Note : This story has been ported from another platform which I used earlier. Images sourced from internet. Copyright belongs to their respective owners. A one pic summary is given at the end of this long page.
Date : May, 2017
(last updated in Aug, 2020)
Definition Of Flight
My 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.
In simple language, flight is a controlled defiance of gravity, by a life form or machine.
Official definition of Flight :
Merriam Webster
- an act of passing through the air by the use of wings
- an act of passing through the air or through space outside the earth's atmosphere
Wikipedia
- Flight is the process by which an object moves through an atmosphere (or beyond it, as in the case of spaceflight) without contact with the surface. This can be achieved by generating aerodynamic lift associated with propulsive thrust, aerostatically using buoyancy, or by ballistic movement.
- Many things can fly, from natural aviators such as birds, bats, and insects, to human inventions like aircraft, including airplanes, helicopters, balloons, and rockets which may carry spacecraft.
These definitions will soon become relevant as I start explaining the secret of flight and you start disagreeing with me :-)
If students or your kids ask you the secret of flight, whats your answer going to be ? Why can some animals & machines fly & others cannot ? Kind of like being asked why a metal nail sinks while a metal ship floats (latter is also answered at the end of this page).
So 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 who pray for a good job tending to automatically rule out earning money thru various other means.
Flight, just like money, can be achieved in multiple ways.
In my opinion, 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 is available, none of the other things can stop something from flying. When power 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) have no use for it at all, to defy gravity. Thinking in terms of power helps us to remain open-minded about the different types of solutions to flight, from a design perspective.
Here are some examples of power being responsible for seemingly impossible flight success.
This craft is not at all aerodynamic and weighs a massive 4 tons with fuel (4,000 kgs) and yet it flies ! It has vertical take-off and landing capability and partial sideways motion.
A house or a battle tank is too heavy and has no aerodynamic shape, yet achieves flight. The skycrane helicopter over it 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 its power 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 of the helicopter are aerodynamic, Morpheus lander type vehicles can be made to lift the house / tank also.
The point is : Power = Flight
The goat is a heavy animal, has solid bones (not hollow) and has no aerodynamic shape at all. Yet, in the video below, 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 similarly, despite all its other drawbacks.
If you feel this not flight, then please read the definition given at the beginning of this article. It is a controlled defiance of gravity. I knew the definition would be needed and that's why I mentioned it right in the beginning itself :-) If the eagle did the same thing with a small fish or a tiny twig for a nest, would that also be "not flying" ? If you consider only flapping as flying, then google "flapless flight of birds". Also, read https://en.wikipedia.org/wiki/Gliding_flight
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 lighter is very wrong info (by the way, the bones are pneumatized, they are not hollow like a pipe). Such bones are denser & hence, heavier than regular bones. The skeleton of a two-ounce bird is heavier than the skeleton of a two-ounce mouse. Even flightless birds like Ostrich have pneumatized bones and many mammals, including humans too have it. Read more on Skeletal Pneumaticity.
Anyway, predatory birds can easily lift and fly away, with their solid-boned prey animals due to having sufficient power. I suspect most birds would fly even if they had solid bones. It just would not be as efficient as 'hollow' bones, that's all. On the other hand, a really hungry old eagle just wont be able to generate the required power to lift a heavy prey despite 'hollow' bones & aerodynamic shape.
The point is that 'hollow' bones are NOT a must for flight. Muscle POWER is, but strangely, this is never mentioned.
In simple language, flight is a controlled defiance of gravity, by a life form or machine.
Official definition of Flight :
Merriam Webster
- an act of passing through the air by the use of wings
- an act of passing through the air or through space outside the earth's atmosphere
Wikipedia
- Flight is the process by which an object moves through an atmosphere (or beyond it, as in the case of spaceflight) without contact with the surface. This can be achieved by generating aerodynamic lift associated with propulsive thrust, aerostatically using buoyancy, or by ballistic movement.
