flights of fancy

A couple of weeks ago -- May 14, to be exact -- a Swiss man named Yves Rossy (a.k.a., "Fusion Man") made headlines (and secured a little piece of history) when he strapped on an 8-foot jet-powered wing and leaped from an airplane, soaring over the Alps. Rossy spent years developing his device, and successfully flew the first jet-powered wing in November 2006. There's been a smattering of R&D on jet packs to propel human beings dating as far back as World War II; Rossy's invention is the first to combine a jet pack with actual wings.

It's been a big month for would-be aviators. In April, another Swiss man -- what is it with the Swiss these days? -- jumped from a hovering helicopter and floated to earth using a pyramid-shaped parachute he built himself, based on a design by Leonardo da Vinci. Olivier Vietti-Teppa found the specifications in a da Vinci text dating back to 1485: four equilateral triangles, seven meters on each side, that Vietti-Teppi made from modern parachute fabric, using a square of mosquito netting at the base of the pyramid. Furthermore, later this year, Red Bull will hold three "flugtag" competitions in the US -- Tampa Bay, FL, in July, Portland, OR, in August, and Chicago in September -- whereby aspiring aviators build their own flying machines and then push them off a 30-foot platform (deliberately built over water) to see how far -- or if -- they can fly. Most drop like a stone into the water, but generally, a good time is had by all. And some of the whimsical designs can be a lot of fun; there have been machines shaped like Homer Simpson, a pimped-out Cadillac, a giant Oompah-Loompah, and even a big red lobster named Larry. (For those not inclined to build their own machines, there's now an online game.)

Almost as long as mankind has been sentient, I'd wager we've been trying to find some means to fly, with more than a few casualties along the way. My personal favorite historical aspiring aviator was Eilmer of Malmesbury, a medieval monk who jumped off the 150-foot rooftop of his Malmesbury, England, abbey in 1010 wearing a pair of crudely fashioned wings he'd put together from willow wood and cloth. All things considered, Eilmer didn't do too badly: he glided a good 600 feet before crash-landing near the river Avon. True, he broke both his legs, but for those brief moments, he must have felt like the king of the world. About a century later, a Constantinople man tried a similar stunt with wings made from fabric and wasn't quite so lucky: he jumped form atop a high tower and was killed. Perhaps the most memorable design was that of a French locksmith who built winds modeled on the webbed feet of the duck. His design didn't meet with much success.

There used to be an amusing, very quirky BBC radio program (several episodes were later adapted for BBC Television) -- "Is there any other kind?" Jen-Luc Piquant murmurs -- called People Like Us which featured a tongue-in-cheek interview with a fictional airline pilot, who is asked how his plane manages to stay in the air. The interviewer, like most of us, took physics and was interested in flight, but complains there was just too much theory, so he lost interest. "Well, theory is why it stays up!" the pilot snaps back. "If you took away, the theory, even for a moment, it would just plummet like a stone!" But the fictional pilot got the physics right, at least the sound-bite version: "Basically, it's all to do with pressure differences between the top and the bottom of the wing."

I'm going to annoy aerodynamic theorists here and bring up the Bernoulli principle -- it's a simplified explanation of how airplanes stay in the air, but we'll leave the bickering over the details to the experts, shall we? Besides, it gives me a chance to show this snazzy image drawn by Daniel Bernoulli himself, an 18th century Swiss physician who loved math but went into medicine at the insistence of his father. His pivotal insight occurred when he punctured the wall of a pipe filled with fluid with a small straw and noticed that the fluid rose up the straw -- also, how high it rose depended on the fluid's pressure in the pipe. The higher the pressure, the higher it would rise, just like your standard tire gauge.

Soon physicians all over Europe were annoying their patients by sticking glass tubes into their arteries to measure blood pressure. But Bernoulli went one step further and realized that per Isaac Newton's laws of motion, a moving body exchanges kinetic energy for potential energy as it gains height, and the same holds true of a moving fluid, like air: it exchanges its kinetic energy for pressure. So Bernoulli principle is this: the pressure of any fluid decreases when the speed of the fluid flow increases. High-speed flow is linked to low pressure and low-speed flow to high pressure. And an airplane can fly because it's wings are designed to create an area of fast-moving (low pressure) air above the surface of the wing, buoyed by the higher pressure air underneath the wing, producing "lift." It's a bit more complicated than that once you figure in drag, thrust, the weight of the aircraft and so forth, but that's the basic underlying principle.

