Planetary Radio • Oct 24, 2018

Sailing to an Asteroid on the Light of the Sun

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Les Johnson

Principal Investigator for the NEA Scout and Solar Cruiser solar sails, NASA Marshall Space Flight Center

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

LightSail 2 is not the only solar sail in the universe. NASA’s Marshall Space Flight Center and the Jet Propulsion Lab are preparing to send NEA Scout on a long, light-propelled journey to a near Earth asteroid. Principal Investigator Les Johnson shares his excitement about this interplanetary cubesat. Emily Lakdawalla reports in from southern France following the successful start of the BepiColombo mission to Mercury. Don’t know a primorial from a primordial? No worries. Bruce Betts will throw both into the soup as he ladles out a new space trivia contest.

NEA Scout artist's concept
NEA Scout artist's concept Image: NASA
NEA Scout sail unfurled
NEA Scout sail unfurled Image: NASA / Emmett Given

This week's question:

In an unrelated coincidence, what sequence of events that will occur for the BepiColombo mission can be characterized by the first three primorials, 1, 2 and 6?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, October 31st at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

On a typical pair of binoculars, what do the two numbers mean?


The answer will be revealed next week.

Question from the October 10 space trivia contest question:

What rocket launched the Apollo 7 crew 50 years ago?


The Apollo 7 astronauts rode a Saturn IB rocket into low Earth orbit.



[Mat Kaplan]: A new solar sail takes wing this week on planetary radio. Welcome. I'm Mat Kaplan of the planetary Society with more of the human adventure across our solar system and beyond. I bet you think I'm referring to LightSail 2. Ha! Not this time loyal subjects. We’ll spend time today with Les Johnson, principal investigator for NEA Scout, a solar sail that will leave Earth on the first space launch system rocket. Propelled by light, it will set out for a near-earth asteroid. Are you a math fan who's been hoping for a more numerological space trivia quiz from Bruce Betts? Your dreams come true on this week's What's up?. We start with a visit to France. That's where our senior editor Emily Lakdawalla reports from on her mobile phone. Emily, where exactly are you in France and what have you been up to?

[Emily Lakdawalla]: I'm in the southern France city of Toulouse [00:01:00] where I have just spent a day visiting CNES, the French national space agency, and seeing all kinds of projects both in Earth orbit and beyond, and preparing for orbiting Earth pretty soon as well.

[Mat Kaplan]: Very exciting, and you got a chance to speak there as well?

[Emily Lakdawalla]: I did. Every time I visit a research institution or a space agency, I always give my presentation about how amateur imagers, amateur image processors all around the world are ready and waiting to work with space image data to make beautiful photos that will help space agency's promote their missions.

[Mat Kaplan]: More evidence of why we call you, among other things, the Planetary Evangelist. Let's turn to your October 22nd blog post at about BepiColombo, which has gotten off to a good start.

[Emily Lakdawalla]: As any spacecraft hopes for, it had a nominal launch, which is the highest praise you can get from an engineer; everything went great, and the spacecraft is on its way for its seven-year trajectory [00:02:00] toward Mercury. As any spacecraft does when it first launches, it’s extended its solar panels, and one of the cool things about this mission is it has three little cameras to monitor deployments, and they got a self-portrait of those solar panels returned the same day as launch, confirming that they had deployed successfully and also that we can expect really cool pictures from those cameras in the future.

[Mat Kaplan]: Some of those images are in this blog entry at, as is this really terrific graphic that displays the incredibly complicated trajectory that the spacecraft is going to follow.

[Emily Lakdawalla]: That's right. And the graphic was produced by our designer, Loren Roberts, for the most recent issue of the Planetary Report, which features an article by Elsa Montagnon of the European Space Operations Center, who is the one in charge of getting BepiColombo to Mercury via Earth, Venus twice, Mercury five or six times before it enters orbit. It's going to be a long journey, [00:03:00] but it’ll be worth it. It's going to be a spectacular mission.

[Mat Kaplan]: And Elsa, a recent guest of this program talking about this mission to Mercury. Just one more thing here, you have included this very colorful -quite literally colorful- infrared video of the launch, how did this come about?

[Emily Lakdawalla]: Yeah, this is really cool. So this video of the launch was taken by a scientist who's in charge of an infrared instrument on the BepiColombo mission, and so, quite appropriately, he used a thermal infrared camera to watch the launch and was really excited about seeing his spacecraft successfully launched towards it's trans-Mercury trajectory. And all of it done in infrared, where you can see that the white-hot flame of the the high temperature launch vehicle, is really pretty cool and just so appropriate because after all that's how the mission is going to be and that's how his instrument is going to be a surveying Mercury.

[Mat Kaplan]: You can even watch the hot passion of some of the people observing [00:04:00] this, they are also outlined in this infrared image. Thank you, Emily, or I should say Merci beaucoup, enjoy the rest of your stay there and we'll talk to you when you get back.

[Emily Lakdawalla]: Will do, Mat.

