Host Andres Almeida: In 2028, NASA’s Dragonfly spacecraft is set to launch on a mission to explore Saturn’s largest moon, Titan. With a dense atmosphere and lakes of liquid methane and ethane, Titan has landscapes shaped by processes that are surprisingly familiar. This faraway world, rich in organic compounds, offers a rare window into the kinds of chemical conditions that may have existed on Earth long before life began. 

In this episode, we’re joined by Dr. Zibi Turtle of the Johns Hopkins [University] Applied Physics Laboratory, or APL, in Maryland. She’s the principal investigator for Dragonfly, which was designed and built by APL and managed by NASA. Zibi will tell us why Titan is such a compelling destination, and how Dragonfly will hop around, visiting dunes made of organic sand, and an ancient crater.

This is Small Steps, Giant Leaps. 

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Welcome to Small Steps, Giant Leaps, the podcast from NASA’s Academy of Program/Project and Engineering Leadership, or APPEL. I’m your host Andres Almeida. 

Okay, so, Dragonfly is an ambitious project. Let’s get into it.

Host: Hi, Zibi, thanks for being here. 

Dr. Zibi Turtle: Hi. Nice to talk with you today.

Host: So, we’d love to know a little bit about what you do. What is your role at Applied Physics Laboratory? 

Dr. Turtle: I’m a planetary scientist at the Johns Hopkins Applied Physics Laboratory and I work with a number of NASA missions to explore destinations in the solar system. 

Host: One of those exciting missions is Dragonfly. Can you tell us a little bit about it? Why should we be excited for it? 

Dr. Turtle: Yeah, Dragonfly is a NASA New Frontiers mission to Saturn’s moon Titan. Titan is a very interesting target, very unique in our solar system. It’s the only moon that has a dense atmosphere. The atmosphere is actually denser than Earth’s atmosphere. The atmosphere’s composition, like ours, is mostly nitrogen, but then there’s methane in the atmosphere. So, that means that there’s a lot of very complex carbon rich molecules in the system. 

Titan being a moon in the outer solar system, the crust is made of water ice. And so, at sites where the crust has melted in the past, say at the site of a large impact into the surface there has been the opportunity for these very large complex carbon molecules to have mixed with liquid water, possibly for extended periods of time. And that’s the same kind of chemical primordial soup that we had here on the early Earth, before life developed here. 

And so, Titan gives us an opportunity to try to understand the chemical steps that may have occurred before chemistry eventually took the leap to biology here on, here on Earth. It’s hard to study that here on Earth, because there’s biology overprinting that that, you know, geologic history and the timescales in the laboratory are, you know, we can do experiments for a few years, maybe. 

But Titan has had, you know, thousands, hundreds of thousands, maybe millions of years for these chemistry experiments to take place. And so, what we really want to understand is whether there are biologically relevant molecules like amino acids or proteins being produced in this or that have been produced in the past. 

Host: Is there anything that compares to Titan’s atmosphere here on Earth at all? 

Dr. Turtle: The atmosphere is actually only a little denser than our atmosphere. The density is about four times our atmospheric density. The surface pressure at Titan is just one and a half times the surface pressure here on Earth. So, it’s actually, from an atmospheric pressure perspective, it’s not terribly different. 

One of the things about Titan, it is, there a couple things that are very different. There’s a lot less gravity. So, as a person, right, If you could go to Titan, it’d be a pretty fun place to explore, because the gravity is about one-seventh that here on Earth. So, it’d be, it’d be pretty, pretty neat to, to try to travel around. 

The other aspect of Titan is that it is very cold. It is 94 Kelvin, which is negative 290 Fahrenheit, or negative 180 Celsius. So, it is very cold. 

Host: Despite having a relatively thick atmosphere!

Dr. Turtle: Yes, but what the thick atmosphere does is mean that there isn’t a big difference in temperature. So, Titan’s got this dense atmosphere, and then it has a very long, very long timescale. 

So, Titan’s day is 16 [Earth] days long, and Titan’s year is 29 and a half years long (Earth years). So, as a result, the atmosphere is pretty calm. 

We don’t have these large temperature extremes driving weather on Titan the way we have here on Earth, where it can, you know, be 20, 40 degrees different from, you know, from day to day. On Titan, the day-to-night temperature difference, the summer to winter temperature difference is about a degree. 

