Planetary Radio: Space Exploration, Astronomy and Science - Landing on Mars: How Hard Can It Be?

Episode Date: June 9, 2008

JPL's Rob Manning explores just a few of the challenges of landing a spacecraft on another planet. We also get a Phoenix mission update from Emily Lakdawalla, who says not everything is going well.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

How to Land on Mars, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. We return to our regular format this week, mostly. We've provided a lot of coverage of the Phoenix mission to Mars in the last three weeks. Most of it has been science-oriented.

This time we've got a gift for the engineers out there that we just couldn't resist. It's Rob Manning of the Jet Propulsion Lab, possibly the world's foremost expert on entry, descent, and landing at the red planet. And if you think that's easy, prepare to have your mind blown. Later on, we'll check in with Emily Lakdawalla for a quick Phoenix status report.

Not everything is going perfectly up there. Finally, it'll be Bruce Betts with this week's What's Up in the Night Sky that happens to include a dull orange-red spot called Mars. You'll also get another chance to win a Planetary Radio t-shirt. I've got to admit there are one or two other things going on in the solar system. Oh, by the way, next week we'll be talking about Saturn's moon Titan. Space shuttle Discovery astronauts have completed their third and final spacewalk at the International Space Station. They finished installing the Japanese Kaibo lab. They finished installing the Japanese Kaibo lab.

They finished installing the Japanese Kaibo lab, changed out a nitrogen tank, and inspected the troublesome bearings that keep the station's gigantic solar panels pointed at the sun. They should be back on the ground June 14. We know you remember Deep Impact, the probe that blasted a hole in a comet. The spacecraft hasn't changed, but the mission has. Now it is studying some of the planets that

have been discovered circling other stars. Call it EPIC, short for Extrasolar Planet Observation and Characterization. And later, it will be whistling Dixie, the Deep Impact Extended Investigation, when it flies by Comet Hartley 2. Together, these missions are called Epoxy. I know, I know, confusing as all get-out. All will become clear if you read the story at planetary.org. Ready for one more acronym? NASA says the GLAST mission won't be launched till at least June 11,

so that a minor booster repair can be completed. GLAST is the Gamma-Ray Large Area Space Telescope. We hope to feature it in an upcoming show. Let's travel back now to the Planetary Society's Planet Fest celebration on May 25. It's getting to be late in the evening. Phoenix has already successfully touched down on Mars, and many of our 750 guests at the Pasadena Hilton have headed home. But those that remain are in for a treat. So are you, as we listen to a presentation by one of the nicest guys in space exploration talking about how very hard it is to land on another planet. Here is PlanetFest Master of Ceremonies Bruce Betts

introducing Rob Manning of the Jet Propulsion Lab, who has the title of Chief Engineer on all sorts of things from Pathfinder to MSL to Mars program, and he's known as quite the guru of entry, descent, and landing, so here he is to give us some update. Thank you. Thank you, EDL fans. I'm one, as you are. And this is the... Oh, there's... Hi, Donna. In fact, I've been at this event just for thank you Donna I really appreciate it

she came just for me but the last time I came I talked the morning after Pathfinder landed in 1997 the 5th of July

the morning after I was on cloud 9 because I was I had been involved in my first landing event now it's I see Pathfinder

then I was outside the window of the Mars Polar Land, that was kind of depressing, and then the two rovers, and now this, I have to say, they're just as exciting, every single one of them, they're very exciting, and I can tell you why, there's a good reason for it. They're really hard, they're really hard, and it's really hard to get it right. Now, I wasn't that nervous, and you may have noticed that some of the team members, we were all tense. You can't help but have clammy fingers. But one thing you do to get ready for these kinds of things,

you can't predict that these things are going to work or not. You really can't. You do the best you can. But that's really the key. You do the best you can. And you do everything you possibly can to make sure you've done it right. And you've tested everything you can think of and peeled the onion. These things are like living beings.

