EPISODE 53: INGENUITY MARS HELICOPTER

Transcript

Bob Balaram: It’s the first time an experimental aircraft is flying on another planet, just like the Wright brothers did the same thing at Kitty Hawk many, many, many years ago, that first experimental aircraft.

There is, I think, an era of aerial exploration, at least for some of the planets that have atmospheres like Mars and Titan, which I think represents a new chapter in NASA’s exploration history.

Deana Nunley (Host): Welcome back to Small Steps, Giant Leaps, a NASA APPEL Knowledge Services podcast where we tap into project experiences to share best practices, lessons learned and novel ideas.

I’m Deana Nunley.

The Ingenuity Mars Helicopter is a technology demonstration to test powered flight on another planet for the first time. After the Mars Perseverance Rover lands February 18, the helicopter will be released from the belly of the rover for its experimental flight in the thin Martian air sometime this spring.

Ingenuity Chief Engineer Bob Balaram joins us now for this second segment of our two-part series on Perseverance. Bob, thank you for being our guest.

Balaram: Oh, glad to be here.

Host: Could you start by describing the Ingenuity Helicopter?

Balaram: The Ingenuity Helicopter, we are a technology demonstration on the Mars Perseverance Mission. In other words, we are hitching a ride to Mars with the Rover. We will be dropped off on Mars. And what we will be doing is for the very first time we will be exploring the aerial dimension of mobility on another planet. So this small helicopter will make a succession of small test flights, and then the results from that will inform the possible design and use of additional helicopters in the future for Mars for exploration and for science. So, we’re really a small little payload. We are about four pounds. We have a wingspan from tip to tip for our rotors which is about 1.2 meters. That’s again, about four feet and these flights will be in the order of about a minute or a minute and a half. And we’ll be executing potentially up to five flights over a course of 30 Martian days, otherwise known as Martian sols.

And that is the plan, and we are currently en route to Mars with Perseverance. We are tucked up under the belly, and within about a month or two after Perseverance lands and does all its checkout, we will be deployed onto our little landing airfield, if you will. And then we will commence our experiments for this technology demonstration.

Host: What are the steps for releasing the helicopter from the rover once it lands?

Balaram: So, there’s a couple of steps. One is that we need to find ourselves a suitable place to do the experiment. Since this is a first-of-a-kind experiment, we’re looking for a little flat spot, about 10 meters by 10 meters, 30 feet by 30 feet, which will be our landing pad, if you will. And we have a flight zone, which extends about 100 meters from that landing pad. And so, the first job of the team, the combined team of Ingenuity and Perseverance, will be to find a suitable spot. And every expectation is that within a few hundred meters of wherever Perseverance lands, we will find such a spot. Then the rover will go to that spot.

And then there’s a sequence of what are called the pyrotechnic release events, which I can go through in detail if you wish, which ends up depositing us onto the ground of Mars, and then the rover effectively unstraddles us because we’ve been underneath and drives away to a safe distance of about 100 meters, and then is there to observe the flights as well as serve as a communication relay to send back our engineering information back to it.

Host: And I’m guessing we’ve got some engineers listening that would love to hear a little bit more, so if you don’t mind going into a bit more detail about how that’s going to work.

Balaram: Yeah. So let me just walk through the deployment sequence in sort of order. We are protected by a debris shield that protects the Ingenuity helicopter on the underside of the Rover. During the Perseverance landing, given the rocket engines from Perseverance kick up a fair amount of dust and rocks and pebbles and we don’t want those to damage our aircraft. So, effectively, if you’ve seen pictures of it, there’s this thing that looks almost like a blackish gray guitar case under the bottom of Perseverance, and that’s a debris shield. So the first thing that’s done is just before we get to the final landing spot that we’ve selected, the debris shield is jettisoned using a pyrotechnic cable cutter. And then the helicopter moves into the actual drop spot. There is a launch lock that’s been holding Ingenuity on one of the ends, which is then released.

