By Byron Perry
At the time of writing this, the world is watching as NASA’s Ingenuity drone prepares to take off from the surface of Mars. If the flight succeeds, it will be the first powered flight on any planet other than Earth. But even as this historic moment unfolds, NASA is preparing for the next step in extra-terrestrial flight. The Dragonfly Mission is set to launch towards Saturn’s moon Titan in 2027. Unlike Ingenuity, which is a technology demonstrator, meaning it’s primary mission is to demonstrate that flight on other planets is possible, Dragonfly will be a full fledged exploratory craft, designed to explore and conduct scientific observations.
Titan is the largest moon of Saturn, larger than the smallest planet Mercury, and one of the most intriguing places in the entire solar system. It is the only place in the solar system, other than Earth, with a liquid cycle. As we know on Earth, we have the water cycle, in which water evaporates from the surface of the Earth, condenses to form clouds, and then falls to the ground as rain. This flows to form the rivers, lakes and oceans of our largely blue planet. However, as Titan is much farther from the sun than Earth, it is far colder. The average temperature is -179 degrees Celsius (-280 degrees Fahrenheit). The very low temperature means that all water on the moon is frozen. Instead methane, which is a gas on the far warmer Earth, can exist as a liquid on Titan, and can evaporate and form clouds, rain, rivers and oceans. Just like water on Earth. This intriguing chemistry and Earthlike weather system leads Titan to be one of the strongest candidates for alien life in the solar system. Although it would be radically different from life as we know it, life evolving in methane seas is unlikely to look anything like life evolving in seas of water.
Titan is the only moon with a thick atmosphere. It consists of mainly nitrogen, with 1.4% methane and 0.2% hydrogen. The pressure on Titan’s surface is 145% of Earth, and the atmosphere is 4 times denser. The thick atmosphere, combined with a gravity only 13.8% of Earth’s means that the Dragonfly only needs a 40th of the lifting power that would be required on Earth. In fact you would be able to fly on Titan by flapping a pair of wings strapped to your arms! Thus, exploring Titan by air would be comparatively easy.
Titan passing in front of Saturn’s rings in this beautiful picture taken by the Cassini spacecraft. (NASA/JPL-Caltech/Space Science Institute)
An artist's impression of the Dragonfly probe landing and taking off on Titan.(Nasa Press release)
The Dragonfly Quadcopter
Dragonfly is an octocopter, meaning a helicopter with 8 rotor blades. These are arranged in pairs so Dragonfly resembles a quadcopter. Dragonfly will mass around 450 kilograms (990 pounds). Each blade will be 1 metre (3.3 feet) in diameter. The probe will be powered by a Radioisotope Thermoelectric Generator, or an RTG. RTG’s generate electricity by converting the thermal energy given off by the radioactive decay of plutonium into electrical energy. The Mars rovers Curiosity and Perseverance use RTG’s, as does every spacecraft that ventures past Jupiter, as the sun is too dim past this point to use solar panels. The RTG will also provide heat to the Dragonfly probe, to prevent it from ceasing to function in the extreme cold of Titan. The flights themselves will be powered by lithium ion batteries, recharged by the RTG. These batteries will allow Dragonfly to fly for 30 minutes, travel 10 kilometres (6.2 miles) and ascend to 4 kilometres (2.5 miles). For comparison, the Ingenuity helicopter will only ascend to 5 metres (16 feet), only fly for 90 seconds at a maximum and be able to travel 100 metres (330 feet). Dragonfly will also require advanced AI to control its flight, as the communications delay from Earth to Saturn varies from 1.1- 1.6 hours, making remote control of the probe impossible. To illustrate just how much more effective Dragonfly will be at exploring than other probes in 5 half hour flights, it will travel further than the beloved Opportunity rover did in 15 years of roving! The Dragonfly probe will launch in 2027, and will arrive at Titan in 2036. It is planned to land in the ‘Shangri La’ region of Titan, chosen due to its highly scientifically interesting sand dunes.
To conclude, the Dragonfly mission, although not launching for many years, is an incredibly exciting mission that has capabilities never before seen in a space exploration mission. Additionally, there is something very exciting about the possibility of a helicopter exploring a world so alien, and yet in some ways so Earthlike from the sky, 1.5 billion kilometres (900 million miles) from home...
John Hopkins Applied Physics Laboratory. (2021, February 26). What is Dragonfly? https://dragonfly.jhuapl.edu/index.php. Retrieved April 16, 2021, from https://dragonfly.jhuapl.edu/What-Is-Dragonfly/
NASA. (2019, June 27). NASA's Dragonfly Will Fly Around Titan Looking for Origins, Signs of Life. nasa.gov. Retrieved April 16, 2021, from https://www.nasa.gov/press-release/nasas-dragonfly-will-fly-around-titan-looking-for-origins-signs-of-life
NASA. (2021, February 4). Titan Overview. solarsystem.nasa.gov. Retrieved April 16, 2021, from https://solarsystem.nasa.gov/moons/saturn-moons/titan/in-depth/