Spaceplanes

[Conte_Vincero]

Heya, I've been trying to build spaceplanes for a while, but have always been thwarted by one simple bug, stability. Pretty much every spaceplane just flails around wildly as soon as it gets airborne, and although activating SAS steadies it, I can't control it for long enough to make any sensible course corrections. I haven't done the calculations, but this doesn't seem to be a simple CoG CoL problem. Does anyone have any idea why this might be?

Secondly engines, what is the purpose of the intakes, narcelles and engines. As far as I can tell it makes little to know difference what engine you fit with which narcelle. Ramjets shouldn't work on the ground and yet they do, how is this possible???

I would be delighted if anyone could help me, I'm not looking for tutorials, just an explanation of why some designs work and others don't.

[bsalis]

There are bugs. But I don't think stability is one of them in a narrow sense. Spaceplanes are not easy.

Got any pictures of your planes?

Also, intakes are not functional at this stage.

[Fuzzy Dunlop]

Hitting caps-lock will activate "fine control" mode, which can help. But it may be that your designs are just dynamically unstable.

First thing is the air resistance, which creates a force called drag. Drag always points in the opposite direction to your planes motion. You want things that create a lot of drag to be at the rear of your plane, i.e. the centre of drag should be behind the centre of gravity. If you put high drag components on the front of your plane the air will try to move them to the back - by spinning your plane round.

So a big tailplane tends to make a more stable aircraft.

[Conte_Vincero]

There are bugs. But I don't think stability is one of them in a narrow sense. Spaceplanes are not easy.

Got any pictures of your planes?

Also, intakes are not functional at this stage.

Also I am a final year mechanical engineering student so I know what drag is

[UNSC]

In this game it is possable to stall the aircraft very easilly. Use the avioncs nose cone, this is an SAS computer that allows you to have some control of the craft.

[EndlessWaves]

Heya, I've been trying to build spaceplanes for a while, but have always been thwarted by one simple bug, stability. Pretty much every spaceplane just flails around wildly as soon as it gets airborne

Which fail does it flail? Tipping back to front? Rolling sideways?

Secondly engines, what is the purpose of the intakes, narcelles and engines.

At the moment? Decoration. Only the jet/turbojet is functional in 0.16 and the engine bodies/nacelles don't do anything.

[Conte_Vincero]

Which fail does it flail? Tipping back to front? Rolling sideways?

At the moment? Decoration. Only the jet/turbojet is functional in 0.16 and the engine bodies/nacelles don't do anything.

Just general flailing, although it does roll far easier than it pitches, but it does both far to easily

[Conte_Vincero]

In this game it is possable to stall the aircraft very easilly. Use the avioncs nose cone, this is an SAS computer that allows you to have some control of the craft.

Yeah I'm using that and it stabilises the aircraft, but after I de-activate it in order to make a course correction, my aircraft becomes uncontrolable. It tends to roll rather than pitch, but it does both far to easily. I will have a look at stalling, but it's not exibiting the classic jerk charactaristics you would normally associate with a stall

[Conte_Vincero]

Oh and pics

[EndlessWaves]

Oh and pics

You've got four engines and ten control surfaces on a plane that can't weigh much more than 20 tons, that's why it handles more like a Eurofighter with the flight computer turned off than a 747.

That thing is flyable with just the vectored thrust from two of the jet engines alone, try removing most of the control surfaces and possibly a pair of engines and it'll be far more docile.

[bsalis]

That thing is flyable with just the vectored thrust from two of the jet engines alone, try removing most of the control surfaces and possibly a pair of engines and it'll be far more docile.

Yes agree. I think it looks stable. My first thought of what was going wrong was ... "Is he flying that at full power? Because that would a handful to say the least".

So yeah, my advice is try flying between 100 to 200 m/s at most.

[UBERDOMINATOR]

One other thing that MAY help, aside from all of the great advice above me, is the option in the main settings menu to lower the sensitivity of controls. I don't know if this is even functional at this point, or it could be that it is designed for joysticks etc., but worth a shot. Psychologically, it made a difference in my flights!

[Conte_Vincero]

You've got four engines and ten control surfaces on a plane that can't weigh much more than 20 tons, that's why it handles more like a Eurofighter with the flight computer turned off than a 747.

That thing is flyable with just the vectored thrust from two of the jet engines alone, try removing most of the control surfaces and possibly a pair of engines and it'll be far more docile.