[Mat Kaplan]: That's the senior editor for the Planetary Society, our Planetary Evangelist, Emily Lakdawalla. You couldn't have thought we'd let the chance to talk about a solar sail pass us by. After all, the excitement is building as the Planetary Society's LightSail 2 waits for its ride into space on the next SpaceX Falcon heavy rocket. But the society is not the only game in town. From a distance, in space anyway, you might have trouble telling LightSail 2 and NASA's NEA Scout apart. Dig deeper, as we were about to do with Les Johnson, and you'll learn that there are important differences in their designs and missions. Les is a physicist [00:05:00] at the Marshall Space Flight Center in Alabama. He was out of town when I visited there recently, so we connected not long ago online for a conversation about this innovative little light ship. Les serves as principal investigator on the mission. Les, thanks so much for joining us on Planetary Radio: it is a special honor to welcome a fellow solar sailer.

[Les Johnson]: Well, it's an honor to be here. It's an exciting topic.

[Mat Kaplan]: It really is. You know, it's one that's a very near and dear to our hearts at the Planetary Society because of LightSail 2, which I know that you are collaborating with with representatives from here. In fact, you told me you were just with my colleague Bruce Betts a couple of weeks ago at a conference that I think will get to but first, tell us about this solar sail, this little six-unit CubeSat and what you're planning to do with it.

[Les Johnson]: Well, the Near-Earth Asteroid Scout is going to be the US’ first interplanetary solar sail, and it will be the first [00:06:00] mission that NASA will have flown with a sail that actually has to go achieve science. We have a have a requirement not just to demonstrate that the solar sail works, but we will be carrying in our little spacecraft a camera and taking about a two-and-a-half year cruise using solar sail propulsion to take us to do science at a near-earth asteroid. It's called 1991 VG. It's got a really exciting name- 1991 is the year it was discovered-and we will be doing a fairly close flyby within about half a kilometer with camera just basically to see what one of our neighbors looks like. We're scouting out the neighborhood, and that's why we were created.

[Mat Kaplan]: And this is a flyby, you're not going to be sticking around. You're going to be moving on possibly to someplace else?

[Les Johnson]: Well with a solar sail, you really can't stop. The sun's always shining- which is one of the benefits of a sail, right, it gives you that continuous low thrust- and that means that when you get close to your destination, if you don't jettison the sail, which is too complicated for our flight, we [00:07:00] really just have to slow down the spacecraft to as slow as we can, which will be a few meters per second (maybe as much as 10 meters per second) and do our sciences. We do a slow flyby, but with a sail you don't run out of gas, right? I mean you're using this solar photon pressure. So after we get the images back, we'll decide if we saw enough of the asteroid, and if we did, we will look at other possible targets and see if we can get approved an extended mission to maybe go visit one of them. If we don't, then we need to get more images from the asteroid. The benefit of the sail is we can use it to basically turn around and go back, and within a couple of months we would do another flyby and take more pictures of it. That's really going to showcase the benefit of the sail not just getting there but the flexibility once we get on destination.

[Mat Kaplan}: That is a great outlook for the the goals of this mission. You say you've got the camera, what other instrumentation, if any, do you carry?

[Les Johnson]: Well, that's it. We are a [00:08:00] spacecraft that's been forced to fit in a very, very small package. People call it a CubeSat, and CubeSat kind of brings up an image of a whole host of components that have flown on these little things in Earth orbit. We would love to be able to use those but most of those aren't qualified for deep space. Once you get out of the Earth's protection, of its magnetosphere, you have to worry about all the solar system, the radiation environment out there, and it's just a very different environment than LEO. So we are a fully functional interplanetary spacecraft in a six-unit CubeSat form factor. What that means is that we don't have a lot of room for a lot of instruments. So long way around answering your question is we only have the camera, and everything else is devoted to the flight system,

[Mat Kaplan}: You found room for one feature that is not on LightSail 2, that is that you've got this thruster system, right?

[Les Johnson]: We do. We have a cold- gas thruster system, and it was necessary for a couple of reasons. One is that when we kicked off [00:09:00] our ride off the space launch system, the uncertainty in the direction we’ll be heading could result in us impacting the moon, and so we had to have enough cold gas to give us enough impulse so that we can miss the moon in case we're on a bad trajectory, and go into orbit around it. And then during the flight, we’ll have some residual propellant which we’ll use along with our reaction wheels to offload the momentum that's built up from the solar radiation pressure on the sail. So it's going to help us a little bit with our attitude control as we fly as well.

[Mat Kaplan]: We will of course put up links where people can take a look at Near-Earth Asteroid, NEA Scout. There are some fun animations as well, really cute one of people who must have spent an afternoon folding your sail. It looks like a nice party, actually. I'm also wondering about additional comparisons to LightSail, LightSail 2. If you saw the two of these side- by- side deployed would they look very different?

[Les Johnson]: No, they would look different at the surface because Light [00:10:00]Sail is four quadrants. The NEA Scout is a whole sail not in quadrants, and so if you looked at the surface of it, it would look like a very different sail technology. But when you look at the back side and the booms that are that are going to be holding the sail, the type of material that’s used is a little bit different but not dramatically different. You can tell they have a common heritage, and the reason for that is we all learned from our NanoSail-d, the ten square meter deployment test that we flew on a 3 unit CubeSat NASA’s Marshall flew in 2010. We shared a lot of that design detail with your team at the Planetary Society, and then they started designing the LightSail and as they were doing that we were doing our design of NEA Scout, and we have an agreement with the Planetary Society to share data. And so we were invited and participated in the Planetary Society's design reviews and they participated in ours. And so there's been a lot of cross talk as we've designed both of these systems. I think we both learned from each [00:11:00] other.

