Entering a planet's atmosphere is a dangerous maneuver for any spacecraft, as it must withstand the intense frictional heat generated by high-speed contact with atoms and molecules.

That's why landers and rovers have heat shields. And new research from the Grainger College of Engineering at the University of Illinois Urbana-Champaign suggests that an atmosphere's composition has a big impact on how heat shields work.

A heat shield "breathes" when it hits the atmosphere. The surface of the shield begins to burn away, in a process called ablation. To mimic the hypersonic speed of a spacecraft's entry, a team of researchers led by Francesco Panerai, a professor in the Department of Aerospace Engineering, experimented with heat shields in the Plasmatron X wind tunnel at the Center for Hypersonics and Entry System Studies, which is housed a few blocks from the university's campus.

"What was very surprising about the study is that, when we changed the gas, the ablation phenomenon behaved in different ways," Panerai said in a March 12 statement. "In a classical air environment where you have oxygen present, the ablation happens in a steady way. The flow around the spacecraft erodes the surface, and particles get ejected as a constant stream."

When material from the outer layer of the heat shield erodes, some of it can collect on the surface of the shield, potentially clogging up some areas and preventing the material below from "breathing." This can impact how well the shield performs. In the new study, the researchers found that changing the gases that the shield comes into contact with also changes its performance.

"When the oxygen is removed, this phenomenon becomes unsteady. Intermittent bursts of particles are ejected and, at times, the process becomes violent," Panerai said. "I've been around ablation research for over 15 years, and I've never seen this. We were all really surprised when we first observed this behavior in the tunnel."

Understanding how an atmosphere's composition affects heat shields is important, Panerai said, because NASA is getting Dragonfly, a robotic rotorcraft, ready for a 2028 launch toward the huge Saturn moon Titan. Titan has a thick atmosphere that's quite different from that of Earth: It's composed of about 95% nitrogen and 5% methane, whereas ours is 78% nitrogen and 21% oxygen.

Dragonfly will study Titan's surface, which could give scientists clues on whether or not the moon's hydrocarbon lakes and rivers hold molecules that are a precursor for life.

"Although this work doesn't directly influence heat shield design, it does have very profound implications on the physics of the material — on the way the material behaves at extreme temperatures," Panerai says. "Understanding at what conditions this phenomenon becomes prominent in flight can help us design better heat shields."

The study was published Feb. 5 in the science journal Carbon.

NASA is one step closer to sending a drone mission to another world.

Technicians at the Johns Hopkins Applied Physics Laboratory (APL) in Maryland have begun building and testing the nuclear-powered Dragonfly rotorcraft, which will launch toward the huge Saturn moon Titan in 2028.

"This milestone essentially marks the birth of our flight system," Elizabeth Turtle, Dragonfly principal investigator at APL, said in a NASA statement on Tuesday (March 10).

"Building a first-of-its kind vehicle to fly across another ocean world in our solar system pushes us to the edge of what's possible, but that's exactly why this stage is so exciting," Turtle added. "The team is doing an outstanding job, and every component we install and every test we run brings us one step closer to launching Dragonfly to Titan."

The car-sized Dragonfly will be the second rotorcraft to explore the skies of a world beyond Earth. The first was NASA's Mars helicopter Ingenuity, whose fuselage was only the size of a tissue box. The solar-powered Ingenuity was designed for just a handful of hops but survived an ambitious flight campaign that lasted nearly three years, from April 2021 to January 2024.

Building on what NASA learned, Dragonfly will be bigger — and powered by nuclear energy, not the sun. The Titan drone is also a full mission, costing about $3.35 billion; Ingenuity was a technology demonstrator with a price tag of just $85 million.

Dragonfly is expected to launch in 2028 toward Titan, the largest moon of Saturn and second-largest satellite in the solar system, behind Jupiter's Ganymede. Titan is thought to be rich in the precursor molecules of life as we know it, which makes it an exciting target for scientists, but it has been studied up close just once — by the European Huygens lander, which survived for a few hours in Titan's skies and on its surface on Jan. 14, 2005.

After touching down on Titan, Dragonfly aims to "explore a range of diverse sites to study the chemistry, geology and atmosphere of the terrestrial moon and ultimately advance our understanding of life's chemical origins," NASA officials stated. But first, the mission needs to be readied for space.

