it’s going to be quite a long time, quite a long time to get there. And there’s more, you — like you said, the life-support systems, you got a plan ahead. You got to have food that’s going to last you that long. You got to have, you know, a life-support system, oxygen, water, toilet —

Stan Love:Yeah.

Host:That’s going to work the whole time.

Stan Love:Yeah, and by the way, the toilet is part of your water and oxygen supply, [inaudible].

Host:Ah, so if the toilet breaks, that also means that you’re going to be able to [inaudible].

Stan Love:Yeah. Yeah, what a way to die, right? I was going to be the brave first explorer on Mars and I died because the toilet broke, that’s not going to look good.

Host:So, I mean besides the distance, I — this is sort of related, and this was actually a part of your talk was to get there, I mean it’s farther away and you have to have systems that work pretty reliably to get you there, but also you have to have the energy to get you there, that sort of requires more propulsion.

Stan Love:It sure does.

Host:Yeah.

Stan Love:Although, interestingly, the amount of proposing you need for a roundtrip to the Moon is just a little bit less than what you need for a round trip to Mars. Robert Heinlein famously said that once you’re in low Earth orbit, you’re halfway to anywhere in the universe, and this is not that big an exaggeration.

Host:Really.

Stan Love:Yeah.

Host:Because — I guess the most of the amount of energy is just getting you off get off of Earth.

Stan Love:Getting off of Earth, right. Then you got to get away from Earth.

Host:Right.

Stan Love:When you approach Mars, you know, in space, there are no free lunches. You got to pay to slow down too. Fortunately, Mars has an atmosphere that we can use to aerobrake in, but the air is too thin to land on parachutes the way we land our capsules on Earth today because we have a nice, thick atmosphere on Earth. So, you do have to pay propulsion to land yourself softly on Mars, just the way we had to pay in propulsion to land ourselves softly on the Moon.

Host:Yes.

Stan Love:Then you have to take off of Mars again and that’s a challenge because Mars is a planet and taking off a planet is hard. If you go down to Kennedy Space Center and see all that stuff down there? That — all those dedicated people, and all that amazing, huge hardware that’s to get ready to launch from Earth. When the first people come back from Mars, they’re going to have to launch themselves off a planet without the benefit of Kennedy Space Center. They’re going to have to do all that themselves.

Host:Yeah.

Stan Love:And the only infrastructure — gantries, towers, vehicle assembly building, they’ll have to bring that themselves, that’s going to be hard.

Host:And yeah, use it themselves, right? They don’t have — they don’t have the ground support.

Stan Love:They don’t have the ground support.

Host:Yeah. Well, I mean they’ll have some people talking to them but it’s going to be a while until their message reaches them.

Stan Love:Yeah, it can be as long as a 40 minute round-trip between asking a question and getting an answer.

Host:Yeah, that’s a — that’s a pretty dull conversation.

Stan Love:Yeah, and not only is the time delay tough but the further away your communication antennas are, the slower the rate of transmission that you have. So, from space station, we have millions of bits per second coming back and forth all the time, it’s awesome. We’ve got good communication satellites, we’re set. But now when you go a million times further out into space, your communication rate, using the same assets, drops by a million squared or a trillion. So, if I have megabits per second and divide that by a trillion. Now we can do better than that with our Mars probes but, you know, we have a bigger — even bigger antennas that we use for those guys. And so, your data rate is not going to be what you expect, it’s going to be worse than dial-up. Nobody wants to live with dial-up anymore.

Host:Well, okay, so we were talking about taking off from Mars is going to be a challenge, right?

Stan Love:Yeah.

Host:You have to — you have to sort of build your own Kennedy Space Center and operate it by your — you know, pretty much by yourself, the communications going to be pretty hard. And launching off a planet. You said the planet is going to be difficult. Now we’ve landed on the Moon and we’ve actually took — taken off from the Moon.

Stan Love:Absolutely, yup.

Host:So, how did that work?

Stan Love:Well, that we’re great because the Moon doesn’t have an atmosphere to create drag and it only has 1/6 of the Earth’s gravity. So, you don’t have to make a pointy streamlined rocket to take off from the Moon, any old shape will do. So, if you look at the lunar ascent module, it’s just kind of this blocky, clumsy looking thing with jets sticking out the side and some angular facets. It looks kind of like a big bug, that works just fine. And you barely need any propellant to get off the Moon, it’s easy.

Host:Wow.

