AB4 JetQuad: Quad-Turbine VTOL Drone
Four identical Microturbines (small jet-engines) power the JetQuad. Each turbine generates 25 Horsepower of raw jet-power for a combined power output of 100 Horsepower. This is a significant amount of power considering the fact the drone is just under 2-feet in diameter and is about 2-feet tall. The turbines consume ordinary Diesel fuel, readily available anywhere in the world.
The drone utilizes four proprietary Thrust Vector Systems (TVS). A centralized Flight Control Computer fuses data from a multitude of sensors which include GPS, Lasers, Gyroscopes, Accelerometers, and Cameras. Advanced algorithms built-in to the computer control the four TVS and four engines. A companion-computer provides Guidance and Obstacle Avoidance.
The JetQuad can lift payloads up to 30lb in weight. The user may mount the payload in a variety of locations: on-top, beneath, on the side, or in front of the drone. Furthermore, the payload can contain additional fuel tanks, robotics arms, sensor kits, or delivery packages. The microturbines of the drone generate a total of 100 Watts of power. The payload system has access to this power and can use it throughout the entire flight.
With a 30lb payload, the drone has an endurance of 8 minutes. However, the jet-engines allow the drone to reach a top-speed of 300mph at an altitude of 500ft (FAA Regulations). Consequently, in 8-minutes, the drone can easily cover a maximum 40-mile distance. Further development of engines and prototype will greatly increase this performance. In addition, the lack of wings, air-foils, and control surfaces means the drone is very stable in adverse weather conditions. Finally, the drone can operate at very high altitudes (up to 2-miles) thanks to the high compression of the turbines.
It is no easy task to test a jet-powered VTOL drone. For this reason, FusionFlight built a custom test-stand with tether attachments and ceramic surfaces. This allows us to test the take-off and landing characteristics of the drone in a safe and controlled manner. In addition, we constructed a rig we call the "Flip-Jig". The test operator uses the Flip-Jig to rotate the drone into a horizontal orientation for engine ignition. Once all engines start, the operator will flip the drone back to its upright position and commence the tests. Below is a photo of the drone on the Flip-Jig during a normal start procedure.
Control System Development
When we throttle up a turbine we encounter a phenomenon called "turbo-lag". This is the amount of time it takes the turbine to spin-up to whatever RPM value we demand. Consequently, this greatly diminishes the response time of the engine. As a result, it is very difficult to program an adequate control system to allow for stable flight. The control system must take into account the slow response of the turbines and the high-response of the Thrust Vector Systems. Before doing any tests with the jet-powered drone, we built an Electrical Simulator (called FanQuad). It is a small-scale version of the JetQuad, and instead of Jet-Engines, it is powered by Electrical Ducted Fans (EDF). The FanQuad has greatly helped us tackle the control system issues. Regard the video below for a field-test of the FanQuad Electrical Simulator.
How does the JetQuad outperform conventional electrical drones?
To answer this question, let us familiarize the reader with two important physical concepts - Energy Density and Power-to-Weight Ratio. Thanks to the use of Diesel, as opposed to Lithium-based batteries, JetQuad has a higher Energy Density when compared to an electrical Multicopter of similar weight. Furthermore, the JetQuad has a very high power-to-weight ratio because the jet-engines are turbine-based.
The energy density measures Energy storage in a unit mass. It has units of MJ/kg. JetQuad uses Diesel fuel which has Energy density of 40MJ/kg. Electrical drones use solid Lithium-based batteries which at most, have an energy density of 1MJ/kg. This means that for the same on-board mass of fuel (or battery) storage, the JetQuad stores 40 times more energy then the equivalent electrical Drone. Of course, jet-engines are heavier then electrical motors. However, they have much higher power-to-weight ratio so this penalty is insignificant. The US Department of Energy (DOE) has recently initiated a 5-year research to develop the next-generation battery technology. DOE targets to achieve energy density of 3MJ/kg energy density. This is still 1/10 of the energy-density of Diesel. As a result, the JetQuad will remain competitive for many years to come.
The power-to-weight ratio determines how much power a given engine outputs for a given mass of that engine. Electrical drones have a large penalty in this regard. The Brushless electrical motor, on its own, has a very large Power-to-weight ratio. But, when added with the weight of propeller, Electronic Speed Controllers, and Batteries, this ratio is greatly decreased. Turbine-based engines, like jet-engines, do not suffer from this problem. More specifically, the JetQuad uses Microturbines - small jet-engines that can run at 150,000RPM. This is an ultra high rotation rate and leads to vast amounts of power produced from a small engine. In addition, electrical drones must limit current flow to prevent overheating of electronics that support smooth motor operation. In contrast, fuel flow-rate is the limiting factor for turbine-based engines. It gives, jet-engine designers the flexibility to extract much more power from smaller motors.
JetQuad: Changing the Game of Drones Forever!
The Drone Market is hot and fast evolving. FusionFlight would like to be on the forefront of this market. Once the appropriate regulations are in place, we will supply the fastest and most powerful jet-engine powered drones to the world. With incredible range and payload capacity, the JetQuad drone has the potential to greatly support a variety of markets. These markets include Package Delivery, Military Surveillance, Fast Medical Response, just to name a few. To find out more about FusionFlight and the team, head on over to the Company Information Page.
We have been developing the JetQuad for several years now and have gone through many different prototypes. Check out one of our first prototypes below.