Flying with Ingenuity: The Mars Helicopter NASA Mars Exploration – NASA Mars Exploration

July 20, 2022

TRANSCRIPT

(music)

Narrator: On a cold and wind-swept December day in 1903, in the Outer Banks of North Carolina, Orville and Wilbur Wright flew a powered, controlled aircraft for 12 seconds the first such flight in the history of the world.

sound effect: aircraft flight

Narrator: More than a hundred years later, in April 2021, another world saw its first powered, controlled aircraft flight when NASAs Ingenuity helicopter lifted up into the skies of Mars.

sound effect: helicopter rise

Narrator: Teddy Tzanetos, team lead for the Ingenuity mission, says the trickier nature of helicopters made the first flight on Mars even more perilous.

Teddy Tzanetos: Helicopters, in general, you're beating the air into submission from microsecond to microsecond. You have these tiny mechanical parts spinning at 2,500 revolutions per minute. Just take a moment and think about that. It's incredibly fast, which means that when things go wrong, they go wrong catastrophically.

sound effect: helicopter

[1:04] sound effect: whoosh

Teddy Tzanetos: If there's some imbalance in your rotor system, because something broke or fell off, your entire rotor system will explode. That's just true of all helicopters, right? All helicopters are precisely and carefully balanced pieces of art. And the fact that helicopters work to begin with is a testament to just engineering in general, and the beauty behind it.

Narrator: The Ingenuity helicopter was a technology demonstration meant to test whether it was possible to fly a rotorcraft on Mars. Ingenuity hitched a ride with NASAs Mars 2020 mission, which sent the Perseverance rover to collect rock samples and look for evidence of ancient life. Ingenuity was strapped to the belly of Perseverance during the journey to Mars, and so had to be small enough to fit easily beneath the SUV-sized rover.

[1:54] Teddy Tzanetos: In terms of the dimensions, we have two counter-rotating coaxial rotor blades. The blades themselves are 1.2 meters from tip to tip. The electronics box, which is that silvery-colored box underneath the rotor blade system, that's where our computers are, that's where our battery resides. That's where all of our critical electronic components exist on Ingenuity. It's about the size of a tissue box. The legs come off from that central structure, and then, of course, our solar panel on top. It's a very compact design. On the surface, when we were fully deployed on the ground, Perseverance was able to clearly drive over Ingenuity.

Narrator: A fixed-wing aircraft, like the Wright Brothers Flyer and most planes on Earth today, wasnt a practical design for the first flight on Mars.

Teddy Tzanetos: With most aircraft, you need a runway. But unless Perseverance was going to spend a couple of weeks paving a pebble-free runway for us, that was going to be a challenge.

Fixed-wing can be a lot more efficient, right? You can glide. You don't have to spend as much energy going from point A to point B. And if you have an anomaly in an aircraft and your motor kicks out, you could glide to safety. But you can't also just stop and hover. On the helicopter side, though, you spend a lot more energy just to hover, but now you can hover. And you can do precision landing precisely where you'd like to land.

[3:14] Narrator: Ingenuity was built to be as lightweight as possible, and yet the team added one extra item, under the helicopters solar panel, to provide an inspirational lift to their mission: a postage-stamp-sized bit of muslin fabric that had once covered a wing of the Wright Brothers 1903 aircraft. Members of the Wright family and Carillon Historical Park, home to the Wright Brothers National Museum in Dayton Ohio, provided the fabric.

This isnt the first time Wright Brothers fabric has flown into space. Neil Armstrong brought some of the fabric, as well as a small piece of wood from the propeller, to the Moon in 1969. In 1998, nearly four decades after he became the first American to orbit Earth, John Glenn carried a swatch of the fabric when he flew on Space Shuttle Discovery. Heres Bob Balaram, chief engineer of the Ingenuity mission.

[4:11] Bob Balaram: I was looking for an artifact to put on the helicopter, and we had considered perhaps putting an American penny there's one where it has the Wright Brothers Flyer on one side. But then once we realized we could actually get to the real Wright Brothers fabric, we jumped on it.

So, it presented its own challenges. We had to sterilize it just right, and we had to make sure that it wouldn't contaminate the spacecraft. My contamination control and planetary protection engineers went to, I think, JoAnn Fabrics and got some samples so that they could try their heat-sterilization process on the samples first, before actually trying it on the piece of the real Wright Brothers fabric.