- Many things can fly, from natural aviators such as birds, bats, and insects, to human inventions like aircraft, including airplanes, helicopters, balloons, and rockets which may carry spacecraft.
These definitions will soon become relevant as I start explaining the secret of flight and you start disagreeing with me :-)
What Is The Secret ?
So 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 low weight, then the flight of extremely heavy weights is likely to appear impossible to you. It is a bit like people who pray for a good job tending to automatically rule out earning money thru various other means.
Flight, just like money, can be achieved in multiple ways.
Power
In my opinion, 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 is available, none of the other things can stop something from flying. When power 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) have no use for it at all, to defy gravity. Thinking in terms of power helps us to remain open-minded about the different types of solutions to flight, from a design perspective.
Examples Of Power Behind Flight Success
Here are some examples of power being responsible for seemingly impossible flight success.
Example 1 : NASA's Morpheus Lander
NASA's Morpheus Lander
This craft is not at all aerodynamic and weighs a massive 4 tons with fuel (4,000 kgs) and yet it flies ! It has vertical take-off and landing capability and partial sideways motion.
Watch On YouTube
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
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.
Can the house and the tank be considered to be flying now at least ?
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 its power 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 of the helicopter are aerodynamic, Morpheus lander type vehicles can be made to lift the house / tank also.
The point is : Power = Flight
Example 3 : Flying Goat
(watch from 5:00)
The goat is a heavy animal, has solid bones (not hollow) and has no aerodynamic shape at all. Yet, in the video below, 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 similarly, despite all its other drawbacks.
If you feel this not flight, then please read the definition given at the beginning of this article. It is a controlled defiance of gravity. I knew the definition would be needed and that's why I mentioned it right in the beginning itself :-) If the eagle did the same thing with a small fish or a tiny twig for a nest, would that also be "not flying" ? If you consider only flapping as flying, then google "flapless flight of birds". Also, read https://en.wikipedia.org/wiki/Gliding_flight
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 lighter is very wrong info (by the way, the bones are pneumatized, they are not hollow like a pipe). Such bones are denser & hence, heavier than regular bones. The skeleton of a two-ounce bird is heavier than the skeleton of a two-ounce mouse. Even flightless birds like Ostrich have pneumatized bones and many mammals, including humans too have it. Read more on Skeletal Pneumaticity.
Credit : Photo by Douglas Currie
Anyway, predatory birds can easily lift and fly away, with their solid-boned prey animals due to having sufficient power. I suspect most birds would fly even if they had solid bones. It just would not be as efficient as 'hollow' bones, that's all. On the other hand, a really hungry old eagle just wont be able to generate the required power to lift a heavy prey despite 'hollow' bones & aerodynamic shape.
The point is that 'hollow' bones are NOT a must for flight. Muscle POWER is, but strangely, this is never mentioned.
Example 4 : Bumblebee
Credit : USGSbiml/flickr
The shape of a bumblebee (big fat body + tiny short wings) does not give the impression that it can fly & is very different to the proportionately bigger wings of birds & planes and their sleek body shapes. For a long time, science even wrongly claimed that the bumblebee's flight defies the laws of aerodynamics & physics.
Bumblebees are heavy weight lifters. They are able to fly back to the hive with almost their own body weight in nectar (up to 91% as per this news). Orchid bees can even lift 100 % of their body weight & still fly, according to some tests.
The double disadvantage of having a bulky shape & having to fly with heavy weights is overcome by sheer muscular power only.
Bumblebees are heavy weight lifters. They are able to fly back to the hive with almost their own body weight in nectar (up to 91% as per this news). Orchid bees can even lift 100 % of their body weight & still fly, according to some tests.
The double disadvantage of having a bulky shape & having to fly with heavy weights is overcome by sheer muscular power only.
Example 5 : Lockheed Martin F-35B plane with vertical take-off & landing
F-35B Vertical Take-off & Landing
If
the wings of this plane were removed completely, it would still be able
to fly, by directing the jet engine's thrust downwards
from 4 different positions around the remaining body.
