My spaceplanes fly like a lawn dart, no matter how I build them.

[KristopherKerblumbus]

Okay, so based on this topic here: http://forum.kerbalspaceprogram.com/threads/105441-Change-in-Stock-Aerodynamics it seems like Squad has not, or at least not yet, made any changes to aerodynamics in .90. That's good, that means that my errors can be chalked up to PEBKACs and can be fixed

These threads:

http://forum.kerbalspaceprogram.com/threads/90747-Kerbodyne-SSTO-Division-Omnibus-Thread/page53

and

http://forum.kerbalspaceprogram.com/threads/93779-SSTO-Spaceplane-Airplane-Design-Contest-II-Akademy-Awards

have several designs that I've tried, not by copying them deliberately (I'd actually never seen those threads before looking through the Basic Aircraft Design tutorial today--most of my KSP experience has been true Kerbal, trial and error ) but by designing planes that *look* like they would fly, and to make a long story short, nothing does. Nothing does well, anyway. I have to push the S key for all I'm worth to drag any spaceplane's tail into the sky, and as soon as I do, it noses forward like it's got lead in the nose, even though my CoM never moves more than 2/3 of the way forwards from the rear of the craft, no matter what I design. My most recent spaceplane design is actually a fair dead-ringer for this (http://s1378.photobucket.com/user/craigmotbey/media/Kerbal/Spaceplane%20economics/screenshot295_zps6686cd4c.jpg.html) in the fuselage anyway. My design had over twice the wingspan to compensate for what I thought was a lack of lift, turbojets instead of RAPIERs, and LVT45's instead of nuclear engines.

So to make a long story short, I'd like any kind of direction this wonderful community can give me as to just what the heck I'm doing wrong here, especially because I'd like to move on to some MK3 VTOLs next, to start building things like polar and Munar and maybe even Dunar bases, but if I can't even get an MK2 into orbit to launch a few CubeSats, I'm in trouble!

I definitely get how basic plane design works--I've been an aero-nut since before I could walk; thought I was gonna be an air force pilot until I went legally blind, and, growing up, had everything "plane" imaginable--model planes, flight sims, airplane collectable fact sheets...the whole deal. So I've got designs for days that *should* fly, both on-paper and in my head, but nothing works when I actually design it in KSP.

Edited January 1, 2015 by KristopherKerblumbus

[Hodo]

So you are running stock aerodynamics or FAR or NEAR? If you are an aero-nut as you said then FAR would be your best choice as it would be the closest you are going to get in KSP to the real aerodynamic forces on an aircraft.

Eitherway push a picture of your craft in the SPH with the CoM and the CoL indicators on and if possible get multiple angles, top, side, and rear with the CoT on.

The thing with a decent SSTO spaceplane is you have to be able to get high enough to build speed where you are not in the thickest part of the atmosphere.

Like this old ugly stock aircraft that I made a while ago for tests in atmosphere.

Now mind you that one was never an SSTO but it didnt take much to get it there.

And that is what the SSTO combat aircraft version turned into. Still flies to orbit and does the job quite well.

The best advice is to start small find a design that works then build up from there.

[StormKat]

I feel your pain. I have been on the rocket side of KSP for a very long time. So for the last few weeks I have been dabbling with aircraft and spaceplanes.

Throw away all those cool designs you know and start small. Super small. A MK1 cockpit, a fuselage, an engine nacelle, basic jet engine, some wheels, and a pair of delta wings with elevons. Then tweak the CoM and CoL until you get something that works.

Use the Rotate Gizmo to change the angle of attack on your wings slightly. That will help some too.

Doh! Ninja'd

Hodo has the right idea.

[Kryxal]

A pic from the side would help, with center of mass and center of lift turned on ... and maybe one from overhead. Just from what you've said, I'd guess either you have too much space between CoM and CoL, or too little pitch authority.

[Hodo]

Use the Rotate Gizmo to change the angle of attack on your wings slightly. That will help some too.

I have to say, DONT DO THIS.

