Carried to altitude by balloon, the Tempest UAV with two wing mounted CICADA vehicles is released for flight to a ‘drop’ destination. Photo: Naval Research Laboratory |
The Naval Research Laboratory Vehicle Research Section has
successfully completed flight tests for the Autonomous Deployment Demonstration
(ADD) program. The final demonstration took place Sept. 1, 2011, at the Yuma
Proving Grounds, Yuma, Ariz., and consisted of a series of eight
balloon-drops at altitudes of up to 57,000 ft, delivering sensor-emplacement
Close-In Covert Autonomous Disposable Aircraft (CICADA) vehicles within 15 ft
of their intended landing locations.
The ADD concept is to enable small unmanned air vehicles
(UAV) equipped with sensor payloads to be launched from aircraft (manned or unmanned),
balloons, or precision-guided munitions, and dispersed in selectable patterns
around designated areas.
“The mission profile is straight forward,” says
Chris Bovais, aeronautical engineer and flight test coordinator, NRL Vehicle
Research Section. “The CICADA is dropped from another airborne platform,
flies to a single waypoint, and then enters an orbit. It descends in that orbit
until it reaches the ground.”
The NRL developed CICADA Mark III UAV is a glider; it has no
propulsion source onboard, therefore. It requires another airborne platform to
get it to an altitude such that it can glide to its destination. Its lack of a
motor and small size, make it nearly undetectable in flight.
The ADD field trials successfully demonstrate that the
CICADA can perform a precision delivery of a notional payload after being
dropped from a ‘mother-ship’ or being carried aloft by a balloon. Standoff
distances of 30 nautical miles and altitudes up to 57,000 ft were demonstrated,
with an average landing error of 15 ft from the commanded location.
During the demonstration, the UAV ensemble was lifted to
altitude using balloons operated by Aerostar International. A UASUSA built
Tempest UAV, with two CICADA vehicles attached on wing-mounted pylons, was
carried aloft to altitudes approaching 60,000 ft. The Tempest mother ship was
released from the balloon, autonomously executed a pull-up maneuver, and then
carried the two CICADAs to a drop location. Each CICADA vehicle was then
released from the mother ship and autonomously flew to the preprogrammed target
waypoint.
“Many remote sensors are currently hand emplaced,”
says Bovais. “The CICADA allows for the low-cost delivery of multiple
precision-located sensors without placing the warfighter in harm’s way.”
The CICADA Mark III is a unique vehicle. The airframe is
simply a printed circuit board also serving as the autopilot, the first known multi-purpose
airframe/avionics implementation of its kind. This novel construction method
significantly reduces assembly time, minimizes wiring requirements, and enables
the manufacture of low-cost and rugged micro air vehicles. The airframe shape
is easily scaled to accommodate various payload sizes and potential acoustic,
magnetic, chemical/biological, and SIGINT sensors. Unique to this construction
technique, additional electronic payloads can be inserted into the system by
updating the printed circuit board artwork and ‘re-winging’ the aircraft.
A custom autopilot for the CICADA, both hardware and
software, was developed by the Vehicle Research Section to be both inexpensive
and robust. The only flight sensors are a 5 Hz GPS receiver and a two-axis
gyroscope. Although having minimal sensors, the navigation solution and the
flight controller proved to be quite robust during in-flight testing, routinely
recovering from tumbling launches. The flight controller also included a custom
NRL algorithm that accurately estimated wind speed and magnitude, despite
having no air data sensors onboard.