Stan Love:Because the gravity is so much less and the speed you need to get into orbit around the Moon so less than it is from the Earth. Mars is intermediate between the Earth and Moon so it’s going to be easier to get off of than Earth but harder to get off of than Mars. One of the things we’re looking at is the chief weight that you would have to bring from Earth if you did a Mars trip the way we did the Moon trip would be the rocket propellant you need to take off of Mars. You have to have haul all that stuff out of the Earth’s gravity [inaudible], send it off to Mars, land it softly on Mars, and then you can burn it to get off of Mars, which is totally wasteful because the amount of propellant you need to move that propellant is going to be, you know, an aircraft carrier’s worth of rocket fuel taking off from Earth and it’s just absurd and we can’t build anything that big. So, we might want to try to make our rocket propellant, for the return trip, on Mars, which means we’re going to bring a little chemical factory with us. And we are going to collect carbon dioxide and water vapor from Mars’ atmosphere, it has some of both. And we can turn that into methane and liquid oxygen, which are dandy rocket propellants.

Host:Nice.

Stan Love:So, that is a possibility. But now, we — so we don’t have to bring a big dang tank full of propellant with us from Earth, but we do have to bring a big dang chemical refinery. And it’s important that the rocket fuel be kind of pure or the engines don’t work and, you know, so we have to do a good job of that.

Host:Right.

Stan Love:But that’s definitely something that we’re looking at very carefully is manufacturing as much as we possibly can with materials we find on Mars, so we don’t have to bring it with us.

Host:Yeah, that’s — the term is Institute Resource Utilization.

Stan Love:Yes, we should come up with a better one. That has too many words in [inaudible]. Living off the land is a term I’ve also heard that people can wrap their heads around a little easier.

Host:Yeah, so there’s a lot of considerations and that’s kind of a difficult thing about Mars, especially — I’m thinking about entering Mars, is you have an atmosphere they have to deal with, but it’s not really going to help you that much for — in terms of using a parachute.

Stan Love:Right. The — the air is too thin to parachute. So, we landed things with parachutes and airbags that lay it weighed less than and a half a ton or so, but bigger than that, that’s not going to work anymore. That’s why we had this crazy sky crane concept for our latest Rover, you know?

Host:I remember that, yeah.

Stan Love:That would come [inaudible] on parachutes, and then it would fire jets, and hover above the ground, and then its cables would unreel and drop the — or gently lower the Rover down to the ground. As soon as it touched the ground, the cables would separate, and the platform would fly away and crash — not on the Rover, and all this worked, and even the engineers who designed it said they were very relieved.

Host:Right.

Stan Love:When it works. So, that’s for a one-ton Rover. Now for a human lander, we probably need — you probably want to land in something you can live in for a while because you’re probably committed to a year — an Earth year or so on the surface of Mars and you don’t want to have to walk over to a habitat when you’ve just landed after nine months in space because people come back from space station, they have a little trouble walking.

Host:Yeah.

Stan Love:And they don’t have to walk in a spacesuit, which you have to do if you go outside on Mars, so very hard. So, you need to land in something biggish, 40 tons-ish. And now, the sky crane isn’t going to be enough, and we’re going to need something special and new, and I don’t know what it is, to land a 40 ton payload softly on the surface of Mars. But let’s not, you know, dis Mars’ atmosphere too much, because you’re going to come in to Mars’s atmosphere at 6 kilometers per second or something like that, and you can dump most of that speed by using a heat shield and slow you down to something like the speed of sound or, you know, one kilometer per second or so, and then you do the rest with the motor. So, you really get a big help from that atmosphere. It just doesn’t help with the last few feet that you care about the most.

Host:Yes, exactly. And I think the word you use that’s also pretty important is softly because now you’re not talking — there’s been a couple Rovers, right, that have just sort of — has slowed down but slammed into the ground pretty hard.

Stan Love:Yeah, they inflated some airbags and they bounced around. I think the first one that landed that way bounced like 18 times. When they got the thing deployed and put the camera up and looked around they found 18 big puff marks on the ground where the thing had bounced and rolled around. It actually rolled into a crater, a little crater, and that’s where it ended up, so they called it Eagle crater, hole-in-one.

Host:I like that. That’s good.

Host:So, yeah, I mean like landing softly, but then also, you know, you have to slow down this larger object in a way that’s not going to snap a human neck either, right? Because there’s been parachutes that have slowed down an — a Rover pretty quickly but to the human body, you — that’s a consideration.

Stan Love:Yeah, you don’t want the opening shock to kill your crew.

Host:Exactly. Exactly. I think — that’s another thing actually is talking about going into the Earth but actually — actually going to Mars. You’re talking about using propellant to get you there and we talked a little bit about the fact that you don’t need that much more propellant, but you need to get there pretty quickly, which means you got to speed up. But then you have to land, which means you have to slow down.