This is a bad idea for any design. The reason for this is it actually changes the way the craft flies when level. If you have 5deg of upward AoA on the wings then the craft will need to be pointed 5deg down to maintain level flight at some speeds. It is best to start simple and keep them inline with the aircraft till you get a bit more advanced in your knowledge. After you are comfirtable with the basics then go to messing around with AoA of the wing placement.

[KristopherKerblumbus]

I'll definitely post some pics as soon as I'm home. Sadly, I'm at work, since I have to find *some* way to keep the internet on long enough to download the updates to KSP

[GoSlash27]

KristopherKerblumbus,

Check out my SSTO spaceplane tutorial here:

http://forum.kerbalspaceprogram.com/threads/102182-So-you-want-to-build-a-space-plane-%28-25-stock%29

If you need further help with how to design your spaceplanes to be not-lawn darts, just give a holler.

Best,

-Slashy

P.S. If you're using FAR or NEAR, my tutorial won't actually work, since it's a turbojet/ booster design, but the aerodynamic and balance principles still hold true.

[Janos1986]

I have to say, DONT DO THIS.

This is a bad idea for any design. The reason for this is it actually changes the way the craft flies when level. If you have 5deg of upward AoA on the wings then the craft will need to be pointed 5deg down to maintain level flight at some speeds. It is best to start simple and keep them inline with the aircraft till you get a bit more advanced in your knowledge. After you are comfirtable with the basics then go to messing around with AoA of the wing placement.

Uhh I do this all the time, at a point that I trim them until they are level to a decent cruise altitude, 7km for fighters and 15kmfor long range recon planes for example.

Never had problems, my planes are pretty nimble.

If you want, trim the angle of attack unti you find a good balance, its not impossible.

[GoSlash27]

Uhh I do this all the time, at a point that I trim them until they are level to a decent cruise altitude, 7km for fighters and 15kmfor long range recon planes for example.

Never had problems, my planes are pretty nimble.

If you want, trim the angle of attack unti you find a good balance, its not impossible.

I'll side with Hodo on this one.

I do not recommend monkeying with AoA until *after* you've got static balancing and dynamic balancing down. It'll just complicate things while you're still learning the basics.

Best,

-Slashy

[DrD]

I'm pretty terrible at planes also but I do have something to add around rotating wings to adjust AoA.

Although this may be a bad idea for the wings, if you've got forward canards you can rotate them a bit to bring CoL forward. Even a tiny bit of positive AoA on canards will move CoL significantly in my (brief) experience.

[LethalDose]

IME, planes flying like lawn darts is due to the CoM being too far in front of the CoL. Adjusting them to be closer to each other should help.

[Alshain]

I'll definitely post some pics as soon as I'm home. Sadly, I'm at work, since I have to find *some* way to keep the internet on long enough to download the updates to KSP

First things first. FAR or Stock? Wanderfound's planes are designed for FAR so if your "inspired" by them and your using stock, it might not work.

[Maelstrom Vortex]

I have a simple solution to your lawndart problem. Position some leading canards near the front end of the aircraft to control initial contact air flow to lift your front end. I noticed most of your craft have a lot of back heavy control surfaces.. you need a couple of forward control surfaces.

[Alshain]

I'm not sure what exactly what a "back heavy control surface" is, but I don't recommend canards for most planes. They have their uses and they are few. Using them to correct balance issues is a crutch which may work going up but will likely be disaster coming back down.

[Hodo]

I have a simple solution to your lawndart problem. Position some leading canards near the front end of the aircraft to control initial contact air flow to lift your front end. I noticed most of your craft have a lot of back heavy control surfaces.. you need a couple of forward control surfaces.

He never posted a pic of his craft so no clue what you are talking about here.

[KristopherKerblumbus]

Okay! Here come the screens. It seems in a mild fit of frustration (and not liking cluttered build-lists) I deleted all but one of my SSTO attempts--but they were basically iterations of this same design with only mild variations, so any and all criticism is welcome. To answer questions earlier ITT: I am currently using stock parts and stock aerodynamics, will look at FAR when I have the chance, but right now I'm kinda building some planes as a gift for a friend who has no mods and won't use them, so I've got to do as much stock as I can for now.