And this is the perfect thing to take, not only for me, but for the team as a whole. There's that connection to the past which is always inspiring.

[5:00] (intro music)

Narrator: Welcome to On a Mission, a podcast of NASAs Jet Propulsion Laboratory. Im Leslie Mullen, and in this fourth season of the podcast, were following in the tracks of rovers on Mars. This is episode seven: Flying with Ingenuity: the Mars Helicopter.

(music)

[5:57] Narrator: The Ingenuity helicopter is of course not a traditional rover: a remotely-controlled wheeled vehicle that roves on the ground. Ingenuity represents a new generation of robotic explorers, but, in a way, its repeating Mars rover history. Sojourner, the first Mars rover in 1997, was a technology demonstration added to the Pathfinder lander mission to test whether we could drive a vehicle on Mars from millions of miles away.

Tech demos are always risky, with high odds for failure, so not everyone at NASA was on board with either Ingenuity or Sojourner. Bob Balaram didnt work directly on Sojourner like he did for Ingenuity, but as a member of JPLs robotics group, he helped develop the necessary technology to make the first Mars rover possible.

Bob Balaram: In terms of being a first-of-a-kind system that had skeptics and needed to prove itself, and there wasn't quite the textbook as to how to do it, yeah, a lot of similarities. For its time, it had its challenges and naysayers. We had ours.

[7:07] We are in some ways a tougher problem. A helicopter is inherently an unstable vehicle so that it needs everything to work to keep it in the air. Sojourner had the advantage that if something had failed, it's at least not going to topple out of the sky and smash into pieces. So you could wait and call home if there was an issue.

Narrator: The success of the microwave-oven-sized Sojourner rover got people thinking about more audacious Mars exploration vehicles, including ones that could lift up into the thin, mostly carbon dioxide atmosphere.

Bob Balaram: The idea of a Mars helicopter was quite prevalent in certain communities back in the 1990s. The American Helicopter Society ran a student competition to say, Take something like Pathfinder, but instead of carrying Sojourner, imagine that if you could carry a helicopter in the same technology, and get it to Mars, what would be your design?

[8:03] So around the same time was a talk being presented by Stanford professor Ilan Kroo, on some of the challenges of flying in a low-density atmosphere. And I attended his talk, and then got to thinking that flying a small thing on Earth which is what he was trying to do, tiny little micro-helicopters is the same as flying something larger on Mars, because that's the way the physics scales with the thinner atmosphere you have on Mars.

So Ilan and I wrote a proposal, and a small company in Simi Valley, called AeroVironment, was going to build us a small helicopter. Remember back in the 1990s, you didn't have all these drones that you could just buy, even to just play around with. And so, we were the three legs of that initial research proposal, but it didn't go anywhere.

We got actually favorable reviews from the review people, and we thought we would have had one year of funding. But it was also the year where NASAs budget was under a lot of pressure. You know, that's always the background story at NASA. So they barely funded anything that year in this particular area. So my little proposal sat on a shelf for about 14 or 15 years.

[9:15] Narrator: In his more than 37 years of working at JPL, Bob is used to working on projects that are so far ahead of their time, they end up taking a lot of space on a shelf.

Bob Balaram: This is the robotics section at JPL where we basically do mobility in all kinds of environments, whether it's rovers or crawlers or walking machines or some flying machines, too. We're always looking to the future, to see what kinds of new mobility technology can we bring?

So along the way, I've worked on things like Mars balloons and Venus balloons. There was even a short-lived NASA idea to go and grab an asteroid and bring it back. Again, there is a (laughs) final report gathering dust somewhere on that one. The ratio of super cool missions to feasible missions is probably 10 to 1. But of those feasible ones, the ones that actually make it all the way to the end is probably like 100 to 1. We do let a thousand flowers bloom, but only one of them gets to the end point.

[10:17] Narrator: The seed of the Mars helicopter idea germinated while NASA was developing the Mars 2020 mission. The team designing the helicopter knew they couldnt be a burden on the planned rover, but getting Perseverance to adopt Ingenuity wasnt easy.

