The US Naval Research Laboratory (NRL) has unveiled a revised configuration of its close-in covert autonomous disposable aircraft (Cicada) micro unmanned air vehicle, with development work now focused on a version optimised for carriage in 120mm mortar round. The new design is based on a flat octagonal wing rather than the folding wing design proposed when the programme was made public in August 2006.

A remotely operated test article based on the new airframe was flown in initial trials in July, the NRL says. The organisation displayed a 2.25% overscale windtunnel test article at the Association for Unmanned Vehicle Systems International Unmanned Systems North America exhibition in Washington from 7-9 August. The NRL says the changed configuration reflects a shift in development priority from an air-launched UAV to the artillery round configuration.


A single 120mm illumination round would be adapted to carry two Cicadas and dispense them once it enters the parachute floating phase of its flight profile. The UAVs would fall from the round and self-stabilise with the assistance of two flaps, with the octagonal wing expected to facilitate a glideslope of 4-5:1.

The wing is stamped out of sheet metal with twin stiffened fibreglass tails extending from the leading edge through to the trailing edge. A box-shaped payload bay, also made of sheet metal, is mounted between the two tail structures above the leading edge and extending to the centre of the wing. The wing area between the tails and behind the payload bay has been removed, allowing multiple airframes to be stacked in an alternating nose-to-tail pattern.

The initial Cicada design had a span of 210mm (8in) based on carriage and deployment of up to 9,800 UAVs from a standard US Air Force Sargent Fletcher stores pod as carried by a Lockheed Martin C-130 transport. The NRL says the mortar-launched version will be required to deal with shock forces of up to 10,000g/s, and that the air vehicle's guidance and sensor systems will use an epoxy compound to help protect them at launch.

Demonstration of the survivability of the UAV in an artillery launched profile is expected to directly benefit the later development of an air-launched version, it adds.

The NRL is two years into a five-year funded development phase for the Cicada, and the July test flights used a remotely operated demonstrator. The developmental autopilot system for the new design was also flown for the first time on a surrogate aircraft in early August, and current plans call for the two to be integrated and flown by October. This work will be followed within six months by a simultaneous test flight of four fully autonomous but non shock-hardened prototypes to be carried and launched from an aircraft to explore air vehicle characteristics including in-flight separation in a swarming deployment concept.

Other potential test scenarios include fitting the Cicada demonstrators with electronic support measures for use to localise a radar emitter, with prototype electronic warfare sensors having commenced testing last year.

Full shock testing of the Cicada's autopilot electronics and sensor boards is planned to take place in 2008, followed in 2009 by their actual launch inside a 120mm mortar round, although not fitted into an airframe. The NRL says that current project plans stop short of demonstrating a hardened UAV fully integrated within a 120mm mortar round, with this step being dependent on programme outcomes over the next two years.