[Mat Kaplan]: I have no doubt, and it sounds like you'll be following the mission of LightSail 2, assuming that it does make its way up into space on the second launch of the Falcon heavy before too long, and probably before the EM1 mission, that first flight of the space launch system, that big rocket that's going to carry you up into into space.

[Les Johnson]: Well, I'm excited. I'm looking forward to the flight. Any flight of a sail is going to have my complete attention. So absolutely I'm looking forward to it and I wish them all the success in the world.

[Mat Kaplan]: Thank you, yeah, we appreciate that. You mentioned deployment, using booms to do this, which is again how LightSail also deploys its sails: describe that a little bit better. I mean, how do you unfurl these big sails?

[Les Johnson]: Unfurling the sails is a huge challenge. Our sail is 86 square meters. If you're like me, you don't think in square meters. So just imagine a school bus by a school bus we can invent our own unit of measurement, call it a school bus squared of area [00:12:00], but that's how big our sail is and it has to fit in a box that is smaller than your typical trash can. You have to fit that in, you have to put your camera in, all your flight system in there. So it has to compact to a very very small volume. In order to do that, you've got to have these big booms. Our booms are over 21 feet long, four of them. And they coil up on a spool and they’re under incredible tension. The strain energy on those is really high, and what that means is if you were just to cut it loose for deployment, it would be like a reverse tape measure retraction. You know when you push a button on your tape measure the metallic tape just pulls right into the to the box, well these booms want to deploy, and they have a lot of energy and they would pop out really quickly. And that would be dangerous because it could damage the sail, they would unfurl so fast. So we have a geared motor deployment to slow them down. So we slowly but surely let them come out of the deployment system with a stepper motor and as these [00:13:00] booms push outward, there were four of them coming out of the central box, the tip of the booms are attached to the corners of the sale which is folded and wrapped on a spool. So as these booms deploy, the spool slowly spins and the sail comes off of it and unfolds. You mentioned you had a link maybe to some of our deployment tests. It's a lot easier to understand it when you look at it than by hearing me.

[Mat Kaplan]: Yeah, and we will, as I said, we’ll put up a link to that, because as I said it’s a really charming video. It's really fun to watch. Similar to what we did with LightSail, although it is really cool to watch this thing unspooling from the center rather than just sort of emerging from the little, the four little containers that we have on LightSail 2. But I'll tell you, can you imagine watching that video what the most entertaining portion of it was? I'll tell you, it was the balloons.

[Les Johnson] Well, you know, you have a problem [00:14:00] trying to test these large flexible structures in the Earth's gravity well because basically gravity wants to pull it to the ground and it causes friction. So when we were doing the deployments we used a low-friction table but that wasn't enough, and as these long metallic booms go out they want to bow down toward the ground which will basically stop the deployment. So we stopped at a local grocery store and picked up some party balloons and attached the helium balloons, attached them to the tips to give them a little bit of lift so that they wouldn't drag during deployment. And you're right, you know, it's one of those low-tech solutions on a high-tech test that worked really well. It was a very cost-effective and it worked, it did exactly what we need.

[Mat Kaplan]: Talk about a party. I mean, actual party balloons.

[Les Johnson]: We had a party, believe me, after this was all finished. We celebrated. It was refreshing after all that work to see a successful deployment, that was, most recent, was of our actual flight sail. So it's our only deployment of the flight sail and it has now been refolded and [00:15:00] respooled, and ready for integration into the spacecraft.

[Mat Kaplan]: What's it going to take to keep this solar sail on the trajectory toward toward the asteroid? I mean, is it any easier than orbiting the Earth, where you're constantly having to reorient the sail?

[Les Johnson]: No, in fact, it's going to be one constant reorientation as we fly. One of the issues that we have is the optimum angle for flying the sale to reflect sunlight to get the thrust in the direction you want isn't necessarily compatible with the best angle for generating power with your solar panels and with communicating to the Earth. So, in fact, we will be reorienting the sail and the spacecraft all the time during our flight. There will be times that we have to leave our optimum thrust angle in order to call home and provide data and status back to the Earth and get commands from the Earth. There'll be other times where the solar [00:16:00] panels are pointing the wrong direction for too long and the battery starts getting drained and we have to point the panels at the sun which causes us to thrust in the wrong direction that we then have to go back and correct for. So our trajectory to get to the asteroid, which is about two to two and a half years depending on exactly when we launch, is filled with both the thrust to get us there and corrections we have to make when we end up thrusting the wrong direction to take care of power and communications.

[Mat Kaplan]: Steering a solar sail, I would imagine, is not yet really a science. Although it certainly has science elements. It really strikes me as being maybe a bit of an art.

[Les Johnson]: Well, it will be. Of course we have the analysis to show what we have to do and we'll have commands that we’ll upload every every step of the way for doing this control. But I would say for the first several weeks or month, we're going to be getting used to how our ship Sails. And when you deploy the sail, if there's one boom that doesn't quite get as much [00:17:00] tension on one side of the sail as the other one, you have a little bit of differential thrust on it, you have to account for that, if you end up with a small tear that affects what your thrust angles end up needing to be and how you balance the solar photon pressure off the sail. So it really will be the same as a shakedown Cruise. It'll be the first few weeks just learning how to fly our ship.

[Mat Kaplan]: Is any of this going to be automated or at least pre-programmed, or do you have to be in more or less real-time touch with the spacecraft?