Bob Balaram: There were a lot of naysayers, like, What do you mean, Mars helicopter? That doesn't make sense. You won't be able to fly. The airs too thin. It took a lot of courageous people to back us up. There was resistance correctly so, I think from the mission that had been asked to accommodate us. That was not something that they wanted to do, so it took some persuasion. And it had to pass all its tests to the satisfaction of the Perseverance folks. So every step of the way, we could have been abandoned.

[11:05] In fact, the way the rover did its belly pan, which is where we are located, there is a version of the belly pan somewhere that doesn't have Ingenuity on it. In other words, it doesn't have all the hooks and things for Ingenuity. Let's say the flight unit had failed a structural test before launch. They would have probably put this other alternative little belly pan onto the rover and flown without us.

So it was every step of the way. First-of-a-kind system you don't know whats going to work, whats not going to work. How much time do you spend refining a design, or is it good enough? How do you make that judgment call? So the metaphor that this is a Wright Brothers moment is not just in the sense that it's the first flight on another planet which is pretty cool by itself but the fact that you're going into the unknown.

Our first scale vehicle was unstable, and it took a lot of engineering and analysis of the physics of flying in thin atmospheres for us to understand that instability and work around it. Even our NASA helicopter experts were surprised by that. So they had to also go back to the textbooks, so to speak, to understand the fundamental physics, just to make sure we even have stability in the air.

[12:12] So, it's just across the board exploring a completely new terrain. Nothing was a given. Literally there was a crisis and I use the word without too much hyperbole there was a crisis on the project every week for the seven years that it took to get this going. But I got used to that, and kind of thrive on it, actually, because any time there's a problem, there's something fun to solve, right? That's what made it exciting.

(music)

Narrator: One of the biggest pressures of the mission was the lack of air pressure on Mars. Air pressure is the collective force of air molecules pushing against a planet, drawn there by gravity. On Earth, our thicker atmosphere and stronger gravity results in an average surface air pressure of over 1,000 millibars. The 6 millibars of surface air pressure on Mars is a mere whisp in comparison.

[13:07] For a helicopter to fly, it needs enough air for the fast-spinning blades to push against, and because atmospheres get less dense the farther you rise from the surface, helicopters on Earth are limited in how high they can fly. So how could a helicopter ever fly on Mars?

Bob Balaram: Mars has an extremely thin atmosphere it's equivalent to flying at 100,000 feet here on Earth. If you had a block of air let's say you spread your arms out wide and made a big cube here on the surface of the Earth it would be about 2 pounds or so. That same cube of Martian air would only weigh an ounce. Which means that if you want to fly, you have to move that air, which means your blades have to be special for that thin air. And theyve got to move quite fast in order to push enough air downwards so that you get the lift upwards.

[14:00] Then, even if you build the system that would produce lift, it has to produce more lift than its weight. And not just the weight of the rotor, but everything else you need to carry with it, right? You're carrying batteries and computers and solar panels and radios and wiring and all those things that have nothing to do with flying, but you've got to carry that with you. So basically 4 pounds was pretty much the upper limit. As I've joked, it's very easy to build a Mars helicopter of the same size as Ingenuity and have it weigh 5 pounds, and it would sit on the surface of Mars and spin its blades, but it wouldn't go anywhere.

And so, I was managing the mass on the design down to the gram and sub-gram level. So if my computer guy said, Hey, I really want 6 grams for this processor, and there was another processor that was only 4 grams, he and I would have a long discussion before I relinquished 2 grams to him to let him implement a slightly larger processor.

Narrator: Such a lightweight aircraft could be at the mercy of high winds. Because of the thin atmosphere, the winds on Mars arent as powerful as winds on Earth, but Ingenuity still needed to be tested to see how it would perform in even the gentlest of Mars breezes.

[15:16] Bob Balaram: When it came time to test how our helicopter interacts with the winds, guess what? There is no wind tunnel that simultaneously does the thin air density of Mars and the low velocities that we were testing. We're not testing winds that are tens of miles per hour. We are testing winds that are a few miles per hour, right? There is no facility in the country that can do that.

And so, yours truly and his team (laughs) built a wind tunnel that we installed in our JPL 25-foot chamber. And it used about 900 CPU fans from your desktop computers to arrange in a square array to basically be a wind tunnel that we could blow air sideways on the helicopter, as it spun its blades up.

