Story by Vinny Chirayil.
Images sourced from internet. Copyright belongs to their respective owners.
Definition : For lifeforms or objects heavier than air, I define 'true' flight as the ability to lift off from ground to air, having control over vertical and horizontal motion in air and being able to land back on ground.
If an insect, animal or a vehicle has to defy gravity and fly in the air, what would be the crucial requirements for it, the absence of which, would keep them grounded ? What is the secret or magic behind flight ? Is it the aerodynamic shape, low body weight, both or something else ?
If your thought process is driven by aerodynamic shape, then you are most likely to miss flight solutions which do not involve a good shape. If your thought process is driven by low weight, then the flight of extremely heavy weights is likely to appear impossible to you. It is a bit like people praying for a good paying job automatically ruling out earning money thru various other means. Flight, just like money, can be achieved in multiple ways.
In my opinion, here is a one-word simplistic answer, which even a kid can easily understand - POWER is the secret of flight ! Everything else is just a useful alternate strategy to bypass the basic problem of insufficient power. When sufficient power / thrust is available, none of the other things can stop something from flying. When it is missing, even shape and weight cannot help in achieving flight. I prefer the word power instead of thrust since thrust is derived from power. (an overloaded plane will fail to take off despite having thrust)
Aerodynamics and low body weight etc. are a poor
person's solution to flight. The rich (who have plenty of
power / thrust) have no use for it at all, to defy gravity.
Thinking in terms of power or thrust helps us to remain open-minded about the different types of solutions to flight, from a design perspective. Here are some interesting examples to further illustrate this point.
EXAMPLE 1 : NASA's Morpheus Lander
This craft is not at all aerodynamic and weighs a massive 4 tons with fuel (4,000 kgs) !
It has vertical take-off and landing capability and sideways motion.
The rocket exhaust nozzle or thruster is not rigidly fixed to main body unlike traditional rockets. The onboard computer can control its direction as it is a loose and tiltable thruster, to allow partial sideways motion.
EXAMPLE 2 : Flying House and Tank
A house or a battle tank is too heavy and has no aerodynamic shape, yet achieves flight. The skycrane helicopter is just a long stick with 2 rotors, engines and fuel tank. There is no body to speak of. Think of it as a add-on jetpack for the house and tank.
If you say this is lifting and not flying, you are absolutely WRONG ! You are simply fooled by the distance between the house / tank and the rotors. For arguments sake, even if the engine and rotors were attached to the house or tank as one unit, the end result of flight is still the same. The power of the engine easily compensates for the heavy weight and lack of aerodynamic shape of a flying house or tank. If you say that both of them don't fly on their own, without extra fittings, well, neither does a plane or helicopter ! They fly only after fitting the engines to the body ! They are not born with it !
A plane's aerodynamic shape and optimal weight ratio does not automatically result in flight unless the engines produce sufficient power. In the case of the Morpheus lander, despite it being extremely heavy and lacking an aerodynamic shape, flight is easy due to availability of sufficient power. If it was a lot lesser, then Morpheus would have to sprout wings and fly like a plane, with engine giving a horizontal thrust.
If you are still stuck on the fact that the rotor blades are aerodynamic, Morpheus lander type vehicles can be made to lift the house / tank also. The point is : Power/Thrust = Flight.
EXAMPLE 3 : Flying Goat
Watch the 2nd attack by the eagle, in this clip below :
The goat is a heavy animal, has solid bones (not hollow) and has no aerodynamic shape at all. Yet it flew with the power from the eagle's muscles. I look at this as goat flight, not lifting by the eagle. If I could create a goat thru genetic engineering, having an eagle's wing and muscle strength, the goat would fly, despite all its drawbacks.
In living creatures, power refers to muscular power to create thrust. In the absence of sufficient muscle power, the role of other compensatory strategies increases - like low body weight, aerodynamic shape, feathers etc.
Teaching kids that birds have hollow bones to allow them to fly is misleading info. Predatory birds can easily lift and fly away, with their solid-boned prey animals. I suspect most birds would fly even if they had solid bones. It just would not be as efficient as 'hollow' bones, thats all. The point is that 'hollow' bones are NOT a must for flight. Muscle POWER is, but strangely, I don't hear anyone talking about it.