EDIT: Yup, okay, so I just confirmed it. I'm building my planes *upside-down* somehow. I don't know how. But this design above (like a few of my others) actually flies more stably inverted than it does right-way round. What the heck?

Edited January 1, 2015 by KristopherKerblumbus
Fixing image links

[Anquietas314]

http://i.imgur.com/MhT9VPu.png

The problem is your center of mass is way too far away from your center of lift. It should be in front, but only just.

[KristopherKerblumbus]

Ahh. I figured that being too close was bad, and only if you had your CoM and CoL at opposite ends would you run into trouble. I guess the closer you get, the better, and only if you get right on top of each other or in front you get problems? Back to the drawing board!

[Kryxal]

Lawn dart, sure enough ... reduce the distance between the centers of the CoM and CoL by at least 2/3, maybe 3/4. Check what happens as fuel drains to be safe, though, if CoL ever moves in front of CoM you're going to have lots of trouble.

[Anquietas314]

if CoL ever moves in front of CoM you're going to have lots of trouble.

Ahem, this is proof to the contrary

It's only an issue if CoL moves far in front of CoM.

[Pecan]

...So to make a long story short, I'd like any kind of direction this wonderful community can give me as to just what the heck I'm doing wrong here, especially because I'd like to move on to some MK3 VTOLs next, to start building things like polar and Munar and maybe even Dunar bases...

Welcome to 2015, would you like to achieve your objectives efficiently or stick with stufff that's SOOO last year?

Spaceplanes look pretty.

Spaceplanes can be efficient launch-vehicles.

Spaceplanes are fun on Laythe.

Now we've got that out of the way ...

"Mk3 VTOLs" - ok, nothing to do with space, effficiency or ability = just do it.

"Polar and Munar and maybe even Dunar bases" - ok, nothing to do with efficiency or (especially) spaceplaes = what's the problem that you really want to solve?

Seriously; what is it that you want to achieve?

If it's a good Mk3 spaceplane then do that - no-one else has yet.

If it's a polar/munar base then do that - nothing to do with 'planes.

If it's a Dunar base then do that - nothing to do with 'planes.

[KristopherKerblumbus]

True. They don't have anything to do with each other at first blush. But what I'm thinking of is using a massive MK3 spaceplane to deliver parts via inverted cargo bay and IR and construct a base that way Skycrane, FTW!

[Pecan]

True. They don't have anything to do with each other at first blush. But what I'm thinking of is using a massive MK3 spaceplane to deliver parts via inverted cargo bay and IR and construct a base that way Skycrane, FTW!

Good - so we have a basic design requirement :-) I don't know how far I can help but I'm pretty sure that collectively we can crack exactly what you're trying to do, if it's possible :-) We now have:

1 - Mk3 parts

2 - 'Massive'

3 - "Inverted" cargo bay

4 - Infernal Robotics

'construct a base that way' not parsed - ... have to delve further here ... 'base'?, 'construct'? What do these things mean to a launch/transfer vehicle? Does it have to position them too?

[so far 300t 'plane (made of Mk3 parts) to deliver a 1t payload is looking good - keep defining/refining the definition and you'll get to the solution ...]

[KristopherKerblumbus]

LOL! You're awesome Thanks for your help, I really appreciate it. But I'm actually not really looking for directions on how to do that *just* yet. One must walk before they can run, after all. I was really just looking to figure out what I was doing wrong with my MK2 SSTOs, and from there I'd start working on launching things like rovers and CubeSats from MK2 SSTOs, THEN I'd work my way up to MK3. Half the fun of KSP for me, anyway, is blowing stuff up in spectacular ways and then puzzling out how I can make it work better on my own. I was just stuck on this CoL thing. But now that I know I totally misinterpreted distances, I think I'm set for a while. Thanks again!

[Pecan]

's good and Happy New Year (again) :-)

You got a lot of "spaceplane" answers from other people but I thought no-one was addressing what you said you wanted to DO with them.

Looks like you know and you're on your way; enjoy it :-)