Basic Aircraft Design - Explained Simply, With Pictures

[RC1062]

Heh, very good tutorial. Simple enough to understand, yet complicated enough to be useful.

One or two minor things, but they aren't relevant to KSP anyway.

(PS love the pictures)

[Dizzle]

Thanks for this tutorial! Had my first successful SSTO mission thanks to this.

[fedemotta3]

Awesome, I'll take note of some of this. Suddenly I feel like studying fluids again.

[RocketBlam]

So one thing I wonder... would designing the angle of attack into the wing be a good idea? instead of having the wing at 0 degrees to the body, would it be better at 10 degrees? Then your aircraft can fly straight while your wings still provide lift.

Also, would a greater angle of attack be good on Duna? It has less air pressure, so I would think a greater angle on the wing would be good.

[keptin]

Would designing the angle of attack into the wing be a good idea? Then your aircraft can fly straight while your wings still provide lift.

Certainly! The angle at which the wing is "installed" onto the plane is called the angle of incidence.

Also, would a greater angle of attack be good on Duna?

Designing wings with a higher angle of incidence for use on Duna won't benefit you anymore than doing so on Kerbin. Because the air is thinner on Duna, one solution could be to generate more lift by adding more wings or going faster. You can also increase the thrust--this always works, guaranteed.

Edited March 9, 2014 by keptin

[RocketBlam]

Designing wings with a higher angle of incidence for use on Duna won't benefit you anymore than doing so on Kerbin. Because the air is thinner on Duna, one solution could be to generate more lift by adding more wings or going faster. You can also increase the thrust--this always works, guaranteed.

As I understand it, the angle of incidence is a balance between drag and lift. If you make it higher, you increase lift but also increase drag. On Duna, increasing lift is very desireable, and increasing drag is not as big a problem because you have less to start with.

Sounds like some wings installed with pivots on them would be a good experiment on Duna.

[keptin]

If you make [the angle of incidence] higher, you increase lift but also increase drag

Yes, to a point, the critical angle beyond which the airfoil produces less lift as it begins to stall. As I understand it, the angle of incidence has more to do with the desired angle of the aircraft relative to the ground when in normal flight, so as to not have to produce more lift by pitching up.

Since lift is determined by speed, airfoil area, and air density, the appropriate angle of incidence depends on cruising altitude, speed, wing shape/size, and aircraft weight.

In extreme cases, such as a B-52, so much lift is produced relative to its unladen weight, it will fly level nose-down...even takeoff nose-down.

[Cerberus738]

Just wanted to say thanks for the info! I'd built a couple of planes but I think they flew purely by accident ha ha. With this I can consistently build planes that take off! High speed, high altitude still gives me trouble. Not for space planes but for planes that would just cruise through the atmosphere. Meh.

After playing with wings for a while I've decided they are over rated.... none of my ssto designs have wings anymore lol

[Amaroq]

I'm a bit torn between changing the guide or not to reflect this new info since it would be teaching the contrary, but maybe I can mention it in a future update. After all, I don't want to teach the wrong thing and the guide's higher purpose is to teach people about aircraft, not necessarily aircraft in KSP.

My advice would be, at most mention that it works differently in stock KSP, and recommend that the reader utilize F.A.R. again, as you do in your section about drag and fairings.

[ShadowDragon8685]

Keptin - thank you.

Thanks to this fantastic guide, I actually built something that wasn't strictly paint-by-numbers (the firespitter biplane) that I've managed to successfully fly.

Here's a picture of it. This is a few minor revisions ago, but the basic principle is the same. I call it the Buzzard. It flies rather poorly and is almost uncontrollable without SAS, but it does fly, it takes off pretty quickly, and with the airbrakes on the back lands even quicker.

[Hodo]

Keptin - thank you.

Thanks to this fantastic guide, I actually built something that wasn't strictly paint-by-numbers (the firespitter biplane) that I've managed to successfully fly.

Here's a picture of it. This is a few minor revisions ago, but the basic principle is the same. I call it the Buzzard. It flies rather poorly and is almost uncontrollable without SAS, but it does fly, it takes off pretty quickly, and with the airbrakes on the back lands even quicker.

Looking at that plane I have a couple of questions.

1- Why so many intakes for those engines?

2- Where is your CoL in relation to your CoM, both empty and loaded.