Stan Love:Yeah. Yeah, the faster you go to Mars, the more prop you pay to go faster, but then the more you have to pay to slow down. And then with the rockets that we have today, we actually spend the vast majority of our time on the way to Mars just coasting. You do — the way rockets work is you do a burn, change your speed, and you are a — you are a Hail Mary pass on a nine-month trajectory to hit a moving target. So, we’re not actually burning engines. People watch, you know, science fiction shows, and that’s — things are burning engines all the time, [inaudible] we don’t do that. If you do do that, you have to bring even more propellant because it’s not the most efficient way of doing it, not even just slowing down. But the most efficient trajectory is very short burns and very long coast periods. If you make it less efficient, you can get there faster, but now your rocket gets bigger, because you got to carry more propellant. And bigger is more expensive, and then Congress says, why are you not using the most efficient way, and then we don’t have a good answer for that.

Host:Right. Yeah. So, you — that’s something you got to think about. Efficiency, I mean that’s — efficiency is related to cost too, it’s related to resources, so there’s a lot that goes into there. Another fact that you sort of pointed out, when — after you land on Mars, you know, you sped up, you used the propulsion to get you there efficiently, you’ve landed, but now one thing that we need to talk about is the orbits of the two planets, Earth and Mars. Now you get there, it’s not like, oh, yay, we’re here, we can spend as much time as we want and then take off whenever we want. There’s orbits to consider and a length of time that you got to spend there.

Stan Love:Yeah. So, this, again, is tied to rocket propulsion. If we had warp drive and could go between the planets any time, no problem. But when we’re on rockets, that means we are restricted to these very precise trajectories. And you only have a chance to throw that nine-month long pass at the moving Mars and have it hit the planet once every 26 months from Earth, so you’ll hear about launch windows for Mars probes. Every two years and two months, we have a chance to put some — to send something to Mars. If we miss that chance, oh, okay, well, you know, go do something in your office, and in two years and two months, we’ll try again. You can’t — you just can’t put stuff toward Mars at any other time. The planets have to be lined up just right and now I can throw that pass, same thing for Mars back to Earth. Every 26 months, the planets line up properly so that you can send something to Mars back to Earth. Any other time, you cannot go, and those periods don’t happen at the same time, they’re offset. So, it turns out that when you have a launch window to Mars, you can throw something to Mars, it takes it 9ish months to get there. Speed that up, but it’s less efficient, more mass, more expense, Congress talks to us.

You land on Mars, now I got to wait for my launch window to come back from Earth, and that happens a year after I land, one Earth year, half a Mars’ year. So, you’re going to go halfway around the Sun on the planet Mars, and then your launch window opens so you can come back to Earth. So, once you have left Earth, and no spacecraft that we can possibly design has enough propellant on board to come back, once we’ve done that burn and headed off to Mars, you can’t abort and say, no, I don’t like this, I’m coming home. You’re committed. You’re committed to nine months out, you’re committed to a year on the surface, you’re committed to nine months back. Now we can mess with things and say, well, what if we do a special different trajectory and we’re going to come back and go closer to the Sun than the Earth and do a swing by the planet Venus and get a little boost from Venus’ current gravity and then we’ll come back to Earth a little earlier. That adds complexity to your mission, now I got a have a bunch of heat shielding because I’m getting close to the Sun. And as with certain other philosophical conflicts in spaceflight, there has been a great deal of discussion and no winner on whether it’s better to just suck it up and do the long haul or try to be fancy and do this faster thing.

The pros and cons on both sides have not shown a clear victor on that one. So, basically, when you are committing to Mars, you’re committing to two and a half to three years away from the Earth and nothing important can break, nothing important can run out. All those engine burns have to work right and you have to launch yourself off a planet without help.

Host:True.

Stan Love:Yeah. So, again, I don’t want to sound too gloomy. The attention here is not gloom and not to — not to say that, no, Mars is impossible and we should just give up.

Host:It’s just hard.

Stan Love:But it’s hard. And, again, we need to go into this with open eyes and a clear understanding of what all the challenges are or we will not be successful.

Host:Now on the topic of trajectories and Mars’ mission profiles, you know, staying there on the surface for a year, is there any other opportunity — maybe a touch-and-go opportunity, or —

Stan Love:The touch-and-go — without waiting the year for the launch window — is one of these things that goes by Venus.

Host:Oh, that’s the Venus option, okay.

Stan Love:Yeah. Once every 50 years, there’s a flyby opportunity that comes — right — goes — whizzes past Mars, uses Mars’ gravity. You don’t land, you don’t stop. But that Mars pass bends your trajectory so that it comes right back to Earth after 12 to 18 months. And the — that opportunity occurred this year.

