It began with the Apollo 11 Lunar module, signaling the historic first manned landing on the moon. In subsequent Apollo missions there were Lunar Rover vehicles, capable of traversing the rocky moon landscape. The Mars Rover captivated a global audience in the new millennium, racing over the red planet's surface. Could the next big thing be an underwater adventure to the watery depths of an alien sea? Perhaps.
At the recent 2015 NASA Institute for Advanced Concepts (NIAC) Symposium in Cocoa Beach, Florida, NASA the Titan Submarine Phase I Conceptual Design was presented which outlines a possible mission to Saturn's largest moon, Titan to explore the seas of liquid hydrocarbons.
Titan is the only moon in our solar system that has a proper atmosphere composed largely of nitrogen and methane. It's pressure is 1.5 times that of Earth and it's temperature is a chilly 290 °F but it could still hold clues to the beginning of life here on Earth.
Thanks to fly-bys of Voyager and Cassini and the Huygens probe landing, we know that there are three polar seas on Titan composed of methane and ethane but with a consistency similar to liquefied natural gas. The largest of these is Kraken Mare covering 154,000 square miles and ranging from 525 to perhaps 1000 feet deep.
NASA's conceptual Titan submarine design unveiled at NIAC is based on experience gained from the building and operation of drone submersibles on Earth. It weighs about 1 ton and uses conventional electric propulsion, modified for the gravity of Titan and its mission would be about 90 days long.
Because of its elongated shape, the sub would need to be delivered to the surface of Titan using a winged spacecraft lifting body that could survive a hypersonic entry into Titan's atmosphere. The craft would then have to make a water landing on the surface of Kraken Mare and release the sub to sink on its own.
Due to the huge amount of data that needs to be sent to Earth, the submarine needs a large dorsal fin that includes a planar phased-array antenna and mast camera. The plan is to have it surface for 16 hours per day to communicate and relay data back to Earth.
Similar to submarines on Earth, ballast tanks would still be used but their design is as yet undetermined because of the differences between the earth seas and the liquid gas seas on Titan.
In addition, the lower gravity on Titan and the possible depth of Kraken Mare means that any nitrogen in the ballast tanks could liquefy resulting in a loss of buoyancy. For this reason, the tanks would need to use a piston to allow in and expel liquid rather than relying on air pressure as in a conventional submarine.
While NASA did not give full details of the mission objectives of a Titan submarine, it is likely that the study of the structure of Kraken Mare as well as the abundant organic chemicals it contains would be a priority. Since Titan is considered to be a very early and almost embryonic version of our planet, any knowledge gained could lead to clues of how life on Earth began.