The Rolls-Royce LiftSystem coupled to a turbofan via a driveshaft.
The engine alone can fly on its own, without a need for the plane's body, when fitted with a fuel tank, controls and a metal frame like this. The body of the plane & its aerodynamic shape is totally irrelevant to its flight success here. Also, the plane would still
fly if the jet engine is replaced with 4 rocket thrusters. An
aerodynamic wing is not necessary for flight. It merely improves flight
& fuel efficiency. Power is the key to flight !
Example 6 : A flying water tower ! (estimated weight of 70-100 tons / 154, 350 - 220,500 lbs)
Elon Musk himself said that water towers can fly, regarding the 150 meter flight test of SpaceX Starhopper prototype. When you have sufficient power to
fly, shape and weight do not matter at all.
Credit : Nomadd, forum.nasaspaceflight.com
Now I hear some people screaming - "BUT THAT IS A ROCKET ! AND ROCKETS DO NOT FLY !"
SpaceX
calls it rocket flight. Don't you think they know what their vehicle
does ? Once again, please read the definition of flight, given at the
beginning of this article :-)
Spaceflight : Another useful definition, in case you did not know.
My
basic point again is this - POWER is mandatory for flight. Aerodynamic
shape and low body weight are just optional, not mandatory.
Only
in the absence of sufficient power to fly, do aerodynamic shape and low
body weight become important in achieving flight. The last two can even enhance
the efficiency of a rocket powered flight but still are not mandatory
for flight when you have powerful rocket thrusters. The reason you are
finding all this a bit difficult to agree with, is due to mental conditioning from your
academic life, a
drawback of the educational system.
Examples Of Power Behind Flight Failure
The above 6 examples showed power being responsible for flight successes. Now here are 3 examples of power being responsible for momentary flight failure, in cases of very flight capable birds & planes. Just to clarify, these flight failures could also be out of choice but the end result is same - no flight due to insufficient power.
The design of some birds & planes pushes the flight threshold, wherein flight is not fully under their will or control & depends on external factors too. They can temporarily lose their ability to fly and have to then wait for favorable environmental conditions or use assisted take-offs.
The design of some birds & planes pushes the flight threshold, wherein flight is not fully under their will or control & depends on external factors too. They can temporarily lose their ability to fly and have to then wait for favorable environmental conditions or use assisted take-offs.
Example 1 : Swans
Heavy
birds like Swans have to run on water/land to gather enough momentum to
take flight, just like a plane take-off. Due to lack of power, these
birds take much longer to get airborne than most other birds. And if
sufficient runway distance is not available, then they cannot get airborne fully.
Compared to many other birds, swans need very long distances just to reach the height of a tree, due to a shallow climb angle. The same thing happens to certain planes, as example 3 shows further below.
Watch On YouTube (from 0:35)
Compared to many other birds, swans need very long distances just to reach the height of a tree, due to a shallow climb angle. The same thing happens to certain planes, as example 3 shows further below.
Example 2 : Vultures
Griffon Vulture vs Jackal
Credit : Photo by Yoram Shpirer
Vultures
can easily over-eat and lose the ability to fly thereafter, till food
is excreted or vomited. Also, vultures that normally roost or nest at
high altitude cliffs or forts, are known to become grounded if they
happen to be feeding at ground level, after sunset. To fly back to their
usual roosting/nesting place at high altitude, they need to wait for the
next day's sun to heat up the air enough to create an upward lift.
There was nothing wrong with the bird's aerodynamic shape or its bone
structure. A temporary excess weight / atmospheric condition defeated
its muscle power to take-off / fly high, in such threshold cases. Lack of
sufficient power was the root cause for these groundings.
Chicks of Andean Condor vulture can fly in 6-7 months after hatching. The chick on left can fly (see video of 1st day day of flight). What stops the chick on right from flying ? Both have flight ready feathers, aerodynamic shape & correct weight & same bone structure. Visually, there seems to be no difference between them. Yet only one can fly. Why ?