Host:So, we missed it.

Stan Love:But we were talking about it.

Host:Oh, yeah.

Stan Love:The other disadvantage to that one is that you come quizzing by Mars at a very great rate of speed over the night side of the planet, so you’re in space for nine months. Then you get this close encounter over a planet that does not have city lights, or thunderstorms, or [inaudible], or anything else that glows, and that was your Mars pass. So — and the technology wasn’t quite ready, but we were talking seriously about this three, four, five years ago, whether we might be able to use the 2018 flyby opportunity to do sort of a Hail Mary Mars mission. And we decided that the odds of the crew surviving probably real good and the next chance is in 2068 and I hope we’re way down the road. I don’t know about that you’re in particular, but it’s way down the road and hopefully we’ll have people on Mars another way.

Host:Yes, exactly. And that — this is a huge consideration for — we’re talking about Mars missions, and we should probably clarify, people. You know, we’ve done a — we’ve done a lot of Rovers before but now there’s a whole people element.

Stan Love:Yeah.

Host:And that’s huge.

Stan Love:Yes, literally. You can have a useful robot that weighs 500 pounds or a ton, right? But if you’re sending people, people got to live in an in a pressurized environment and the tin can gets real big, and then the rockets get real big, and you’re talking about gigantic things.

Host:Yeah. Yeah. You’re get — people are pretty picky when it comes to —

Stan Love:Yeah, and they’re fussy about being alive when they get there, and some of them are even fussy about coming home. If you don’t need to come home, it gets easier. But, you know, in a habitat we could land, plus the radiation environment on Mars is not super healthy for you, you need to, you know, get 30 feet or so dirt over your head to block the cosmic rays. The Earth has a nice magnetic field, a nice thick atmosphere that protects us from that stuff. Mars doesn’t have that. So, nobody wants to emigrate to Mars to live in a room the size of a bathroom until they die of cancer three years later, that’s just not fun.

Host:No.

Stan Love:So, again, not to cast gloom, we can do this.

Host:Yeah.

Stan Love:But we have to be smart about it.

Host:Exactly. And we’re thinking about it, that’s the whole — that’ the whole point is we’re considering every option to make sure that the mission is successful. And one of the options is to — so if you’re talking about a Mars habitat, that habitat is not — the pictures of the domes that you’re seeing, the science fiction things, you’re talking about going underground.

Stan Love:Yup. Your dome is going to blow out, because the atmospheric pressure inside. Mars’ atmosphere is essentially no pressure, like being on Earth at 100,000 feet, and there’s just nothing to breathe there. So, yeah, you’re probably going to need to be — need to spend much of your time in — with a lot of mass between you and those cosmic rays, which usually means going underground. There may be solutions to that. Right now, the radiation environment, as we understand it, you could spend that year on Mars and come back and you’d have a slightly higher risk of cancer than we allow administratively right now. Right now, our career limit I think is at 3% excess rate of cancer in your lifetime and if you’ve gotten that much radiation, then you’re not allowed to get any more radiation exposure. The numbers I’ve seen for a Mars mission are about 5%, so not hugely more than our limit, but more than our limit. But if you walked up to the astronaut office right now and said, okay, who wants to go to Mars? By the way, you got a 5% risk of cancer instead of just 3%, every single hand would go up.

Host:Really.

Stan Love:Yeah, everybody would be willing to [inaudible].

Host:Everybody would be willing. Interesting.

Stan Love:To be that first person on Mars.

Host:Oh, yeah. Well, I mean it’s a huge accomplishment and that’s why we’re striving so hard, so.

Stan Love:And that’s an administrative limit, a stroke of a pen can make it go away.

Host:Yeah, plus 2, right?

Stan Love:Yeah.

Host:So, yeah. That’s huge. But just the radiation environment. And then — so you’re — off of that point, you’re monitoring — even now on the space station — how much radiation a crew member is receiving from being up there X amount of time.

Stan Love:Yeah, we’re measuring it a lot.

Host:A lot.

Stan Love:We have film badges on the crew members and they wear them when they go out [inaudible] because you have less mass between you and the cosmic rays when you’re out on a spacewalk. We have radiation counters inside the space station at various places. We’ve had mock-ups of human bodies made out of like plastic with about the same radiation properties as your body with radiation detectors on those to see how the radiation affects the interiors. And we have a radiation detector on the Mars Rover that’s on Mars right now measuring that radiation environment with an eye toward what the exposure of a person would be, okay? We are also preparing for the next Mars Rover a tiny little experiment to make oxygen out of Mars’s carbon dioxide atmosphere with an eye toward making rocket propellant and breathing air when we get to Mars. So, we are — we are thinking and doing what we can right now, even though we haven’t embarked on the huge quest of launching a person. But we’re working on these problems and getting to understand them so that we know what we really have to do.