Then there is a cable cutter, which lets Ingenuity swing down towards vertical. And there is a dynamic breaking from a motor on the Perseverance Rover that makes sure that that swing down is slow and gentle. Then the motor continues to engage and pulls the helicopter into a vertical position. We are actually mounted sideways for reasons of accommodation and space. So once we are vertical, it also happens that the same process releases two of our landing legs. There is another final cable cutter, which releases the remaining two landing legs. So, at that point, we are perfectly vertical ready to drop on the ground. We then ask the rover to charge our lithium ion batteries that are inside the helicopter to a full 100 percent charge, because we want to make sure that we survive overnight if needed as the rover drives off, because til our solar panels are exposed, we don’t get charge into our helicopter.

And since we are shadowed under the Rover at the stage, we get charged to a full 100 percent. And at that point there is a device called a frangible, which basically is a thermally activated nut and bolt combination, if you will, that breaks when heated, and that ends up dropping the helicopter about a few inches from the ground. It drops it onto the ground. There’s a whole sequence of intermediate steps. What I’ve described to you takes a little over a week. The Perseverance team is being very careful, making sure they take images of us at all the intermediate steps. And then there’s a final drive where they unstraddle us and park about five meters, about 15 feet away, take a bunch of inspection images. And then we move on to our commissioning phase and they move off to their safe 100 meter distance.

Host: And then what’s the plan for the technology demonstration?

Balaram: So, as I said, we have up to five flights is what we are planning for that 30 sol window that starts the moment we drop. So, in that 30 sols, we expect to do about five flights and we have effectively about a three-day cadence, where we do a flight, we get back the data, we analyze the data. The team then decides what the next flight would be. We have preplanned the first three flights in considerable detail. The fourth and fifth flight depending upon how well we do, they’ll either be contingencies for the first few flights, or we might try something sporty. The very first flight is designed to be an almost exact repetition of a test flight we did in our space simulator chamber at JPL in Pasadena. And that’s just to allow us to do an apples-to-apples comparison between what we observed here on Earth, where there are test-related artifacts. Gravity is different.

And so, we’ll find out for the first time what the Martian atmosphere and the Martian conditions, environment mean to us. And we also will get a good sense whether we have any issues that we have to deal with. So that’s just a straight up and down going to about three meters, about 10 feet up in the air, hovering for about 30 seconds or so and then coming back down. Once we analyze the flight and deem it successful, we’ll take progressively more complicated steps. So the second flight would be to do some lateral motions. And then third flight is to do even more lateral big excursions, going off to many, many tens of meters from our landing spot and then coming back to land again. Flights four and five, as I said, a little bit more, could be more sporty. We might attempt to fly higher. We might attempt to fly in higher winds. We might attempt some really long distance moves.

So, there is a possibility that the flights number four and five would be considerably more exciting than the first one, but even the first one, our team thinks of it as our Wright brothers moment. It’s the first time an experimental aircraft is flying on another planet, just like the Wright brothers did the same thing at Kitty Hawk many, many, many years ago, that first experimental aircraft demonstrating powered, controlled flight. So they took that small step and we are hoping to take that similar small step on Mars, and hopefully that leads to great leaps in Mars exploration.

Host: And what can we expect in terms of images from the flight test on Mars?

Balaram: So, there are two sorts of images. One is the helicopter itself and the other one is the rover. So let me talk to the helicopter side first. We have two cameras. One camera is a black and white framing camera, which is used by the helicopter onboard navigation system to see how much lateral motion it’s achieving. So basically it compares successive images many, many times a second, and looking at the offset in each image to the previous one, it knows how much it has moved. This, when combined with the onboard inertial measurement unit and the LIDAR altimeter that we have on the helicopter, lets us know how much we moved and where we have moved. And it’s all part of the flight control and guidance system. There is another camera, which is very comparable to the camera you have on your cell phone. It’s a 13 megapixel Sony camera, color camera, and that is looking off more towards the horizon.