[ShadowDragon8685]

Looking at that plane I have a couple of questions.

1- Why so many intakes for those engines?

2- Where is your CoL in relation to your CoM, both empty and loaded.

1- Amateur airhogging.

2- The CoL is behind and above the CoM when the plane is full. the emptier the tanks get, the further forward the CoM goes.

This is the Razorback, the second plane I managed to make by consulting this guide. It's more stable than the Buzzard (Jebediah knows how,) after some invisible struts to make it not flop like a fish.

Yes, that is a nuclear reactor. I needed more weight forward because of the aft-mounted cockpit, and I figured I'd kill the bird of power supply issues (which plagued the Buzzard) at the same time.

[keptin]

Basic Aircraft Design v28.1 has been posted. Thanks /r/kerbalspaceprogram for helping me find some errors! These have since been fixed.

In this update:

-section on Angle of Incidence

-updated illustrations

-rotating engines to offset asymmetric thrust

-landing gear positioning for proper tilt-back

-rewording and other minor changes

[Amaroq]

@keptin Thank you thank you thank you. At 3am Saturday night, after re-reading your guide this week and installing the Procedural Wings mod to go along with F.A.R., I finally achieved stable level flight.

Design looked very much like the F-14 style in your "flat spin" example. Takeoff was a joy, less-than-full throttle straight down the runway, the lift picked the nose wheel up, and the gentlest tap on the "up" key put me into flight.

Best KSP feeling I've had since my very first successful docking.

Landing .. well, let's not talk about the landing.

[keptin]

Awesome, it's great to hear the guide helped you out. Landings can be a little...tricky

[Amaroq]

Hahahah ... yeaaahh. Took me 'til about 1:00am tonight but I got it, and got good enough at it to line up my approach with the (location-spoiler-redacted) airfield on my first pass. Where I proudly EVA'd to plant a flag .. and then discovered that I hadn't installed a ladder.

Jump, Jeb, jumP!

He jumps about as well as I do.

So I sent another plane, WITH a ladder, out to pick him up.

[ShadowDragon8685]

I'm the epic fail at spaceplanes, but I'm still having fun, thanks to this tutorial.

This is the Kerbin Kondor Mk. 2. The Mk. 1 was two S2 LFO tanks (and an engine) shorter and 1 S2 raised tail longer. That's about the only difference.

She's only getting to about 23,000m before the engines dramatically lose power, and that L2 Atlas wasn't nearly strong enough to get it into orbit from there, especially since I had to cut all the engines and manually shut down the jets to prevent them from flaming out unevenly and putting me into a flat spin before I could start the rocket.

I tried to go into space, but all I managed was another continent. Still, it was a fun ride.

Here's a few dramatic shots:

Liftoff! I find liftoff is very, very easy just by tapping the action key set to the airbrakes. The tail drags massively, nose comes up, and lift happens. Just remember to tap the airbrake button again real quick, or you'll quickly have the lift profile of a rocket, followed immediately by the landing profile of a lawn dart.

"Hullo, it's Jebediah Kerman!" Jeb's losing his **** at being airborne again in such a cool glass cockpit. Meh... Could use more MFDs. I like this one in that it keeps the full range of analog instruments as well, though. Pity you can't see jack **** out the window, and there's not enough MFDs to put up some flight cameras and still have instrumentation. Still, could be worse. It could be an opaque box.

Night shots of a well-lit aircraft are so cool and dramatic. I put red and green nav-lights on my planes and spacecraft. Remember: Red goes on the left, and green on the right. If you see someone's red lights. they have the right of way. If you see someone's green lights, you have the right of way.

The inboard engines going purple (overheating) before the outboards. I don't understand this, since the three engines are all equidistant from one another. Still, they can fly at ~90% indefinitely, so it's not a big deal.

Atmospheric reentry effects are cool, but this one was mostly moderated. This vehicle can do so much better if it tries.

Glowing grass looks like a nice friendly place to land. It was this or turn around and fly back to KSC.

Coming in for a landing. This thing usually lands pretty well. It's got two different forward landing gear; the first is a tall gear, the second is short. Land on the short gear to make her landing profile a nose-planter, stand up on the longer gear to take off again with the nose pointing skyward.

