If Darth Vader hadn’t lost his right hand, he could stick it out the window just like we did as kids did while our parents drove. While you probably didn’t realize it, you were tactilly experimenting with the same things that allow Luke and Darth to dog fight (like fathers and sons eventually fist fight over power).
As a science fiction author, I spend a lot of time with, not my hand out the window, but my face. Yes, just like Yappy the dog. While my wife is at the wheel, I’m enjoying 70pmh wind shooting up my snout and I’m thinking, “How can space craft do all those nifty maneuvers when there’s no air in space?”
I got to noodling and here’s what I’ve come up with.
In my previous blogs, you learned that clouds weigh zillions of pounds, and air also weighs a lot too. Once I pointed out how quantifying large volumes of the stuff, your mind was probably quite blown. If not, it will be after this blog.
First, a bit on how planes fly.
Remember how you felt when you stuck your paw out the car window? You tilt your hand upward, and the air pushes your hand up. You tilt your hand downward, and the air pushes your hand down. But keep in mind, it’s not the “wind” pushing your hand up or down. On a still summer day (really, who would do this in winter), when there is no wind, it’s the forward movement of your hand through stationary air that makes it feel like wind.
Now, think about standing in waist deep water. You swoosh your arms around, your hand making a wave in front of it, you splash your friends in the face, ha ha, very funny. But then you notice a little valley in the water behind your hand. Cool! You then play like that for hours and hours until you discover girls (or boys, or comics).
If you’ve ever ridden in a power boat, you see a huge valley, or trough, in the water behind the boat. The hull of the boat has pushed the water out of the way, and the water hasn’t yet had time to fill in. When it does so, from the bottom and each side, it crashes together creating a magical ‘mound’ of roiling water that follows the boat. That trough has zero water pressure, cuz there’s no water since it was pushed away.
Now, because of that dang fooling around with your hand out the window, you always picture an airplane’s wing exactly the same. When you fly in one, you look out the window and – admit it, you recall your dabbling in aerodynamics and feel brilliant. But this time, think of the plane rushing past you. The wing cuts through stationary air, and while the bottom of the wing pushes the air down, conversely forcing the wing up. Also, just like that trough behind the boat, the air that is pushed upward leaves a similar trough above the wing with little air pressure, effectively pulling the wing upward. Weird, I know. Together these form what is known as “lift”.
Now, lift, and thrust, and drag and bird strikes, and aerodynamical shapes, and flight attendants who only take credit cards, and blah, blah, blah. Look, here’s a link that gives you all the gory details by Chris Woodward.
Let me get to the secret that is overlooked. Collision!
Your hand goes up and down, planes fly fat tourists to Europe, all because of collision.
Little bitty molecules of air collide with the little bitty molecules of the plane’s wing. Just like billiard balls on a pool table, when you knock them together, they each bounce off in different directions. Energy is transferred between moving and stationary objects. I got this from Newton’s Law of Billiards for Dummies. It’s easier to understand the magic when you think of, not little bitty air molecules, but floating billiard balls. The wing cuts through a zillion of those, hitting the surface, bouncing off, and forcing the wing up. Okay, well enough.
Let’s think for a moment about density of air. Starting at sea level, the number of air molecules in a given cubic dimension decreases around 3% for each thousand feet you climb in elevation. By the time you’re officially allowed to use your laptops (bong bong) at 10,000 feet, the density of air is down to 70% of what it was at sea level. Interestingly, the percentages of the air we breathe remain consistent, which is 78% nitrogen, 21% oxygen, 0.93% argon, 0.039% carbon dioxide (look how teensy weensy CO2 is!). As you go higher in elevation, the ratio remains the same, but there’s just fewer molecules. Here’s a nifty site to calculate all this.
When you reach cruising altitude, around 35,000 ft. the number of molecules is down to 26% of that at sea level. The Lockheed SR-71 BlackBird spy plane flew as high as 85,000 ft… at a whopping 2% of the air molecules of sea level.
How could these planes keep flying with such small amounts of air molecules. The answer… velocity!
A 747 takes off at roughly 190mph when air density is at optimum. At cruising altitude, it’s chugging along at 560-ish mph. Gotta go a lot faster to get the fewer air molecules to do the heavy lifting. Our friendly little spy plane revs it up to 2,200 mph.
Now, the space shuttle of late did NOT fly through space. It simply orbited Earth at 17,500 mph (although it’s really drifting). Even at that velocity, those wings were useless, orbiting in the neighborhood of 300 miles up. However, when it started falling to Earth, those little bitty molecules would strike the wings at 17,000 mph, it came at it so fast and furious that the friction (collisions) would heat up the shuttle’s surface. So much so that the engineers had to create specialized tiles to withstand the 3000 degree heat. Mmm… toasty!
We were all taught in high school science (maybe sooner) that space is a vacuum. However, it really is not. It has all kinds of microscopic particles, dust, sand, rocks, asteroids, and so on. Did you know that 80 million pounds of space dust and debris fall to the Earth every year?
Well, it’s safe to assume that there are molecules of gases in that mix as well. Heard of a comet? They blaze through the universe at tremendous speeds and create all kinds of heat and light as they collide with particles of something or other! They’re zooming up to a million miles per hour. Nebulas, anyone? Vast expanses of gases and dust that will some day create a new star and planets.
The reality is, space is filled with lots of stuff with which Luke Skywalker’s nimble X-Wing Starfighter can collide with to allow the flaps and ailerons to make the craft turn, spiral, and do flippy-dos. Just hope it’s not the size of a billiard ball.
The next trick is getting the velocity to have enough molecules to bounce off the wings. Answer, George Lucas engines! But that’s for another day…
John Murphy is the author of Mission Veritas…Candidates for an elite fighting force must qualify on a planet of truth.
Killian must hide his past as a ruthless rebel fighter at the risk of imprisionment.