[Les Johnson]: No, no we’ll, after the first few weeks, we’ll be more and more automated in terms of how the system flies. Now it would cost way too much money to have to have real-time control over this 24/7. So I would expect there will have some pretty intense operations for the first few weeks, but we'll upload software that will take care of most of this autonomously and then just check in with the craft periodically.

[Mat Kaplan]: Let's talk more about your ride up into space on that big SLS. You’re with quite a crowd of CubeSats that are catching that ride as [00:18:00] secondary payloads.

[Les Johnson]: That's correct. There are 13, at last count, six-unit CubeSats that will be in the upper stage of the SLS, and after the Orion is sent on its way to the Moon those cubesats will be kicked out one at a time in an order that's been established- I'm not sure exactly where we are in that order-and the CubeSats will be kicked out to start their operations, and it's kind of interesting, the school bus analogy continues because the points at which these CubeSats are deployed are called by the launch vehicle “bus stops”. And so they'll be different bus stops that'll be places where these CubeSats will be deployed, and we're at one of those stops.

[Mat Kaplan]: It's quite a mission, and I imagine it's pretty exciting in itself just being on the first flight of the space launch system.

[Les Johnson]: Well I've been focusing on the sail craft, I think we are exciting by ourselves. We are excited to be on the rocket and it's exciting to see us developing that [00:19:00] capability for sending humans and large payloads into space for the first time in a long time, and deep space, really big payloads into deep space. To be out there as a demonstration on that first flight of the capability is awesome and I have to mention that the reason that we're there is because there are very few rides beyond Earth orbit. Most rockets that launched today, including what you're riding on with LightSail is an Earth-orbital mission, and for us, in order for us to really showcase the capability of a sail to go anywhere in the inner solar system, the optimal way to start is to be on a rocket that takes you beyond Earth orbit that puts you out into space where you've already got Earth Escape. You don't have to spend any of your time spiraling out of the gravity well and so it's really an optimum right for us.

[Mat Kaplan]: I want to talk to you about the what appears to be the promising future of solar sailing in general and you know, the pretty limited experience that we humans have had so far, but, I guess we could point to the the [00:20:00] Ikaros mission from the Japanese Space Agency. Man, that was a pretty innovative sail, wasn't it?

[Les Johnson] : It was. In 2010, the Japanese flew approximately a little over 200 square meter sail, a spinner- a spin stabilized as opposed to three axis- which means ours and yours basically are like a sail and are stable and you can steer it but it's not spinning all the time. They did a complete spinning spacecraft. Theirs demonstrated that you could use a sail to change the thrust of a spacecraft in deep space. And they successfully did that and sent data home, but they really didn't use the sail to go anywhere. They didn't have a destination-driven mission where they had to get from point A to point B in a certain amount of time. It was a very good proof of concept and it was something that helped motivate our team, because it proved for the first time that you actually get the solar radiation pressure that you think you can get with these large flexible structures. So it was a great first step, but it really didn't demonstrate the [00:21:00] capability I think we all want to see with sails, which is using these to take, for now anyway, small spacecraft anywhere in the inner solar system.

[Mat Kaplan]: What is the promise of solar sail technology? I mean where should or where where can these be taking us?

[Les Johnson]: Well, I think for science, the killer app, to use that term, is probably for advanced warning of solar storms. In the future, both NASA and NOAA want to take spacecraft closer to the Sun and have it stay there on the earth-sun line to give you more advanced notice of solar storms, space weather events. Right now, those warnings come in from spacecraft that are in the L1 region, which is kind of a quasi stable position between the Earth and the Sun, where, spacecraft will stay there and always between be between the Earth and the Sun so it's a storms coming out you can get warning of that back here by radio and batten down the hatches on some spacecraft, but you can use a sail to go closer to the [00:22:00] Sun and thrust continuously so you're not in a different orbit. And you stay on that Earth Sun line and you can have instruments there to give you much more warning of these storms coming. There's another application for studying the sun, which is looking at the North Pole of this sun if people have been following news from space over the last couple of years, you'll have the surprising views of Saturn's north pole with the hexagon.

[Mat Kaplan]: Yeah

[Les Johnson]: Cloud structures there that no one expected. The recent pictures that have come back from Jupiter's polar regions from Juno, which I gave structures that no one expected and we very rarely almost never had glimpses of the sun's polar region. And there are a whole host of scientists who want to study that and a solar sail is a way you can do that, you go toward the Sun and use that solar radiation pressure to slowly but surely increase your orbital angle so that you're flying over higher and higher inclinations over the Sun and you can do science there. Those are in my opinion; will be the near-term applications of the technologies [00:23:00] that we're developing.

[Mat Kaplan]: How about additional missions to near-earth objects that would be you know, relatively inexpensive by the nature of solar sailing?

[Les Johnson]: Well, that was the reason NEA Scout’s was originally funded it was to show that you could use these spacecraft as low-cost reconnaissance of the neighborhood. NASA is interested in studying Asteroids for science. There's also interest in potential reconnaissance for planetary defense applications. You have commercial companies out there that say they want to mine asteroids and I would suspect that before you want to do any of these things you want to do a survey Mission and you want to do that as low cost as possible. We believe that a solar sail cubesat approach like we've developed with Nia Scout can do that. In fact, we looked at what the the cost of a second unit where you've done all the design work, which is what puts people in tents and what's expensive, but a second flight unit, if you wanted to build just a copy of it without any changes, it be on the [00:24:00] order of less than 10 million dollars. Which is a pretty low cost interplanetary science Mission. Also once we've flown, will have demonstrated it and anybody who wants to go send a swarm of these out they'll have the ability to do that.

