Planetary Radio: Space Exploration, Astronomy and Science - Basics of Interplanetary Flight With Dave Doody

Episode Date: April 8, 2013

JPL’s Dave Doody doesn’t just fly around the solar system, he teaches others how it's done. We talk about what students learn in his non-technical class, the Basics of Interplanetary Flight.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

The Basics of Interplanetary Flight, this week on Planetary Radio. Welcome to the travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. Don't start that mission to Neptune till you hear today's conversation with the Jet Propulsion Lab's Dave Doody. He hasn't just written about getting from here to there. He teaches it. Bill Nye has the latest ups and downs regarding NASA funding for planetary science. And Bruce Betts will join me in a wake-up call for the night sky.

We'll get off to a great start with Emily Lakdawalla. Emily, something very different this week. Actually, a few things that are very different. You've got some slightly doctored photos, a robot shaming, but also these very pretty pictures, really beautiful photos of Spaceship Two. Yeah, the one of Spaceship Two poised next to the moon just really has to be seen to be believed. It's an amazing shot. The photographer must have planned it far ahead with the big long lens in order to make it look. It's just stunning.

So you definitely have to check that one out. Yeah, I suspect that Richard Branson is smiling about that one. And this robot shaming, you really have to see just if you want a good laugh. But let's get to the one that you posted on April 4th, because if there is anything that more of us share, perhaps even more than our fascination with the cosmos, it's the incredible frustration of having to sit through an endless poorly designed presentation. And you've done complaining about it in the hallways, which is obviously not an effective thing to do. So finally, I decided to write what turned out to be a rather long post. It's more than 4000 words in which I lay out some of the things that I've learned about how to make conferences conference talks more effective. But really, it all comes down to one thing, which is to respect your audience,

is to think about who those people are in your audience, what they come into the room knowing, and what the best way is to reach them, to deliver them the most information in the form that will be most useful to them, that will leave them happy to have spent some time listening to you. And so I lay out a lot of tips for that,

and it's been great, actually. It's been a great discussion as well. Yeah, you have some terrific comments there, too. And there are five principles, and we won't give those now. We'll just tell people, take a look at the blog at planetary.org. Look at Emily's blog.

It's an April 4th entry. It is something that should go far beyond planetary science because bad presentations are the universal constant Yes, they are So thank you very much, Emily and we'll talk to you again next week Thank you, Matt. She is a senior editor

and a good one for the Planetary Society and a fine presenter If you get the chance, check out one of her presentations sometime. We even have some, I think, in video at planetary.org. She is also our planetary evangelist and a contributing editor to Sky and Telescope magazine. That's Emily. Here's the CEO of the Planetary Society, Bill Nye. Bill, I think you probably want to talk about the latest developments out of Washington. Yes, I do. Yes, I do. Planetary Society had a victory last week. We got Congress to restore $200 million to the line item at NASA for planetary science. However, there's this

sequester, and then there's this other little thing called the congressional rescission, sequester. And then there's this other little thing called the congressional rescission, where they rescind a little bit. And it looks like we'll lose about all the money that we got added back in practice. And this wouldn't matter, except these people have been very diligent. The scientists and engineers of the decadal survey, the 10-year survey, as stipulated by the National Research Council, They went out and they said, here are the missions we want to do. Here's how much they're going to cost. We understand the budget's been reduced. Okay, we've taken it into account. And it's all, I won't say been tossed out the window, but let's call it called into question for what NASA would call higher priority

programs, which include the James Webb Space Telescope and the Space Launch System, which is this giant rocket that is not being designed for a specific purpose. It's just being designed to be big and powerful. And it is somehow tied, we hope, to this thing called the Asteroid Retrieval Mission. They want to find an asteroid, first of all, with money from the planetary science budget. Then they want to, they, powers that be, want to build a special spacecraft that will envelop this seven meter diameter asteroid, drag it to a orbitally balanced point, a Lagrange point out beyond the orbit of the moon, and then send astronauts there on the space launch system. Everybody's got to realize that all these ideas are a result of compromise.