[16:02] Narrator: JPLs 25-foot Space Simulator is a stainless-steel cylinder 25 feet wide and 85 feet high. Normally, spacecraft placed in this chamber are subjected to extreme cold, airless vacuum, and simulated solar radiation to make sure they can survive a trip in outer space. The Ingenuity team turned the chamber into a one-of-a-kind Mars testbed.

Bob Balaram: That facility has the ability to pump down this big chamber to vacuum. In our case, we said, Please fill it back with carbon dioxide to the same density that's there on Mars. So we got the atmosphere right, and we did most of the testing at room temperature because that was the cheap and easy thing to do. But we did do a few critical tests where we cooled down that air in the cylinder to Mars temperatures, and so we made sure that nothing funny was happening as the temperatures dropped.

[16:58] Now, of course, the gravity is almost 2.5 times more gravity here on Earth than it is on Mars. So what we did is we basically built an offload device. Think of it as a high-tech fishing line that we attach to the top of the helicopter, and it pulls with an exact constant force equal to the weight difference that we want, so that we get the Mars versus Earth gravity. And it does that regardless of whether the helicopters flying up or down. And so, that allowed us to basically understand the behavior without the extra gravity that we get here on Earth, and making Ingenuity think that it was flying on Mars.

We used various fishing line types of cord material and all kinds of very interesting knots to hold that safely. I think we had three reviews on knots, from climbing experts to top mechanical engineers here on Lab and knot experts, to make sure that there were other safety knots and back-up knots. Literally we were hanging the entire project by a thread, right?

[17:57] Ingenuity test: Spin up. (sound of helicopter flying) Steady.

Bob Balaram: So we did many, many, many months of testing in the 25-foot chamber. And once you bump down the chamber and you put on the carbon dioxide, it's not like you can say, Oh, okay, let's break for the weekend. No, you're going to test right through the weekend. So there was an entire year where every weekend there was testing nonstop. And the testing would be there late.

And my wife, who's a super awesome baker, she'd bake all these wonderful foods. Any time we were testing, she'd bake for the entire test team. And that's what sustained many of us. So she got an official title on this project called CMO, Chief Morale Officer, working to keep the test team happy.

Narrator: After the well-nourished team developed a helicopter that could fly on a simulated Mars, the aircraft had to go through other tests to make sure it could survive the journey to an alien planet.

[19:06] Bob Balaram: It's not only an aircraft, but it's also a spacecraft. You normally don't think of spacecraft design and aircraft design in the same breath. We had to. So we had to survive launch, which has vibrational G-forces where things get really rattled by the very loud noise that the rockets make, and it just shakes the whole structure up.

(sound effect: NASA rocket launch rumble)

Bob Balaram: And so, theres structural requirements. You have to be strong in a certain way to withstand entry, descent and landing forces. You have to survive the radiation of space and continue to operate. We had to survive the vacuum of space, and not just survive, but we had to be a good passenger.

In the vacuum of space, gas likes to travel and condense. A lot of materials like adhesives and glues or plastics, you know, if you leave something on your car on a hot day, and sometimes youll notice an oily film that may have coated the glass that's called outgassing, and its just like little organics in your system that condense on the coldest thing. Anything sent to space cannot have any of those kinds of things, because you don't want your goo to go and land on this camera lens of this wonderful science instrument that is three feet away.

[20:19] Since we were hitching a ride, we had to be extraordinarily safe to the rest of the mission. It's an astrobiology mission looking for signs of past life. We had to be super-duper clean so that we didn't carry, you know, spores and stuff. So we had to be treated like every other instrument that's on the spacecraft.

Narrator: The space capsule carrying the Perseverance rover and the Ingenuity helicopter was ready to leave Earth on July 30, 2020. During the launch coverage, a 4.2 magnitude earthquake hit Southern California.

Announcer Raquel Villanueva: Ingenuitys project manager MiMi Aung joins us now to talk about the set of milestones Ingenuity needs to hit in order to take flight on Mars.[21:03] Ingenuity project manager MiMi Aung: Hi by the way, we just had an earthquake in this room! But anyway, with that, Mars helicopter demo is motivated.