[Mat Kaplan]: Let's go farther out, a lot farther out. I bet you're familiar with the work of the late Robert Forward and others on on using sails to go Interstellar distances?

[Les Johnson]: Absolutely, Robert Forward was a personal friend of mine. We talked at length about this, both with his science work and his science fiction work. He's been in: he was in my home; wonderful creative thinker. And he pioneered the original analysis to prove that this would be possible that you could use large solar sails and extremely powerful lasers to augment the radiation pressure on the sale to give spacecraft high velocities to get to other stars. I really would encourage listeners to go check out some of his pioneering work done for the British [00:25:00] interplanetary society and in open literature out there. I mean very very creative thinker. The Technologies aren't here yet. I think we're taking the baby steps toward enabling those, but these beamed energy sails are one of the few technologies that doesn't require new physics to enable us to go to the stars someday.

[Mat Kaplan]: Yeah, we'll leave warp drive out of the discussion and keep it in the real world for the time being. What do you think of, it's really an embryonic effort at this at this stage, but, of what the Breakthrough starshot project is? Hoping to lay out with these very tiny sails one meter wide and very very tiny electronic set at the center of that sail.

[Les Johnson]: It's really interesting actually, because when you look at the trades of how you would do these beamed energy sails, you have the forward approach which is fairly large sails and still powerful lasers. The other option is much smaller sails and even more powerful lasers, right? And so their idea is to [00:26:00] use these extremely powerful ground-based lasers deploy these small sails with very very lightweight payloads and send those very rapidly out of the solar system. The physics works. The engineering is going to be tough. We don't have the materials in hand. Currently the laser system technology looks like it's scalable from what we have today, but it's a huge scale up. So I'm excited by it. I'm pleased to see that there are groups out there looking at what might be possible and not just looking at it but putting money into it. I think it's exciting. And I think the work that the planetary Society is doing and that we're doing with Nia Scout are basically the first steps toward enabling these kinds of interstellar missions. It’s great.

[Mat Kaplan]: Speaking of materials, I'm going to go back to that conference that you attended, Actually. You told me you were the co-chair of that, Bruce Betts was at and we talked to him on the show while he was still in DC actually. What was that about and what kind of Promise does that these meta materials [00:27:00] offer? You better tell us what they are first of all.

[Les Johnson]: Well, I'll give a shout-out to the actual, the father of this meeting. It's Dr. Grover Swartzlander at Rochester Institute of Technology. He has a NASA Innovative Advanced concept study to look at these metamaterials for applications to solar and being energy sailing and basically metamaterials are thin film materials that have optical properties tailored to specific applications. So in other words with with our sail and with your sail, you basically have a reflective sheet some kind of plastic that has aluminum on it that reflects light. Well, what if when the light hits the sail instead of reflecting off according to the laws of just standard Optics? You can direct that light to emit from the sail in whatever direction you want, which means that the reaction force from that light is not necessarily in the direction you think it's going to be, it can be in whatever direction you want it to be [00:28:00] and what's Innovative about that for what we're trying to do is and it gets lost in the math pretty quickly. So forgive me, but when light falls on the sail, you are, if you have any imbalance in the center of mass of your spacecraft versus the center of light pressure your sail is going to want to tip over. There's also a roll, actually a spin that's induced from sunlight on the sail over long period of time that on our spacecraft we have to get rid of that induced spin because we can't really control the sail very well by these spinning reaction wheels. But you could put thin film materials, embed them in your solar sail to change the direction in which light is emitted from the sail to basically passively stabilize them and you don't have to do any kind of active control, to control all this momentum. Now for solar sails, that's great because it doesn't take a lot of area and you have a lot of time and you can manipulate that material to do what you want. But for these beamed energy sales where you're really accelerating [00:29:00] rapidly. It could be an enabler for them because they may have to manage their momentum very very rapidly. And that means you want to have as much passive control as you can built into the sail material and these tailored materials and the way they reflect and emit light could do that for you. So it was at the Optical Society of America in Washington sponsored by several different organizations, including NASA and others and it was exciting.

[Mat Kaplan]: Very exciting and we can hear this in your voice. I'm sure anybody listening to this right now can hear the passion and enthusiasm that you bring to this. And since you said that you were a longtime friend of Robert Forward who liked you as you said was not just someone who dealt with the real world and real science, but was a science fiction writer, I'll come back to that. Is this something that you've been passionate about for a long time?

[Les Johnson]: Well, it is for me. And in fact, it's when I look at the roots of my [00:30:00] introduction to solar sails, it came from a science fiction novel I read in high school by the great writers Larry Niven and Jerry Pournelle.It was called the Mote in God's eye.

[Mat Kaplan]: I know it well.