The space launch system is a result of a huge amount of compromise. The asteroid retrieval mission is this huge amount of compromise. Whether it's the best science, whether it's the best engineering, whether it's the best use of the money is not clear. But it is a result of compromise, and you've got to respect that. So here we're going to try to get the sequester and the rescission rescinded and get the funding restored. Well, in the meantime, Matt, you and I are both traveling next week. Yeah, I'm headed to the Broadcasters Convention to look at all the toys that we can't afford. Ben, you're doing something I think much more interesting, going to the Space Foundation. Yeah, the National Space Symposium, which is held every year in

Colorado Springs. And you're going to be awarded the Douglas S. Morrow Public Outreach Award. Congratulations. Thank you. It's largely through your good work, Matt, to make me look good. Thank you. It's largely through your good work, Matt, to make me look good. No, but it's cool. I've been promoting space and space science for many years, and this is quite an honor. Have a wonderful time. Thank you. And you, too. Enjoy the broadcaster show. Now, everybody, Matt is a gearhead. He loves his microphones, his cables, his recording devices. He could quit if he wanted, but he just doesn't want to quit. That's all. That's all. Have a good time, Matt.

I've got to fly. Bill Nye the Planetary Guy. Yeah, yeah. He's the CEO, the head of the Planetary Society. We will be back in just a moment to talk to a friend of the Planetary Society, Dave Doody, about the basics of interplanetary flight. JPL's Dave Doody built his first spaceship when he was six years old. He has worked on many more since then, including the Voyager and Magellan spacecraft. Now he serves as operation lead for the Cassini Mission Support and Services Office.

When he's not working on interplanetary missions, he's often writing or talking about them. His books include Basics of Spaceflight and Deep Spacecraft. That last book is the optional text for a class he teaches in the Pasadena area where he has lived and worked for over 30 years. The course is Basics of Interplanetary Flight, and that's what I'd like to talk about. Maybe beginning with, how do you get them there? I mean, and we're talking about way out there, like Cassini that we just talked about last week. Yeah, that's what I love to address in talks that I give around, actually around the country, books and articles and things that I write. I think it's lacking in the public media.

What are we doing in interplanetary space? That's the major question that we address. We get 12 or 13 people once a year and we take apart subjects such as what are these spacecraft? How are they designed? What are they made of? How do they survive in the environment that they're in? And that's the second line. What is the environment? What are the forces that are dominant in the regions where they operate? What routes do they have to follow? How do they get where they're going? and then we look at the results. Everything changed in what, 1961? 1961. The current thinking was to get to the outer

planets beyond Jupiter would be almost impossible because you'd need enormous launch vehicles, nuclear-powered launch vehicles. And then a summer student, Michael Minovich, working at JPL, used computer time at JPL and UCLA and developed the idea that you could steal momentum, angular momentum, from the planets to boost your spacecraft. Astronomers knew that comets would have their trajectories changed when they passed by a big planet like Jupiter. But it was never realized until he worked out all the numbers that you could plan a spacecraft flight to go by, for example, Jupiter,

steal a little bit of momentum from Jupiter's orbit around the sun, if you will. Jupiter would never feel it. But your spacecraft certainly does, and it gets a huge kick, the exchange in there. Nothing is free. You have to take something from somewhere. And the spacecraft takes the energy from the planet that it's going past in a way that can add energy if you want to do that, or even subtract energy if you're going to the inner solar system. You can get rid of some of this excess momentum that you have.

Sitting on the launch pad, of course, you're going around the sun with a lot of momentum, the Earth's momentum around the sun. And you need to get rid of that to get into Venus or Mercury. And so Gravity Assist really opened up the whole system, the whole solar system for exploration. Yeah, I think of Messenger, which had to do exactly this to get to Mercury, right? And once it got into Mercury's distance from the sun, it did additional gravity-assist flybys from Mercury itself to further soak up some of that momentum. What was the ultimate statement of this kind of gravity assist stuff so far?

I mean, do you have to look back to Voyager? Voyager. I look at that as the main application. And back in those years, it was amazing that they could pull together a mission, build a spacecraft, design the mission. Of course, we know the mission designers that have been on your radio show. Yes. designers that have been on your radio show, to actually pull it together and take the enormous opportunity of a launch window that was really only one year and only one season out of that year in 1977 that could give you the beautiful flybys of Jupiter, Saturn, Uranus,

