Space planes flipping out when launched vertically

[KerballianDummy]

Hi all,

I'm not the best of designers, I'm generally better at flying things, so I've probably made a massive mistake with the design somewhere that I can't see - that's where I hope someone/some people from the community can help me.

So, I've been trying to get a space plane over to Laythe the last few hours by sending a space plane up into Kerbin orbit, docking it onto a tug craft then sending it to Laythe. However, I've been encountering the same issue again and again when I've launched the space plane: when I get to around 10,000m, the whole craft pitches up suddenly and I cannot keep it stable, even with heavy use of RCS.

For reference, this is what I'm trying to send up:

Javascript is disabled. View full album

It's basically the White Dart created by Rune with some modifications to turn it into a rover/plane hybrid. I tested it out on Laythe using Hyperedit (as a kind of "simulation"), then reverted the flight back to the SPH so nothing was left on Laythe. When I launch, the SRB's fire and get me up high, doing most of the lifting, where I then drop them and switch to the liquid fuel engine (a modded part from the SpaceX pack). Then, when I reach around 10,000m, the entire craft pitches upwards and I can't control it.

My guess for this is that the wings of the space plane are creating too much lift for the rocket's controls to handle, but I don't understand why they didn't do it when I lifted off. Does anyone have any suggestions, both for an explanation as to why it's only happening high up and how I can counteract it?

Thanks in advance, fellow players!

P.S. Yes, I did look around the forum but I didn't find anything. Apologies if there is already a thread for this. If there is, please could you leave a link and have an admin/mod lock the thread?

Edited March 31, 2014 by KerballianDummy

[Skorpychan]

Maybe it's happening higher up because it's moving faster and in thinner air?

[merendel]

I notice you have most of your reaction wheels on the SRBs, once you drop them they obviously are not helping stability anymore. You could try adding some additional wheels to the main body. One or two of the big ones between the orange tanks and possibly a couple on thos small pods just below the plane. That might be enough to overcome whatever stability issues you are having.

Also have you considered just flying it as a single stage to orbit plane off the runway. Asumeing your useing a saber engien you should be able to get to orbit, dock with a refuler/tug and off to layth without needing the big ass rocket to launch it.

[GoatRider]

I'm surprised it doesn't flip over sooner. With all that wing area up front, it's like throwing a dart backwards.

[KerballianDummy]

I notice you have most of your reaction wheels on the SRBs, once you drop them they obviously are not helping stability anymore. You could try adding some additional wheels to the main body. One or two of the big ones between the orange tanks and possibly a couple on thos small pods just below the plane. That might be enough to overcome whatever stability issues you are having.

Also have you considered just flying it as a single stage to orbit plane off the runway. Asumeing your useing a saber engien you should be able to get to orbit, dock with a refuler/tug and off to layth without needing the big ass rocket to launch it.

Ah, good idea; I'd totally overlooked that.

And I had thought about it, but I disregarded the idea because of where the docking port is. If I'd docked a tug there, it'd spin the ship around when burning, therefore I can't use it. At least, I think it will.

I'll go attach some more reaction wheels to the tanks and I'll get back to you, Merendel. Thanks for the help as well, Skorpychan.

[Tarrow]

Sounds daft, but I wonder if there's an issue with asymmetric drag. Does the game model drag accurately enough for 40+ solar panels all on one side of the vessel (each with a drag of 0.2) to cause an imbalance?

[KerballianDummy]

Well, Merendel, it worked! I finally managed to get the plane into orbit and ready for the tug to dock and take it to Laythe.

Tarrow, you make an interesting point. I considered it myself but I figured the wheels might counteract it. Now I think about it again, you could be right. Doesn't matter too much now, it's up in space without too much of a problem and ready for it's trip to Laythe.

Thanks all!

Could a mod lock this thread for me and change the title to show it's been answered? (I can't find a way to do it myself, unlike on other forums)

Edited March 30, 2014 by KerballianDummy

[Taki117]

To change it to answered edit the first post, then click "go advanced" and there should be an option near the top.

[KerballianDummy]

To change it to answered edit the first post, then click "go advanced" and there should be an option near the top.

Ah, thank you. I didn't think to look in there - just shows why I should never try to manage a thread (even basic things like changing the title) when it's 2am in the morning.