At APL, the first weeks of testing will focus on the spacecraft's integrated electronics module — a sort of "brain" for the mission that focuses on items like guidance, navigation and data handling — and power-switching units.

Testing and integration is expected to continue into early 2027. The spacecraft will next be shipped to Lockheed Martin Space in Littleton, Colorado for systems testing, before a brief return to APL to assess how Dragonfly will do in the space environment. APL will send Dragonfly to NASA's Kennedy Space Center no earlier than spring 2028, to launch aboard a SpaceX Falcon Heavy rocket.

Dragonfly's protective shell for flying through space is also being tested: the shell finished aerodynamic assessments in wind tunnels at NASA's Langley Research Center in Virginia and is now in the integration and testing stage at Lockheed Martin. APL is also assessing insulating foam intended to keep Dragonfly from freezing in Titan's frigid atmosphere, and other items like the science payload and flight radio are also coming together.

While several years lie between now and launch, entering the build-and-test phase is a big milestone.

"We've spent years designing and refining this amazing rotorcraft on computer screens and in laboratories, and now we get to bring all those elements together and transform Dragonfly into an actual flight system," Annette Dolbow, the Dragonfly integration and test lead at APL, said in the same statement.

Testing is now underway on NASA's Dragonfly rotorcraft, a nuclear-powered, car-sized aerial drone that will look for potential precursors to life on Saturn's moon, Titan. But before Dragonfly can take to the sky, NASA has to make sure it can withstand the moon's unique environment.

Dragonfly's main goal is to study the complex chemistry on Titan that may give insights into the origins of life in our solar system. Equipped with cameras, sensors, and samplers, this vehicle will investigate areas of Titan known to contain organic materials, especially those regions where such materials might have encountered liquid water beneath the moon's icy surface in the past.

The lander will traverse Titan's nitrogen-rich atmosphere using four dual-coaxial rotors, but to ensure that these rotors can perform under such conditions, the Dragonfly team has conducted numerous tests at NASA's Langley Research Center in Hampton, Virginia, including operating the drone's rotors in an wind tunnel that can simulate the atmospheric conditions on Saturn's largest moon. 

Related: NASA's Titan Dragonfly will touch down on a field of dunes and shattered ice

"All of these tests feed into our Dragonfly Titan simulations and performance predictions," Ken Hibbard, Dragonfly mission systems engineer at Johns Hopkins Applied Physics Laboratory (APL), said in a NASA statement.

Four Dragonfly test campaigns have conducted: Two in a 14-by-22 foot subsonic tunnel, and another two at a 16-foot Transonic Dynamics Tunnel (TDT). The subsonic tunnel is used to validate fluid dynamic models developed by mission scientists, while the variable-density heavy gas capability of the TDT is used to validate computer models in simulated atmospheric conditions Dragonfly will likely encounter on Titan.

The most recent testing, held in June, involved a half-scale Dragonfly model with hundreds of test runs, said Bernadine Juliano, APL's test lead for the project. 

"We tested conditions across the expected flight envelope at a variety of wind speeds, rotor speeds, and flight angles to assess the aerodynamic performance of the vehicle," Juliano said. "We completed more than 700 total runs, encompassing over 4,000 individual data points. All test objectives were successfully accomplished and the data will help increase confidence in our simulation models on Earth before extrapolating to Titan conditions."

Analyzing this wealth of data involves a collaborative effort, with specialists from institutions ranging from the University of Central Florida to NASA Ames Research Center in Silicon Valley. Rick Heisler from APL, who oversaw the TDT test campaigns, emphasized the value of these tests in understanding Dragonfly's rotor performance in Titan's unique atmosphere.

"The heavy gas environment in the TDT has a density three-and-a-half times higher than air while operating at sea level ambient pressure and temperature," Heisler said. "This allows the rotors to operate at near-Titan conditions and better replicate the lift and dynamic loading the actual lander will experience."

As the pieces of the mission come together, the enormity of the task and the historic nature of the mission is coming into focus for the team.

"With Dragonfly, we're turning science fiction into exploration fact," Hibbard said. "The mission is coming together piece by piece, and we're excited for every next step toward sending this revolutionary rotorcraft across the skies and surface of Titan."

The fourth in a line of groundbreaking NASA missions that could redefine how we understand life in the universe is set to launch in 2027. 