Neptune. So these opportunities, they come up pretty frequently if you just maybe have one destination in mind, but that grand voyage, that grand alignment, that was pretty rare? Yeah, that was rare. On the order of once every 175, 176 years. But to go other places, inward towards Venus, inward towards Mercury, or out to Saturn, like the Cassini mission that I have the privilege of working on, the opportunities are much more frequent because you don't have to plan for all

the planets, just the ones that you want. And let's talk a little bit more about Cassini, which had a pretty complex trajectory, didn't it, to make it out to Saturn? Well, we had the benefit of the designers who gained all their experience with Voyager, with Galileo, with many other flight missions, interplanetary missions. And all that knowledge and experience really came to fruition in a very robust spacecraft, Cassini, and the flight plan. Just as the Galileo spacecraft going to Jupiter turned out to be too heavy for its eventual final launch vehicle, it did gravity assists

using Venus and Earth before getting out to Jupiter. So did Cassini. Cassini was intentionally built too heavy to go out directly to Saturn. So we launched from Earth, going around the Sun at the same energy level that Earth goes around the Sun, fired the rocket engine to slow down a little bit and fall in towards the Sun, flew by Venus, got a kick from Venus, came out. Each of these kicks takes about a year to go around the sun. Came out to about the orbit of Mars, fell back in towards Venus the next year, did another Venus flyby, followed quickly by an Earth flyby, slowing down Earth a little bit in its yearly progression around the sun. Don't tell anybody.

And that gave us the kick to get out in the outer solar system. Another flyby, a gravity-assisted Jupiter, took some year or two, I think it was, off of the total trajectory. So we got out to Saturn by 2004. I was quite willing to give up an infinitesimal portion of a second of Earth's orbit of the year so that we could get out to Saturn and explore a little bit. Well, when I said it slowed down Earth, that's the quick answer. What it does is steal momentum from the planet. And when you take momentum from the planet, it actually falls in towards the sun. And that means it goes around faster. So you can't measure it,

but the navigators compute it, and the spacecraft certainly sees it. JPL's Dave Doody. We'll hear more when Planetary Radio continues. Hey, hey, Bill Nye here, CEO of the Planetary Society, speaking to you from PlanetFest 2012, the celebration of the Mars Science Laboratory rover Curiosity landing on the surface of Mars. This is taking us our next steps in following the water and the search for life, to understand those two deep questions. Where did we come from, and are we alone? This is the most exciting thing that people do,

and together we can advocate for planetary science and, dare I say it, change the worlds. Hi, this is Emily Lakdawalla of the Planetary Society. We've spent the last year creating an informative, exciting, and beautiful new website. Your place in space is now open for business. You'll find a whole new look with lots of images, great stories, my popular blog, and new blogs from my colleagues and expert guests. And as the world becomes more social, we are too, giving you the opportunity to join in through Facebook, Google+, Twitter, and much more. It's all at planetary.org. I hope you'll check it out. giving you the opportunity to join in through Facebook, Google+, Twitter, and much more. It's all at planetary.org. I hope you'll check it out.

Welcome back to Planetary Radio. I'm Matt Kaplan. My guest is Dave Doody, who has spent over 30 years designing and supporting missions throughout our solar system, including his current work on the Cassini mission at Saturn. Dave wrote Basics of Spaceflight, and he teaches exactly that in a non-technical course that begins again in early May at Pasadena, California's Art Center College of Design. Before the break, Dave was telling us how spacecraft get to both the inner and outer reaches of our solar system by getting gravity assists along the way. What kind of computation is involved with this? I mean, is it pretty straightforward now?

Is there off-the-shelf software to figure this stuff out? Yes. Wow. It's been developing for all the decades that we've been doing interplanetary flight. Friends of mine on the navigation team have recently completely rewritten the software that does all this. And, of course, you need computers and fine software to be able to do all this navigation. It's been building over the years, improving, getting refined, as well as knowledge of the solar system itself, the ephemeris,

exactly where each planet is at any given time, what its path around the sun is, not to mention all the satellites of the planets and whatnot. It's all input to the navigation programs. If you put all the information in properly, of course, no garbage in, then what you get is how to fly your spacecraft, where to perform the little corrections along the way using your rocket engines and get to where you want to go. You've hit the keyhole. You've got your spacecraft on its way and you're making little mid-course adjustments as needed, hopefully

not too many, but it still takes a long time to get there. And then in the case of Cassini, as we've discussed with Linda Spilker as recently as a week ago, nine years nearly now circling that planet. How do you build a spacecraft to last that long in this horribly challenging place called space? That's the same answer. It's the people who designed and built Voyager, Galileo, Mars spacecraft. who designed and built Voyager, Galileo, Mars spacecraft, all of the intelligence, the learning, the experience of many different spacecraft, key you into how to build a spacecraft that really will be robust. A thermal design, an electrical design that will survive.

