Wings. Who needs em? (Serious question.)

[Franklin]

- They provide lift, but also drag, and each wing "piece" adds its own drag and lift, and since [presently] the aerodynamics don't care about shape or profile, just adding more engines and removing those drag-causing wings is typically more efficient.

- They look pretty.

[Franklin]

And since typically the goal is to get to and move through space, wings are only useful in niche environments, and if you can reduce drag and mass (and part counts) by not adding wings, without any significant negative effect thanks to our [currently] awful aerodynamic model, you're usually better off without wings.

Want control? Add a SAS unit and some massless RCS blocks.

[Laie]

Why not try it? Orange tank, basic jet, lots of wing. TWR < 0.4, yet it takes off easily and climbs at ~9m/s.

Coming to think of it, if wings wouldn't work, no ion-powered plane would ever take off.

[Bobnova]

Generating 10 lbs of lift does not have to cost 10 lbs of drag.

There's a lift to drag ratio: http://en.wikipedia.org/wiki/L/D_ratio

A U-2 for instance has a lift:drag ratio of ~28. That's not 0.28, that's 28 times more lift generated by the wing than drag (drag being resistance opposing the direction of travel) generated.

Thus your spaceplane with with wings can use the wings to hold itself up, which do so very efficiently, while the wingless version has to use thrust directly to oppose gravity.

[KerikBalm]

This... seems like magic to me, but I'm no rocket scientist. Thank you for actually answering the question

However, now I have to ask, is this in real world physics only? Or does this work in KSP as well? So far my experiments with wings tend to end in less efficient flights, but this could because I'm doing it wrong.

KSP with NEAR/FAR -> maybe

KSP stock - no: KSP stock has wings generating lift proportional to velocity, whereas IRL it is velocity squared. In KSP drag, like the real world, is a function of velocity squared. Thus the faster you go in KSP, the lower your L/D. In the real world, L/D is basically fixed for a given angle of attack (excluding mach effects)

Its a matter of the difference in equations for momentum vs kinetic energy.

You need to look at both the acceleration of your craft, and the reaction mass

Its very closely related to why air breathing engines are more efficient, and why its easier to make a VTOL rotorcraft than a VTOL likea harrier IRL.

To provide force, you need to "push against" mass.

You can move a small amount of mass very fast, as with a rocket pointing down...

or you can move a large amount of mass very slow, as with large wings deflecting a large mass of air.

Wings give you more "working mass" reaction mass to supply the lift forces, allowing you to get more force for a given amount of energy.

Also note you don't just add the horizontal and vertical velocity components...

Take 100 kn of thrust at 45 degrees... the horizontal and vertical components are sin(45)*100, (and cos, but at 45, that is the same)

You get about 71 kN thrust vertically, and 71 kN thrust horizontally. This doesn't magically mean you have 142 kN of thrust by pointing your engine at 45 degrees.

For very low angles of attack on a wing, the cos component is still close to 1.0, while the sin component rises approximately linearly with increasing AoA.

[Hannu]

This... seems like magic to me, but I'm no rocket scientist.

You can think about wedge, lever or hydraulic systems. They can also change small force to much larger, although they depend on different interactions than wings. As with mechanical parts, you always lose speed when you gain force and are not able to make perpetual mobile.

[RizzoTheRat]

Generating 10 lbs of lift does not have to cost 10 lbs of drag.

A U-2 for instance has a lift:drag ratio of ~28. That's not 0.28, that's 28 times more lift generated by the wing than drag (drag being resistance opposing the direction of travel) generated.

Yeah but the other thing that KSP doesn't replicate is that at 21km ish altitude its stall speed is only 10kts slower than its maximum speed

[Riph]

A bunch of really useful stuff, with numbers and math to back it up

Thank you so much, this is exactly what I was looking for. All this information should be posted to the wiki. (Unless it already is, but I sure couldn't find it there.)

[KerikBalm]

I should have explicitely mentioned the KE equation, 1/2 MV^2

Basically, if you're pushing your working mass to twice the velocity, you need 4x the energy.

Its like the opposite of a rocket

In the air, you can use the air as essentially unlimited working/reaction mass, and you are limited by energy. You actually want to push the air as slowly as possible to generate the needed thrust.

In a vacuum, when you are using solar power, or nuclear power, you aren't so much limited by energy, but you are limited by reaction mass (I'll ignore the chemical situation for now).

As a result, you want to push your reaction mass as fast as possible.

Wings allow you to generate a lot of "thrust" perpendicular to your direction of motion, for a small penalty to your KE.

Also note, conservation of energy does apply here. Work done is equal to Force * distance -> of course that is force in the direction of motion.

As the force is perpendicualr to the direction of motion (assuming perfect wings, and perfectly horizontal flight), then sin(0)=0, and no work is done.

Just as when a 1kg weight sits on the floor, even though there is a constant 9.8 m/s/s force upon the weight sitting on the floor, no work is done, there is no change of energy.

The same is true if this 1kq weight starts sliding along the floor (assume it is frictionless, or nearly so.. like a sled on ice, or really low friction wheels over a smooth surface)

"sliding" through the air with wings isn't as efficient... the air is disturbed a bit, which means the craft is imparting energy to it as it travels through it... but if you take a sailplane weighing 300 kilos, gliding along for 20 minutes with a L/D of 60:1, compared to hovering on rocket thrust ... which one do you think disturbs the air more?

Which one takes more energy?

Wings get your "free" reaction mass by deflecting air.

With free reaction mass, you can move the reaction mass much slower to produce the needed thrust, which gives you huge savings thanks to KE = 1/2 MV^2

In KSP, the wings L/D turns to crap at high speeds.

So the benefit is mainly seen at lower speeds.

Also, in KSP, the air breathing engines are already 16x more efficient than they should be, making the benefits of wings much smaller in comparison.

In NEAR/FAR, the engines are not quite as OP'd (the ISP is still ridiculous, but the max speed, and particularly the TWR are reduced), and the wings properly produce lift proportional to the square of velocity.

Lower TWR engines, and wings that produce more lift, with a general decrease in drag, favor winged craft much more than stock