Even though we design them with our brains or our hands, they're more complex than we are. And so we have to actually peel the onion and learn more about it. For example, you probably don't know. Here are some facts about this mission you're probably not aware of. One is, you know, this is the first entry vehicle to be intentionally entered into another planet without any attitude control

at all? You know, guys go, hmm, whoa, no way, Pathfinder, you guys didn't have control jets. No, we spun it at two revolutions per minute, slowly, but it was attitude control like a top. Well, I said, wait, wait, wait, wait, I could have sworn I saw pictures, you might say to yourself, that Phoenix had little rockets stuck in the back shell sticking out so we can control it. In fact, wasn't this based on the O-1 lander that was supposed to, the MSP-01 that was supposed to be guided and fly itself in and do the thing that MSL is planning on doing and steering itself so it lands in a nice tight little spot?

Isn't that right? Yeah, but we decided to turn them off. Huh? You might say. Well, you'd be right when you say, huh? Because that's what we said when we discovered something. We discovered that we really didn't understand how hypersonic thrusters flowing in the wake field of a back shell actually worked. I said, whoa, whoa, you guys are rocket scientists. Aren't you supposed to know this stuff? Didn't Viking come in that way?

Whoa, whoa, whoa, whoa, what are you telling me here? I'm telling you that we don't really know this stuff. That's what I'm telling you. Even the shuttle, even the shuttle, we didn't know how to do this. In fact, the shuttle had to turn off the reaction control jets too for similar reasons because, A, it's very hard to model. We don't have the tools to model what happens when it comes out of a rocket plume and how it interacts with the flow, turbulent flow along the back shell,

and what kind of a pressure distribution it has in the vehicle. We don't know anything about that. And so we discovered, the one thing we did, we did have better software. And our software said, hey, we started doing some, well, we should do some work to make sure this is right. We kind of dilly-dallied around. This was about two years ago in Phoenix. And we said, hmm, we should really some work, we should do some work to make sure this is right. We kind of diddly-daddled around, this was about two years ago in Phoenix, and we said, we should really do those simulations in more detail. Okay, well, let's do that. It's part of the job.

We're doing our due diligence. We'll just check the box. I'm sure it will be fine. We did the simulations. Guess what we found? We found that when you fired your rocket to move the vehicle this way, it went this way. What? We said to ourselves, we realized

that this pressure flow on the back shell was something that's almost impossible to predict. And if you use one computer simulation, you get one answer. You do another computer simulation, you get another answer. So which one do you believe? We couldn't believe either one.

And if we believe one, you'd have one result that might be bad. And if you do the other one, you get a different result that might be also bad. And so our best choice was, let's just turn them off. They're too dangerous to fly. In fact, one of the entry criteria we have is making sure those engines don't get turned on. We actually do enable them just in case you start to really tumble. But this is the first time. So what we said, the one thing we said, well, of course, when we discovered

this, we said, oh, we're in big trouble here. So we said to ourselves, what are we going to do? And we said, well, let's really see how stable the vehicle is if we just let it go. Just put it in the right position, aim it right into the atmosphere perfectly. And just before you get to the atmosphere, let go and let it fly in with the heat shield. And it turns out, during that phase of the mission, it's aerodynamically stable. Now, remember I said it's really hard to do any modeling when you have engines firing,

but when you turn the engines off, it's easy to simulate. And good news. And so we did some ballistic range testing and more simulation, wind tunnel work, and much more compressible fluid dynamics, CFD simulations, and it proved to us it was going to work.

So there we go. Passed that one. That was about a year and a half ago. This is like the MIR has, the rovers, we had their airbag troubles and parachutes exploding. This one,

we had a couple parachutes explode, but they were fine. We fixed those. Rob Manning of JPL speaking at PlanetFest on the night Phoenix landed on Mars. We'll hear more from Rob, along with a mission update, when Planetary Radio continues. Hey, hey, Bill Nye the Science Guy here. I hope you're enjoying Planetary Radio. We put a lot of work into this show and all our other great Planetary Society projects. I've been a member since the disco era.