At 5 months, the chick on the right lacks sufficient muscle power to fly. No power, no flight.
Credit : Left, BBC One. Right, Gavin Emmons.
Chicks of Andean Condor vulture can fly in 6-7 months after hatching. The chick on left can fly (see video of 1st day day of flight). What stops the chick on right from flying ? Both have flight ready feathers, aerodynamic shape & correct weight & same bone structure. Visually, there seems to be no difference between them. Yet only one can fly. Why ?
At 5 months, the chick on the right lacks sufficient muscle power to fly. No power, no flight.
Example 3 : Planes
Certain planes cannot fly in "hot and high" conditions, specially after overloading. So they stay grounded till atmospheric conditions improve or use rocket assisted flight. In the case of overloaded planes, thrust is still happening but the power isn't enough to lift-off within the available runway distance. So either extra power has to be arranged or the extra weight has to be reduced.
Rocket Assisted Take-Off (RATO) system helps this overloaded Hercules C-130 plane in take-off, by providing additional thrust.
Read more about rocket powered flight
A Rocket Assisted Take-Off (RATO)
system was often used to either overcome the poor thrust of early jet
engines at low speeds or for assisting heavily loaded planes to take-off. Without
these rockets, once a plane like the Hercules C-130 lands on a short
runway at high altitudes, it will not be able to take-off again,
specially under "hot and high"
conditions or if it is overloaded. So a perfectly flight capable
machine temporarily loses its ability to fly due to lack of power. RATO provides that extra power & gets it airborne in an otherwise impossible scenario.
Flight Of Lighter-Than-Air Objects
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.
Why Can't Humans Fly
Many would say bcos we dont have wings or we are too heavy. Assuming an artificial bird-like feathered wing is strapped onto our arms, we still cannot fly bcos we simply don't 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 :
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. All I can say is that you are falling into the same mental trap again :-)
Is the man flying or is it a flying jetpack lifting the man ? :-)
https://en.wikipedia.org/wiki/Jet_pack
https://en.wikipedia.org/wiki/Jet_pack
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.
The first half of the video below shows a practice desert flight and the 2nd half is over Dubai city. Awesome soundtrack and visuals !
The first half of the video below shows a practice desert flight and the 2nd half is over Dubai city. Awesome soundtrack and visuals !
Jetman taking off from ground
There
are videos of him flying like Iron Man in formation with various planes, clearly showing that he really is flying and not
gliding. During flight, the Jetman speaks to plane pilots directly via radio in his helmet to coordinate the moves. He usually lands with a parachute, with the wing remaining attached to his
body.
Jetman flying in formation with 8 aerobatic planes
https://www.youtube.com/watch?v=pNaZCDhvh88
Jetman flying in formation with an Emirates A380 plane
https://www.youtube.com/watch?v=_VPvKl6ezyc
Jetman flying in formation with two L-39 Albatros fighter jets
https://www.youtube.com/watch?v=MEimNSiVHQQ
Jetman flying in formation with 8 aerobatic planes
https://www.youtube.com/watch?v=pNaZCDhvh88
Jetman flying in formation with an Emirates A380 plane
https://www.youtube.com/watch?v=_VPvKl6ezyc
Jetman flying in formation with two L-39 Albatros fighter jets
https://www.youtube.com/watch?v=MEimNSiVHQQ
If you think all this is no big deal, then you must visit this site and be totally surprised : https://secretofflight.wordpress.com
Secret Of Floating
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.
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. The same nail, if beaten into a flat sheet, will float and the same ship, if crushed, will sink.
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.
The test of education is in practical solutions. After teaching kids about volume of displacement and density, if they are now asked how to make the nail float, I suspect most will fail. Bcos they did not understand the concept in the first place ! But with my explanation, most students, if not all, will know how to make the nail float, even if I had not mentioned the solution. Bcos they would have UNDERSTOOD the concept.
Summary
& even post links relevant to the topic.
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