NASA's Dragonfly drone is headed for Saturn's largest moon, Titan, an active, icy world with a nitrogen-rich atmosphere and underground liquid-water oceans, where the skies rain methane to fill lakes and flowing rivers on the surface. Dragonfly is poised to get an up-close look at all of it, and possibly discover clues to the origins of life on the moon.

Dragonfly will be NASA's first interplanetary rotorcraft-lander probe outfitted with a full suite of scientific instruments, and will be capable of flying several miles between geological points of interest on Titan's surface. Currently being designed and built at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, Dragonfly is part of NASA's New Frontiers program, which includes the OSIRIS-REx probe's study of the asteroid Bennu, Juno, sent to orbit Jupiter, and the New Horizons probe that performed a fly-by of Pluto and is now studying the Kuiper Belt.

Related: Titan: Facts About Saturn's Largest Moon

Saturn's largest moon also happens to be the second largest moon in the solar system, with Titan weighing in just behind Jupiter's moon, Ganymede. As a planetary body, Titan is larger than Mercury, with an atmosphere quadruple the density of Earth's. Its size and lower gravity, paired with the moon's thick atmosphere make it the perfect candidate for a robotic explorer like Dragonfly.

Another drone is already in-use by the space agency on the surface of Mars. Measuring only a few feet (about a meter) across its rotors, Ingenuity arrived on the red planet stowed beneath the Perseverance rover and became the first human-built craft to perform aerodynamically controlled flight on an alien world. The Martian helicopter was originally sent just for a series of test flights, but performed well enough that NASA decided to extend its mission as a scout for its rover companion.

Ingenuity is only equipped with cameras and a few basic instruments to ensure vehicle health and flight performance. When Dragonfly arrives at Titan, it will be carrying an entire laboratory. Because of Titan's geological diversity, Dragonfly is being designed to test the gamut of the moon's properties, including its atmospheric composition and the chemical makeup of its differing liquid bodies above and below ground. 

In addition, the drone will analyze samples extracted from Titan's surface. Dragonfly will use the Drill for Acquisition of Complex Organics (DrACO) instrument to dig out surface material less than a gram at a time. These specimens will be stored and analyzed internally, inside part of the lander's main body known as the "attic". Dragonfly's attic houses another instrument, called the Dragonfly Mass Spectrometer (DraMS). DraMS works similarly to the Sample Analysis at Mars (SAM) spectrometer built into the Mars Curiosity rover, and was designed by the same team at NASA's Goddard Space Flight Center. 

The spectrometer works to identify the chemical composition of a sample by breaking down its molecular makeup through a process of ionization (which involves vaporizing samples with a laser inside a tiny onboard oven) that allows DraMS to examine a specimen's individual compounds. What exactly makes up the surface of Titan may have enormous implications for astrobiology researchers, scientists and humanity as a whole. 

Scientists plan to use DrACO and DraMS to probe Titan's extraterrestrial environment to determine its habitability and search for the type of chemical markers indicative of life, or pre-life. Dr. Melissa Trainer is NASA's project lead on the DraMS instrument, and is one of the researchers hoping clues to the beginning of life on Earth can be found on the Saturnalian moon. "We want to know if the type of chemistry that could be important for early pre-biochemical systems on Earth is taking place on Titan," Trainer said in a NASA statement. 

When it launches in 2027, Dragonfly will have to contend with a journey through interplanetary space nearly seven years long. If everything goes smoothly, when Dragonfly finally touches down on Titan's surface, sometime during 2034, the rotorcraft-lander will have at least 32 months (2.7 years) to complete its mission. If everything goes very smoothly, and Dragonfly follows in the successes of continued missions like New Horizons, Juno, Curiosity, or its rotary-predecessor Ingenuity, it's possible for the lander's expedition of Titan to go beyond 32 months.

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The spacecraft that have peered through the yellowish haze surrounding Saturn's moon Titan discovered a strange, yet strangely familiar world where life could theoretically take root. Now, scientists want to return — this time buoyed by Earth's fascination with drone technology.

That's precisely what a team of scientists working on a proposed mission called Dragonfly want to do: combine terrestrial drone technology and instruments honed by Mars exploration to investigate the complex chemical reactions taking place on Saturn's largest moon. Later this year, NASA will need to decide between that mission and another finalist proposal, which would collect a sample from a comet.