Narrator: Since the mission was launching from NASAs Kennedy Space Center in Florida, the quake only rattled those speaking from JPL. After enduring the tremors of a rocket launch and a seven-months-long spaceflight, the mission landed in Jezero Crater on February 18, 2021.

Announcer Raquel Villanueva: Weve just heard the news that Perseverance is alive on the surface of Mars, congratulations to the mission (applause)

Narrator: Now that Perseverance had arrived safely, the Ingenuity team had their own, second Mars landing to worry about. Ingenuity was still tucked under the rovers belly like a baby kangaroo, and needed to hop out. Heres Teddy Tzanetos again.

Teddy Tzanetos: Right after entry, descent and landing, and Perseverances arrival to the surface, the game was on. There were a handful of weeks where the rover was first trying to go through some systems checks. And on the helicopter side, we were confirming that all systems were green across the board, and looking for our first good airfield to fly in.

[22:15] Thankfully, where Perseverance landed in Jezero crater, there were a lot of good locations right nearby where the rover would drop off the helicopter and we would begin our mission. What we were looking for was effectively a parking lot on Mars. We wanted a nice flat surface that the rover could drive to, and would be free of rock hazards. If one of our feet gets stuck on a rock, we'd be landing on a tilt. Or if we landed directly over a rock, a rock could actually puncture our thermal shroud and cause us to have an early end to our mission.

Narrator: Once Ingenuitys landing spot in Jezero Crater was selected, Perseverance drove over to the center of the area, nicknamed Wright Brothers Field. Ingenuity now was ready to be born.

Teddy Tzanetos: She's our little baby and she's very tough, but we needed to make sure we took good care of her all the way through delivery to Mars. As soon as Ingenuity is finally separated from Perseverance, there's no way to go back. That umbilical is a one-time separation.

[23:13] We were located under the belly of Perseverance. We had a debris shield, so the first step was dropping the debris shield. Then the rover drove up a little bit. Second step was starting our leg releases, and our launch-lock releases. What those mean are different mechanical restraints that were holding the helicopter in a folded config. And we started our multi-step process to, one by one, unfold the legs, rotate the helicopter to its vertical orientation. During our deployments leading up to the final drop, we were using Perseverances camera there's a camera on its arm that it could look underneath the belly. And that helped us determine, yes, deployments were going well.

[23:57] That final separation, there's effectively just a single bolt holding Ingenuity to Perseverances belly. When that bolt snaps, gravity does the rest and Ingenuity falls a handful of inches to the surface. A single circuit, a single wire on the umbilical interface between Perseverance and Ingenuity, went from being a closed circuit to an open circuit. That gave us the indication on the engineering side that, yup, Ingenuity has successfully separated from Perseverance. And from that moment on, Ingenuity is on her own.

And Ingenuity is solar powered. Unlike Perseverance, which has a nuclear-powered energy source, Ingenuity needs photons on its panel. It was critical that soon after Perseverance dropped Ingenuity, Perseverance needed to drive to expose Ingenuitys solar panel to the Sun.

As soon as Ingenuity was deployed, we're on a clock. The timing is dictated by, A: how much energy you have inside of Ingenuitys battery, and how much do you need to recharge? But, B: the time windows when you can receive and send commands from Earth to the rover. You can't do that 24 hours a day. So those comm windows when we could inspect the state of the vehicle, identify if Ingenuity successfully dropped, and then send commands to override if needed, only provided us really about 15 minutes in which to react.

[25:17] So it was a very stressful couple of days leading up to that final deployment, and an even more stressful, it was called the drop-and-drive activity. Thankfully, everything went smoothly, and we were ready to begin our 30-day tech demo mission.

Narrator: After Ingenuity was safely delivered on the surface of Mars, and the Perseverance rover had rolled a short distance away, leaving the helicopter exposed to the open sky, there was a pregnant pause. Ingenuity was not yet awake. The rover silently faced the helicopter, waiting in the deep quiet of Mars to see what would happen next.

Teddy Tzanetos: It could have woken up immediately after it was dropped, but we built in a delay to allow for a whole series of contingencies that could have occurred. As with all space missions, you want to avoid moving too quickly, because that's when mistakes are made. So we had a good margin window 2 hours and 15 minutes after the drop and then Ingenuity woke up. Perseverance was there waiting to communicate, and we established a link, and we were off to the races at that point.

