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Fly Like An Insect -

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Fly Like An Insect (04/03/2010)

TRANSCRIPT

NARRATION

History shows that for a human-powered machine to fly with flapping wings takes courage, clever
invention, and a sheer disregard for safety. But to build a machine that can fly like an insect
needs a complete rethink of aerodynamics. The wings of insects work in unique ways, unlike any
other flying animal.

Dr John Trueman

At one extreme you've got things like houseflies and they've got one pair of wings, it's rigidly
attached to the side of the body and they make it fly by a pair of muscles which pull from front to
back and the whole thorax just pings out, and that pinging mechanism makes the wings go down.

NARRATION

At the other end of the spectrum is the manoeuvrability and control of damselflies and dragonflies.

Dr John Trueman

Dragonflies use the big muscles that go from north to south, to actually power the wings. They
control each wing individually, they control each vein in each wing individually.

Mark Horstman

Now this may look a little like a dragonfly, and it does have four wings - but that's where the
similarity ends. In fact, the way it flies is unlike anything that you can find in nature.

Dr John Trueman

There's nothing like this. Nothing like this in the insect world with the wings one on top of the
other like that. You never get that.

NARRATION

While building an exact copy of an insect may still be beyond us, we can use the best ideas their
evolution has come up with. Locusts are the Boeing 747s of the insect world, able to fly
efficiently for long distances for days at a time. We can read their flight secrets from the smoke
patterns in this wind tunnel. They provide hard data to build a computer model - and that's the job
of aeronautical engineer John Young.

Dr John Young

One of the great things about doing flow dynamics, computational flow dynamics, is we can do things
we can't actually do in nature. So we can make some changes to the wings and see what effect they
have.

NARRATION

The simulations aim to capture every detail, right down to the veins in the wings.

Dr John Young

You can see all the wing folding, the veins here and the sort of corrugations in the rear wing and
you can see some slight curvature in the forewing.

NARRATION

The colour coding shows air pressure, blue for low pressure to red for high pressure. Simplifying
the complex wing into a flat plate shows a larger blue area, which means lower air pressure over
the wing.

Dr John Young

That generates a lot of lift, in fact more lift than the real insect. But the downside is it comes
at about twice the power requirement. So the efficiency of the animal has gone down by about 50 per
cent or more when you have this flat plate model.

NARRATION

That's crucial information to know if you want to use the locust as a model for a micro-flying
machine.

Dr John Young

We need to put all the details in, we need to put all these veins, all this folding, we need to
precisely control what the wing is doing.

NARRATION

The trick is how the wing changes shape.

Dr John Young

The locust is controlling the shape it needs to throughout the wing beat and it's not necessarily
doing that by thinking about it. It's doing it by passive mechanisms that are built into the wing,
with the elasticity of the wing elements in just the right size, just the right way, such that the
wing takes up the form it needs to in response to the airflow over it.

NARRATION

Other insects like hoverflies, moths, wasps and dragonflies are being studied to learn their tricks
- and build machines that mimic them.

Dr John Young

As you go to these smaller animals, smaller sizes or smaller speeds, the animal feels the air quite
differently to the way we feel the air. If I move my arm through the air there's not really much
resistance. But for a tiny little hoverfly, the airflow feels a lot thicker, a lot stickier. It's
almost a bit more like swimming or sculling than we would think of as flying. And so the
aerodynamics changes quite a bit.

NARRATION

That's why some researchers simulate airflow over insects by moving scaled-up wings through tanks
of oil. It all has to do with what's known in fluid mechanics as the Reynolds number - the ratio
between inertial forces and viscous forces, or in this case, the drag of the wing and the
stickiness of the air.

Dr John Young:

For a large aircraft, a passenger aircraft, the Reynolds number is very large, like a million. For
an insect like this, the Reynolds number might be a thousand or several hundred. And that means the
flow, the airflow seems maybe a thousand times stickier, maybe a thousand times more viscous for
the insect than it does for us or a large aircraft.

NARRATION

Decoding the secrets of aerodynamics at this tiny scale unlocks the potential for micro airborne
vehicles - and that's got the military's attention.

Dr John Young:

Anything that's useful for search and rescue, anything that can fly into a building, or peer
through a window, will also be very very useful for counter-insurgency and counter-terrorism work
as well. These vehicles are being built and particularly in the US with the Defense Advanced
Research Projects Agency (DARPA) they're quite well advanced.

NARRATION

And this is it - a remote controlled prototype that hovers with flapping wings, and weighs less
than ten grams - a bit more than a big dragonfly - while able to carry a tiny camera.

Dr John Young

I would say these would be in field trials within ten years. We look to build up I guess a range of
techniques, a bag of tricks if you like that we can apply and it could do something that any given
single insect may not be able to do but taken together it, there's the potential to do better than
nature.