Now I'm the Society's Vice President. And you may well ask, why do we go to all this trouble? Simple. We believe in the PB&J, the passion, beauty, and joy of space exploration. You probably do too, or you wouldn't be listening. Of course, you can do more than just listen. You can become part of the action, helping us fly solar sails, discover new planets, and search for extraterrestrial intelligence and life elsewhere in the universe. Here's how to find out more. You can learn more about the Planetary Society at our website, planetary.org slash radio,

or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Rob Manning of JPL is telling us just a few of the reasons it is so difficult to land on Mars. Rob's next big challenge will be setting down the huge Mars Science Laboratory rover in 2009. Here's more of what he shared during the PlanetFest celebration on May 25th. Another interesting situation is where just before we launched we said, well, we should do one more test where we take the lander, and when it separates from the back shell,

make sure it cleanly falls apart. Okay, we've done this before. It'll be fine. We started doing that. We lowered it down really slow, and we were looking, and I said, huh, something is not moving just right. Guess what? The vent, the hole that covers the thrusters had some soft good thermal blanketing to protect it. Very strong material that had hooked onto the thrusters and caused them to bend as the vehicle got lowered.

The whole thing was going, eh, eh, eh, eh, eh. Now, thrusters aren't supposed to bend. And they're kind of useful after you separate from the back shell. You remember that? We had to land that, what, 60, 40-some-six seconds worth of landing that was so exciting this morning, this evening, 60, 40-some-six seconds worth of landing that was so exciting this morning, this evening, I should say. Well, they were bent, and we realized we had

to completely redesign how they interfaced, and not to mention buy new thrusters in a hurry, and we did. Well, that was among the errors. Another thing, another disaster we almost had was the radar. You may not have heard about that, but our radar was not really designed to be a descending radar. It's a great radar if you're a cruise missile or an aircraft that's going horizontally.

But if you're coming straight down, you want to know the speed and the altitude. It turns out it has all sorts of weird, punny properties that we didn't know about. And we didn't know about it when we first built it for Mars Polar Lander. And? And? Oh, one. That was where Phoenix was supposed to be derived from. And fortunately, we had one test that didn't work.

The reason that was so good, if we had not done that test, we wouldn't have discovered all these problems with the radar. And once we did one test, we did another test, another test, we discovered, whoa, whoa, whoa, this radar is not working like we thought. So we go to the vendor. Now, it wasn't because it was a design defect. It's just we're trying to adapt something

that was never intended for this application for Mars. So what do you expect? You get what you pay for, right? If you're going to get something free for an aircraft, you better check to see and make sure it works. And we didn't do a good job before. Now we do. And as a matter of fact,

Mars Science Laboratory is repeating many of the same tests, in fact, all the same tests, plus some, that Phoenix did with its new radar that it so desperately needs in order to land the rover on its wheels using the sky crane architecture for MSL. So those were all some of the traumas that we had. But this

landing, and one thing we've said about this vehicle, if you can fly it in its sweet spot, right in the middle, it will do pretty darn good. In all our simulations, it seemed to show that it works very well, provided you don't do anything funny with it. And one of the things that concerned us about coming in, and what made me personally very worried, was, not recently, but over the course of the last year, was these little thrusters. Now, if you're trying to make a vehicle that can move anywhere in space like this and be able to turn around,

you want to put enough thrusters on it in different directions so that when you turn this way, you don't cause it to move that way. Well, Mars Polar Lander has thrusters that if you turn the vehicle this way, it takes off that way. If you turn this way, it takes off another direction. Well, if you're trying to target something

to another planet precisely, you don't want it to do that. You want it to kind of like, if you want to just get a better view of the sun with the solar panels, you don't want to have to go off in that direction. Hey, hey, it's like hitting the brake pedal and having the car make a left. It's not good. It's because we didn't have enough thrusters, because the heat chills in the way, you couldn't put thrusters in all the right directions. Whereas, remember, the rovers spun also 2 RPM, and their thrusters weren't used at all.

So we said to ourselves, well, how do we make sure that this thing works? How do we get it so that it's actually quiet and it doesn't fly around like this toward Mars? So we came up with some really neat tricks of figuring out how to fly it and how to do maneuvers and do it very precisely. And that's what we'd end up doing, these last few maneuvers, especially one last Saturday, a very, a very,

very tiny maneuver for TCM-5 where we turned the vehicle just a little bit to what we call the null vector and then fired our thrusters. And it turned out you can, you can move around in the sky all you want, provided it doesn't move you where you are on the ground. And that's what we did. We ended up changing the time of arrival by a little bit. Now that's a little bit different than what happened tonight. One of the things that are still kind of a mystery is the parachute opened up about seven seconds late tonight, which is kind of very familiar to me because Pathfinder we opened several seconds late. Spirit we opened several seconds late.