Now, components fail, and so you put on extra components. For example, reaction wheels control the orientation of the spacecraft. On Cassini, the cameras are bolted to the side of the spacecraft, so every time you want to point a camera or a spectrometer or whatever, you have to turn the whole spacecraft. This is unlike Voyager that had that little platform with the cameras, right? Yeah, yeah. Voyager could point the cameras independently of spacecraft orientation. But Cassini chopped off the ability to do a scan platform to save money, and now we turn the whole spacecraft. So the reaction wheels that turn the spacecraft— Which are just flywheels, right?

They are massive wheels. They're about 10 kilograms, the size and weight of a garden stepping stone, that are spun with electric motors. If you want to turn your spacecraft, rotate your spacecraft one way, you spin the wheel the other way and trade off that momentum. Pretty soon you're going to want to turn your spacecraft back, so you just slow down the wheel. And in three axes, you just balance that out.

And again, software and computers on board take care of that. Still, though, big moving parts, fairly fast moving parts in the vacuum of space. They fail. Yeah, exactly. Yeah, so you have extras. And you have extra radios and duplicate whatever you can duplicate on a spacecraft. Extra rocket thrusters. And Cassini has all of that.

So when things fail, and they do, Cassini has had some failures, you switch to the backup. All, of course, by radio command across the hour and a half or so lifetime distance. across the hour and a half or so lifetime distance. Before we wrap up, say something about this class that you've got and have offered a number of times at the Art Center College of Design, which happens to be here in Pasadena, called Basics of Interplanetary Flight. You've already talked a little bit about it. My guess is this would intimidate some people because they're going to think, oh, it's rocket science.

Well, it does not intimidate. The prerequisite is curiosity. You must have some interest in what's going on out there. Nothing else. You don't need the math. You don't need the science. We get together with 12 people, 12 or 13 people, once a year and talk about what's going on, how you build the spacecraft, what is a spacecraft that can operate in interplanetary space, and look at some of the results.

Now, today, as we're recording this, Friday, Cassini is flying close by Titan, Saturn's largest satellite with the atmosphere thicker than Earth's. We're coming in 1,400 kilometers off the surface right now as we speak, and who knows about it? So I think there's a dearth of information about some really exciting stuff that's going on in interplanetary space right here in Pasadena, controlled from Pasadena. So let's get together and talk about it, figure out what's going on.

We'll put up a link to where you can learn more about this course, Basics of Interplanetary Flight, taught by Dave Doody. It actually starts May 13, is the beginning of the seven Thursday nights. But there are other things that you can do, too. There's your book, first of all, which you told me you wrote specifically with this class in mind, except I guess it gives all the real rocket science. Well, to say that we don't touch on a lot of math might raise some eyebrows, because interplanetary flight is math.

Yeah. But there's so much to talk about and other aspects of how we do what we do that I would touch on a little bit of math in the course. But for those that are interested in delving further into it, there's the book. It covers everything and references to as deeply as you want to go. And the book is Deep Spacecraft, an Overview of Interplanetary Flight by our guest, Dave Doody. Just one more thing I want to mention, and we'll put up a link to this as well. There's a website, a free website, part of the JPL website, called Basics of Spaceflight Tutorial. Yes.

And I guess even if people are not going to make it to Pasadena for your class, that's something you'd recommend? Yes. Is that something you'd recommend? Yes. Lay people, students, teachers have all found it useful, the basics of spaceflight. It's just at the JPL website, JPLNASA.gov, slantbasics. Dave, I wish we had more time, but maybe another time we can pick this up and talk a little bit more in detail. What I really wish is that I could go to the class. Join us. Thank you very much.

Dave Doody has been our guest on Planetary Radio. He is about to teach basics of interplanetary flight again and is somebody who is well known where he works at JPL, has worked on many missions and has worked for many years on the Cassini mission, just about to complete nine years, nine extremely successful and impressive years in the Saturnian system. Thanks, Matt. It's been a pleasure. This is What's Up, how we finish every Planetary Radio program.

Bruce Betts is the Director of Projects for the Planetary Society, sitting across from me in the Planetary Society Library slash conference room. Welcome back. Slash recording studio. Yes, slash recording studio. Slash poor acoustics recording studio. Yes, indeed. Poor for recording.

