This episode of Real Engineering is brought to you by Brilliant, a problem solving website
that teaches you to think like an engineer.
In the past few years there has been a lot of buzz around the possibility of drone delivery
services.
Most think companies like Amazon will be the first to deploy them in their distribution
centres, but few realize the technology is already in use for a far greater purpose in
the developing world.
More than two billion people across the world lack access to essential medical products,
like blood and vaccines, due to poor quality or even non-existent infrastructure.
Last month I visited Rwanda with Sam from Wendover Production and Joseph from Real Life
Lore.
We were all struck by how modern and clean Kigali, the nation's capital, was but just
a short drive outside the city the quality of roads deteriorated quickly.
The country has been working hard to improve their transportation links over the past 2
decades, but of the 14,000 kms of roads in Rwanda, only 2,600 kilometres are paved.
The rest consist of uneven dirt roads that become incredibly difficult, if not impossible
to navigate during the countries raining season.
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We got a taste of this while on Safari when our 4x4 got stuck in the mud, forcing us to
get out and push, keep in mind we were looking for lions on this trip.
Medical supplies, by nature, need to be on hand quickly.
If a mother is bleeding out during childbirth, she cannot afford to wait 3 hours for blood
to arrive.
Leaving people living in remote rural villages in danger.
Zipline, the real reason we visited Rwanda, is working to solve this problem with their
fleet of autonomous drones.
Each capable of carrying 1.6 kilograms of medical supplies, about the weight of a three
500 millilitre blood bags.
These amazing little drones have a TONNE of geeky engineering design that was influenced
by Zipline’s design philosophies.
Several unique factors influenced their designs.
The first is the speed the plane needs to get into the air.
The moment an order comes in, the clock has started and Zipline aims to have the drone
in the air in as short a time as possible.
This is, after all, an emergency and seconds count.
Currently they are averaging just 5 minutes from order to launch.
That’s the time it takes for an order to arrive in their on-site pharmacy to launch.
Getting a plane into the air that quickly is pretty astounding, some would struggle
just to get a drone out of its case and flying in that time, and Zipline have come up with
some amazing solutions to reduce those seconds.
Just like a DJI Drone, Zipline’s plane needs a GPS connection in order to fly as they are
not piloted, they are autonomous.
If you have ever flown a drone you know it can sometimes take a little while for the
drone to boot up and make a connection with a GPS satellite.
So, to remove that delay, Zipline moved the GPS circuitry from the plane to the battery.
This means it’s always on and always connected.
This innovation alone removed on average 10-15 minutes off the launch time.
The battery is one of 4 pieces of the plane that need to be assembled prior to flight.
First the order is placed inside the drop hatch of the fuselage, which is then placed
on the launcher, the wings are then attached followed by the battery.
This modular design makes the plane much easier to handle, allowing staff to easily lift it
into place.
More importantly, it separates components so if there is a problem found with the wings
during the pre-flight check, they are simply swapped out without having to start the entire
assembly process over again.
Pre-flight checks are often a lengthy process and Zipline have come up with some cool solutions
to hasten this step too.
Checking the flight surfaces is done with a mobile app that connects to the launcher
system.
The launch technicians simply point the phones camera at QR codes on each control surface,
sending a message to the plane to actuate the control surface.
The phone then utilizes a computer vision algorithm to make a pass or fail judgement
for each control surface.
Once the plane is ready and assembled on the launcher, the next time saving measure kicks
into gear.
Rather than telling you how this works, I’m just going to show you.
-Cut to launch footage.-
We spent 2 days at Zipline and this never got old.
The rail uses a pulley and an electric motor to quickly and safely get the drone up to
speed.
Accelerating the plane to its 100 kilometre per hour cruising speed in just 0.3 seconds.
It launches the same way every time and reliably clears the obstacles in front of it.
Take-off and landing are the most difficult stages of a flight.
To avoid having to land at the destination the plane simply drops the supplies in a insulated
cardboard box with a simply parachute, which can be thrown away.
Meaning the clinics need no infrastructure to sign up as a client of the distribution
centre.
When the plane does eventually need to land, the procedure to allow it to land with no
pilot is even more incredible.
Once again, I think it’s easier to just show you how it works.
Cut to footage - It may be difficult to keep track of everything
that happened there, so here is that again in slow motion.
There is a small hook at the end of the tail boom, which will grab a wire strung between
two actuated arms on either side of the capture system.
It’s hard to see it in real time, but in slo-motion to can clearly see that the arms
actually raise up at the last moment to catch the hook.
The plane is communicating its location in 3D space with the radio receivers next to
the platform, allowing the wire to stay out of the way until the last moment.
Minimising any risk of collision with the wire.
The capture system misses about 10% of the time, but the plane is programmed to immediately
detect a miss and throttle up it’s engines to gain altitude and make another pass.
