Picture standing wearing a heated suit, with homemade wings clipped to your arms. You take a few running steps across a plain of dark sand, feel far less weight pulling you down, and beat the wings once, twice. And you lift off.<\/p>\n
On Earth this is a child\u2019s daydream. On Titan, the largest moon of Saturn, the physics genuinely allows it.<\/p>\n
It sounds like science fiction, but it comes straight out of two facts about Titan: its air is very dense, and its gravity is very weak.\u00a0<\/p>\n
The physics that makes it possible<\/p>\n
Flapping flight is a tug of war between two things: how much air your wings can push against, and how much weight that push has to lift. Titan helps you on both sides at once. The air is dense, so each wingbeat shoves a lot of it downward. And you weigh far less, so there is much less holding you on the ground.<\/p>\n
The Planetary Society\u2019s Kate Howells puts it bluntly. Howells writes<\/a> that \u201cBecause of its combination of low gravity and dense atmosphere, Titan is the easiest place in the Solar System for flying.\u201d That is her characterization, not a measured fact, but the reasoning holds up. She goes further, describing how a human might strap wings onto a spacesuit<\/a>, get a running start and flap into the air. Note the conditional. It\u2019s a possibility, not a promise.<\/p>\n On a related note \u2013 we created a video on Titan\u2019s unusual rainfall:<\/p>\n<\/p>\n What the numbers actually say<\/p>\n Titan\u2019s surface air is unusually dense. An engineering profile of NASA\u2019s Titan mission notes that the moon\u2019s surface air density is 4.3 times<\/a> that of Earth, while NASA puts its surface pressure at about 60 per cent greater<\/a> than Earth\u2019s and its gravity at roughly one-seventh of ours. You would feel like you weighed a seventh of your usual self.<\/p>\n That difference is bigger than it sounds. A bigger wing lowers the running speed you\u2019d need to get airborne, and the effort drops fast as the wing grows. Randall Munroe, working the same problem for his xkcd \u201cWhat If?\u201d series, reckons a person in artificial wings could take off on Titan with no more effort<\/a> \u201cthan walking.\u201d Treat that as a sense of the scale, not a design spec.<\/p>\n Why Dragonfly uses the same physics<\/p>\n The same conditions are central to a machine now being built. NASA\u2019s Dragonfly is a nuclear-powered drone the size of a car, with eight rotors, and the whole design leans on Titan\u2019s dense air and weak gravity.<\/p>\n The NASA science team writes that these features should \u201chelp Dragonfly stay easily aloft above Titan\u2019s surface and to fly faster and farther with little energy.\u201d<\/a> That is the design goal, not a proven result yet. Dragonfly is scheduled to arrive on Titan in late 2034<\/a>, and is expected to cover more than 100 miles<\/a> during its planned 3.3-year primary mission<\/a>.<\/p>\n The catch you can\u2019t ignore<\/p>\n This is the part the daydream skips. Titan\u2019s surface sits at about minus 179 degrees Celsius<\/a>. There is no oxygen to breathe. The lift is relatively easy; staying alive is not. Any real attempt would need heated, oxygen-fed suit, and that suit\u2019s bulk and mass are problems the tidy physics ignores.<\/p>\n Munroe treats Titan\u2019s cold as an engineering problem<\/a>, then immediately undercuts the optimism. If humans strapped on wings there, he suggests<\/a>, frozen or failing wings could turn the flight into a Titan version of the Icarus story. He\u2019s joking, but the point under the joke is real: on Titan, the flying is the easy part.<\/p>\n What I keep coming back to is how Titan rearranges the word \u201cimpossible.\u201d Human-powered flight isn\u2019t impossible in some absolute, physical sense. It was only ever impossible in the specific conditions we happen to have been born into. Change the thickness of the air and the pull of the ground, and the same muscles, with the right wings, become airworthy. The limit was never us. It was the room we were standing in.<\/p>\n Editorial process<\/p>\n \n\t\t\t\tSpace Daily articles are produced with AI assistance and reviewed by editorial staff before publication. See our editorial standards<\/a> and masthead<\/a>.\n\t\t\t<\/p>\n","protected":false},"excerpt":{"rendered":"Picture standing wearing a heated suit, with homemade wings clipped to your arms. 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