Aero dynamics in Aircraft

[Creator]

Hi I am writing Alpha Omega, sci fiction tale set on future Earth.

But I have been looking thru many aircraft and I see that I am rather restrict to the archtypal plane shape or helicopter

Cause I am an budding artist too and I don't very much want to be uncreative.... I need a lesson on planes and aerodynamics and I do not wish to bend the rules like Star Wars aircraft.

Star Destroyers will crash airports if it were to land
I just wonder how did that thing manage to get the lift anyway?!!!!

LEt discuss on realistic aircraft design and aerodynamics....
Zeppilins are welcome too as well as supersonics..... <the glass breaks all of a sudden!>

[Delvo]

Is there something specific you're trying to find out?... such as why fighter planes' wings have evolved in the particular way that they have over the decades, or why some cargo planes have engines way up in their tail fins...?

[chrispenycate]

Shapes change with speeds, energy requirements, stability, lots of factors.
If you're going to want maximum energy efficiency and minimum polution, and accept slower speeds, then you're stuck with a fairly conventional looking wing desighn (though it can be a flying wing, with no body as such.
If you want a reasonably efficient sub-orbital, you're going to need variable geometry or a launch system, such as a big linear accelerator.
If your society has energy a plenty, cheap hydrogen fusion with reactors small enough to fit into the craft, for example (and we can assume any star-travelling society will have at least that) it's possible that the wings would disappear completely, and the lift would come from a slightly flattened tear-drop shape of the body. A plane microwave powered from a circuit of satellites would be different again, with the wing probably mounted above the body as receptor and shield, as well as providing lift. Military crart, police craft, small "executive" machines, all change the economy/speed/manouverability/stability equations, and give different optima, as do the surfaces over which you're intending to fly it low. Of course, if you discover gravity control, all this goes out of the window, and you start afresh…

[Creator]

In Alpha Omega the fuel source has many faces..... solar-power, ammonia power, hydrogen power and helium power/ steam power for Hybrid Airships.....

And the shape of the aircraft on Earth appears to be restricted to those that have worked so far.....

And the Zepplins's ressurection might come in the near future.

I am an artist too so I have to observe the "patterns" of the evolution of aircraft.

And I have one question if a helicopter has 9 blades will it still be able to fly?

[chrispenycate]

Any number of blades greater than one can be balanced, and will give lift, which is all that's important (helicopters are inherently inefficient and wasteful, but can do things, like hover or go backwards, the no lifting-plane design will do. Smooth curves generally lose less energy in turbulence than sharp edges, but angular structures have flown.
What shapes were you considering? Flying things would generally be bilaterally symetrical, but if there is a real need even this could be compromised by asymetrical aplication of drive.
Airships - dirigibles, great; but weather forecasting (or even better weather control) become critical. With that much surface area for air friction, finding a wind at some altitude which is going where you want to is a major energy economy. Still, they'll never go as fast as heavier than air craft; days of travelling, rather than hours, with considerably more comfort than today's commercial flights.

[Creator]

So should a so-called Transonic Attachment to a Hybrid airship needs a cigar shape to reduce shockwaves...

Supersonic - Wikipedia, the free encyclopedia

Sears-Haack body - Wikipedia, the free encyclopedia

[Delvo]

What you're thinking of with the idea of "folding" the wings is the swing-wing mechanism. The idea is to get both sides of an aerodynamic trade-off in one plane. If your wings stick out straight, you catch more air, which allows you to produce more lift at slower speeds and to make sharper turns, but increases drag and thus keeps your speed and fuel efficiency down. If they're swept back, you catch less air, which means you have less drag and can cut through the air more cleanly, so your fuel efficiency at any speed is higher and your top speed is higher, but you lose some maneuverability and can't generate as much lift at low speeds.

(Lift is upward pressure created by the plane's forward movement. More lift means you can carry more weight, or your stall speed, the speed below which you would just fall to the ground instead of flying, is lower.)

So normally, wings that stick straight out are on planes that won't be going very fast, or on planes that just need to carry lots of weight, while swept-back wings are on planes that need as much speed as they can get, or on planes that need high fuel efficiency for a given cruise speed. Swing-wings let you switch back and forth between the two options in flight. The main example of them is the American navy's F-14, a long-range interceptor/fighter. It would launch, land, dogfight, and do other low-speed or maneuvering-intensive functions such as reconnaisance and ground-target-bombing with its wings out, but cover the distance to and from a mission site with its wings back.