"At first blush, I think a lot of people think [Dragonfly] sounds like the literal meaning of incredible," Melissa Trainer, a deputy principal investigator with the mission and a scientist at NASA, told Space.com. "Not only is this an incredibly exciting concept with amazing, compelling science, but also, it is doable — it's feasible from an engineering standpoint." [Landing on Titan: Pictures from Huygens Probe on Saturn Moon]

Dragonfly, if chosen, would aim to launch in 2025 and arrive at Titan in 2034. The world it will explore is oddly reminiscent of Earth for a strange moon so far away. On Earth, sunlight powers organic life growing in fields and forests; the same sunlight triggers chemical reactions in Titan's upper atmosphere that create large organic molecules that pour down on the moon's surface, like Earth's rainwater. While Earth has a landscape made of rock covered in places by water, Titan's landscape is made of water ice covered in places by organic compounds.

Knowledge of those Titan traits comes primarily from data gathered by the Cassini mission to the Saturn system and the Huygens probe that traveled with Cassini and touched down on Titan in 2005. Taken together, those two spacecraft completely reshaped scientists' ideas about the moon.

"We didn't know how Titan worked as a system before Cassini got there. We had tantalizing hints, but Cassini and Huygens really took it from [being] this mysterious moon to [being] a place that is incredibly familiar," Elizabeth "Zibi" Turtle, principal investigator for Dragonfly and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, told Space.com. "Cassini really showed us Titan as a world and how it works and the different processes that are acting on it."

But Cassini never got a good view of the surface through the moon's thick atmosphere, and once the Huygens probe touched down, it ran out of battery power in mere hours. If all goes smoothly, Dragonfly would be able to explore dozens of sites over the course of two Earth years. And some aspects of the proposed mission aren't as difficult as you might expect. 

Consider landing, for example. Trainer, who also works with the Curiosity rover on Mars, remembers well the so-called "7 minutes of terror" during that rover's action-packed landing, as the spacecraft fought to slow itself quickly enough to touch down gently. "Compared to that, landing on Titan is just this leisurely, gentle float down to the surface," she said. "It takes something like over 2 hours because of this dense atmosphere."

That atmosphere, which Trainer compared to a pillow, combined with the low gravity on the moon (about a seventh the strength of Earth's) also makes putting an aircraft on a distant moon much more feasible. With its rotor-copter design, Dragonfly can lift itself off the surface and fly away using the nuclear power source that NASA had available for this class of mission.

But incorporating extraterrestrial drone technology is a means to an end, not the final goal. "We focus so much on the flight, and that's what we show in the pictures, because that's part of the really exciting part. But the truth is we really spend most of the time on the surface," Trainer said. "We're really a landed package, a science laboratory — we're doing [most of] our science on the ground, and then we fly to relocate and to get some data on the surface. We move to a new place and then we do more landed science." [Amazing Photos: Titan, Saturn's Largest Moon]

That science will tackle the chemistry on Titan. Scientists know that the moon hosts huge amounts of organic compounds, but Cassini and Huygens didn't gather enough data to clarify the details of the planet's chemistry. Dragonfly would be able to identify precise organic compounds, so scientists could determine just how close Titan's molecules are to those that terrestrial biology relies on.

"Dragonfly is first and foremost a mission to understand prebiotic chemistry. What happened to get from chemistry to biology?" Turtle said. "Of course, we can't study that on Earth, because biology has kind of overprinted everything, but Titan is actually the place that is most like the early Earth in the solar system."

Scientists have run experiments to try to mimic Titan in the laboratory, testing what compounds the ingredients and conditions they replicate produce. Those experiments have had intriguing results — the reactions can create amino acids, for example, the building blocks of proteins — but they can never run indefinitely. "In the laboratory, you're always limited by time. Titan has been doing this for millions and millions of years," Trainer said. "Titan has basically been doing these experiments for us, and all we're trying to do is go and get the results."

And if the mission's impetus comes from the Cassini and Huygens missions, the methodology to fetch those results is inspired by a very different suite of spacecraft: NASA's Mars rovers. After all, Titan isn't the first place NASA has studied organic compounds; that's precisely what the Curiosity rover was designed to do. So, Dragonfly would carry some of the same instruments adapted for a new context.

Whether Dragonfly takes flight is now up to NASA. The Dragonfly team submitted a detailed concept report in December and is expecting a decision from the agency this summer. The team members said they think they've made a compelling case for both the science that the mission could do and its feasibility.

"It's amazing, but it's not crazy," Trainer said.

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us @Spacedotcom and Facebook. Original article on Space.com.