[26:19] Narration: Take note this 2 hour and 15-minute delay between Ingenuity separating from and then talking to the rover will have surprising consequences later in the mission.

After Ingenuity left the warm embrace of Perseverance, and was going through system checks to make sure everything was working well, Bob was fretting about what came next.

Bob Balaram: The most nervous time I had was when we were dropped off onto the ground from Perseverance. It was not obvious that we would survive the night.

(music)

Bob Balaram: When we were on the way to Mars, we had a separate heater that was energized by the rover, which, with its radioactive RTG source, effectively has power to spare, especially for a small little helicopter. But once we were on our own, it was our battery powering our helicopter. And if the battery was drained so much overnight that by morning, if it wasn't enough juice to keep the computer alive, then we would be in big trouble.

[27:24] Were a very small object, and it's always difficult for something small to stay warm. You know, you have a small cup of coffee compared to a big barrel of something, it just cools down faster, right? So the helicopter uses almost three quarters of its energy just staying warm through the night. Its collecting all this energy from the solar panels, harvesting it all day, sticking it into the battery, and then it spends most of that energy depleting the battery to run a bunch of heaters. We couldn't let the batteries freeze out. We couldn't let the electronics get so cold that some little soldered joint somewhere would pop free.

Then on top of that, we really didn't know what kind of winds to expect on Mars that night. And it's the nighttime cold winds that would have really sapped our system.

[28:05] sound effect: wind

Bob Balaram: We had an instrument on the rover called MEDA, which was a weather meteorology station. But it was only just beginning to get commissioned. So we didn't know whether the winds would be twice as much or three times as much. Now, it turned out that the winds are not that bad, and especially the closer you get to the ground, it's even less of an issue. But we didn't know that. So that to me was the most harrowing time.

Narrator: Ingenuity endured its first freezing Martian night on its own, and still had enough power remaining by dawn to run its computer. Now Ingenuity needed to bask in the sun until its solar panels recharged the battery.

[28:56] Bob Balaram: There was indeed a scenario where we could have potentially survived on Mars, but never had enough energy during the course of the day to charge up our battery to the point where we could fly. And you have to fly with a battery that's fairly topped up, because if you don't, the moment the rotors kick in and start drawing high power, the battery voltage will droop and all your electronics will brown out. And you have to be able to have enough energy left to have enough flight time to climb up and do something useful. And so just surviving itself is not enough.

Mission Control 1: This is downlink, confirming battery data has been received.Mission Control 2: Rotor motors appear healthy. Swash plate servos appear healthy, overall actuators appear healthy

Teddy Tzanetos: The mission was really about that first flight. We wanted to prove that humanity could build something that could, in fact, fly on Mars. And that first flight where we took off, hovered, we rotated, came back down, and landed 39.1 seconds later that is the most important flight of Ingenuitys entire lifetime.

[30:04] Mission Control: Altimeter data confirms that Ingenuity has performed its first flight, (shouts, applause) the first flight of a powered aircraft on another planet.

Teddy Tzanetos: I was elated. I was extremely excited. And then it quickly came back to business. We still had a job to do. Yes, Ingenuity had flown, but we still needed to assess its health. Was it still capable of flying again? How did all of our subsystems fare? How did our actuators perform, the battery perform, the thermal system perform? Across the board, we quickly dove back into the data to finish the job at hand.

Narrator: Ingenuitys altimeter data, which tracked how high the helicopter had risen, was the main indication a flight had actually happened.

Teddy Tzanetos: The altimeter data just showed a simple square. So the helicopter rose up, you saw the altimeter data go up. It stayed there, it hovered, had a little bit of noise, then came back down. And when it came back down and stayed at a steady level, we knew that wed landed, and we stayed upright. That was the key success moment there is to know that, yes, the flight was a success, but we also safely landed. And we remained upright, and we had a healthy vehicle that could again fly for flight number two days afterwards.

[31:19] There's a whole rover imaging team that was in the room adjacent to us. And while our data came down, in parallel, the rover imaging team was also quickly trying to come up with their own secondary confirmation that, yes, flight was a success. So within seconds of having our altimetry data, the imaging team was ready to roll and show the video feed to immediately support that conclusion. It was a beautiful one-two punch of emotion.

(audio: team reacts to video of first flight)

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