Great to consider the night sky. Oh, exactly. It's inspiring. Look up in the night sky. In the evening sky, you can see Jupiter still super bright over there in the west after sunset. It'll be getting lower and lower as the weeks pass. Orion will be over

to its left with the bright stars and Orion's belt. And if you follow the line of Orion's belt and draw a line off to the right, it'll kind of go through the Jupiter area and Aldebaran, which is a dimmer than Jupiter bright reddish star, and go farther over to the right, and you'll find a little fuzzy patch of little stars, and that's the Pleiades star cluster.

Later in the evening, you can check out Saturn coming up in the around 10-ish at night over in the east looking yellowish. I saw the Pleiades from the southern hemisphere. Wow. It was really exciting. We thought, that's not the Pleiades, is it? And then we looked it up, and yes, it was.

I never talked to you about the night sky in the southern hemisphere. How was that? Gorgeous. I mean, also, you were at a beautiful observing site. We walked out into the middle of this riverbed near the little village we were in, and it was, oh, my God, Magellanic Clouds. Saw the Southern Cross for the first time. Very nice.

Very nice. I still haven't. That's not important right now. We move on to this week in space history. In 1959, the Mercury 7 were selected, the first U.S. astronaut selection. And in 1970, Apollo 13 was launched. the Mercury 7 were selected, the first U.S. astronaut selection. And in 1970, Apollo 13 was launched. They were thinking, hey, this is a good day.

Yeah, right. Spam in a can. All right, we move on to Random Space Fact! Yeah, if I'd asked Dave Doody to say random space fact for us, you wouldn't have had that humiliating experience just now. So Sedna, Sedna, way out trans-Neptunian object, out, goes really, really far out in its orbit. And, you know, even when it nears its perihelion, its closest point to the sun, which we'll reach in 2076.

The sun would still, if you were hanging out on Sedna, would still look merely like a really bright star in the sky. Only 100 times brighter than a full moon appears from Earth. And too far away to be visible as a disk with the naked eye. And the moon would be not very bright at all. I'm thinking not bright at all. So yeah, it's really far out there. That's on the close part of its orbit. Okay, we move on to the trivia contest. I asked you, what is the term for where the solar wind slows down from supersonic to subsonic? So I thought, as did one or two of our listeners, that this was just something that happens to a lot of people in their employment life. The termination shock.

We had a very good response. Our winner. I thought that this person had won before, but I could not find any record of it. Maybe quite a while ago, Maeve, Maeve Hamrick from Felton, California, was our winner this time. Indeed, responded with termination shock. And so, Maeve, you are getting the Science Guy's voice, Bill Nye's voice, on your answering system. Congratulations. I have a couple of other to mention. They're really off topic. And like this one is just a warning to Jody Chapman, who entered, who wanted to do a shout-out to her brother, Corey Chapman, from one of his biggest fans. Jody, we can't do that. This is a radio, this is a broadcast.

We're professionals. Yeah, we don't do that kind of thing. So, we're sorry. Don't ask again. But this one is just great. Anders Brolin, longtime listener. But he's never mentioned this before. Kudos for keeping my nights bright despite no light.

I sleep lightly and always have all, yes, all Plan Rad shows running randomly on my mobile phone in speaker mode during the night. Okay. Oh, my gosh. We are white noise in Anders' life. Wow. Many people view us that way. Okay. Okay. You ready? Okay. Here we go' life. Wow. Many people view us that way. Okay. Okay. You ready? Here we go. Wake up, Anders! Wake up! Wake up!

Oh, now he really doesn't like us. Moving on. And Anders is from Sweden, right? Yes. Yes. Yeah, yeah. Yes, yes. Yeah, yeah, up in the polar night. Okay, what reflective coating is used on the mirrors of the Chandra X-ray Observatory? There are multiple mirrors on weird designed X-ray telescope. What are they coated with to make them reflective? And X-rays go to planetary.org slash radio contest to enter you

have until monday april 15 at 2 p.m pacific time to get us the answer to this latest question all right everybody go up there go up there go up there and out there and look up in the night sky and think about flowers and trees and bees and grass. Thank you. Good night. You know, the Southern Cross is laying on its side. That was a shock. None of us expected that. He's Bruce Betts. He's the director of projects for the Planetary Society,

who joins us every week here for What's Up. You know, it used to be upright, then it fell. Damn those alien hooligans! Planetary Radio is produced by the Planetary Society in Pasadena, California, and made possible by a grant from the Kenneth T. and Eileen L. Norris Foundation, and by the wide-awake members of the Planetary Society. Clear skies. Thank you.