Host:And that’s something that we would definitely have to consider is if we are considering landing humans on the surface of Mars, there will most likely be a lot of other stuff that has landed on Mars first.

Stan Love:Yes.

[00:25:53]

Host:Okay.

Stan Love:So, yeah, we would definitely want to pre-place a big habitat. We would probably want to pre-place our propellant tank. And we would — or our propellant plant. And we want that propellant plant working. And we would want it to report that the tanks were freaking full, before we even launched first, because of the tanks can’t get full, I can’t come back. So — and we might even pre- and place our Mars ascent vehicle, the thing we’re going to use to launch off of Mars. If you saw the movie, The Martian, that’s the tactic that they use there, and that’s probably a pretty good one. But you want that thing there, you want to know it was in good health with full tanks before you even committed your crew to launching from Earth because if something goes wrong there, you can’t come home.

Host:Yeah. That’s several years’ worth of work to put everything — and then to dig, to build a habitat, to fuel your rock.

Stan Love:And all those things are huge. They’re going to need a giant heavy lift rocket, such as our SLS heavy lift booster. We can’t produce those superfast, so we might only get two launches each launch window. So, basically, on average, you’re going to get — you know, every two years, you get two big rockets — two big payloads that go to Mars, and that’s about as fast as we can produce those things, unless a miracle occurs, and we get a giant budget, then we can do a lot more a lot faster, but I’m not holding my breath. I’ve been interested in space my whole life and Apollo doesn’t seem to be happening again. So, we could do more with more. With what we have, you know, sort of every two years, two big payloads, and you send those there. One thing that I’ve noticed is that each year, our robots get better and our rocket engines don’t. So, I expect that as we are formulating our Mars plans and robotics get better — and oh, by the way, let’s build a 3D printer that can make things out of dirt, okay? You heat the dirt up to a high temperature, you [inaudible] the little grains together, like glass beads melting together.

And I can make a habitat on Mars before I even send a person. And I don’t even have to send a habitat or — so I send a big 3D printer and a robot. It sucks up sand and dirt. It spits out bricks. It builds me a big enclosure with a nice big, heavy roof that blocks radiation. And then later, I go inside with a plastic bag to hold the air in. So, I have the surrounding structure that’s not airtight, and I make that airtight with a lining and bingo, I’ve got a nice house, and I didn’t have to build it. I did it all remote ops from Earth.

Host:Nice.

Stan Love:Okay, and that’s just one of the little tricks that we can think of now that we might be able to do in the future. That robotic propellant plant, we could do now, we know how to do that. We haven’t done it yet, it’s going to be expensive. But as the robots get better and people get smarter, we will be able to do more remotely with machines on Mars so that the Mars crew has more resources when, they get there they have less work to do when they get there, they know that everything is checked out and ready before they even launch. And that, as we go forward in time, I think will get better and better. And the prospects will get better and better for sending our people because we can have more things ready for them when they arrive.

Host:So, the habitat and the vehicle to get off, very important stuff to have ready before they get there. So, what else would probably be a huge consideration to have ready by the time they get there? My thought is food, right? Would you — would you bring food with you or would you stock it up?

Stan Love:So, one of the problems that we’re working on with food is that thermal stabilized food, which is freeze-dried, or dried, or the stuff that they have in pouches in MREs for military troops, that’s the kind of stuff we eat on the space station. That stuff — actually, the molecules that your body needs out of that to be nutritious don’t last more than about a year.

Host:Oh, they break down.

Stan Love:So, you eat the food, it would taste normal, and it would fill you up, but it wouldn’t sustain your body. Now we can preserve food for decades and have it be perfectly healthy if we freeze it, but now that food has its full weight of water, and I have a big freezer. Freezers are heavy, and freezers suck a lot of power. Your refrigerator is probably the thing in your house that uses the most energy, and now I’ve got to have a giant walk-in freezer with five years’ worth of food for six people and the freezer gets really big. So, I don’t think we can pre-place food, that’s probably what you’re going to want to bring with you.

Host:Interesting.

Stan Love:But anything that doesn’t degrade in a year, you could. You could have a giant tank of water waiting for you, big tanks of oxygen to breathe. You can even pull nitrogen out of Mars’s atmosphere, it’s the it’s also a common component in there. So, we can make up the nitrogen part of our atmosphere that we breathe that our bodies don’t use but it’s nice to keep a comfortable pressure so you’re not breathing pure oxygen and things burst into flame and pure oxygen, so we really like to breathe the normal mix of air. So, there is a lot that we can do with machines that use what’s available on Mars to be really ready, but I don’t think food is going to be one of those.