An older design of this system, had a retractable tail hook that caught an actuated wire closer
to the ground, which then slowed the plane down enough for it to landed softly on an
inflatable pad.
This system was fraught with design issues.
When it rained the inflatable would pool with water, which was no problem for the water
proof plane, but forced the staff to crawl through it and lift a relatively heavy plane.
It was neither comfortable or ergonomic.
The retractable tail boom needed a motor to control the retraction, which could fail and
added weight compared to the simple metal hook attached to the carbon fibre tail boom
of the current generation plane.
Factoring safety into an autonomous drone network is another unique factor that has
shaped Zipline’s designs.
Zipline works on a philosophy of redundancy of parts in order to ensure safety.
It has two of everything.
Two motors, when it only uses one during flight.
Two of every actuator, and if somehow two of something breaks the plane will automatically
deploy a parachute.
Allowing it to softly touch back down to earth.
This procedure can also be initiated by the control tower if a command from the air space
authorities is received.
As a result of this focus on safety Zipline has had zero accidents causing injury since
they started service in October 2016.
The next design factor, which will be common to any aeronautical design.
Is the weight of the aircraft and in turn it’s range.
Zipline uses planes because quadcopters use far more energy to fly, and just can’t get
the range necessary from batteries and are relatively slow.
Map Animation: These planes cruise at 100 km/h with a range
of 160 kms, allowing the drone to serve an 80 km zone around this location.
The inner skeleton consists nearly entirely of a light weight carbon fibre composites,
which is then covered in a light weight foam shell which is easy and cheap to replace if
it gets damaged.
As a result, the entire fuselage weighs just 6.4 kilograms.
The wings weigh 2 kilograms with wing span of 3 metres.
The structurally integral wing spar, that is the beam that runs along the length of
a wing, is also made from a high strength carbon fibre composite.
With the aerodynamic surfaces being formed with high density polystyrene, and 3D printed
plastics.
The batteries are by far the heaviest part of the vehicle, making up half of the total
weight of the aircraft at 10 kilograms.
Zipline employed lithium ions batteries with a total capacity of 1.25 kwhs.
For comparison, a Nissan Leaf has 24 kWhs and your average Tesla has about 120.
As mentioned before, these removable sections aren’t just batteries.
They contain the GPS circuitry, but also include the data storage that hold the flight data
from all the sensors on board.
The moment the battery is hooked up to charge at this charging station, the data begins
to poor into Zipline’s server.
For every hour of flight these drones generate 1 gigabyte of data.
This for me, is Zipline’s greatest asset.
These drones don’t just face engineering challenges, but regulatory challenges too.
Fitting a large autonomous network of drones into the already busy and highly regulated
American airspace would be incredibly difficult.
Rwanda serves as not just a worthy cause, but a valuable test bed for integrating a
network of autonomous drones into a countries air traffic control.
Zipline communicates directly with Rwanda’s central air traffic control in the Kigali
Airport, in the nation’s capital.
Having this test bed, in my mind, is more valuable than any hardware technology Zipline
has developed.
Ryan Oksenhorn, one of Ziplines founders, gave us a guided tour when we arrived.
He’s Zipline’s head of software and has worked tirelessly to make Zipline’s autonomous
drone control system the best in existence.
A quick look through patents attributed to Ryan will uncover a slew of designs related
to automated drone management systems, like Patent 9997080 “Decentralized air traffic
management system for unmanned aerial vehicles”, which describes software solutions to allow
multiple UAVs, which have no way of detecting other UAVs in their airspace, to avoid collisions.
This testbed and data is going to allow Zipline to continue to churn out designs and concepts
to optimize the control of the drone delivery network, and ultimately allow them to expand
into new territories with busier airspaces.
This month they are expanding within Rwanda opening a second location to serve the east
of Rwanda.
This could eventually grow into a supply chain, allowing drones to hop between bases, get
their battery swapped out in a couple of minutes, and be on their way once again.
This technology is useful outside of just developing countries.
It could be used in disaster relief scenarios when roads become impassable due to flooding.
It also allows supplies to be centralized.
Hospitals often have to carry more medical supplies than they need.
Keeping stocks of medical supplies with short shelf lives inevitably leads to waste.
Incredibly expensive waste that costs the taxpayer money.
This is a problem Zipline could potentially reduce by allowing centralization of an emergency
supplies that can quickly be dispatched when needed.
When quarantines are an issue, these drones could minimize human exposure to contagious
diseases, and so help stop the spread of disease.
These are both scenarios that Wendover Productions and Real Life Lore explore in their videos
released today.
We could not have made this trip without the help of Brilliant, so if you would like to
see more videos like this please check them out.
If you have an interest in this kind of design, I would highly recommend you take this course
on classical mechanics, which will form the bedrock of understanding for you to start
applying physics, like figuring how much batteries to include for a drone design.
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things like automotive engineering and Python Coding.
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