The closest thing to it in the civilian world is the Concorde-type passenger jet. Its wings didn't move, but its nose did. It needed to be long and pointy for supersonic flight, and its high drag when in the drooping position wasn't very important or useful for aerodynamics, so why didn't they just make it permanently pointing forward? Because then it would obstruct the pilots' view during launches and landings.

Since the F-14's decommissioning by the U.S. Navy last year, there are very few swing-wing planes left flying. It didn't catch on very widely because most planes don't need such a combination of speed, maneuverability, and low stall speed, or they could meet their needs with other more modern wing types, and the swing-wing's structural reinforcements, joints, and machinery just added more weight, complication, and expense.

In modern planes with similar performance requirements to the F-14 (in other words, fighter planes that have been designed since then), a single fixed shape is used, combining some traits of both the sticking-out wing and the swept-back wing. Essentialy, these days they all have a front edge that sweeps back fairly steeply and a back edge that either sticks straight out sideways or even sweeps forward... which means the "base" of the wing (where it attaches to the body of the plane) is now much longer in fighter planes than than in non-fighters and older designs. Also, tail fins on these planes now stick out farther back behind the jet exhaust openings than they have before, where they can apply more leverage and make sharper turns even in a very fast plane at high speeds.

I'm attaching a file that I happened to have made recently for another purpose. I wasn't into this stuff before but started learning it because of the American political issue over the F-22. I ran into comparisons among the F-22 and other planes (and the distinction between light fighters and heavy fighters), so I gathered the numbers for length and width, found some diagrams I could scale and turn into silhouettes, and made this thing so I could SEE the planes together beside each other.

These are all American jets that are designed to shoot at enemy targets: Air Force in the top row, Navy below. In each row, their noses are all lined up exactly, for size comparison.
Left to right, Air Force: A-10, F-15, F-16, F-22, F-35
Left to right, Navy: F-14, F-18A-D, F-18E-F, F-35 (aircraft carrier version)

The numbers they have for names, which you might notice increasing in each row from left to right, also correspond to the planes' ages; the A-10 is older than the fighters, and the fighters' numbers, which start at 14, are sequential.

The A-10 is the only "attack" plane here. Attack planes are for clobbering targets on the ground to support your side's infantry and cavalry in land battles against other infantry/cavalry. They have to fly slowly in order to stay on the scene for a decent length of time instead of just zipping by, and they expect to get hit so they're very heavy with armor and designed to keep flying even if parts of the wings and/or tail get perforated or even blown off. All of that means they need lots of lift. Notice that the A-10's wings just stick straight out and don't look sleek and swept and pointy like the fighters' wings; the A-10's aerodynamic design sacrifices efficiency and speed for lift and low stall speed.

Below it is the F-14, the only other plane on here with the old-school wing shape: mostly narrow and not very tapered because the base is narrow and the choices are whether to stick them out or sweep them back. It's shown in its spread-out mode, even though the wings are still slightly swept; in its swept mode, it would almost be just a black triangle in the image. It was designed in a time when wing shapes were always very similar and the only thing they changed for speed was to slant them back instead of sticking them out.

Next to the A-10 in the top row is the F-15, in which you can see a change in wing shapes for pretty much the first time in filght history. The base of the wing is elongated, taking up much more of the plane's length from front to back, and the angle between the front and back edges is steeper, essentially making the wing both swept back (along the front edge) and stuck out (along the back edge) at the same time without any need to move parts back and forth.

To the right of the 14 and 15 are the 16 (top row) and 18 (bottom row). These planes are what happened when the USA noticed that its fighters were getting big, heavy, and expensive, and decided to balance them with lighter, cheaper little brothers, although the second 18 in the picture shows a slightly enlarged ("mid-sized") version the Navy started getting when they found out they couldn't keep their 14s mouch longer. The 16 has the first wing with a back edge that isn't swept back at all, not even for part of its length like the 15, and the 18 has the first wing with a back edge that's actually swept forward.

But the most modern planes in the American armed forces (last two in top row and last one in bottom row) have moved beyond that to a serious forward sweep of the wings' back edges. Also notice how far back in the back their tail fins hang out now. This seems to give the best combination of lift, maneuverability, speed, and such with the least sacrificing of any one of them for another or getting other penalties like excessive stall speed. But even between them, you can still see a bit of a difference. Although they all have wings swept back in the front and forward in the back, it's the most drastic in the 22 (fourth in top row), which is the fastest of them all, while the 35s (at the right in both rows), have their wings swept just a bit less and sticking out just a bit more, and aren't as fast but get more maneuverability from their wings & fins. (The 22 might be about as maneuverable or even more, but I don't know, and if so, it's only because they can also pivot their engine exhausts instead of using flaps alone.) Also, as you can see in the two versions I've shown of the 35, the Navy asked for bigger wings and fins because they're a bit more interested in control at low speeds and the Air Force is a bit more interested in high speed.