And Opportunity we opened the parachute several seconds late. I'm starting to see a pattern here. I'm slow, but I get it after a while. And so this pattern seems to show that something weird is going on. And yet, it landed at the same time as we predicted. In fact, it's within, someone had told me it was within a second of the press announcement. I go, how did the press know about that? In advance, the press release, in advance. I mean, it's like, geez, how did they, I should put them did the press know about that? In advance. The press release. In advance.

I mean, it's like, jeez, how did they? I should put them on the team. What's happened is the vehicle's not slowing down fast enough to get down to the pressure, the deceleration expected to feel as it's winding down. And so it's the software using its inertial measurement unit, or IMU, which is like its inner ear. It's sensing the slowing down. Like, not quite yet, not quite yet, not quite yet. It's too early. If I open the parachute now, I'll rip it.

Not yet, not yet, not yet. Okay, now. So seven seconds later, it's late. Well, so if you're late, it shouldn't be late landing, too. Turns out, because you're late opening your parachute, you're a little lower, too, and you're hanging on the parachute less time that makes up for the difference, and you end up landing about the same time as you would anyway,

which is kind of handy. But you end up going a little south a ways. It's just the spacecraft's smarter than we are. That's right. They're a lot smarter than we are. And that's why you have to be so humble about these things because these things are smarter than we are. And it's very easy for us to get them.

That's why we fail so often. It's so easy for these systems to be smarter than we are and know something about how they work that we don't know about, and it's usually not good. Well, I'm not sure. We still don't know where it landed yet. Brad Hack back in Lockheed Martin did an estimate tonight of the inertial measurement. He integrated the data he got back from Odyssey, that wonderful 32 kilobits per second.

Wow. Jim Erickson's MRO, the Odyssey spacecraft, Mars Express, this incredible confluence of spacecraft flying overhead like some sort of swarm of bees, just all listening to this lander coming in. What a thrill. You can only do that at the poles. You know that. You can't do that anywhere else.

MER, we were lucky to have even kind of a weak little signal in Mars Global Surveyor out there kind of recording for us. But this has been really stunning. So the nice thing, we have this great data, and we were able to take this data and turn it around now, and these guys are estimating that we went long, that we went further down track all the ways. Still all in a nice, great place for doing science,

but now we're going to scratch our heads and say, what the heck happened? And why are these missions seem to be going long? Why are we underestimating how thick the atmosphere is up here? Maybe we're getting it wrong. We'll think about it. The team's coming together next week to all come together. We're think about it. The team's coming together next week

to all come together. We're going to do a big huddle here at JPL and try to figure out what happened and why. So maybe we'll write a paper on it. I'm done. Thank you. That was Rob Manning of the Jet Propulsion Lab speaking at the May 25 Planet Fest

where we celebrated the successful landing of Phoenix above the Martian Arctic Circle. And how is Phoenix doing? For that, we'll turn to our own Emily Lakdawalla, the Science and Technology Coordinator for the Planetary Society. Emily has been following the mission very closely. We spoke just before finishing this week's show. Emily, welcome back. We're glad to get another report. Tell us what's new from Phoenix other than the fact that they're dropping dirt on our DVD.

Yeah, the Phoenix digging arm has been a little messy recently. It dumped some dirt on the DVD and it's dumped dirt elsewhere on the deck. They didn't plan on doing that, so they're having to go back and be a little bit more careful with how much they make sure that they've dumped all that dirt out of the digging arm before they swing it over the deck. Well, probably a dust devil will probably take care of it at some point. Well, you don't necessarily need a dust devil. Most of it's straight line winds that would blow things off there, although these dirt clouds are pretty big, so I don't expect to see them go away during the mission. I think you have a little bit more serious news for us.

