Planetary Radio: Space Exploration, Astronomy and Science - Rob Manning Says Landing on Mars is Hard!

Episode Date: April 24, 2006

Landing people on Mars will be hard, but JPL's Rob Manning and other engineers are working on solutions.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

landing on mars is harder than you think this week on planetary radio hi everyone welcome to public radio's travel show that takes you to the final frontier i'm matt caplan airbags they save lives cars, and they got spirit and opportunity safely to the surface of the red planet. But Rob Manning of JPL says bigger rovers and human beings will need another solution. He'll tell us what NASA engineers have in mind. Later, we'll join Bruce Batt's pool side for this week's edition of What's Up and your chance to win a Planetary Radio t-shirt. Let's see what's up around the solar system this week's edition of What's Up and your chance to win a Planetary Radio t-shirt. Let's see what's up around the solar system this week.

Both the Mars Reconnaissance Orbiter and Venus Express are slowly settling into their final orbits. The Mars Express Orbiter says, don't just follow the water, follow the phyllosilicates, Emily Lakdawalla explains in her blog at planetary.org. Meanwhile, Spirit has settled down for a quiet winter. The little rover with the gimpy leg is on a hill dubbed Low Ridge Haven. It is tilted a bit toward the north so that its solar panels will catch a few more rays, hopefully enough to keep the probe going through the next eight months.

At least it has a lovely view. Check out the scene at Emily's place. Finally, we want to mark the passing of test pilot and near astronaut Scott Crossfield. Back before the spam-in-a-can Mercury program, there were these guys like Scott and Chuck Yeager who strapped themselves into rocket planes and went faster and higher than any human ever had. Crossfield had several close calls in the amazing X-15, but he also made aviation history in the sleek black needle. He never lost his love of flight. At 84, he was at the stick when his small plane was lost in bad weather last week. He had the right stuff right up to the end. A wedding ring may be forever, but not so Saturn's rings. Emily explains. I'll be right back with Rob Manning.

Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, when did Saturn's ring system come into being and when will it dissipate? There are several features of Saturn's ring system that make scientists think that the rings must be young. For example, they are very clean. Most small bodies in the solar system, like asteroids and comets, are very dark because they have been exposed to a constant bombardment of dark meteoroids since the beginning of the solar system. By contrast, Saturn's rings are brilliantly icy.

Also, models of the motions of the ring particles and ring moons seem to indicate that the ring system shouldn't be stable for more than 100 million years or so. But these youthful features don't necessarily mean that the rings haven't been around as long as Saturn has. It just means that they could have looked very different 100 million years ago. The material that makes up Saturn's rings can't really be anything else than leftover material from the formation of Saturn and its moons 4.5 billion years ago. Impacts onto small, ancient moons can shatter them, exposing fresh material and producing young-looking rings.

So how long will the rings last? Stay tuned to Planetary Radio to find out. Could it be easier to land on either the moon or Earth than the red planet? Rob Manning says yes, at least in some ways, and he should know. He helped get the Mars Exploration Rovers down to the surface of the red planet. Before them, he did the same for the Pathfinder mission. Now he is chief engineer for the Mars Exploration Directorate at the Jet Propulsion Lab, and he's working toward pulling yet another Martian rabbit out of a hat.

He sat down with me right after stepping out of a Mars conference so that we could talk about the next big thing. Rob, thanks for coming back to Planetary Radio. You had to remind me that we talked to you during those early halcyon days of Mars exploration rovers. That's right, man. That was a lot of fun. Very different setting here as we sit outside near the pool at the Holiday Inn near Pasadena, where you've just come out of this conference, considering, I guess, places where you might want to set some either humans or even more advanced rovers down on Mars. Well, that's right.

One of the things we've been looking at these past few years is figuring out a roadmap for how to get larger things on Mars. Now, we've been lately trying to get a new rover built, a larger one that's called Mars Science Laboratory. It will be launched in 2009. It will get there around 2010. It has a lot of really fascinating, amazing science on it, and it's going to last a lot longer than the rovers, knock on wood. And we're very, very excited about this mission. But it's bigger.

