About 800 million miles (1.2 billion kilometers) from Earth lies cloud-cloaked Titan, largest of Saturn’s 146-strong retinue of moons. In this dark, subfreezing patch of the outer solar system, the Sun glows at barely 1 percent of its strength in Earth’s skies. It’s hardly an ideal place to search for life, but impossible as it may seem, the building blocks of life might once have taken root in this radiation-drenched wasteland.
Now, NASA is set to explore this world — and soar above it — with a dronelike robotic rotorcraft named Dragonfly that will scour the alien moon for signs of habitability. Last Friday, the agency announced that the mission has passed its critical design review, a key milestone. This means the design of the craft — essentially a car-sized, nuclear-powered quadcopter — is approved, and the mission can begin construction.
In July 2028, Dragonfly will launch aboard a SpaceX Falcon Heavy rocket from Florida’s Kennedy Space Center. The mission will scout diverse geological locations, study prebiotic chemistry, and assess the past and present habitability of this world. If successful, it will achieve the first powered, controlled flight in a moon’s atmosphere.
Despite being approved to progress to its final design phase by NASA in April 2024, Dragonfly has fallen three years behind schedule and slipped beyond its tightly mandated budget, due to the COVID-19 pandemic, supply chain increases, and federal funding cuts. Between 2020 and 2022, Dragonfly underwent multiple mission replans, but clever tweaks of its trajectory and a powerful launch vehicle will ensure it wastes no time getting to Titan by 2034.
Feels like home?
Discovered in 1655 by the Dutch astronomer Christiaan Huygens and initially known as Saturni Luna (“moon of Saturn”), Titan earned its name in 1847 courtesy of Britain’s Sir John Herschel. Larger than the planet Mercury, its equatorial diameter of 3,200 miles (5,100 km) positions Titan comfortably as the solar system’s second-biggest moon (after Jupiter’s Ganymede), and the only one known to possess a substantial atmosphere.
That soupy, orange-hued, gaseous veil is four times denser than Earth’s own. As on our planet, nitrogen predominates on Titan, albeit in greater relative quantities of 94.2 percent compared to 78 percent on Earth. Methane contributes another 5.6 percent. But oxygen — a mainstay in biological systems and sustaining life as we know it — is markedly absent.
Surface temperatures of –290 degrees Fahrenheit (–180 degrees Celsius) and pressures 50 percent higher than terrestrial sea level paint a picture of a gloomily alien world — yet Titan offers hints of the familiar. Its atmosphere and climate produce clouds, sluggish winds, and methane “rain.” And its surface features are evocative of Earth, with swirling dunes not of sand but of coffee-grain-sized hydrocarbons, and rivers, lakes, and seas not of water but of slow-flowing methane.
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These surface processes, weather, and complex organics may resemble how Earth looked in its infancy, some 3.8 billion years ago. The roughly 1,000-pound (450 kilograms) Dragonfly could reveal clues about our planet’s first billion years of existence, with Titan providing a laboratory to uncover the prebiotic chemistry that precipitated the earliest stirrings of earthly life.
Several past missions observed Titan from afar: Pioneer 11 in 1979, Voyager 1 and 2 in 1980–1981, and Cassini in 2004–2017. Additionally, Europe’s Huygens probe alighted on Titan’s surface in 2005. But none could explore the world’s surface widely enough to study its potential for life, assess how far prebiotic chemistry might have progressed on Titan, or search for biosignatures.
Flying an aerial vehicle on Titan and relocating an entire package of scientific instruments from one location to another to gather samples from diverse sites with dissimilar geological histories carries great appeal. Titan’s low gravity — just 13.8 percent as strong as ours — and thick, calm atmosphere make it ideal for powered flight and rotorcraft.
But cryogenic ambient temperatures, low light levels, and higher atmospheric drags on Dragonfly’s airframe will carry their own challenges.
Designing Dragonfly
Dragonfly was born during an over-dinner conversation between scientists Jason Barnes of the University of Idaho and Ralph Lorenz of the Applied Physics Laboratory (APL) at Johns Hopkins University. In June 2019, NASA selected the mission as part of its New Frontiers program, cost-capped at $850 million and targeted for launch in June 2026 for arrival at Titan in 2034.