Yes. Unfortunately, the TIGA instrument, the Thermal and Evolved Gas Analyzer, which is the one that they've been having some trouble with pretty much since landing. It's been one thing after another. Well, this time they delivered a sample over to TIGA, and you can see from the images that they returned from SAL-12 that there is a huge pile of dirt that landed right on the open doors of the TIGA instrument. But as far as they can tell, none of that sample got into the oven that was supposed to cook the sample. And that's not really very good news. So they're going to have to go back to the drawing board and try to figure out what went wrong.

Either they have to do more work to try to shake a sample in there, or maybe their detector that tells them whether or not the oven got full is flawed. So they've got to figure out what's going on there. Now, you mentioned in the blog that there is a screen that is only supposed to allow particles of like a millimeter or less into the oven. Could that be part of the problem? Well, that's what a lot of people are asking. You know, why did they put a screen with millimeter-wide holes? And the answer to that question is very simple, because their oven is one millimeter wide. And so that's the size of the particles that can be accepted into the oven. The oven is a very tiny chamber at the bottom of this hopper. That's interesting. I had this idea that it was some kind

of, you know, double fist sized container. And obviously, I was way off the mark. Yeah, I don't think most people realize that the oven is made of quartz. It's about a millimeter wide by roughly three centimeters long. It's very tiny. And so that's why they need that screen to make sure that the entrance to the oven doesn't get blocked by larger particles. And so what they intended to do is to shake that screen. And they can shake it at a variety of speeds. They could shake it as low as five times a second, which is kind of like tapping on it with your finger, or as high as 100 times a second. Tell us what else is happening with the lander. I guess the other instruments are doing okay. Yeah, the other instruments are doing fine. And while they troubleshoot TIGA, they're going to go ahead and deliver a sample to

the Mecca Optical Microscope and to the Mecca Wet Chemistry Lab. And they're going to do a lot of other work with the arm. They're going to do more imaging on the underside of the lander. I understand they're going to do some more digging at Dodo to try to see if they find more of that white material. Dodo is the first trench that they dug. And so they're proceeding with the mission as they troubleshoot Tiga. And there are pictures and good descriptions of all of this at your blog, of course, planetary.org. Also in articles from our colleague AJS Rail, articles on the homepage at planetary.org, there's a pretty humorous sequence about the little wind vane, the telltale,

that you found on somebody's website. That's right. It's pretty funny. This little telltale is a tiny weight. I hadn't realized how tiny it was, but it's this little tiny thing that gets blown back and forth in Mars's wind. And so they return images of it every day. And sometimes the telltale is hanging straight down. Sometimes it's blown out to the side. But yeah, somebody on unmannedspaceflight.com made a little joke out of that with a picture of what it might look like after a dust devil hit it. And as you can imagine, there's no telltale left there. Emily, thanks a lot. I know you're going to take a few days off now, a little vacation, and you're going to have a couple people filling in for you at the blog. That's right. I'll make

sure that the Phoenix coverage continues. I've got a friend of mine, James Canvan, who's going to be posting a lot of his images and the raw images from the Phoenix website on the blog. And also, Jim Bell, the head of the PanCam instrument on the rovers, is going to be writing blogs about his adventures this week. All right, Emily, have a great vacation. Thanks for the update. Thank you, Matt. Emily Lactawala is the Science and Technology Coordinator for the Planetary Society, author of the blog, and, of course, does our Q&A segment right here

that will be returning next week. Got Bruce Betts on the Skype connection. He has joined us for another edition of What's Up. Of course, he's the director of projects for the Planetary Society. He was also the emcee for Planet Fest. And, Bruce, we are getting so many nice comments from listeners, not only about the last three weeks of this radio show and our special coverage of Phoenix, but all the stuff that the Society has been doing, including that

DVD, which is now having dirt dropped on it on Mars. Yes, we're very excited that our hardware is basking in the Martian dirt now. Getting soil on it with the quarter million names and visions of Mars with all the Mars literature and art content it's got. So it's exciting, and we're excited, obviously, about the Phoenix mission and all the great success they're having. Do we have Mars up there in the night sky? We do, just for you. I arranged to have it brought in, and it's not quite as spectacular

as in the Phoenix images, but it is a reddish-orange-ish, kind of bright-looking star-like object up there in the early evening sky. You can see it kind of midway up in the west. Above it is Saturn, and they are getting closer and closer in the sky over the coming weeks. Saturn in Leo, near its brightest star, Regulus. Saturn looking kind of yellowish. And that's the evening sky, although the king of the planets, self-proclaimed king of the planets, Jupiter, is moving into the evening sky late, late, late in the evening. It is rising in the east.