It's about the size of a small car. Of course, getting something of that size on the surface of Mars is presumably, you know, is a real challenge. Getting our little rover's spirit and opportunity were one thing, but getting something even bigger is even harder. In the process of learning about hard things, heavy things, and how to get heavier things to Mars, we also began a process about a year ago to do some road mapping and figure, well, if it's so hard to do small robots to Mars. We also began a process about a year ago to do some road

mapping and figure, well, if it's so hard to do small robots to Mars, well, what about big things? What about things with people in them? How are we going to land habitats? How are we going to land landers with not one metric ton of mass, but something maybe 30 to 70 metric tons per landing event. Wow. Because you get to bring, if you're going to go to Mars, you're going to be there for a while if you're an astronaut. Hardly worth going if you don't stick around for a while.

And not to mention the dynamics of the orbits, the astrodynamics, to force you to either be there for a very short while and then leave, or to stay for quite a long time, a year. Because up until now, everything we've landed on Mars has just dropped right in. Right. And, I mean, you've had great results overall with those wonderful airbags. Thank you. But you can't just scale those up. That's correct.

In fact, I think most of us who design this system, in fact, all of us, believe that this is about as big as you want to take that particular design. Really? Yeah. And using the landing system that's being used for the next rover, it doesn't use airbags. It uses a very new architecture altogether that we've sort of dubbed the Sky Crane in honor of the Sky Crane helicopter design, which basically we hover a propulsive, not a helicopter, but a propulsive system above the rover and lower the rover to the ground on a rope.

No kidding. Exactly. I haven't seen any pictures of this. Most people look at this and they go, are you crazy? And I go, well, yeah. They said the same thing about airbags. They said the same thing about airbags. And we've been thinking about this and thinking about this and looking at designs,

trying many, many, many permutations of designs. And we've come to the conclusion that if you want to land something like a rover on the surface of Mars, you don't want to land it with a dry set of fuel tanks below you. There's also issues with the engines getting close to the ground. If you want to land something very softly, you have to go slowly, and the engines like to dig holes, and Mars has particular problems with its atmosphere. So we said, well, let's put a propulsion system above the rover. And it's actually very much like the propulsion system we use for MER,

is where we put a solid propulsion system above some 20 meters above these airbags and bring the whole thing to a stop, and then we'd let go. We said, what if there was a nice high-quality control system up there and use it to carefully lower a rover to the ground? Then you don't need airbags. You don't even need a land or cocoon to surround you in the land. You don't have to worry about bouncing around because you can do it very precisely,

and that's what we're doing. So you put it down, you cut the cable, and then your little skyhook gets out of the land. You don't have to worry about bouncing around because you can do it very precisely. And that's what we're doing. So you put it down, you cut the cable, and then your little skyhook gets out of the way. It flies out of the way, does a divert maneuver, and lands over there somewhere, in a probably nasty landing when it runs out of fuel. And you're ready to roll, and you're ready to drive within minutes of landing.

And so this is our architecture that we're currently building here at JPL. Even that is not enough to get heavy things to Mars. So what happened about a year ago, this road mapping effort, and I had the great fortune of co-chairing this team of people to do this committee to look through this to produce a road map with Dr. Harrison Schmidt, former Apollo astronaut, wonderful guy.

Been on the show. Yes, and he's a smart guy, a very smart guy. But like many people, he wasn't that familiar with this particular problem. And, in fact, very few people are. It turns out very few people have worried about the details of how you get something heavy in orbit around Mars and get it safely to the surface of Mars. Now, of course, this problem was solved for a very different kind of body in 1969. Is that approach, the lunar module type approach, is just not?