So that is the other camera that we have. So during the first flight, especially, we plan to take a few, a handful of images, with both the cameras. And we definitely, after the very first flight we’ll link the, send back the first black and white image, because we need that to know exactly where the helicopter has landed. Just before the helicopter lands, it takes a sort of a descent image. And based upon that, we sort of confirm and localize where the helicopter ends up. We will also return a few of those color images back to Perseverance, where we have a base station that serves as a relay and that black and white image and the color images which will come on the next day will be returned back by the Rover back to earth. Now while all of this is happening on that first flight, there is an opportunity and a plan for the rover cameras.

The rover has a camera called Mastcam-Z, which is a very powerful camera with a zoom capability. This is a new capability that has not been there on previous Mars rovers. And so there is an expectation that Mastcam-Z will try to image us during that flight. And we should be able to see, it’s not going to look very big, even at full zoom, 100 meters away, but we should expect to see in those images, when they’re eventually returned, sort of a far vantage point view of the flight. So those are the image sources that we expect to get back. But the very first day of the flight, I think the only thing that we are guaranteed to get back for sure is the one black and white image downward looking, which is really an engineering product. But once we get past that, I’m sure we will be releasing and obtaining and downloading from Mars a lot of the other images we take both on the rover side, as well as the helicopter side.

Host: Let’s talk about the commands that you’ll be sending from the ground. How do you communicate with Ingenuity?

Balaram: First of all, let me just start from, we have a helicopter operations team, which is now embedded within the larger Perseverance Operations team. So we build up command sequences for two things on Mars. One is that we have the helicopter itself and then we have a base station which serves as this communication gateway to the helicopter. So as far as the rover is concerned, it only knows about the presence of the helicopter to the base station. The base station looks just like any other science instrument on the rover and, just like any science instrument, can receive commands and return telemetry and data products. From the rover’s perspective, it’s just commands to the base station. It’s the base station’s job to relay on using a radio, using a small radio that we have on both sides of the base station and the helicopter, the specific commands to the helicopter itself.

So, the command sequences really are the helicopter commands, the base station commands to sort of wrap around it and the rover instrument commands, which allow the rover to command this instrument, like turn the base station on, ask it to return the data. So those commands are generated by the combination of our Helicopter Operations team, as well as the Rover Operations team. And then they’re radiated by the Deep Space Network to the rover through an orbiter pass on Mars. So, the rover receives the commands and then it executes the commands, which involves all of the sequence that I mentioned and a lot of the helicopter commands will be either flight today or just send me data on Day Two while we’re sitting on the ground. So those commands happen. There are routine telemetry data products that come back, everything from sort of event type of data, as well as detailed logs of all the activity and how did the motors do, how did the control systems do, how did the navigation do?

Those all are telemetry files and they make the return journey hopping from onboard storage on the helicopter back to the base station and then the rover says, ‘Okay, give me all those products.’ And the rover takes them and then sends it through a typical afternoon telecom pass on one of the overhead orbiters. And eventually it makes its way through the Deep Space Network back to the Operations Center at JPL. So it’s almost identical to the way any other instrument is operated, except that one of those instruments, if you will, has a little helicopter attached to it.

Host: And what makes it hard for a helicopter to actually fly on Mars?

Balaram: Well, the main thing is the Martian environment. The atmosphere on Mars primarily made of carbon dioxide is extremely tenuous compared to what we have here on the Earth’s surface. It’s approximately 1 percent of what you would find here on Earth. So, if you stretch your arm out about a meter wide, three feet wide, and thought of a cube about that big, here on Earth that cubic meter of air would be about one kilogram, little over two pounds, but same cubic meter on Mars would be a few tenths of grams, about an ounce. So, it’s about exactly 1 percent or thereabouts of what the density is, which means that any aircraft has to move a lot of air downwards in order to get the reactive force, Newton’s law, to get the lift to send the whole vehicle upwards. So that’s kind of the main fundamental aerodynamic challenge.