Yeah they were an attempt to make it take off with a shorter run, but removing most of them, and the two outrigger engines worked!!!! (more or less), but the engines ceased to work properly once I left the lower atmosphere, so is it not possible to attain orbit with a ramjet (also I'm assuming that they will be updated as I can take off with them which is physically impossible). Thanks a Ton for the help so far, and I will now attempt to complete the first ever orbital biplane

[UNSC]

Assuming you mean a decaying orbit, i'm not sure if it will be possable to achieve orbit with just jet engines even with Ram intakes. The speed is just not there.

[AmpsterMan]

Also, I don't think the turbo jets are supposed to be Ram engines.

[jurfburf]

I'm having a problem with pitch control; I've built 2-3 planes, all generally using canard-delta configurations. They've got the power to get off the ground, but as soon as they do, they start spinning end-over-end and crashing. What's the secret to pitch stability? Longer fuselages? I've tried canards/control surfaces (both overkill and minimalist) but I'm still not sure what to do. All other axes seem fine, just pitch is totally uncontrollable.

[EndlessWaves]

but the engines ceased to work properly once I left the lower atmosphere, so is it not possible to attain orbit with a ramjet (also I'm assuming that they will be updated as I can take off with them which is physically impossible). Thanks a Ton for the help so far, and I will now attempt to complete the first ever orbital biplane

The turbojet will generally start to lose power around 10km and by 20km is operating at around 10% of it's power (actual amounts also depend on forward speed). An orbit may be possible given that there's no atmospheric drag on craft you're not currently piloting so as long as you could raise your perikee above the auto-burnup limit you could have an orbiting jetplane.

Edited September 14, 2012 by EndlessWaves

[Vanamonde]

pitch is totally uncontrollable.

We'd have to see your plane to give any specific advice, but as always, I refer people to perhaps the single most useful thread in KSP history: http://kerbalspaceprogram.com/forum/showthread.php/13851-The-woes-of-building-a-space-plane?highlight=woes+spaceplane

[zekes]

I have found that it helps to understand CG, and build off of that. Remember the engines are heavy, so the space plane almost always starts nose heavy and lands tail heavy (as fuel weight goes away) also if you have a ship that comes in with fuel to spare, keep it form draining from the front tank until the very end, so you have some nose weight on landing. RCS tanks also add weight, but i find the best way to build it is to build it with the landing CG in mind- i.e. without fuel weight. Then build the plane so when on the ground it is sitting on the gear with pitch up attitude (slightly) or take off vertically. Also adding lots of corntrol surfaces helps add lift so the SAS can hold the ship steady on reentry.

Also reference this:

http://kerbalspaceprogram.com/forum/showthread.php/11214-The-K-Prize-100-reusable-spaceplane-to-orbit-and-back

Best of luck!

[djnekkid]

Try looking at my spaceplane. Youtube link is in my signature, and there are .craft files in the youtube discription. Generally you want your ship to be symetrical in the horizontal plane, and also trying not to add too much weight under or over it. For example try to make a good balance between the weight of the landing gear and the tailsection.

Also, if you hold ALT while pressing the W/S-keys (or even the other ones i would assume) you can trim your pitch up or down, so you can keep your forward motion steady

[EndlessWaves]

I'm having a problem with pitch control; I've built 2-3 planes, all generally using canard-delta configurations. They've got the power to get off the ground, but as soon as they do, they start spinning end-over-end and crashing. What's the secret to pitch stability? Longer fuselages? I've tried canards/control surfaces (both overkill and minimalist) but I'm still not sure what to do. All other axes seem fine, just pitch is totally uncontrollable.

If it's pitching violently then there's a force acting to rotate it around the centre of gravity. This is generally either wings creating lift too far forwards/backwards or engines generating thrust too far above or below.

[deltaflyer_19]

Well... if u own the C7A Aviation Pack (which most us should of own) i know that issue. The center of lift is dictated by the placement of ur wings. Use the delta wings for ideal lateral stability. Remember, add movable canards for delta wings placed aft of center of gravity; this will ensure stability. Add one or 2 tailfins with rudder attachment to dampen excessive longitudinal oscillations. Reduce the use of thrust-vectored engines, those usually cause overcontrolling conditions that can upset ur spaceplanes aerodynamic balance. Finally, use an avionics nose cone realistic flight control (if u don't have that, use ur SAS mods or MechJeb). I hope this helped u. Chin up fellow kerbinaut! Don't let physics thwart ur flights. Post me back if ur successful, good luck.