Vultures can over-eat and cannot fly thereafter till, food is digested and excreted or it vomits some food or the next day's sun heats up the air enough to create an upward lift for the vulture to fly. There was nothing wrong with the bird's aerodynamic shape. A temporary excess weight defeated its muscle power to take off. Lack of sufficient power was the culprit. Humans too over-eat but their legs are still powerful enough to help them walk, despite the excess weight.
In the case of overloaded planes, birds or insects, thrust is still happening but the power isn't enough to lift off the extra weight. So either extra power has to be arranged or the extra weight has to be reduced.
If you still believe the secret of flight is something else,
please add it and your logic for it, as a comment below.
To defy gravity and rise to air, one doesn't always require power. Buoyancy of gases which are lighter and less dense than air, can be used to rise into the air. Example - hot air balloons but they merely drift in the wind ; they only have vertical control of movement. So, strictly speaking, I don't consider that as flight. A modern blimp, on the other hand, is a good example of buoyant flight. But then again, its flight secret = power + bouyancy. Buoyancy alone doesn't result in flight. It just helps you float. And float is not flight.
Many would say bcos we dont have wings or we are too heavy. Assuming a wing is provided to us, we still cannot fly bcos we simply dont have the muscular power for flight. But by adding external power via a jetpack, we can fly. Suddenly our heavy weight, the lack of wings or aerodynamic shape is no longer an obstacle for flight. If you imagine the skycrane helicopter as a big jetpack (2 rotors, a fuel tank and a powerful engine), almost any shape or weight can suddenly fly. Just add more engines to make the heaviest things to fly.
If we had complete mastery over genetic engineering, I suspect we can create flying humans with big wings and a lot stronger hand and chest muscles, keeping the rest of the body same. The human body's shape or weight is not at all a constraint for flight. The missing muscular power is the only hindrance. If that is solved, we can just strap-on some artificial wings, flap like a bird and fly away.
For now, we sure can fly in other ways ! Some examples shown below :
Those of you who felt the house, tank and goat were not examples of flight but were lifted, might say this example is a case of a machine lifting the man and that he is not flying. I can only laugh and have nothing to say 😀
Is the man flying or is it a flying jetpack lifting the man ? Ha Ha.
Yves Rossy, the famous Swiss Jetman and pilot, built his initial flying setup in his garage by himself, using mini jet engines made for toy remote controlled planes. The engines only provide thrust. All the flying is really done by his body movements, like a bird. Though he doesn't take off from ground (jumps from helicopter), I suspect it is for safety reasons and fuel conservation only. His engines have the necessary thrust to take off.
There are videos of him doing aerobatics with Swiss air force fighter planes (like Ironman), clearly showing that he really is flying and not gliding. He lands with a parachute, the wing remaining attached to his body.
The first part of this video shows a practice desert flight and the 2nd part is over Dubai city. Awesome soundtrack and visuals !
If you think all this is no big deal, then you must visit this site and be surprised : https://secretofflight.wordpress.com
As a kid, I remember asking my dad why nail sinks, while ship floats. He gave me a noble prize winning, scientifically accurate, high-level-engineering type of answer about volume of displacement and density. Obviously, I couldn't understand and he could not simplify his answer either.
(Most of my teachers and lecturers had this irritating defect. If I tell them that I could not understand their explanation, they would repeat the same damn thing again like a parrot ! Poor communication skills, thats what this is. National Geographic and Discovery channel are able to communicate even the toughest subjects in a easy to understand manner. Learn from them, teachers ! Don't blame the students for your poor communication skills.)
For objects heavier than water, according to me, the secret / magic of floating is in the SHAPE, not weight. Any weight can float if its shape is adjusted. If the shape is NOT right, something as light as a nail will sink. If the shape IS right, then something as heavy as a ship will float on water.
Submarines and whales etc. float or sink at will by adjusting buoyancy internally with air, without any shape adjustment. Of course, my answer is kept simple enough for the masses, including kids, to understand easily. I deliberately avoided the word density in my explanation. Engineers and scientists can stick to their 5 page complicated explanation while I stick to my one-word explanation - SHAPE 😃