NASA 'aerobot' to float on Titan

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Autonomous blimp could explore Saturn's giant moon

NASA's Dryden research centre is hoping to follow up the Cassini-Huygens mission to Saturn with a mission to one of its moons, Titan, in the 2010-2015 timeframe. The mission would explore the giant moon using an autonomous blimp.

Dryden researchers have been exploring concepts for a self-inflating "aerobot" that would self-deploy from an aeroshell atmospheric-entry vehicle 7km (4 miles) above Titan's surface. The blimp would be required to extract itself from the aeroshell, then inflate and achieve stable flight in just a few seconds.

A half-scale aerobot demonstrator has been built and has been undergoing testing at the Edwards AFB test complex in California for the past year. The demonstrator uses a helium-filled airbag and two electric-driven propellers to manoeuvre.

Dryden researchers are anxiously awaiting data on the composition of Titan's atmosphere from the Huygens probe when it lands on the moon in December before they can determine more details of the aerobot design. The Huygens data will provide guidance on atmospheric density, which is already expected to be greater than that of the Earth, potentially allowing the use of methane or nitrogen to fill the aerobot gasbag. Hydrogen is also being considered.

The Titan aerobot would carry two 1m (3ft) propellers, with electric power supplied from a radioisotope thermal generator. The power source is expected to provide sufficient reserves to enable medium- to high-altitude exploration for between six and 12 months.

Dryden researchers say the craft would require sufficient autonomy to allow it to maintain stable flight and perform exploration functions for more than three days at a time without human operator involvement. The three-day target is mandated by the time it takes for Titan to pass behind Saturn in its normal orbit, with that blackout preventing any contact with mission control operators on Earth.

The aerobot could piggy-back a ride to the outer solar system on one of several different missions being explored by NASA, including the planned Jupiter Icy Moons Orbiter.

PETER LA FRANCHI / EDWARDS AFB