[Les Johnson]: Yeah and it was about aliens that were about to invade riding these big laser powered light sail ships, right and that was way exciting for me in high school and at the time I knew I wanted to study physics and I knew I wanted to work for NASA. But I never in my wildest dreams imagined that I would get to NASA and have the opportunity to work on solar sails and light sails. So it was an inspiration and my in career probably almost 20 years ago the opportunity arose, in basically a meeting the said hey, is there somebody who could start working this area? And we need to investigate the opportunities. The first thing that came to mind were Niven and Pournelle and the work of Robert forward. And so I raise my hand and the rest is how I ended up spending the next part of my career. It all goes back to that point and those kinds of interactions. I can't emphasize enough [00:31:00] the importance of getting young people fired up about science and the things that they get their curiosity piqued about when they're teenagers, they can take it and run with it some time in their career if they're very lucky.

[Mat Kaplan]: We could leave it at that. But I also want to ask you about your team and something that is maybe not unique about this team is that this project is the work of two different NASA centers, yours, Marshall space flight center and the one in our neighborhood, Jet Propulsion Lab. How's that working out?

[Les Johnson]: Well, it works out really well. I should have mentioned early in the interview with the solar sails system Marshall space flight center here in Huntsville is developing the sail propulsion system. The people who have had a lot of experience developing deep space spacecraft are those folks at the Jet Propulsion laboratory. And so they are developing the spacecraft and Dr. Julie Castillo Roche is the project scientist, who is developing and will be doing the asteroid reconnaissance [00:32:00] work, the science once we get to the target. Me and my team are responsible for getting her and her camera there so she can do that science.

[Mat Kaplan]: What's the outlook for launch of EM1 with any scout on board?

[Les Johnson]: Well, I think the Outlook is promising. I don't really work on the launch vehicle side of things. They give us these documents which are all the environments and the interfaces we have to meet. All I can say is that we are currently on schedule that we've been given to deliver our Hardware to the launch vehicle and when it flies we're looking forward to having a good ride.

[Mat Kaplan]: Les, I don't know where you find time to write books as well. But you had to that came out this year in February, one about the real world of science and one science fiction. Tell me just a word or two about graphene, which maybe I should have asked when we were talking about Innovative materials.

[Les Johnson]: Well, I have to give the caveat that my science fiction writing is totally different and separate from my work at Nasa, I do that all on my own time. I don't want people to think [00:33:00] I'm doing that while I'm on the NASA clock because I don’t. But there is an overlap and the overlap is actually you can see it at this Osa metamaterials Workshop. I was intrigued, graphene first off for those who don't know what graphene is, graphene is a form of carbon that is just carbon in a unique bonding relationships so that it's flat like a sheet of paper one atom thick. It was discovered in 2004. The discoverers got a Nobel Prize in 2010. What's so cool about it though it is one atom thick, three hundred times stronger than steel by weight.

[Mat Kaplan]: Wow

[Les Johnson]: And one of the most electrically conductive materials that we've ever discovered and when I heard about it, my first thought was this would make a great lightweight strong and robust solar sails substrate and so my interest in graphene started with solar sailing because I thought we've got to build a sail out of this. Unfortunately the technology isn't there yet. The material samples are very very small, but it got [00:34:00] me interested in graphene and then I had an opportunity to write a popular science book nonfiction, for the layperson actually with a good friend of mine, recent PhD in applied chemistry, Dr. Jo Meany. The rest is history. The book came out last February and we were reviewed by the journal Nature and excerpted in American scientist. And there's a whole chapter in there about how we can use these for solar sailing in the future. So I've got a foot in both worlds with that book.

[Mat Kaplan]: Anything you want to say about this latest science fiction, which I hope, I pronounce this correctly, Mission to Methone.

[Les Johnson]: ‘Metheny’ or ‘Methoney’. It's debatable as to what the right way is to say. Methone is actually a really interesting moon of Saturn. It's shaped like an egg. It's less than a mile long and it's the lightest, least dense moon in the solar system. So for a science fiction writer like me, of course, it's an old alien spacecraft, right? So in the story it's my attempt at first contact. We all look up. [00:35:00] the sky and the folks at the search for extraterrestrial intelligence have been listening for signals of ET and we all wonder if we're alone. The novel is my attempt to answer the question of are we alone and what's out there. So it's a near-term science fiction novel set in about the 2060’s. I will say that in the opening chapter solar sails feature prominently. The idea for the book actually came to me in a risk-management meeting here at work. I had to quickly put it out of my head to finish the day at work, but I went home that night and outlined the novel. Sold it to the publisher at Bay & Books, who's been my publisher of my novels, and it came out actually on the same day as the graphene book came out from Random House. So it was a it was a big month for me last February.

[Mat Kaplan]: Yeah, a big day I would say as well.

[Les Johnson]: Big day. It was exciting. It's been fun. Both books have done very well, and I'm excited because, quite frankly, I know what an influence reading stuff like that had on me and I've reached the point in my [00:36:00] career-I've been at Nasa 28 years- that I'm really thinking about that next generation and I'm trying to, in a way, I'm kind of trying to pay it forward, I guess.

[Mat Kaplan]: You and us both, and you've got at least one more big inspiring day ahead that we all look forward to with the launch of EM1 and the release of NEA Scout, NEA, or Near-Earth Asteroid Scout solar sail that will begin to make its way out to one of those asteroids as it crosses the path of our planet. Les, it has been great fun talking with you, best of luck with this mission as it goes forward and and with everything else.

[Les Johnson]: Well, thank you so much and best of luck with LightSail 2.