Host:Okay, and that makes sense because you want to make sure that the food that you’re going to eat is going to give you the nutrients that you need to survive, and yeah, that makes a lot of sense. Kind of off of that point is, you know, you’re building stuff ahead of time, you’re doing a lot of planning, and now let’s say you have everything ready, and you’re on your way to Mars. Everything is planned for you, but even on the way, you already mentioned that you can’t really turn around. And the reason you would probably want to turn around is if something was going wrong.

Stan Love:Yes.

Host:So, there’s a lot of things that could go wrong on the way to Mars, right?

Stan Love:Yes.

Host:That means you have to have systems that are super, super reliable.

Stan Love:Yes.

Host:And including — I mean it could be something that you can maybe control from an engineering perspective, like systems, but maybe there are some things that you cannot control, like a solar event.

Stan Love:Yeah, solar flare. There was a solar flare during the Apollo program, but when an Apollo mission was not in the air, that would have killed the crew.

Host:Really.

Stan Love:Yeah.

Host:And —

Stan Love:It’s amazing what’s on Wikipedia [inaudible] You go, wow, [inaudible] that up. So, yeah, that is a possibility, but it is a rare possibility. Flares that size, I don’t think there has been one since that one.

Host:Really.

Stan Love:I mean been that big, so that is a risk. Micrometeoroid hit on your spacecraft, you have no way of detecting that ahead of time. Bang, and you got a hole in your in your hull and you have to do that. The — but the odds are low, and I don’t consider those higher risk than things like mechanical reliability and keeping people healthy and happy in that confined environment for that long time. If you read the journals from Polar Explorers from a hundred years ago, they’re isolated, they’re confined, they’re in an environment that they can at least go out and take a walk and, you know, and cool off if they’re mad at their at their tent mate, literally cool off. So, you don’t have that option on a spacecraft on the way to Mars, but you read what became important to these people and it’s just strange, like food. It’s all about the food after the first few months. There’s a wonderful book called Farthest North by Fridtjof Nansen. He was a Norwegian Polar explorer in the late 1800s and at that time, people were trying to reach the North Pole and all the expeditions had their ships crushed in the ice and a few men trying to haul supplies back to land over the shifting Polar ice cap in the cold they all get scurvy and at some point, they have to eat the dogs.

Yeah. And so, Nansen got the idea that he was going to achieve the North Pole by building a super-strong little, tiny ship and deliberately freezing it in the ice and using the natural flow of ice across the Arctic Ocean to just drift across the Pole. And he found out about this ice drift by doing exploring on the north coast of Greenland and finding debris from one of the previous failed Polar expeditions that had gotten crushed on the other side of the Arctic Ocean, plus logs that had washed down rivers in Siberia that were trees that don’t grow in North America that only grow in Siberia that washed there. So, he did a lot of science first.

Host:Yeah.

Stan Love:So, he built this ship that had walls two feet thick. He had a crew of about 13 people. They had supplies for five years and they sailed around to the, you know, north of eastern Siberia, deliberately froze the ship in the ice, which was like the death knell for all previous expeditions. And for three years, they drifted across the Arctic Ocean. And they missed the pole, but they got closer than anybody else ever had. And as they realized they were missing it they — two of the guys, Nansen and one companion, got the dogs and tried to make a push across the ice to Pole, and they had to turn around, [inaudible], and then they ended up living in a — spending the winter in a 6 by 6 foot stone hut made out of walrus hides in Franz Joseph land and they only had one sleeping bag between them and they didn’t have to eat the dogs, but they had to feed the dogs to the other dogs, so it got exciting there. But the rest of crew just fat, dumb, and happy ended up on the other side of the ocean, broke out of the ice near Spitsbergen, and all of them actually reunited in Norway a in the same month.

Host:No way.

Stan Love:Yeah, so that is what a Mars mission is going to be like. Rad those journals. They did a lot of science but most of the journal ended up being about the food. There was — you know, the environment was the same, the people were the same, and so they were going through the almanac looking for other nations’ holidays to celebrate so they could have a feast, and it’s all about the food. So, we need to be careful about the food on a Mars mission and there’s a lot we can learn from the expeditions of the distant past that hardly anybody’s ever heard of that will make this an easier and better trip.

Host:Yeah. I mean you — like you said, there’s a lot of science you can do ahead of time to prepare, but then you — ultimately, once you go do it, there’s stuff that you’re figuring out along the way, food being a very important component.