Bob was glad for a chance to get out of the 2m crew capsule and stretch his legs, even if he had been hoping to do his EVA in space.

Bob checks on the reactor core. Yes, this plane flies with a reactor core in the cargo bay. Power supply issues? What power supply issues?

[Togusa]

Night shots of a well-lit aircraft are so cool and dramatic. I put red and green nav-lights on my planes and spacecraft. Remember: Red goes on the left, and green on the right. If you see someone's red lights. they have the right of way. If you see someone's green lights, you have the right of way.

I keep forgetting how the red/green lights should be placed on an airplane and why they're there. Thanks for the reminder.

The inboard engines going purple (overheating) before the outboards. I don't understand this, since the three engines are all equidistant from one another. Still, they can fly at ~90% indefinitely, so it's not a big deal.

I think the inboard engines are overheating because there's less surface for the heat to radiate from the engines (being close to the fuselage, the outboard engine, and each other). Throttling back does help with exhaust heat management, so I don't think the overheating is a big problem in this case.

Bob checks on the reactor core. Yes, this plane flies with a reactor core in the cargo bay. Power supply issues? What power supply issues?

I'd be more worried about the crew getting a more-than-healthy dose of radiation, but that's just me.

A very nicely done large-span aircraft, and one of the few nuclear-powered aircraft I've seen so far. If I may ask, what mod is the reactor core from?

[ShadowDragon8685]

I keep forgetting how the red/green lights should be placed on an airplane and why they're there. Thanks for the reminder.

It's the same way on boats, too. I had to check Wikipedia, but I initially started using that because I was rubbish with the navball (well, I'm less rubbish now, anyway,) and that would let me easily tell which side of the ship was which in the dark. (And I put white navlights on "top" of my spaceships, but that's not an issue with planes, since they have big tail-planes.)

Technically it's an unnecessary habit on atmospheric planes in KSP, as even in the dark it's hard to mistake the front of a ship for the back, and you will know if you're inverted even if you're absolute garbage with the navball... But it's a good habit to stay in. And it looks so very pretty, does it not?

I think the inboard engines are overheating because there's less surface for the heat to radiate from the engines (being close to the fuselage, the outboard engine, and each other). Throttling back does help with exhaust heat management, so I don't think the overheating is a big problem in this case.

That actually makes sense, but this is Kerbal Space Program we're talking about. I somehow doubt they have that modeled. More likely the outboard engine is a hair forward of the inboards and is exposed to a hair more of its exhaust.

I'd be more worried about the crew getting a more-than-healthy dose of radiation, but that's just me.

They're Kerbs, they'll be fine! They're a tough, hearty breed.

A very nicely done large-span aircraft, and one of the few nuclear-powered aircraft I've seen so far. If I may ask, what mod is the reactor core from?

KSP Interstellar. I got tired of planes draining their batteries if left to idle, I got tired of the planes somehow not carrying enough juice to operate the damn antennas and alternator output not being enough to run the antennas continuously. So I stuck a 1.25m fission reactor (I have fusion unlocked, but honestly I just want something that just plain works, and the 1.25 fission core is wonderfully reliable and insanely long-lasting for a mission on Kerbin,) a Brayon Cycle thermal generator, and two radiator stacks in the belly of the plane. They're quite beneficial to the plane's center of mass, since they're centered left-right but lower than the fuselage's center, which helps offset that gigantor tail.

The hilarious thing is how badly this thing breaks reality. It's rather obviously a big, wide-winged, wide-bodied cargo type, but this thing gets into and beyond blackbird territory. It just doesn't want to fly straight, so the ride is basically a long series of slow climbs and slow falls between about 10Km and 20Km.

[etspets]

am i the only one who is seeing blurred, unreadable text on the image?

[keptin]

Could be image scaling. Try another browser or download the image directly, http://i.imgur.com/GqLQktX.jpg

[Gristle]

How come this thread isn't stickied? It need to be, 1st post is excellent.

[phoenix_ca]

Excellent? It's godly. And it's great that it all still applies.

Thanks. I'd had quite a few problems with planes yawing right or left on the runway. Now I know what's up. (That and I think I've been chronically putting my gear way, way too far back. >.< )

[linkxsc]

Great thread. Should be linked to by the wiki for spaceplane design

[Xaelath]

The OP has nice drawing skills.

Good tutorial too.