Now there are during the process of development, we discovered that it wasn’t just the fact that the air was thin. It’s equal to it being flying here at 100,000 feet here on Earth, but there were also some other nuances in flight control that we discovered because of the thin atmosphere. So that’s the main challenge. You have to build something that has to be light enough to be able to benefit from the thrust of the vehicle, which has to fight this constraint of an extremely thin air. So having a very light aircraft is very important because you have a very thin atmosphere. The second challenge is that Mars gets very cold at night. Temperatures of minus-90 degrees centigrade are not uncommon. And so we have to survive the night. We have batteries and we have a fair mix of commercial off-the-shelf parts as well as other more robust parts.

But nevertheless, we try to keep them warm. So a lot of our energy budget on the helicopter is just spent on keeping the electronics and the batteries warm. So surviving the Martian nights is especially a challenge. And then on top of it, we have all the usual challenges of anything that goes to space. You have to be very strong to withstand launch vibration loads. You have to be strong enough to withstand the G-forces you feel during entry, descent and landing. You have the radiation environment of Mars. And then of course you have Mars, which has a dusty atmosphere, so that all sorts of things related to sealing any mechanical parts. So that makes the aircraft challenge hard because not only are we trying to build this very lightweight, I would almost use the word gossamer, aircraft that is going to be as light as possible, coming in at four pounds.

But it has to also be strong enough to withstand all the rigors of space travel. Launch vibration loads are equivalent of a 60 g-force. Of course, it’s a vibration and not a sustain. Entry descent loads when you hit the atmosphere are many, many Gs. And so you have this very lightweight, delicate thing that has to be strong. So that’s been a big challenge. And a third challenge is that we also have to accommodate ourselves on a flagship mission to Mars. So safety, accommodation constraints. We have a little bit of space on the belly, which we have to use optimally. That actually drove the size of how big we could make the blades. And we have to make sure that all our systems, the batteries, the deployment systems are all very safe to the primary mission of this rover, which is the first astrobiology mission in terms of really looking for signs of previous life. But we don’t want to jeopardize anything there.

So, there is an extraordinary consideration in terms of safety, in terms of planetary protection, keeping ourselves extremely clean. And so that’s been the other big challenge of this particular mission. And lastly, and there are many more, but I’ll stop at this one. We had to invent a complete test program to test this helicopter system and convince everybody that not only could it fly, but it could also survive the environment. And it’s also safe to the rover and there’s no textbook on how do you test a Mars helicopter. So we essentially had to write that textbook along the way, and to be perfectly honest, if I had known the intricacies and nuances and the tribulations of our test program, if I had known that way up in front, I might not have taken up the whole thing. But so it’s a combination of things. It’s an aircraft, it’s a spacecraft, it’s a stowaway on a flagship mission and it needed to be tested to everybody’s satisfaction, all extremely challenging each in their own way.

Host: And you’re talking about everything that it’s taken to bring this together. Let’s reflect on the milestones along the way as the team developed the helicopter. What did it take to give you assurance that Ingenuity is ready for flight on Mars?

Balaram: Well, we started off by developing some scale models of what the helicopter flight would be, and we found some issues with the flight on Mars. So one of the first efforts was a risk reduction program where we took the exact design of the helicopter rotor system, if you will, the blades, the shape, the length, and we built a prototype helicopter that was powered from an external source. The computers was an external source, but we first flew that and convinced everybody that we knew how to fly in Mars. Once we did that, we got the green light to build what we call as two engineering development models. These are essentially the same as the flight designs. So they essentially add in all the other subsystems that you have, not just the flying part, which we demonstrated with a risk reduction vehicle, but that the telecom, the solar panel, the avionics, the batteries, the sensors, the land, the full flight design.