Stan Love:Things about the people, the people in that environment and things that you might not predict.

Host:Yeah, and actually off of that point, you were talking about a transit vehicle to Mars, making sure they’re healthy and happy on the way, and that’s a pretty big consideration. You have to have enough food, you have to make sure that they are going to be healthy, that their bones are not going to deteriorate, stuff we’re learning on the International Space Station. What is that vehicle going to look like and how is it going to help?

Stan Love:I don’t think anybody knows what the Mars vehicle is going to look like. But the space station is about — actually about the right size to send 6-ish people on a multi-year expedition in space. We carry enough spares and food in case a couple of car — robot cargo ships don’t make it. You’re looking at something in the size-ish of the International Space Station. In the movie, The Martian, they did their homework. And you saw their transit ship was — looked a lot like the space station.

Host:It was big, yeah.

Stan Love:Yeah, and that’s — that’s not crazy. The interiors were too big. No engineer is going to make, you know, a 12-foot vaulted ceiling in the gym. You can get — how high are you really get a bounce on that treadmill? He’ll do a 7 foot ceiling, it’s going to save us a lot of math.

Host:Yeah.

Stan Love:But have that idea in your mind, something the size of the International Space Station is going to be our transit vehicle. And, of course, we’re not going to land that whole thing on Mars. That guy’s got to stay in orbit for a year while the crew is on the ground, which means it has to be super automated, which means the crew doesn’t have to do anything to keep it running while it’s in orbit around Mars for a year. But then also, it doesn’t need any help on the way out to Mars, so you now the crew doesn’t have much to do. And healthy and happy also means meaningfully occupied, so they don’t just — you’re not just playing cards the whole way.

Host:Yes.

Stan Love:So, stuff for the crew to do during cruise before they get to Mars, and then on the way back to Earth is also going to be very important. And these are problems that engineers aren’t that interested in, they are human problems. But I like to say the thing that makes human spaceflight interesting is that it has humans in it. It’s just not quite the same. The robots are great, but it’s even better when it’s — when it’s a person, and the whole world can imagine what it would be like to be that person much better than they can imagine what it would be like to be that robot.

Host:That’s all the questions we get really is like, you know, what is it like, what is your perspective change? It’s that human element of the traveling, not so much the engineering/ And the engineering, to me, is very interesting, but that human element is something that you can easily connect with because we’re human.

Stan Love:Well, and it makes a difference. I was a planetary scientist before I was an astronaut and I would go talk to school kids and they were kind of interested.

Host:Yeah.

Stan Love:And — but I became an astronaut, I put on that blue suit, and those kids are really interested.

Host:That is huge, it really is. It makes a huge impact. So, one more thing I wanted to talk about before we let you go is, you know, we’re talking about the Moon now, the Moon being sort of a stepping stone on the way to Mars and designing missions around that. How can the Moon help us to explore even further?

Stan Love:Okay, I think this is an awesome idea. The Moon is so much less hard than Mars. It’s so close. If you burst your appendix, you can be home in four days, right? It’s also, I think, better from a public support standpoint. Nobody can walk outside and identify Mars, except for a few astronomers and amateur astronomers. Everybody can walk outside and identify the Moon. And they can look up at that thing and they know exactly what it is, 3-year-old can identify it and think there are people living up there right now. And maybe if — you know, if they had a bright light on their station, if their part of the Moon was dark, you could look at a telescope and see that light, see there are people there are people living on that light. Just the way right now, we can — if you watch for the space station to go over, you know, every few weeks or so, your place will probably have a good ISS pass, and that big, bright star comes over. And you can look at that say, people made that and people are living in that little star right now, it’s a great feeling. I love it. I never get tired of it. So, the Moon is more accessible to the public in their imagination, and what they can see, and Mars is so distant and abstract that it’s tough.

Plus, it’s 1,000 times further away than the Moon. So, the Moon is close, it’s big, it’s familiar. It is not quite as sexy as Mars, okay? It’s dry, there’s no water, there’s no polar caps, there’s no weather. Mars has polar caps and weather and more interesting stuff going on. But the Moon is so much closer and effectively, I mean from an environment standpoint, you take your helmet off on the Moon, you’re dead. You take your helmet off on Mars, you’re dead in about the same amount of time. It’s — you know, from an environmental standpoint, it’s quite similar. The radiation problems are similar. You have the extremes of temperature on the Moon, although Mars, cold winter night gets as cold as the Moon at night. So, you have the hot days on the Moon that you have to deal with. You don’t have that atmosphere that you can make propellant with, that’s a biggie. The Moon is really just dry rocks and I can make oxygen out of those rocks, but the energy cost is enormous compared to the energy I need to crack oxygen out of Mars’ air. So, I have resource — I have a little fewer resources.

