JetQuad: Quad-Turbine VTOL Drone
Introducing the world's first smallest and most powerful jet-drone with vertical take-off and landing capabilities: AB4 JetQuad
Propulsion
Four identical Microturbines (small jet-engines) power the JetQuad. Each turbine generates 25 Horsepower and is about the size of a large soda can. The total power output of the drone at full throttle is 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. These turbines consume ordinary Diesel fuel and once ignited produce very consistent amounts of power for prolonged periods of time.
Parallel Engine Start
The JetQuad features an easy to read display terminal located right on the drone. The terminal displays engine status so that the operator knows when the drone is ready for flight. A similar interface is also built into the ground-station software on the tablet located on the remote control. All four engines start in parallel - this ensures that the drone is ready for flight as soon as possible. Check out the video below for an example start, throttle, shut-down sequence for all four turbines.
Control
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.
Payload
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.
Performance
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.
Airframe
The JetQuad is designed to be both light and very tough. Made from a combination of Carbon Fiber and Aluminum, we created a truly industrial drone that can withstand the harsh environments encountered across the world. There are no wings, air-foils nor blades exposed on the exterior of the drone. This means that the drone has higher resistance to impacts and adverse weather conditions.
FanQuad - JetQuad Electrical Simulator
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 consider 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.
Energy Density
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 than 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.
Power-to-Weight Ratio
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.
Potential Applications
The JetQuad drone has the potential to revolutionize a variety of industries. The key markets that could greatly benefit from the advantages of the JetQuad are: Medical, Maritime, and Construction.
Medical
JetQuad can provide ultra fast transportation of medicine or organs between hospitals in a metropolitan area, roof-top to roof-top. The drone can easily re-use the existing infrastructure of helicopter landing-pads.
Maritime
It is imperative to protect large ocean-crossing container vessels against shallow waters, adverse weather conditions and piracy. A JetQuad drone can be permanently stationed on the ship and provide 24-7 automated surveillance of the surroundings areas.
Construction
Need to lift a heavy bucket of cement to the top floor of a sky-scraper? Renting out a crane or a helicopter may be simply out of questions. A heavy-lift JetQuad may be easily leased for an hour, delivered on a back of a pick-up truck to get the job done.