[Mat Kaplan]: I will pass that along to Bruce and all of my colleagues. We've been talking with physicist Les Johnson. He's the principal investigator for NEA Scout. He's out at the Marshall Space Flight Center that we visited not too many weeks ago in Huntsville, Alabama, and as you heard he's the author of well, actually several science fiction and science fact books including Mission [00:37:00] to Methone just published in February. You can find these books in all the usual places like Amazon and they're getting good reviews. We're going to talk to yet another recent author, it's time for our regular visit with Bruce Betts. He's back home, Bruce Betts is back home at the Planetary Society. He's the chief scientist for the Planetary Society. And, and I'm back home from vacation. It's good to be back. And I hope you're happy to be back as well.

[Bruce Betts]: Oh always happy to be back home.

[Mat Kaplan]: I don't know if you've heard yet, but your name came up in our discussion with Les Johnson today. You both were at that metamaterials conference, but he talked about how closely his team has been working with the Planetary Society to develop solar sails.

[Bruce Betts]: Yeah, and we're very excited about working with this team and the NEA Scout mission. They're kind of taking the next step beyond what we're doing and and we’re transferring what knowledge we gain in our missions to them.

[Mat Kaplan]: Good deal. [00:38:00] What's up? Other than solar sailing.

[Bruce Betts]: Well, by popular demand, I am shaking up the evening sky. And I already sent Venus aways so I said get out of here Venus, and now I'm going to send Jupiter away, but before it goes away completely I'm going to have Mercury join the mix because we just haven't hung out with Mercury in a while. It's so...what's the word mercurial? Yeah here. Uh, it's so, it's so BepiColombo. It's so, we'll come back to that. Look in the evening sky. You're going to have to look low in the west. Jupiter's getting lower and lower, looking like a super bright star soon after sunset, low in the west. Mercury will be rising higher as the nights go along for the next couple weeks while Jupiter gets lower. They'll be closest on October 30th, Mercury being much dimmer, but still looking like a bright star. And then, over towards the south to southwest is [00:39:00] Saturn looking yellowish and Mars in the south still looking very nice, bright, reddish star-like object. That’s Mars and let me also give you, at least for our Northern Hemisphere people, it's Autumn. So you should check out the summer triangle. I'm traveling up so it works out. If you look pretty much straight overhead in the early evening once it's nice and dark, you will see three bright stars, not surprisingly, forming a triangle, kind of a spread out triangle, its Vega, Deneb, and Altair. They also have their constellations including the Northern Cross, Cygnus the Swan, which is tied to Deneb. You can look it up if you're confused, but try just looking straight up in the evening and check out three bright stars and know that it's the summer triangle.

[Mat Kaplan]: Well, thank you. That's a nice enhancement and I assume that you are inspired by that lovely book that we're going to give away again in the new contest today, the one that you wrote, Astronomy for [00:40:00] Kids.

[Bruce Betts]: I am indeed. I'm trying to inspire others, but writing it, inspired me. It's a beautiful, beautiful thing. We move on this week in space history to one of the veteran spacecrafts. It's not at Voyager levels yet, but Odyssey. The Mars Odyssey spacecraft went into orbit 17 years ago this week and it's still returning great data.

[Mat Kaplan]: How long can this last?

[Bruce Betts]: It is one of the few spacecrafts that's older than Planetary Radio.

[Mat Kaplan]: That's true I guess. Yeah. Yeah, I will never catch up with Voyager 1 and 2, but neither will anybody else, so that's okay.

[Bruce Betts]: Well, that's true. No, no one yet. No one launched so far. That's for sure. Alright we move on to ‘Random Space Fact’. You mentioned BepiColombo. It's the European Space Agency-led mission with the Japanese Space Agency. And you may have wondered, why is it [00:41:00] called BepiColombo? Well, it's named after Giuseppe, nickname Bepi, Colombo, who is a scientist-mathematician-engineer at University of Padua, Italy. He was the first person to really outline and implement the interplanetary gravity assist maneuver, which was used by Mariner 10 for the first time for a gravity assist going by Venus to get to Mercury. Hence, that be Colomba.

[Mat Kaplan]: Isn't that a great nickname? Would you call me Bepi from now on?

[Bruce Betts]: Sure, Bepi. I hope you meant it, because now you have to live with it.

[Mat Kaplan]: Oh, yeah, what have I got myself into. Well, I'm not Italian, so I might get a nasty letter from the consulate.

[Bruce Betts]: Married to Italian, sort of.

[Mat Kaplan]: But yeah, I don't think she will ever call me Bepi.

[Bruce Betts]: Will you just leave it to us? It's Planetary Society, we’ll call you Bepi. [00:42:00] All right, we move on to the trivia contest. No, we don't because you have to tell me what we're doing for the trivia contest. I keep getting confused.

[Mat Kaplan]: Oh, we are indeed having a trivia contest. We're back in business, fully. We have a winner to name this week. You asked people what rocket launched the Apollo 7 crew 50 years ago.

[Bruce Betts]: So I asked what rocket launched the Apollo 17 crew 50 years ago. How did we do, Mat?

[Mat Kaplan]: I'm so glad you asked. We did well, everybody is back in the swing. I think that people missed us for that week because we got a big response. Here is the answer that we got from Wayne Likely. Wayne Likely in Seattle Washington has not won in four and a half years, but he is a three-time winner, so it’s been a long time Wayne. Thanks for sticking with us. I hope that it was worth it. I hope for many reasons. He says it was the Saturn 1B that carried those three guys up [00:43:00] into low earth orbit.