The science is less interesting and the — you know, just the vistas and the prospects are less planet like because that black sky and those alien landforms all made by impact instead of, you know, volcanoes and river valleys and stuff like that and polar caps like we have on Mars. So, the Moon is not as sexy, but it’s way closer, and it’s way more accessible in every way. The physics is going to drive us, I think, to the Moon before it allows us to go Mars. And if we can get enough of an infrastructure on the Moon, that low gravity is going to make launch off the Moon trivial compared to launch off of the Earth. Ae talked about this already. So, why not build that Mars ship on the Moon and launching it is going to be easy and then off you go to Mars.

Host:Yes. Oh, something to consider.

Stan Love:Yeah.

Host:All right, so we have like a couple more seconds, but I wanted to ask you one thing before we leave, is you’re — you seem so passionate and you know so much about traveling to other planets. So, in your eyes, why is it important? Why is it sort of our mission to send humans to explore the cosmos?

Stan Love:I think exploring is a natural human drive. We do it, right? When the ice age brought sea level down, people walked across the Bering Strait into North and South America. And, you know, they wanted to see what was over that next hill or past that next river and they eventually peopled the entire Americas and so that the folks in the original continent forgot about them and were surprised when they landed in this new land and found people there already. I also think exploration is one of the things we do that that brings out the best in us, as a species. Many of the things that we invest a lot of our time and effort in are violent, or greedy, or both. Exploration is a little tidier from a moral standpoint, especially if you’re in a place that doesn’t already have inhabitants. We haven’t always behaved well when we’ve found, you know, new places with people there already, Mars and Moon, we’re safe there. So, I think it makes us better. I think it allows us to be the best of what humans can be.

And now that we have explored the Earth extremely thoroughly, only the ocean floor, deep caves, the upper atmosphere remain. You know, we’ve climbed almost all the mountains, we’ve sailed all the seas, you know, there’s — and there’s — you know, a lot of those mounds have snack bars on the top of them now. We, as a species, love to explore, it’s built into us. And the only places left now are the deep ocean and space. And space will never end it. It goes out as far as we can imagine and even further than even specially trained people can imagine. So, we could keep exploring there forever and we’ll never run out of new things to explore out there, so that’s one of the things that made me a science-fiction fan as a kid, why I studied astronomy, why I became a planetary scientist. When I had a chance to become an astronaut, I did it, flew in space. And that’s why I continue to study and work on a daily basis on making more of space accessible to more people.

I think we’re at our best when we’re doing that.

Host:I love it. Let’s go. I’m so ready.

Stan Love:All right. Well, thank you so much, Stan, for coming on and sharing this why Mars is hard, but then also your passion for space exploration, I love it. Thank you so much.

Host:You’re so welcome. I was glad to do it.

[ Music ]

Pat Ryan: Thanks for hanging in with us. Today, Gary talked with astronaut and all around smart guy Stan Love about the problems being worked on right now so we can successfully send human beings to Mars in the years to come. A heads up, you can hear more from Stan during the month of August. He’ll appear in a few episodes of a series of podcasts we’re doing about the hazards of human spaceflight. Part 1 of 5 in that series is slated to post August 10th. I mentioned that this is episode 53 of our weekly podcast [inaudible] here at the Johnson Space Center, so the first episode of the second year of Houston, We Have a Podcast. If you’re new to the podcast, I recommend giving a listen to number 52, Houston, we Have a Birthday, where you can hear clips from many of the first year’s shows and get a sense of the range of topics we’re working to cover. I can also recommend some other NASA podcasts, including Gravity Assist from NASA headquarters with Dr. Jim Green, he’s one of the smartest guys ever, about Mars exploration and other topics of planetary science.

There’s the new Rocket Ranch podcast from the NASA Kennedy Space Center. Their first episode is about Mars too. And don’t forget the NASA in Silicon Valley podcast from our friends at the NASA Ames Research Center, where they talk about their research, including some of it that’s taking place on the International Space Station. Your home online for everything NASA is nasa.gov, including the latest on our deep-space exploration projects. Please join us on your favorite social media platform. You can find us on Facebook, Twitter, Instagram. Use the hashtag ask NASA to submit a suggested topic. Be sure to mention that it’s for Houston, We Have a Podcast. This episode was recorded on May 18, 2018. Thanks to our audio wizard Alex Perryman, Kelly Humphries, Bill Stafford, Mel Whiting, and Brandi Dean, and our guest, Dr. Stan Love. We’ll be back next week.