However, COVID-19 and budget constraints prompted NASA in 2020 to request the Dragonfly team to pursue an alternate launch readiness date of June 2027. And by the time the mission passed its Preliminary Design Review in March 2023, its total projected cost had swollen to $3.35 billion.
In November 2023, NASA again postponed the launch — this time until July 2028, directing Dragonfly’s team to use a more powerful, heavy-lift launch vehicle to ensure the 2034 Titan arrival date could still be met.
Last April, NASA approved the mission to progress to final design, construction, and testing of both the spacecraft and its scientific payload. In November 2024, SpaceX’s Falcon Heavy was chosen to launch Dragonfly during a three-week window extending from July 5–25, 2028. And in the mission’s most recent milestone, NASA announced April 25 that Dragonfly had passed its critical design review, and that “the mission can now turn its attention to the construction of the spacecraft itself.”
Designed, built and managed for NASA by APL, Dragonfly is a dual quadcopter with four pairs of rotors in a coaxial configuration — one rotor above the other — bearing a resemblance to a terrestrial drone. Each rotor spans 4.4 feet (1.35 meters) and the entire unit provides a measure of redundancy to tolerate failures or partial loss of functionality.
The entire craft measures 12.5 feet (3.85 m) in length and is powered by a nuclear generator designed for spacecraft called a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG); it furnishes 70 watts of electrical power to charge Dragonfly’s 134-ampere-hour lithium-ion battery during the eight-day-long Titanian night. Flying at 22 mph (36 km/h) and capable of reaching altitudes of 13,000 feet (4,000 m), Dragonfly should be able to travel up to 10 miles (16 km) on a single battery charge.
Mission goals
The mission features contributions from U.S. industry and academia, as well as the national space agencies of France, Germany, and Japan.
The Dragonfly Mass Spectrometer (DraMS) will identify chemical compounds in surface and atmospheric samples. This U.S./French instrument owes its heritage partly to the Sample Analysis at Mars (SAM) tool aboard NASA’s Curiosity rover. Honeybee Robotics’ Drill for Acquisition of Complex Organics (DRACO) will employ a rotary-percussive drill to extract regolith; a pneumatic transfer system will whisk samples into DraMS for analysis.
The Dragonfly Gamma Ray and Neutron Spectrometer (DraGNS), built by APL and Lawrence Livermore National Laboratory, will characterize Titan’s surface composition directly beneath the spacecraft on Titan’s surface.
The APL-led Dragonfly Geophysics and Meteorology Package (DraGMet) comprises a suite of sensors to monitor atmospheric conditions and characterize the nature of the regolith and measure seismic activity. Such measurements could offer insights into the thickness of Titan’s crust and deep interior, including the possible existence of a subsurface salty ocean of liquid water.
And Malin Space Science Systems’ DragonCam provides a suite of microscopic and panoramic cameras to image Titan’s terrain and scout for potential landing sites.
On arrival
Using the Falcon Heavy and an Earth gravity assist maneuver allows NASA to preserve Dragonfly’s 2034 arrival at Titan — which will come almost one full Saturn year (equal to 29.5 Earth years) after Huygens landed in 2005. This ensures the prevalence of similarly calm, predictable atmospheric conditions when Dragonfly touches down.
Entering Titan’s atmosphere, a protective aeroshell will shield the spacecraft for the first six minutes of descent, after which drogue and main parachutes will deploy to slow its velocity below subsonic speeds. In view of the atmosphere’s thickness, this parachute phase of descent should last about 105 minutes. Finally, at an altitude of 0.75 mile (1.2 km), Dragonfly will separate and commence a powered descent to the surface.
It will touch down among dunes at the edge of a dark organic region called Shangri-La. Two decades ago, Huygens provided a glimpse of the moon’s landscape: a gloomily orange sky, no brighter than civil twilight here on Earth, and a claylike surface that scientists have compared in color and texture to a crème brûlée.
Shangri-La has been likened to Namibia in southern Africa — its dunes likely rise to 300–600 feet (100–180 m). Key targets include the 56-mile-wide (90 km) Selk impact crater, which might hold organic compounds and perhaps liquid water.
Once Dragonfly arrives in Shangra-La, its mission will begin in earnest. If all goes well, over its three-year operational lifetime, Dragonfly will cover about 100 miles (160 km) and visit dozens of locations by landing on safe terrain then navigating to more challenging points.
It promises to be an epic aerial journey on the most distant world where an aircraft has ever flown.
