Heal my spaceplane!

[Evanitis]

Leapfish Mk II .craft file

Yes, it has many problems. Most of those are deliberate design chocies my engineers are quite proud of. It definately won't be the most graceful SSTO you ever flown. But one of it's silly properties isn't a planned feature: when I fire the rocket engine it veers slightly to the right.

I didn't notice the plane doing it in jet-mode. It isn't a huge problem, as it can be corrected mid-flight, but it's an annoying thing I'd prefer to fix before we start mass production. I have taken the plane apart a few times, reatached everything with angle-snap, but I couldn't fix this phenomena, nor I could find the problem. Care to take a look?

Attaching a picture too:

[Tex_NL]

Your problem most likely originates in an CoG imbalance. It can be an optical illusion but it looks like the 'tank' under the nose sits slightly right of the centre line. If this is indeed the case that's probably what causes your right yaw.
You could compensate for the imbalance by reducing thrust a few percent on the right hand engine or by moving a bit of fuel to the left. And you should not go full throttle, stay at a low engine power to give your SAS time to compensate with reaction wheels.

Edited January 25, 2016 by Tex_NL

[Evanitis]

2 hours ago, Tex_NL said:

CoG imbalance.

That was my though too, thought I can't visually confirm that - the CoM ball in SPH is huge. That tank is straight - it holds a gear too, so if the problem would be there, the veering would start on the launchpad.

It's a two wiplash - one swivel setup, so it shouldn't be an inbalanced thrust issue.. but it to think of it again, the jets keep going on for a while in rocket mode, so it's possible. But I'm pretty sure I would have noticed if the problem stoped after the jets flameout. I know I could work around the issue by shifting some fuel, but I'd prefer to eliminate it... it would look too ridiculous to include pumping fuel to the left tank in the operating instructions.

About decreasing thrust... I had a few SSTOs before, and I never had to do such. I have planes where it wouldn't be an issue to do so, but here... it kinda' needs all the power it can amass to reach orbit. Will test this too, but I feel if it solves the problem, it will generate an even bigger one.

EDIT: had a thought... on it's belly, the two wings touch. I added an RCS port to the very middle of it. But technically it's only attached to one wing. Is it possible that the center position of the port doesn't matter and it only adds it weight to that wing?

*runs to test*

EDIT EDIT: Yup that was it. Glued it to the main fuselage, and nudged it to be on the exact same position where it was before. How silly.

Edited January 25, 2016 by Evanitis

[SSgt Baloo]

On 1/25/2016 at 5:36 AM, Evanitis said:

EDIT EDIT: Yup that was it. Glued it to the main fuselage, and nudged it to be on the exact same position where it was before. How silly.

...And that is how we learn new things.

Glad you found the problem.