First of all I would like to thank Airbus and Local Motors for creating this competition. I enjoy challenges and this one is definitely fun and challenging! It also provides a great learning experience for everyone around the world. Thank you!
Kind regards, Gary Lai
Brief Design Description
The purpose of this drone is to deliver medical or emergency supplies to far and/or remote regions of the planet where terrain is difficult. The drone must satisfy the following constraints and requirements:
1. Modular – must be able to adapt to different job scenarios. I have made several other design modifications based on this drone. It may be possible to modify this for long range (lacking VTOL) This has been one of my first priorities when design this drone. Also wing components can be taken apart for ship-ability.
2. Cost – Design of drone must be easy to produce and manufacture, as well as easy to replace parts and repair.
3. Ease of handling – The drone must be less than 4 metres in length and less than 5 metres in wingspan.
4. Weight–drone including all equipment (but excluding payload) is <20kg
5. Fail safe components – all push and lift electric motors are fixed, to minimize failure of electronics. Flight termination launcher and parachute are included in design.
6. Cruise speed-at least 80km/h – a powerful motor will provide the necessary thrust for this drone. Weight of the 8 lift motors and batteries limit the speed significantly.
7. 8 Lift motors have been considered to provide the necessary power to lift weight + payload. If weight savings allow, 8 lift motors would be much more advantageous and in the event a 1 lift motor fails, the other one will provide some stability and emergency landing.
General Inspiration for Design:
This current design has been inspired by aircraft such as the Saab J21-R I made numerous design brainstorms, trying to figure out a design which will glide, as well as have VTOL ability. You can see some of my rough sketches below.
· Manta ray/sting ray – animals that glide over water gracefully
· Stealth bomber – gliding ability and quiet
· Exploring Numerous delta wing aircraft types – Tailed delta, canard delta, forward swept wing, variable sweep wing variants
· Saab J21-R/Eurofighter Typhoon/F-16 fighter aircraft
· Hand gliders that allow a person to glide over large distances
· Concorde aircraft
Explanation of Design Details-
Fuselage is shaped similar to a torpedo to minimize drag. ‘flat Cylindrical’ or ‘double bubble’ design as mentioned in the design briefs and may ‘rest’ on the ground given 4 landing fins. Fixed landing gear/wheels may be added if weight allows. (see Design Study 1 jpg)
Wings have cambered airfoil to generate lift during cruise mode.
Wings may be taken apart and replaced with different wing types for different scenarios/situations. The wing span is total length of 4.5 metres, which means when taken apart, the wing should be less than 2 metres (excluding fuselage) when taken apart for ease of transport. (See Exploded View jpg)
Pure delta wings suffer from some undesirable characteristics, notably flow separation at high angles of attack (swept wings have similar problems), and high drag at low altitudes. Tip of delta wing has been cropped and a tailed delta design has been used to overcome some of these problems.
Drone weight is heavy but will be able to achieve minimum cruise speed of 22m/s. For this particular drone design, it allows: distance flight (60km)+ minimum cruise speed of 80km/h + VTOL take off + 5kg payload OR 100km + 3kg payload -whilst keeping an aerodynamic package.
Motors are encased in sleek ‘package’ to reduce drag during cruise mode.
In cruise mode, drone will fly similar to a tailed aircraft –like a Saab J21 airplane.(see cruise variant.jpg)
Safety-Exposed propellers may pose a danger to the drone itself(hitting a concrete wall, solid objects etc ) or endanger nearby people. I have considered adding propeller guards like the Parrot Drone,(for the for lift motor blades) if weight savings allow. Otherwise there will be no guards to reduce the weight of the entire vehicle.
Landing gear- Similarly, wheels and fixed landing gear have been considered, but have been left out to reduce weight. May be constructed from lightweight plastics.
Weight-lift motors and batteries take up significant weight of the entire vehicle.
Wings-the wing may be constructed with plastic film / membrane (similar to a human hand glider) to decrease weight. Otherwise Carbon fibre shall be used for maximum durability.
Fail Safe components– Fuselage is round (for aero dynamic efficiency) and fuselage/tail is made of Carbon Fibre composites to with stand rain/hail/sandstorms
Camera compartment -Shall be made of plastic rather than glass. (to reduce weight)
Water-proofness- Cargo bays are not airtight. Camera module is protected by gorilla glass if weight allows, otherwise the dome is plastic and preferably be airtight. (see Design Study 2 jpg)
Ideally, I had the vision of creating a water proof / ocean floating drone, so it could be retrieved easily, however this was not possible given the cargo bay design.
Battery compartments should be airtight, if the drone lands on water to prevent short circuits (and even perhaps able to take off from water!)
Cargo payload should be made from cardboard and harnessed onto the drone to prevent accidental ejection. Other than this, the drone will be able to withstand most punishment from most weather conditions with the exception of hurricanes.
Cargo Bay-the bay shall be opened and closed via the carbon lid, fastened using Velcro using the plastic buckles/loops. (see Cargo Bay design jpg)
Cargo Bay only opens on one side.
The lid will also have 2 ‘teeth’ to help secure and prevent lid from moving during flight.
The box itself will be at the dimensions as requested in the design brief. It will also be made out of cardboard to save weight.
Having the VTOL certainly hampers the aerodynamic efficiency for long range flight, however since this is a 1 way trip flight considerations have been made to make the drone as light weight and ‘small’ as possible.
If this vehicle is to be made with carbon fibre, if it is hot and humid, this will definitely affect the properties of carbon fibre composites, but as weight saving is a priority, CFC must be used for the fuselage and wings. Otherwise wings could be made of plastic membrane like gliders.
Contains parachute and necessary equipment as required by design brief.
Modular nature allows ease of reconstruction and transportation.
Drone structure has been modified slightly by adding a carbon fibre 'skeleton' with multiple panels latched on.
The cargo box is not only accessible from the bottom, it may be accessed by removing the bottom panel.
The carbon fibre ribs to help strengthen the fuselage and hold the equipment are exposed (which kind of makes the design cooler in my opinion)
The front plastic dome is there to protect the camera from the weather (snow/rain) but is not water proof so try not to crash land on water!
Charles Hugentobler, Cambridge University-for engineering advice and opinion
Mike Juang, NYU - for kind words and helpful advice
My family - for general encouragement