A lot of people immediately come to the conclusion, here's the moon with no air, small thing. We know how to land on there. Here's big old Earth, much bigger. It's got an atmosphere, a lot more atmosphere than the moon. We know how to land on there. Here's big old Earth, much bigger. It's got an atmosphere, a lot more atmosphere than the Moon. We know how to come down on that. Now Mars, between the size of Earth and Moon, has less,

a lot less air than Earth. It should be a piece of cake. Sounds so logical. Well, it turns out that there is too much atmosphere to land on Mars like you do with the Moon, because the atmosphere burns you up, because you move so fast through it. too much atmosphere to land on Mars like you do at the moon because the atmosphere burns you up because you move so fast through it.

And it's too little atmosphere to land like you do on Earth. It's the opposite of a Goldilocks zone. Exactly. It's really a poor excuse for a landing system. It's very difficult. And it turns out there's all these different streams. Well, how about if you want to land like you do at the moon and Mars, well, why don't you just use your engines to stop and land above the air

and then with your rocket engines lower yourself straight down and not too fast so you don't have to worry about supersonic effects and propulsion working together and just lower yourself to the ground. Well, you can do that, but the amount of fuel to do that, because Mars is a lot bigger than the moon, is really huge. And you have to take that with you and put it in orbit. And that translates into extraordinarily large fuel mass fractions in low Earth orbit. I mean, imagine launching massive, massive fuel tanks

or putting large fuel depots in Earth's orbit. Literally all fuel and hardly any payload. In fact, the ratio is something approaching 100 times the fuel to the mass that you're bringing to Mars if you didn't use the atmosphere. So everyone said, well, let's just use the atmosphere and do it like we do it on Earth. Well, let's try to land the shuttle on Mars. What happens? Okay, well, first off, the atmosphere at the thickest part of Mars, down at the ground,

is about the same density as the atmosphere on Earth if you go 120,000 feet up. Now, can you imagine landing the shuttle 120,000 feet? Well, that's the altitude that it's still entering the atmosphere. It's still going Mach 6 at that time, and it's a little bit fast for this landing gear. So if you look at the extremes, this is, well, then how can you use the atmosphere to slow down? Well, one way to do it is to increase the drag area and create totally new systems that we haven't designed yet. For example, you could imagine these heat shields that slow you down that

are really big, say something between 20 and 30 meters in diameter, big, big inflatable structures. You could imagine building chunks and actually doing assembling of a very large heat shield and putting all the thermal protection tiles and building it all in orbit, but that's still a huge manufacturing job. So our thinking is we could maybe do this with inflatables. These are all new technologies that no one has really invented before. We'll have more with engineer and Mars landing expert Rob Manning right after this message. This is Buzz Aldrin.

When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds, and we're building the first ever solar sail. We didn't just build it. We attempted to put that first solar sail in orbit, and we're building the first ever solar sail. We didn't just build it. We attempted to put that first solar sail in orbit, and we're going to try again. You can read about all our exciting projects and get the latest space exploration news in depth

at the Society's exciting and informative website, planetary.org. You can also preview our full-color magazine, The Planetary Report. It's just one of our many member benefits. Want to learn more? Call us at 1-877-PLANETS. That's toll-free, 1-877-752-6387. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio.

We're talking with Rob Manning, Chief Engineer for the Mars Exploration Directorate at JPL. Getting bigger rovers and humans safely down to the surface of that strange planet is one big challenge Rob and his team are working on, but it's not the only one. What about the interest with, at least I assume with a human mission, if not with MSL, with putting these humans down on the surface of the red planet exactly where you want to put them. I mean, I think of Neil Armstrong saying,

okay, a little bit to the right, a little bit this way, a little bit this way. Okay, I like this spot. We'll land. You didn't have that luxury with the Mars Exploration Rovers. You had a nice ellipse. No, and it's not inconceivable those systems can be designed to be more precise. Mars Science Laboratory, MSL, is actually going to use something that the Apollo and Gemini entry capsules on Earth used, which is hypersonic guidance. It actually steers this big space capsule and steers left, right.

