Aerospace, Military and Defence
Drones pioneered for hover-in-place communications and surveillance applications
Vicor explains how its Ultra-High-Voltage (UHV) BCMs are enabling a power-dense, thermally-adept power system for high-voltage power conversion from tether to drone
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ixed-wing, airplane-style drones have been the standard in the skies for many years, widely used for military applications where unmanned flight is advantageous, particularly for long-duration missions. But while fixed-wing drones offer the ability to traverse airspace at high speed, they aren’t equipped for applications requiring stationary aerial flight, which is especially important for persistent airborne surveillance and communication relays.
Early experimentation with tethered, unmanned blimps revealed their relative inability to remain stationary in high-wind conditions. A new approach to unmanned aircraft systems (UAS) was needed, and Dragonfly Pictures, Inc. (DPI) developed a new class of drone, the hover-in-place tethered drone.
Unlike battery powered multirotor drones which require battery changes every 20 minutes, tethered drones receive their power through an electrical cord connected to a base station. This enables them to stay aloft for hours, even days. DPI’s tethered multirotor drones are designed to track and follow mobile host platforms including ships, boats, trucks and other unmanned surface and ground vehicles. They offer several benefits over fixed-wing drones, including vertical takeoff and landing capabilities. There is no runway, launcher or recovery equipment required. Unlike a blimp, they also offer the ability to achieve persistent, stationary positioning – even during turbulent weather and fast-changing wind speeds.
Tested extensively in real-world operating conditions, DPI tethered drones are currently being qualified for use by the U.S. Navy in marine and maritime environments for intelligence, surveillance, reconnaissance (ISR), communications and video applications. They are commonly employed
14 March 2022
stationary positioning under severe maritime storm conditions. This challenge is often compounded by turbulent waters impacting the positioning of the host vessel. Therefore, the drone requires the power capacity and agility to accelerate rotor speeds for lift and yaw in short or prolonged bursts as needed to maintain their altitude – with instantaneous responsiveness. Within the drone, the high-voltage conversion must be achieved in the smallest possible footprint and lightweight profile. The eight independent rotors onboard require sophisticated, interconnected PCB circuitry, so any space savings enabled at the power component layer can be repurposed for other value-add components.
DPI tethered multirotor drones are designed to track and follow mobile host platforms including ships, boats, trucks and other unmanned surface and ground vehicles.
as mobile masts or “instant towers” to support RF-based communications over long distances to unmanned vessels monitoring for security threats.
Overcoming extreme design challenges
The DPI military and industrial-grade Unmanned Multirotor Aerial Relay (UMAR) tethered multirotor drone is weatherproofed for rain, snow, dust and heat, and has been fortified for saltwater marine environments. The system has been designed to withstand harsh temperatures from zero to 120 degrees Fahrenheit.
These drones are especially beneficial in that they can provide 400+ hours of nonstop uptime and operations – at up to 500 feet altitude – because of continuous power through the tether. But there are significant design challenges inherent to the tethered architecture. The power needs to be delivered from the host vessel to the drone at high voltage and low current to enable the use of the thinnest and lightest possible tether,
Components in Electronics
which in turn enables greater drone mobility and larger airborne payloads. Operating at power levels from 8 to 10kW, the UMAR is extremely powerful and ruggedized to maintain persistent
“Using Vicor power modules we have been able to lower the weight of all the components onboard the drone to increase altitude and airspeed while carrying the required mission payload,” said Joe Pawelczyk, vice president of operations at DPI. “Nobody else really has the power
Dragonfly UMAR drones can provide 400+ hours of nonstop uptime and operations – at up to 500 feet altitude – because of continuous power through the tether.
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