So, that is actually helpful from the perspective of planning a mission there, because you’re not having to deal with big temperature extremes like you would have to deal with, you know, on the surface of the Moon, say, from day to night, or on the surface of Mars, from day to night. The temperature is very constant on Titan, which helps, but it’s very cold, so that is definitely a key aspect of the mission development. 

Host: What does Dragonfly look like, and how will it tolerate this extreme environment? 

Dr. Turtle: Dragonfly is a large rotorcraft. It’s an octocopter. It’s actually an X8 octocopter. So, it’s got four pairs of counter rotating rotors, three-bladed rotors. And it is about the size of a small car. 

It’s also about the size of Perseverance or Curiosity, actually, which gives a sense of physically how much easier it is to fly on Titan than it is on, on Mars. Because a vehicle the size of Curiosity or Perseverance, we can take to Titan and actually fly from place to place instead of driving across the surface. 

It is like the Mars rovers, designed to carry everything with it, from place to place, to be able to be mobile and explore different environments on Titan, to take the scientific payload into different environments to understand the chemistry that exists on Titan. It is also a very well insulated vehicle to keep the interior of the lander at a good temperature for the, for the equipment, for the electronics and the instruments. 

Host: Does that draw on lessons from the Ingenuity Mars helicopter? 

Dr. Turtle: So, it’s so exciting to see, you know, flight on another, another planet, and Ingenuity has really demonstrated that beautifully. 

It’s much harder to fly on Mars. The gravity is pretty high, and the atmosphere is not very dense. So that’s, been a, you know, that’s really an impressive mission. The rotors, actually, for Ingenuity, are about the same diameter as the, the rotors for Dragonfly, which is kind of a neat parallel. 

One of the things that has been really valuable, in terms of what we’ve learned from the rovers on Mars, is autonomous operations. 

Even at Mars, which is much closer, of course, than Saturn or Titan, there’s enough of a light delay that everything has to be, has to be operated autonomously. So, the commands have to be sent up and then the vehicle itself, Ingenuity, executes those commands autonomously and then sends back information. 

At Titan, the one-way light time is 70 to 90 minutes, so it’s a lot longer, but it’s the same, the same situation. We need to do all of our operations autonomously. And so, we’ve been able to learn a lot from the experience of exploring in-situ on Mars about good strategies for doing, for doing that. 

Host: You have to balance science goals, risk, technical feasibility. Could you share any tradeoffs, or any major tradeoffs in mission planning? 

Dr. Turtle: The mission development process is always a series of trades. 

We’ve absolutely been working to reduce complexity, to reduce risk across the system. So, there are a number of trades and things that we’ve done to simplify the system as we’ve gone through our development cycle. 

We’ve actually just passed our critical design review coming up on a year ago now. Integration and Test just started this week), and we’re on track for our launch in July 2028. 

But to get back to your question about tradeoffs! Initially, the legs of the lander had dampers to, kind of, as we land, to kind of reduce the, you know, the motion that the lander feels. And the team actually came up with a design that uses the structure of the legs under the body of the lander to absorb that instead of needing dampers. 

And so, that reduced the need for a, for a mechanism, for a system, you know, a dampening system, because we could actually use the structure itself. So, there have been a number of things as we got into the detailed design that we were able to find ways to simplify. There are tradeoffs all the way along the system. 

Because we’re in the Titan environment, it’s a very coupled system, compared to a spacecraft that’s in orbit. A lot of the spacecraft that you know that are in orbit, you can design different subsystems, different elements, kind of separately, and they all kind of can fit together. 

But in the lander, it’s a very coupled system, and so things that you wouldn’t really expect to, to affect each other, actually, we’ve had to really be very careful to make sure that we know how a change in one subsystem or instrument affects something else. 

Host: Can you share a little bit about the timeline of Dragonfly? When could we hope to see it launch? And when do we hope to see it arrive at Titan? 

Dr. Turtle: Yeah, so we started working on Dragonfly 10 years ago, actually. In the New Frontiers Program, Titan and Enceladus were added to the list of targets just 10 years ago. So, we’ve been working on the on the concept for 10 years through a competitive selection process. 