We built two of those to explore two aspects of the design in a test program. One was, does this final spacecraft know how to fly on Mars? And we went through a very long test campaign and accumulated many, many, many tens of minutes of flight time in a test chamber. At JPL, we have a 25-foot diameter chamber that’s quite tall, and we do all our flying in there. So, one of the engineering development models was basically a flight test campaign vehicle to show that it could fly safely, that we understood all the control issues. We understood all the details of the navigation. The other one went through an environments test campaign. It was basically designed to make sure that it would survive things like the vibration environment, that it would survive the terminal cycling through the night.

And so that particular vehicle went through all the test chambers we have at JPL, through vibration and shock and cold temperatures and so forth. So once we had success in both of those, they informed slight design modifications in the final flight vehicle. For example, we slightly increased the insulation gaps that we had along the fuselage. And there were some other changes to small things that we discovered along the way. And so, we then commenced building what we call the flight model. So, we have the two engineering development models, and then we have a flight model. And the flight model was treated much more carefully. It did not see the extensive flights that the engineering models did. We just flew it enough to make sure that it could fly, but it was handled very delicately. It was handled with a lot of care because it was the one flight unit we had.

And that flight unit went through then a combined test program with the rover, making sure that it could be deployed safely. So the rover had a two-week test campaign, for example, where they were inside a big environmental chamber simulating the whole Martian environment and multiple days there, and we were part of the test program. And at the culmination of the test program, they actually deployed the flight unit onto the surface of what was the test chamber, which would of course be the surface of Mars on Mars. And we went through this combined test program to make sure that we integrated extremely well with the rover and that we were safe to the rover. At that point, we were ready for a final integration with the spacecraft itself, which happened at the Kennedy Space Center. And then we were launched.

Host: Have you and the team been able to apply lessons learned from previous Mars missions and technology demonstrations?

Balaram: In some ways. Sojourner was sort of the first technology demonstration that paved the way, if you will, for all the much more capable and bigger rovers that we have seen. So I think the lessons are really more in terms of how we teamed. We had small agile teams that were very capable of moving very quickly to work through all the issues and problems we faced. But I don’t think there’s any direct precursor that we would say is obvious place for us to go with lessons learned. We did talk to folks who were doing the MarCO CubeSats to see what they had when they were doing their little CubeSats that did the relay for Insight, what kind of tips and pointers they had. We talked to them, but given that we were sort of really first of a kind, we really had not much in the way of people or documentation or anything to look to.

Host: This attempt to fly a helicopter on another planet for the first time is an engineering marvel. Bob, what has it been like for you to be the chief engineer on the project?

Balaram: Well, it’s been a very exciting ride of almost seven years now. Even though I had initially broached this idea in the 1990s as sort of more of a research effort, that really didn’t go anywhere. We didn’t get funded. There were folks at NASA Ames who had been also been thinking along similar lines way back then. The American Helicopter Society had also floated student competitions for this back then because of all the excitement of the Pathfinder Mission. But it basically sat on the shelf till 2013, when the JPL Lab Director, Dr. Charles Elachi, wanted a briefing about this possibility, and that got us going. And so it’s been a seven-year journey, and I think I have joked, but not really as a joke, that there’s been a crisis every week, fun crisis. I like to think of these things as opportunities to learn, but there’s something technical that we had to discover and deal with pretty much almost every week on this project over the seven years and it spans every possible engineering discipline that you can imagine.

And as I said, we were really fighting the whole issue of keeping this as light as possible. It’s very easy to build something that looks like a helicopter, which is robust and bulletproof from all the issues I mentioned. But guess what? It won’t be able to lift off on Mars, even though Mars has gravity that’s about 40 percent of what Earth is and that helps a bit, you can’t have it too heavy. So I was managing the mass of the helicopter and all its components down to the gram and even the sub-gram level. I’m a backpacker in my spare time. And I know that that strategy works. Cutting a little bit here, a little bit there works. We had to do a much more holistic design than traditional spacecraft because in traditional spacecraft you have subsystems which are given allocations and comfortable margins, and that lets them be a little bit separate from each other.

