Tag Archives: Aerospace

Of Honeybees and Helicopters

A trend that I’ve always found quite galling is the bantering about of “well-known facts” that are, in fact, complete myths — especially those that  skitter up against science for a moment before careening off into Cloud-Cuckoo Land.
Case in point: this particularly treacly bit of nonsense, intended as a Motivational Thought:

Gaaah! What nonsense!
Gaaah! What nonsense!

By the way, yes — it’s that Mary Kay, the MLM cosmetics queen who left behind a personal fortune of nearly $98 million, and whose personal motto was “God first, family second, career third.” But that is another rant for another day

Here is the real story, according to Cecil Adams at The Straight Dope:

“According to an account at physics.org, the story was initially circulated in German technical universities in the 1930s. Supposedly during dinner a biologist asked an aerodynamics expert about insect flight.The aerodynamicist did a few calculations and found that, according to the accepted theory of the day, bumblebees didn’t generate enough lift to fly.

“Hummeln nicht fliegen! Mein Gott!!!”

The biologist, delighted to have a chance to show up those arrogant SOBs in the hard sciences, promptly spread the story far and wide.

“Once he sobered up, however, the aerodynamicist surely realized what the problem was — a faulty analogy between bees and conventional fixed-wing aircraft. Bees’ wings are small relative to their bodies. If an airplane were built the same way, it’d never get off the ground. But bees aren’t like airplanes, they’re like helicopters. 

Kind of like this, but not really.
Kind of like this, but not really.

Their wings work on the same principle as helicopter blades — to be precise, ‘reverse-pitch semirotary helicopter blades,’ to quote one authority.A moving airfoil, whether it’s a helicopter blade or a bee wing, generates a lot more lift than a stationary one.”

The take-home lesson here is that there can be quite a difference between a real-life concept and its mathematical model — especially if the initial model doesn’t reflect the structural reality.

And now for your viewing pleasure, some really, really cute bees:

The Physics of Vertical Takeoff

No, this isn’t trick photography. This is a very good pilot at this year’s Farnborough Air Show, performing a vertical takeoff in Boeing’s new Dreamliner — roughly 225,000 kg taking off like a rocket.

But — isn’t it common knowledge that

vertical flight = stalls = crash?

Remember Colgan Air 3407?

So — what’s going on here?

What you’re seeing is a vertical flight path. Flying horizontally first, the airplane pitches up until the nose is pointing straight into the sky.

Rocket

You don’t need thrust for this. Even gliders can do it. What you’re seeing is  kinetic energy (speed of the plane on the runway)  converted to potential energy —  and accelerating 250 tons to nearly 200 miles per hour builds tremendous kinetic energy! With so much potential energy, vertical flight can be maintained for several seconds, until the aircraft runs out of speed and stops in midair.

In the video, I count about 6 seconds of vertical flight before the pilot drops the nose. 

In aerobatics, this maneuver is called a stall turn or a hammerhead stall.

hammerhead

Numbers: 

For a craft weighing x kg you need g*x Newtons of thrust, minimum, for sustained vertical flight. For each metric ton of weight you need around 9.81 kN of thrust. The Dreamliner has a operational empty weight of 225 tons, so it would need 2453 kN of thrust to sustain a vertical climb. Its 2 GEnx engines, each producing 330 kN, don’t provide nearly enough power. This is why it is necessary to pitch up to vertical while shedding speed — making this awe-inspiring manouever  possible without thrust.

Back in the Saddle Again

I’ve been away. I’m back. Poland was tremendous. Work is pressing, but then, I’m lucky to be doing original mathematics research with such great people.

For now, I just wanted to share this awe-inspiring (and quite large) infographic for those of us with our eyes turned towards the heavens:

The SLS is derived from proven technology used for decades in      America’s moon program and the space shuttle.

I had to pass this along because it’s going to be a reality in 3 short years: the vehicle that will be used for the next manned spaceflight. Did you know that no human has traveled beyond low-Earth orbit since Apollo 17, the final mission in NASA’s famed moon program, returned home in December 1972? 1972 — 42 years ago.
It’s time we both get back in the saddle.

Oh, did I mention, this is the kind of applied math that I plan to do? I want to work in aerospace research. I can’t think of a better job to have.