As I said, we, at this point, are through our critical design review, and we are coming up on launch in July of 2028 so it’s two and a half years away, which sounds a lot longer than it’s going to feel like as we get through integration and test. 

It’s a long way to the outer solar system. So, we have a six-and-a-half-year cruise. So, we’ll launch in 2028 and we arrive at Titan in December of 2034. And then we have our nominal mission on Titan is about 3.3 years exploring the surface. 

One of the interesting things about, about the Titan arrival, right: On Mars, we’re used to a very short descent. For Titan, it’s actually a two-hour descent from the top of the entry interface down to the, down to the surface. So, it’s a very, it’s a very different experience. It’s going to be a very different experience than we’re used to on, on Mars where you have several minutes.

Host: And that’s because of the friction? Potential friction in the atmosphere?

Dr. Turtle: It’s because of how extensive the atmosphere is. 

So, the entry interface for, for Dragonfly at Titan’s atmosphere, is 1,270 kilometers [790 miles] altitude. So, it’s a very, because there’s a, is a dense atmosphere, and the, the gravity is so low, the atmosphere is very extended. The Cassini orbiter that was at Saturn from 2004 to 2017, the closest flyby was 900 kilometers [560 miles] altitude. And that took, like, a year of planning, because there’s so much drag even at that, at that high altitude. 

So, because the atmosphere is so extended, Dragonfly will have about a two-hour descent. 

Host: Is there wind on Titan? 

Dr. Turtle: Absolutely. So, Titan has weather, but Titan’s atmosphere is really sluggish. Because it’s dense, because the timescales are so long, the, the atmosphere is much more sluggish than we’re used to here on Earth, where we have this very dynamic atmosphere with, you know, with dramatic, dramatic changes from day to day. 

Titan winds on, on a kind of usual day, are at the scale of a few miles an hour. And even a high wind would be kind of several, 10, maybe several, or maybe 10 miles an hour. So, it’s not really a windy place compared to what we’re used to. 

It is interesting, though, from a thermal perspective, because we have this very well insulated vehicle, we’re powered by an MMRTG [Multi-Mission Radioisotope Thermoelectric Generator], the same power sources Curiosity or Perseverance on Mars, we use all of the heat as well as all of the power that comes off of the MMRTG. So, the MMRTG is within the encapsulated, insulated vehicle, and we use the heat to keep the interior of the vehicle warm. 

But where the where this comes back to your question about the wind is that we need to plan. We need to, we need to design Dragonfly to stay warm, even if there’s a light breeze of a few miles an hour. And if you then have a completely calm day, and you don’t have that cooling from a very low breeze, you could actually overheat on the surface of Titan, which is kind of incomprehensible at these very low temperatures! 

So, the thermal team has had to do a lot of work to, you know, we basically have the same kind of HVAC system, right? That you can, you can heat the interior, but also reduce the temperature if things actually get too warm, given the exterior conditions and the, the instruments and things that are generating heat on the inside. 

So, it’s been a really interesting development process for the thermal system. 

Host: What sites will Dragonfly explore while on Titan? 

Dr. Turtle: Titan being a satellite in the outer solar system, it’s got an icy surface, but it also has a surprisingly Earthlike geology. 

Because Titan has this dense atmosphere, it’s able to support a lot of geological processes. The terrain would look very familiar. The area that we’re going to land in actually has sand dunes, sand dunes made of organic sand, not silicate sand that we have here on Earth. But, nonetheless, the terrain would look very familiar. 

And what we want to be able to do is traverse the interdune areas, fly over the dunes to get to an area where there’s an impact crater. And this is a site where there may be, may have been an opportunity for these complex organic molecules to mix with liquid water in the past, at the time of the impact. 

And the environment at Titan, and the fact that we have this dense atmosphere and low gravity, makes it actually physically easier to fly there than it is actually here on Earth. 

And so, that’s why Dragonfly is designed as a rotorcraft, to be able to take advantage of that to fly from place to place. And that will give us access to environments with different geologic histories and different types of materials, to really get at understanding the chemistry on the surface of Titan and the kinds of chemical processes that have occurred there in the past. 

Host: What do you expect the weather to be on Titan when Dragonfly arrives? 