[Bruce Betts]: That is correct.

[Mat Kaplan]: Wayne, congratulations. Guess what? You're going to get a Planetary Radio t-shirt a two hundred point astronomy account, and, remember we offered a signed copy of John Logsdon's new book, The Penguin Book of Outer Space Exploration: the Incredible Story of Human Space Flight? It’s a really fun. It's all those original documents that put us where we are today in in space across the cosmos. It's a fascinating read. Anyway, thank you Wayne. As you sure know. I have some others. Dennis Hands, in Greensboro, North Carolina. He says Alan Shepard and Deke Slayton were not on that mission. I don't know if they like the Saturn 1B. They called it an “angry spitting snarling wolverine which shook and rattled its human cargo”.

[Bruce Betts]: Oh, yeah, that sounds like someone who likes something. That's what I call you.

[Mat Kaplan]: That's, I was on that ride, I think, at at a [00:44:00] local amusement park too. David Shanks in Schererville, Indiana. He says that the three guys who did go there, their Command module didn't have a name other than CM 101. It wasn't until Apollo nine’s launch with a lunar Excursion module and a module that the two vehicles needed names, all three guys, though, had head colds and they made them kind of cranky. Wally Schirra was kind of famous for getting cranky on that flag, right?

[Bruce Betts]: Indeed. There is a miniature rebellion.

[Mat Kaplan]: Here's another one from Mark Little our friend in Northern Ireland. He says and I'd forgotten about this. But if you look at the diagrams of the Saturn not diagrams, if you look at the photos of the Saturn 1B on the launch pad, it's the same launch pad that the Saturn V use, but it was shorter quite a bit shorter. So it used a quote. “Milk stool” unquote, to raise it up to the complex’s 39 umbilicals and then he adds, probably unnecessarily, the stool was a reuse of one design [00:45:00] for farmers with 128 foot tall mutant cows. But you've seen those pictures right?

[Bruce Betts]: Moo.

[Mat Kaplan]: No?

[Bruce Betts]: I said Moo

[Mat Kaplan]: Yeah right, I get it.

[Bruce Betts]: oh stop it. Yes, milk stool. I really not have, never thought of it that way.

[Mat Kaplan]: Steve Peterson finally, this is terrific. He's in Clayton North Carolina now, but I guess he wasn't always. He says, it was fun working at North American, that's North American Aviation when the Apollo program was active. We got to go to the Downy facility and see the capsules when they return. He says he has pictures. I assume that he took of Apollo 7. I'm sorry. He doesn't have them of Apollo 7, but he does have them of 8 and 11 through 17, which is a what.a .wonderful memory too.

[Bruce Betts]: Yeah

[Mat Kaplan]: I have thank you for sharing it with us Steve. And we're ready to go on.

[Bruce Betts]: As you know, I was late because I was getting weird with this trivia contest. So, hopefully you all will like [00:46:00] it. You can let Mat know if you never want something like this again, gotta concentrate for this one; out of this strange mind of Bruce Betts.. In an unrelated coincidence, what sequence of events that will occur for the BepiColombo Mission can be characterized by the first three primorials? Yes. That's right, Primorials the multiplication of prime numbers. So the first three primorials would be 1, 2 and 6. What sequence of events that will occur for the BepiColombo Mission can be characterized by the first three primorials one, two and six. Go to and say how much you love or hate this as well.

[Mat Kaplan]: Okay,I would say that everybody who enters this is going to get a prize, but it don't think we'll do that. Primorials. That's a totally new term to me. At [00:47:00] first, I thought you said primordials and that we were going to have some soup.

[Bruce Betts]: Well, you know you can have soup, but that's not it. No. No, I thought hey, that's the sequence of factorials. But factorials technically are 1 1 to 6. But primorials, multiplying the first prime numbers with each other, you get 1 2 and 6 which is oh so wonderfully weird and significant.

[Mat Kaplan]: Alright mathematicians. You've got until Halloween. You have until 8 a.m on October 31st, 2018, to get us the answer to this one and you will win yourself a: Planetary Radio t-shirt, you can check it out in the Chop Shop store, that's where the Planetary Society store is, all of our great merchandise; a 200 point account which you could also donate, if you would like, that worldwide network of telescopes; [and] last but far from least [00:48:00] a certain book that has already been mentioned on the show, Astronomy for Kids, how to explore outer space with binoculars or a telescope, or just your eyes. And what eyes they are by Dr. Bruce Betts.

[Bruce Betts] Alright, everybody go out there, look up the night sky and think about calling Mat Bepi. With one ‘p’, appropriately. That's because of the one ‘t’ in Mat.

[Mat Kaplan]: Yeah, I got it. I got it. Can I ask you an ethical question because now I want soup. How early can you have dinner and still call it dinner and not a late lunch?

[Bruce Betts]: I believe you have to finish the last bite of lunch, and I'm good to go straight on.

[Mat Kaplan]: I knew I could count on you. He's the chief scientist for the Planetary Society, Bruce Betts, and he joins us every week here for What's Up?. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its members who sail on the light of the sun. MaryLiz Bender is our associate producer, [00:49:00] and that special Halloween version of our theme comes from the delightfully demonic mind of Paul Brugelle, music director for Phantom Creep Theater and Phantom Creep Radio in New York City. I'm Mat Kaplan. Ad Astra.