It uses what's called bank angle modulation. There's a center of mass offset from the axis of symmetry. And by steering left, steering right, you can control the direction. Because the center of mass is, there is an offset, the vehicle actually is tilted in the atmosphere. And because the angle of attack is increased, it gets lift. Not a lot, but it's enough for you to steer this boat back and forth and actually gets a fairly good degree of precision at the time the parachute opens up. I'm ashamed to say I've never heard of this concept.

I had no idea that that capability was used. In fact, the great Claude Graves, who just passed away a few years ago at Johnson Space Center, was among the main developers of this idea and the technology back in the 60s for both Gemini, Apollo, and later, he applied many of the same ideas that he's learned on the shuttle. People from his team are still working with us today to help us develop the same hypersonic guidance techniques to fly out the position uncertainty. Well, that's great up to the point the parachute opens up, but winds can move you off course.

Even the precision is not that perfect. It's still miles of uncertainty at the time the parachute opens up. So after the parachute opens and the system descends a ways on the parachute, finally the vehicle separates from the parachute, still less than a mile above the ground, and if there's any errors, now this is something MSL doesn't do, but if it had enough fuel and it had a way to sense what position it was using cameras, for example, they could fly out and fly horizontally.

But unlike Neil Armstrong, this has to be able to deal from any initial direction. Neil Armstrong was aiming for a point, because there's no air on the moon, you can keep your target very accurate all the way to the ground. Whereas the density variations on Mars are so large, and there are winds, between those two phenomenas, it's very hard for us to know before we get there that the trajectory is going to take you to your landing point. So you have to fly out those airs. We call it flying out, just the same way that a pilot does. Adjusting its wings, flying back and forth, and just like the shuttle, it makes these big S-turns in the sky. Move left, move right.

If you're going too far, you make more S-turns. If it looks like you're going too shallow, you stay on a more direct course. So at this point, will this be a winged vehicle or a lifting body? It's a lifting body, but it's a space capsule. It looks just like an Apollo, in fact. It was a lifting body. It was a lifting body, too. And certainly the CEV will also be that.

In fact, they have no choice if you want a precision target to landing areas such as Edwards Air Force Base or other places like that in the West Coast. We are almost out of time. Obviously, you've identified this problem, which people hadn't really thought about much. You're beginning to come up with the solution. How long do you think it'll take before we say, yes, this is the way we're going to put people on Mars? Well, it's going to take a while. Right now, NASA has higher parties.

It's got to get the shuttle back on its feet. The ISS completed the shuttle replacement. The CEV has to work. Then there's the plan for the lunar missions. NASA's budget is fixed. So NASA is going to have to pick one battle at a time. We know this battle is ahead of us. And I think once we get to the point where we can spend big efforts to solve this problem, I think we will. And I think within a matter of 10 years or so, we will be able to lick it. But unfortunately, it is a hard problem. It's not just hard to develop from Mars, but it's also difficult to test because you can test these systems at Earth,

but very large systems that you launch into space and try it out not just once but a few times to make sure that these systems will really do the job. One of the best things about this conversation has been the fact that you're facing all these challenges. You don't sound like you've lost any of your enthusiasm. You're still having fun. Oh, of course. Listen, you know, there's two aspects. One, I'm an engineer, so the engineering challenges are just absolutely wonderful.

An engineer couldn't ask for a better job. The flip side of it is we are really truly discovering things about this fascinating universe that we're living in. And that is a reward all by itself. You know, we've spent time today looking at wonderful photographs of Mars, new data that's now just starting to stream back from MRO. And as soon as it gets done with aerobraking, MRO, the Mars Reconnaissance Orbiter, is going to be just overwhelming us with images and data. It's like drinking from a fire hose, actually. It's going to be difficult for us to assimilate it. These instruments are going to give us totally new insights into Mars. And those of us who, like me, I

spend a lot of time worrying about how to get to Mars. Well, this is a big, important aspect. Where do we want to go? Why do we want to go to this site over this site? And this is a big challenge that MSL is going to face. It's very difficult to pick the best science site because there's a certain scale. Mars, when you fuzz your eyes, Mars looks orange. When you look with your high-precision binoculars, you see incredible detail, and that detail is going to have to be sorted out to help us figure out what's the best science to do at Mars.