It's still really high overhead in the pre-dawn sky, and it is the brightest star-like object up there right now. That's kind of what's going on. I am the king, which is something only L.A. television viewers would get. But anyway, if you're really curious, send us a note. We'll explain. Obscure local TV references. And now moving on to Random Space Fact. Too early in the morning for you?

Oh, yeah. Much too early in the morning to concoct a powerful random space fact tune. I'll try to give you a powerful random space fact. Let's take a look ahead for the listeners who may not know. We've got Phoenix just landed on Mars, still have a ton of spacecraft operating at Mars, but we've also got ones coming up in the future Mars opportunities, good Mars launch opportunities, because the orbital interplay between Mars and Earth

come about every 26 months, roughly every two years. So in the 2009 opportunity, which is roughly October, there are two scheduled launches right at the moment. We've got the Mars Science Laboratory, big old hanging rover from NASA, the size of a small car. And then also the Russian Phobos Grunt mission, Grunt meaning soil, which we're excited that Planetary Society has a biological experiment on to test whether you can send microbes out and back and have them live. And then you move on to 2011, and 2011 looking a little sparse, actually, maybe the first Mars opportunity in a while that we don't have a launch. But 2013, coming back in with ExoMars, big European rover, also a NASA scout mission, which Phoenix is the first scout, the second scout, although it's not selected, will be

one of two exospheric orbiters studying the very high atmosphere and things like atmospheric escape from the planet, what's getting away in terms of molecules. You know, I'm glad you mentioned that European rover because the pictures I've seen of it look like it's made of stainless steel. You know, they have a flair for style. It's very European, I'm telling you. But anyway, let us move on to the trivia contest. And we asked you about Phoenix.

Anyway, let us move on to the trivia contest. And we asked you about Phoenix. We asked right before landing, what was the horizontal and vertical velocity of the Phoenix spacecraft? How'd we do? Hey, we got a lot of answers and a lot of people did take an extra moment or two to tell us how much they've been enjoying the coverage. Like Pat Foster, who said he loved every minute of it i guess he followed the landing live separately but then he said it was just as emotional listening to it here on planetary radio the second time around and he said this is what it's all about well he's

right but we did also get uh this one from and i hope i get his name right ramesh or ramesh but he's got ramesh hanumaya he neglected to give us his mailing address, which he's going to need to do because he is the winner of the T-shirt with the correct answer. Vertical velocity of about 5.4 miles per hour. Horizontal velocity of less than 0.2 miles per hour. Basically dead on the design plan for the Phoenix lander. So, Ramesh, congratulations. We're going to send you a shirt if you tell us where you are. Yeah, it went brilliantly with their landing.

The engineers really don't like the horizontal velocity because that's how you run into things and get flipped and things like that. So the fact that it was nearly zero was making them very happy and part of the reason it landed so fabulously successfully so let's go on to how uh how you can win a planetary radio t-shirt with our next contest speaking of phoenix how tall was the rocket that launched phoenix go to planetary.org slash radio and find out how to enter and you've got until Monday, 2 p.m., June 16th, Monday the 16th at 2 p.m. to get us that latest answer to the space trivia quiz. Okay, we're done. I hope to see you in person next time. That would be great. All right, everybody, go out there, look up the night sky, and think about

whales, dolphins, and porpoises. Oh, my. Or as my friends in college used to say, lions and kaplans and boars, oh my, speaking of inside comments. He's no boar, he's Bruce Betts, the director of projects for the Planetary Society. He joins us every week right here for What's Up, bringing in the bacon. Join us next time for a conversation

with planetary scientist Ralph Lorenz, who has co-authored Unveiling Titan, a great new book about Saturn's weirdly Earth-like moon, and the Cassini-Huygens mission. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.