So, although they've found a wing form that gives a better combination of performance traits than in the old days and rendered swing-wing systems unnecessary, they can still tweek the new modern wing shape a bit to emphasize one purpose or another. It's just that the modern wing type makes the performance trade-offs much smaller now instead of being such major sacrifices like they used to be with older wing shapes.

[Delvo]

Great, you changed the post while I was answering it...

[Delvo]

Originally Posted by Creator

So should a so-called Transonic Attachment to a Hybrid airship needs a cigar shape to reduce shockwaves...

There's no such thing as a "transonic attachment". The whole vehicle is moving together, so it's all at the same speed, so either it's all transonic or it all isn't. And there are no attachments to airplanes that affect whether they have transonic ability; it's all about the shapes of the same few basic parts they all have, not attachments.

And the cigar shape you're looking at doesn't represent an attachment to or part of any plane. It represents the increase and decrease in cross-sectional area of the entire plane from nose to tail... idealized, as if it didn't need intakes and exhaust openings for the engine and a cockpit, so the doesn't even show anything real, just a mathematical concept. The idea is that gradual changes in the plane's shape and area from one cross section of its body to the next cross section behind it are better than abrupt, drastic changes; this is part of the reason for the changes in wing shape that I've outlined above, and also the reason why wings have been getting more blended in with the shape of the body (not really visible in my silhouettes) starting with the F-16.

And a "hybrid" vehicle, aside from being impossible as I've already said, would never be supersonic for the same reasons why any lighter-than-air vehicles aren't: too little momentum and too big of a cross section add up to too much resistance from the air at even moderate speeds, and too much engine power sucked up in fighting against that, especially for a vehicle that needs to have small engines in the first place in order to be so light. Make the vehicle dense enough and its engines proportionally big enough and its shape non-bulbous enough so that it can really be supersonic, and you've made it thoroughly heavier than air, nothing "hybrid" about it.

[Creator]

So a Hybrid airship with the cigar area rule being slender and sleek and fold back wings like the now defunct Concorde would be able to fly at supersonic better than a good old blimp which is fat and slowly...

[Delvo]

No.

First, a hybrid ship could not even exist; its density would be lower than that of air, in which case it's a lighter-than-air vehicle, or not, in which case it would have to work like planes and helicopters. There's no overlap there, just one or the other.

Second, if a vehicle's density is low (either lighter than air or just even too close to air's own density), then changing its shape won't help its performance like it does with real planes. Lower density means less mass and/or more volume, and more volume means more surface area and cross-section area. Having more volume and area to catch air with and less mass with which to cut through the air on momentum means having a severely reduced speed limit. Making something go fast in the air means reducing its volume/mass ratio; you can test this for yourself by throwing a styrofoam packing "nut" and throwing a real nut, rock, piece of wood, or such of about the same size and shape. The denser thing keeps going faster and farther, while the low-density one gets bogged down in the air and stops going forward much sooner.

That means if you started with a lighter-than-air blimp/zeppelin type of vehicle and wanted to modify it to become supersonic, the first thing you'd have to do is make it much denser, in which case it becomes much heavier than air, just like airplanes. And then it's not lighter than air anymore or even any kind of impossible "hybrid". It's just a plane. If you only tinkered with the lighter-than-air vehicle's shape without shrinking its size or adding more mass, you'd accomplish nothing because if it were to stay lighter than air, then it would have to still be too big for its weight and have too light for its size.

[Creator]

Yah... maybe the era of airships is over.... maybe Concorde Aircraft carriers are the next gen...

[Delvo]

Originally Posted by Creator

Concorde Aircraft carriers

What do you mean by that phrase?

[woodsman]

Yeah I'm wondering that.
Look up Barnes Wallis something goose or hypersonic jet. He came up with a brilliant idea which never got past prototyping but should still work IMO. I'm too tired to describe/look it up now I'm afraid but....

[Creator]

basically I am looking at a good alternative to the aerial aircraft carriers which were kinda Zeppelin in design... which they are.... So I was thinking if an aerial aircraft carrier is feasible.... if it was heavier than air and even better it can travel at supersonic speeds... into battle.

Airborne aircraft carrier - Wikipedia, the free encyclopedia