We have only one chance for 2009, one lander and one rover. We need to pick the best place that's safe and exciting, and we will do that with this data that we're getting back soon. So one step at a time, and we're on the right path. I think we are, and we've got a lot ahead of us, and we've got a lot to do to ultimately figure out what the long-term future for Mars is. All right, Rob. We're counting on you. Thank you.

We're all behind you, and we want you to get us up there. Thanks, Matt. Rob Manning is with the Jet Propulsion Laboratory near Pasadena. He is the Mars Exploration Chief Engineer, I should say, for the Mars Exploration Directorate, and he's going to figure out how to get us up there to crawl around with a much bigger rover and someday to walk around on our own. We're going to walk over and visit with Emily for a moment, a return visit for the rest of her Q&A for this week. And then it's Bruce Batts for this week's edition of What's Up.

I'm Emily Lakdawalla, back with Q&A. How long will Saturn's rings last? The rings lose material in two ways. When high-energy particles from the Sun in Saturn's magnetosphere strike ring particles, they cause individual water molecules to fly off in a process called sputtering. Also, when meteoroids strike the rings and raise a cloud of dust, some of that dust is inevitably lost into Saturn's atmosphere. Because of these processes, Saturn's rings are constantly evolving, and they may look very different in a few million years. However, sputtering and meteoroid erosion are both very slow,

so most of the ring material should still be orbiting Saturn in four or five billion years, when our sun has swelled into a red giant. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time for What's Up on Planetary Radio. Bruce Betts is here.

Dr. Bruce Betts is the Director of Projects for the Planetary Society. He's here every week with us for this segment. But why are we at a Holiday Inn near Pasadena? There's so many answers I could try to come up with. We're sitting by the pool. I mean, basically we ducked out of work. But the real reason is, of course, we are at MEPAG, the Mars Exploration Program Analysis Group. God, I love those acronyms. Aren't they great?

The great thing is that these PAGs are like breeding or something, because it started with MEPAG, with Mars, and then now there's OPAG, with the outer planets, and VEXAG. That's Venus? Yes. VEXPAG? VEXAG. I'm sorry, it's just an ag, not a PAG.

How about New and Improved VEXAG? New and Improved, and they're meeting in a couple weeks. It's just the season for ags. But what they're doing, you gather a bunch of scientists together, in this case who care about Mars, a few engineers, mostly scientists, and NASA says, hey, give us some of your input. We may ignore you, we may take it, but give us some input and go think about things like, in this case,

they're talking about things like the next decade of Mars exploration. What do we do? And instrument development, and how long does does it take and how challenging is it? And then there are also nice little updates on each of the missions of which we've got tons of them doing all sorts of successful things, as well as ones in development like Phoenix and Mars Science Laboratory. And I saw a bunch of familiar faces in there. Of course, one of them was Rob Manning, our guest that we just finished with a couple of minutes ago. Yes, indeed.

There's all sorts. It's the crowd. This is really the Mars crowd. It is the Mars crowd. An awful lot of the players in Mars. What's going to be up in the sky above this lovely setting in just a few hours? Well, fortunately, Mars will. But it's going to be kind of dim and kind of in the west, low.

But it's still there. Also, Saturn hanging out also in the west. They're growing closer together. Mars and Saturn, they'll be tight soon. You can check them both out. Saturn will look kind of yellowish and in between Gemini and Leo. But also, we've got coming up not that long after sunset these days, Jupiter. But also we've got coming up not that long after sunset these days, Jupiter.

