The rugate filter employs a sinusoidal refractive index depth profile to produce high reflection in a narrow band of wavelengths. Fabrication relies on a continuously variable index of refraction in the wavelength regime of interest. The near IR refractive index of amorphous silicon-nitrogen films decreases continuously as the composition varies from pure silicon to stoichiometric silicon nitride (Si(3)N(4)). Ion implantation was found unsuitable as a fabrication method for rugate filters. Homogeneous and inhomogeneous films up to 5 microm in thickness have been produced by simultaneous deposition of electron beam evaporated silicon and of energetic nitrogen particles arising from an ion beam. The relative fluxes of beam and evaporant are found to determine the ratio of nitrogen to silicon in the films and therefore to determine the index. Single-band reflection filters of the rugate design of high peak optical density were fabricated under computer control using a quartz crystal oscillator shielded from the beam to monitor the silicon evaporation and three suppressed Faraday cups to monitor the ion beam current.

No abstract

No abstract

The availability of commercial single antenna GPS units at low cost and discontinuation of selective availability of the system has cased an increased interest in flying a stable fixed-wing aircraft using GPS alone. Utilizing such an inexpensive sensor, along with a relatively simple processor, a flight control and guidance system could be developed that would be so inexpensive as to be practically disposable even for some commercial applications. A flight control and guidance system that can operate on single antenna GPS measurements is also a candidate as an ultimate backup mode for any uninhabited air vehicle or piloted airplane given failures of sensors. In this paper, necessary hardware and software developments will be described, as well as particular solutions explored in a flight test program.

The CICADA (Close-in Covert Autonomous Disposable Aircraft) is a new and novel micro air vehicle design based on a monolithic circuit-board/structure. The CICADA is a glider which once dropped from a host vehicle will automatically fly to a preprogrammed recovery waypoint. A key design goal for the guidance and control system was to enable the CICADA to recover from a wide range of initial launch conditions and altitudes. Recording temperature and wind profile data during the decent was also a design objective. This paper will describe the navigation, guidance, flight control, and environmental control developed for this simple yet capable aircraft. Flight test data will be presented showing the performance of the CICADA vehicle from a drop of over 29,000 feet in altitude.

No abstract

The Naval Research Laboratory (NRL) Vehicle Research Section (VRS) has developed an expendable Micro Air Vehicle (MAV) called CICADA (Close In Covert Autonomous Delivery Aircraft) for missions such as payload delivery, meteorology, or electronic warfare. The design concept is an inexpensive, high packing density, flyable sensor node that can be deployed en-masse to quickly seed an area with networked sensors. Four design iterations of the airframe explore the concepts of high packing density configurations and unique PC-board avionics and flight structures. The development culminated with flights dropping CICADAs from a mother-ship carried aloft by a weather-balloon. Over 100 flights of the vehicles were performed and three flights took the ensemble to above 50,000 ft and back.

No abstract