Use a container full of lighter than oxygen and nitrogen gas (like hydrogen or helium) to lift a balloon or blimp. zeppelins, etc.
Have wings where the air transfer over the wing is not the same speed as below the wing. I forget the name of this process, begins with a B. This is the method used by most aircraft.
The magnus effect of spinning rotors
Biological methods. I’m not sure of the physics of these, or if there are different kinds. Do different birds use different methods, or do birds and insects use different methods?
Use a rocket full of fuel to create thrust and propel an object
Solar sails (are these workable on earth, or do they only work in space)?
Use the difference between hot air and cold air to create lift like a hot air balloon does.
Do helicopters use the same method as method 2?
Also I’m asking about flying, not gliding though. Flying would be something on the ground becoming airborne, gliding would be something from a higher perch obtaining some glide, but eventually landing on the ground w/o any kind of propulsion and having a very limited distance it can travel whereas flight has a very long distance it can go and it can increase the height at which it travels.
As far as point 6, I’m curious about methods on earths atmosphere, not interstellar space or a foreign planet’s atmosphere. I do not know if solar sails are a feasible method of flight on earth or just for interstellar travel.
I’m not sure your categories are really distinguishable.
Virtually all flying vehicles work by throwing gases in a direction which counteracts the force of gravity, aerodynamic drag, etc.
Some of this gas is provided by the atmosphere; the rest by the propellant. In a pure rocket, the gas is all combustion products from the propellant. In a typical helicopter, it’s all air. In a jet plane, most is from air (from the fan) and the rest combustion products (from the turbine core).
Even in a lighter than air craft, this is true, though only at a microscopic level–fewer air molecules undergo a velocity change (as they bounce off the balloon surface) on the top as compared to the bottom. So overall there is a net momentum transfer to the atmosphere as the balloon accelerates upward.
Although you could try to design a vehicle driven only by photon pressure, in practice you would have a lot of weird dynamics from the air being heated that would dominate the flight behavior. You could have one in space, but within the atmosphere it would essentially be the same as the others, with air acting as the propellant.
You are probably thinking of Bernoulli. The wing accelerates air downward and lift is the resultant opposite reaction. Bernoulli equations can be used to calculate the pressure differential around the wing. You can also use Newtonian equations to measure the mass of air accelerated and come up with the same answer.
Is basically the same as 2 except the method by which the air is accelerated is different.
Birds are basically the same as number 2 but they have more control over the air by flapping their wings. They are still accelerating an airmass to get an opposite reaction in the form of lift.
In very broad terms is the same as 2, you are accelerating mass in a direction opposite to that which you want to move.
Helicopters use method number 2.
Gliding and flying are really the same as far as lift mechanisms go. The only real difference is that for sustained flight you need some self contained source of energy while for gliding you use gravity as the energy source. You also use external airflow patterns such as areas of thermal activity under cumulus clouds to maintain sustained flight in a glider but as the energy source is still external you are not completely self sufficient.
Helicopters use wings, they just rotate to get the air to flow over them instead of being fixed to the aircraft and having the air pushed over them by the movement of the aircraft.
You might choose the categories below to distinguish different types of flying machines. While 2,3, and 4 all use wings they implement them in flying machine very differently.
The fact that air often (but not always) moves faster over the top of the wing than under the bottom is unrelated to the cause of lift. In simplest terms, wings produce lift because they’re tilted, which causes air to be deflected downwards. Really, that’s it.
Airplane wings, helicopter rotors, and bird, bat, and pterosaur wings all work in the same way. Some insect wings are a little different, but don’t work on anything much bigger than an insect.
The Bernoulli principle says that faster-moving air has a lower-pressure than slower moving air. So it’s sometimes said that the higher pressure on the lower side of an airplane wing exerts a force on the wing that produces lift. But actually the Bernoulli effect is a minor part of lift in most planes, it’s really the surface of the wing forcing air downward that produces most of the lift. I’m sure this must have been discussed on this board previously.
Hang on… yep.
Solar sails theoretically produce thrust on Earth, but the amount of thrust is far too small to lift even the sail itself. One square mile of solar sail produces less than five pounds of thrust, at the Earth’s distance from the sun and outside the atmosphere. I imagine it’s less under all this air. There’s also a slight geometric problem in that on Earth sunlight generally points down, the opposite direction from where you want to go.
As others have mentioned, there’s a lot of overlap in your categories, depending on what you consider a “difference”. 1 and 7 use the same physical mechanism of buoyancy, although they require different technology.
I don’t think lightcraft, driven by laser propulsion, fall into any of your categories.
Not unrelated at all. And not “deflected”. The air is accelerated downward. The air above and below the wing is turned (accelerated). An inescapable side affect is that the wing across the top is moving faster and the lower air is moving slower, or perhaps an inescapable side affect of the top air moving faster and the lower air moving slower is that the air is turned.
I’d be interested if you can show me some examples of a wing creating lift but not having the top air moving faster.
To markn+, Bernoulli is not a “small part of the lift”, it is one way of measuring ALL of the lift. Measuring acceleration of air mass is another way of measuring ALL of the lift. It is not a bit of this and a bit of that, they are just different ways of measuring the same effect.
Gliders can be sort of a combination of 1 and 2. They use fixed wings but in theory can stay up indefinitely in the right terrain with continuous thermal updrafts.
I’d say the terrestrial equivalent of this would be a kite. It uses wind instead of solar emissions but the principles the same: have a craft with minimal mass and maximum surface area and let moving forces in your environment push you.
I considered 1 and 7 to be different because they are using different mechanisms to cause a gas to rise. One is using lighter than air elements like hydrogen and helium, while the other is using temperature differences to cause a gas to rise.
So both cause a gas to rise, but the mechanism is totally different. If the world suddenly runs out of gaseous hydrogen and helium tomorrow, hot air balloons will still work but zeppelins will not.
Most acrobatic planes have wings with the same shape on the top & bottom although this is not necessary.
Most aircraft wings can be made to work up side down so to speak if the angle of attack is in the correct place and your power source keeps working. And is big enough.
It may not be as efficient but it will fly.
Old saying from the 60-70’s. The F-4 Phantom is proof that a brick will fly with big enough engines.
By “top” I mean in the direction the lift is being generated.
Turn a wing upside down and give it sufficient angle of attack to counteract any asymmetry in its shape (many aerobatic airfoils are symmetrical anyway) and it will create lift as well as have the air moving over what used to be the bottom of the wing faster than the air moving over what used to be the top.
What I am after from Chronos, or anyone else, is an example of a wing that creates lift along the surface of the wing that has the slower air velocity to support his contention that the variation in air velocity around a wing is unrelated to lift.
If all Chronos meant by his comment is that you can make a wing work upside down, then don’t worry about it.