Dr. Turtle: When we get to Titan, it will be northern winter. And like on Earth, when it’s northern winter, the Sun isn’t up in the sky, and so it’s not illuminated at the North Pole. 

But that also means the Earth isn’t up in the sky, and because (unlike Mars) we don’t have a fleet of relay satellites at Titan, we’re doing direct-to-Earth communication from the surface. 

And so, we need to for Dragonfly to go to a place that will have good, a good line of sight to Earth at the time of, of our mission. So, the equatorial region is, is, is perfect for that. 

And it’s also really built off of what we learned from Cassini-Huygens because from one of the, one of the biggest mysteries remaining after Cassini-Huygens is what the composition, the detail, composition of the surface materials are. And in this environment, where there was liquid water in the past at the site of an impact crater, what kinds of chemistry can have occurred. 

So, there’s a lot of information that you know from the development of the time proposal, the time mission, proposal that we were able to leverage for Dragonfly. But going back, proposing to go back to the poles of the north pole of Titan, we’ll have to wait to a to a future mission to be able to explore the seas and the shorelines there, which would be absolutely fascinating.

Host: How do you keep focus and keep that team continuity over a long duration? 

Dr. Turtle: Yeah, I mean the outer solar system, the timescales are, the timescales are long. For any mission, developing the mission is a several year process, and then for getting to the outer solar system that takes several years before you actually get into science operations. 

 So, one of the, one of the key things to think about, in fact, one of the opportunities one really has with that kind of timescale is an opportunity to bridge generations of scientists and engineers working on the on the mission. 

So, we have team members who worked on the Cassini-Huygens missions. Cassini was an orbiter at Saturn. It carried with it the Huygens probe that the European Space Agency developed and that was designed to study Titan’s atmosphere, descend down through Titan’s atmosphere. 

So, we have some team members who actually worked on the initial development of the Cassini-Huygens mission. We have other team members who worked the operations, who are earlier in their careers and worked operations for Cassini-Huygens. 

And we also have, you know, earlier career team members who can learn as we go through the Dragonfly process, the Dragonfly development process, who can learn from people who have that, experience at Titan, from a previous mission to and then hopefully, you know, that generation can teach the next generation. 

But it is, it is absolutely something one really needs to think about, is the timescale of the mission and being able to transfer information from, you know, from the team that does the development to the team that will do the operations. 

We certainly have team members developing operations who we expect to be performing operations at Titan, but, but you need to think through the, the timescales of the mission and the timescales of people’s careers as well. 

Yeah, but it really is an excellent opportunity to bring in, you know, early career team members and have them be the ones leading the, you know, the operations and then leading future missions. 

Host: Zibi, what was your giant leap?

Dr. Turtle: I would, I guess I wouldn’t, wouldn’t think of it as more as a leap, per se. My career has kind of been a series of steps, learning, taking what one learns from one, you know, from one mission. 

I got to work with the Galileo mission during operations at Jupiter, and then the Cassini mission during operations at Saturn. And taking, taking that experience into looking toward developing future missions, working with Europa Clipper and, and with Dragonfly. 

And also learning from the proposals and concepts that were not selected. and there’s still, there’s a lot, you know, a lot that goes into any, any proposal, R&A [research and analysis], mission, or instruments. And even if those are not selected, there’s a lot that is, that is learned there, that is valuable in future endeavors. So, I think, I think those are really important steppingstones as well. 

You can look at someone’s CV and kind of look,it looks like a very neat progression, linear progression from one project to another. But what you don’t see on the CV are those steppingstones where things weren’t, you know, where a project wasn’t selected or a project didn’t continue. But I think those are, those are just as important (sometimes more important) steppingstones along one’s career path. 

Host: Yeah, it sure can be. Thank you, Zibi. We appreciate your time. Thanks for being here and sharing all about Dragonfly. 

Dr. Turtle: Thank you. It’s a pleasure to talk with you. 

Host: That’s it for this episode of Small Steps, Giant Leaps. For a transcript and to hear previous episodes, visit nasa.gov/podcasts. While you’re there, you can check out our other podcasts like Curious Universe, Houston, We Have a Podcast, and Universo curioso de la NASA. As always, thanks for listening.

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Outro: This is an official NASA podcast.