Obviously, all those losing flugtag projects failed to achieve aerodynamic lift. But the physics of freefall is frankly just as interesting, and (for the fall-ee) can be even more exhilarating if done under controlled conditions. The Six Flags theme park in New Jersey has a terrific ride designed to put you into freefall. You're strapped into a body harness, then lifted to the top of a very tall tower structure. The best part: you get to pull the release yourself, which sends you hurtling down toward the ground at faster and faster speeds. Before you hit terminal velocity and/or go splat, the rope catches and swings you out in a lovely arc, where you can see out over the entire park. I did this several years ago, and frankly, it was quite the rush. Loads of fun! I did not, alas, have the foresight to order a video of my brief adventure in freefall (or possibly, the funds), but here's a grainy YouTube video of two guys taking the same "ride."

There are freefall rides at amusement parks all around the world, including one at Disneyland (or perhaps it's the California theme park adjacent to it) that mimics an out-of-control plummeting elevator, and another called the Hell Drop in England's London Dungeon intended to imitate what it's like to be hung -- dropped suddenly from a height. (I just visited the London Dungeon last week, but alas, the ride was out of order. Another time. There's plenty else in that particular "tour" to keep one amply entertained.) Or you can opt for an even less controlled environment and try bungee jumping. Or skydiving. It's probably one of the easier things to simulate, since a freely falling object is doing nothing except moving under the influence of gravity alone, with no other energy sources contributing to that motion.

When you're strapped in that harness at the Six Flags featured ride, and the mechanism starts to lift you, your potential energy is increasing along with your altitude. All that potential energy converts into kinetic energy as you fall after the "release," so you fall faster and faster until you hit terminal velocity. Unless you hit the ground before that point, in which case, it's best to have some survival tips on hand to increase your chances of survival. My favorite bit of wisdom from author David Carkeet: "Don't let negative thinking ruin your descent."

Should you happen, say, to fall out of an exploded jetliner -- just like Vesna Vulovic, a flight attendant, did in 1972 -- and plummet 33,000 feet, you'll have a good amount of time to reflect on things as you fall. Far better to focus less on your almost certain demise, and on more pleasant thoughts. I suggest reflecting (even reciting!) this poem by occasional guest blogger (and personal stylist to Jen-Luc Piquant, i.e., she creates the avatar "looks") Lee Kottner, called "On the Fringes, Falling Up."

I am untethered here, solitary. ...

No earth hugs my knees like children;
no tug on my limbs but
my own sinews, muscles,
neurons.

I stand on aurorae with my back to oases
not green but other spectral colors,
blue Spica, orange Arcturus, yellow Procyon,
white Altair,
with a waste black as volcanic sand
between.

The air's envelope blues as I view it:
haloed Tibet
so close to nothing,
where snow falls like meteors,
fast, trailing vapor,
the air too thin to hiss:
or grows in layers like shed pelts
left as clouds scratch against peaks.

From this vantage, this pedestal,
this lookout, this exile
on the fringes,
old air sulfurous with smelting steel
clears --

My Roman 'chute skids on the orbiting wind,
half-open, half candle.

Copyright 1985, Lee Kottner. Reprinted with permission.

 

 

Comments

[arby]

Neat. But a question from a hydraulic ninny: Is the left vertical tube in the Bernoulli illustration pulling water up? If so, what is that space between 'r' and 't'? Indicating negative pressure? Suckage? If not, what is it doing, and why? Fun article, thanks. rb

[gg]

As long as we're talking about crazy freefalls, I should mention that one Michael Fournier is attempting a world-freefall height record within the next day or so. It was supposed to happen today (the 25th), but didn't for some as yet unmentioned reason. The official website for the jump is here.

[gg]

Whoops, lost the html. Try:

http://www.legrandsaut.org/index.php?Message=main&lang=eng

[eingram]

That must be a masterful poem because I didn't understand it.

[roger]

"And an airplane can fly because it's wings are designed to create an area of fast-moving (low pressure) air above the surface of the wing, buoyed by the higher pressure air underneath the wing, producing "lift"."

This is false and is known as The Equal Transit Time fallacy. I'm sure the Blue Angels would love to hear that they cannot fly inverted...

I feel better now!

ref: http://en.wikipedia.org/wiki/List_of_works_with_the_equal_transit-time_fallacy

[Dave]

How can you mention free-falls and parachute jumps without mentioning Joe Kittinger? :-)

http://en.wikipedia.org/wiki/Joe_Kittinger
http://www.balloonlife.com/publications/balloon_life/9510/balloonm.htm

Also, Yves Rossy may not be the first jet powered human. A few years ago, there was a Norwegian who used ankle mounted jet engines with a soft wing.

Dave

[Fred Cunningham]

A more complete explanation of how airplanes fly can be found at http://www.allstar.fiu.edu/AERO/airflylvl3.htm

The Bernoulli effect is vastly overrated.

[Stephanie C]

Others have already commented on this, but I'd just like to point folks to my own blog entry on this commonly held myth about why airplanes fly: http://sciencegeekgirl.wordpress.com/2008/04/18/myth-5-how-do-airplanes-fly/