Jupiter reaching opposition on May 4th, where it is on the opposite side of the Earth from the sun. And so rising around sunset, setting around sunrise. That's where it can see Vulcan, right? The twin of Earth that we can never see? Yes, exactly. Well, no, because there's still a sun in the way. Oh, you mean when they can see. It's over there.

No, no, that's when it's something else. That's when their what's up says it's high in the sky. I'm sorry. Let's just go with that. Venus up in addition to Jupiter, which by then will be in the west, Venus is up in the east looking really, really bright, as always, in the predawn sky. So that's what's going on. What else you got for us? I got random space fact.

That was a nicely done exterior random space fact. Well, that's what I thought. I didn't want to scare people. Yeah. I wanted to bring it back a notch. But my space fact, random space fact doesn't, comes from this con... I learned it here at MEPAC. No kidding.

Just moments ago. It's true. This random space fact has been true for a long time. But I just learned it, which is a little analogy for how big the Mars Science Laboratory rover will be. They say it's going to be about the size of a Mini Cooper car. That's good. I haven't heard that one. And I'll give you an extra fact, just a bonus, which is its nominal minimum mission is 20 kilometers. That's compared to a few hundred meters for the two MERs, which now combined have gone about 7 kilometers in their really, really, really, really extended missions.

So by extrapolation, this thing will circumnavigate Mars. Yeah, exactly. Well, maybe not, but if you shoot for 20, maybe it'll do 100, 200. I don't know. How far can a Mini Cooper go on a tank of gas? A long way. No, it's not relevant. All right, let's go on to the trivia contest.

Sure. I asked you about moons of Saturn. What's the moon of Saturn that's really, really bright on one side and really dark on the other, and has a light side and a dark side? How'd we do, Matt? We got more entries for this than we've ever had before, substantially more. Go figure. I don't know if it's just that Iapetus is such a popular little guy

or just that our audience is growing. Maybe it's both. We're huge. Yeah, we're getting bigger all the time. We love it. Size does matter. Our winning entry came from Thomas Hendricks. Tom Hendricks, who is a regular, I happen to know.

You know, I've also just noticed Tom didn't give us his address. So it's going to be hard to get him. He's a planetary radio teacher. It's in there. Is it? Oh, you're absolutely right. He is poor formatting. Quincy, Florida is where Tom is from.

I think he's a past winner. And he apparently really likes it. He talks a lot about it. He calls it the Lord of the Rings, Iapetus. And he loves that mysterious wall, that high ridge that goes around this bizarre. It looks kind of like a walnut with a bright and dark side. Weird place. A lot of weird places in the solar system.

What's up with that? Speaking of weird places, let's give you another one. Also, fairly simple, and since you seem to dig the the moon question let's move to the neptunian system off at neptune simple one for you what's the name of the moon that was found to have geysers geysers on this moon what's the name of the moon go to planetary.org slash radio to find out how to email us your answer and try to win a planetary radio t-shirtshirt. How much time do they have, Matt? When do they have to get that in by? Boy, not as much as they would like, but the usual amount. April 31st, Monday, April 31 at 2 p.m. Pacific time.

Oh, Matt? Yeah? April doesn't have 31 days. Oh, you're absolutely right. May 1. Or alternatively, May 1st, whichever you prefer. Mayday, Mayday. Mayday, Mayday, that's going down.

2 p.m. on that first day of May. And you be sure and get that into us. And, boy, let's go for another record number of entries in the trivia contest. And I will leave you with this as another one of our entries in the, another one of our entrants in this week's contest said, you know what Obi-Wan said about Iapetus? That's no moon. Wait, I don't think that was, oh, I see dark side.

It's all coming together for me. I'm a little slow. All right, everybody, think about that, but also go out there, look out in the night sky, and think about swimming pools. He's Bruce Betts, the director of Projects with the Planetary Society. He joins us every week here for What's Up, and may the farce be with you. May the farce be with you as well. Planetary Radio is produced by the Planetary Society in Pasadena, California.

We'll see you next time. Have a great week, everyone. Thank you.