But we had to do very integrated designs. Our solar panels serve as a telecom communication back plane. It has to accommodate an antenna. So we couldn’t just tell the power people to go buy the solar panel and the telecom people to do something else. We had to make them work together. There are all kinds of very interesting trade spaces in the system engineering of this. So it’s been a tremendously exciting journey and we have a tremendously talented team that has been very enthusiastic. And so that’s been a lot of fun, and each milestone that we have achieved. That risk reduction flight that we did way back, that was the first time anybody has flown something like this in the equivalent of 100,000 feet, the atmosphere, as a rotorcraft. The engineering development models, their success, the whole accommodation onto the rover, the test programs, the launch.

And even right now, we have a healthy a helicopter that’s being periodically charged up. Its batteries get charged up every week or so, topped off if you will, to a safe level. So, all of those things are milestones that I celebrate, the team celebrates, and so it’s quite a ride.

Host: How could Ingenuity influence future missions to Mars?

Balaram: Well, I think the main thing is it’s the adding the aerial of dimension to Mars exploration. I think people will appreciate perhaps grudgingly what drones have done here on earth, right? Now, Ingenuity is not quite a drone. It wasn’t something you could buy at Radio Shack and fly or so forth, but it’s the fact that you have that vantage point. And now, of course, no Mars science helicopter would be as capable as a flagship billion-dollar rover with multiple science instruments. But what a Mars science helicopter will benefit from, and then even future sort of more Mars exploration helicopters that maybe help the human exploration program, what they give you is reach and range. We can get to places where no rover could drive. We can travel many, many kilometers a day if needed and we have been working on future designs in kind of our internal research programs on what such Mars science helicopters might look like.

We are thinking about Mars science helicopters in the 25-kilogram class carrying multiple kilograms, three, four, five kilograms of science payloads. So what are the kinds of exciting missions that you can think of if you have that kind of science payload and you can reach places you could never reach before and you could traverse distances you could never traversed before? The analogy I would make is the Earth’s landmass area is exactly the same as the total area of Mars. So they’re comparable if you leave out the oceans. Imagine if you had explored Earth with a few landers and a few rovers that had driven about 15, 20 miles from wherever they landed. That would still leave a lot of Earth to explore. Of course, you’d be doing it a lot of it from orbit, just like you do at Mars, but really the possibilities of exploration, whether it’s for science or whether it’s in support of human exploration is tremendous.

These things can act as scouts so that if you do have a rover or an astronaut who needs to get from point A to point B, they can scout ahead, look for the best routes, give you a preliminary assessment of what a final destination might look like in detail. The resolution that you can get from a camera or any other instrument on a helicopter is much more than what you can get from orbit. It is almost the same in terms of visually as what you might be able to get from a rover, but the rover is a relatively static object on the planet. And here you have a capability that would allow you to roam far and wide and look at things at high resolution. And so I think it has a potential to change things, provided we have a successful test flight here and we learn from it and then fold that into future designs. So, it’s still a high-risk, high-reward proposition in my view, but JPL’s motto has always been ‘Dare mighty things.’

So, in that spirit, I think we are attempting to push that frontier and get the aerial mobility as part of exploration. And I think some of the things we learned, especially in the operation side and other things will also benefit other aerial missions that will happen in the 2030s. Dragonfly will come to Titan. So, there is, I think, an era of aerial exploration, at least for some of the planets that have atmospheres like Mars and Titan, which I think represents a new chapter in NASA’s exploration history.

Host: Bob, this has been so fascinating and we’re all so excited and really can’t wait to see what happens once Ingenuity makes these test flights on Mars. Thank you so much for joining us today.

Balaram: Yeah. Thank you. And I would welcome your audience to be with us every step of the way. We will celebrate every small victory, getting deployed, that first flight and whether we have success or failure, it will be a tremendous journey. And we hope that all your listeners join us in this journey for the next few months.

Host: Many thanks to Bob for joining us. You’ll find his bio along with links to topics discussed on the show and a transcript of today’s episode at APPEL.NASA.gov/podcast.

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