Space Plane Lift Problem

[cookiedamage]

Hi guys. Recently I crafted my first successful space-plane, the "Hopeful - 2". Let me get straight to the point: When taking off and becoming airborne, I've noticed the plane's tendency to continually drift upwards, almost becoming vertical. Sometimes it locked up and fell back down, and other times it flipped. The only way I can stay horizontal is to frequently kill or throttle down the engines.

Notes:

-I've added parachutes to the tope of the plane

-The four engines are connected to the plane via decouplers. The largest engine is attached directly to the plane.

Any ideas of what is going wrong and what I should change? Thanks!

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[sal_vager]

Hi cookiedamage, nice aircraft, you may be one of the few pilots to have designed a craft that needs down trim instead of up trim (at least that's how my planes turn out)

You could try moving the wings rearwards a little so there is more lift at the back of the aircraft, another thing that might help would be less weight at the rear, or even add some extra wings at the back to help keep the back of the plane up.

[semininja]

The engines are below the center of pressure of the plane, and are basically levering it upward. The huge tails on top aren't helping, either. Try putting one basic steerable winglet vertically in the back as a tail, and maybe two horizontal ones at the tail as elevators. That should help somewhat. It may actually be better to have the side winglets angled downward on the underside of the plane to counter the engines somewhat.

[Vanamonde]

Your engines are thrusting below the center of mass, which will impart a bit of rotational force, bringing the nose up. That's actually a good thing, if it's not overly strong. You could shift some or all of those engines higher and closer to the center line, but again, you wouldn't want to lose the effect entirely. Or you could add a couple of fins with control surfaces up at the nose, where you could call upon them to help counter the torque (though HarvesteR, who should know because he makes the game, strongly advises against using canards at the front of a vehicle for stability reasons). You could shift the whole wing structure, engines still attached, further back, which would leave the nose heavier, but that might create problems while descending and landing. In short, balancing a plane is EXTREMELY finicky and tricky, so play around with it until it works. Just keep in mind that whatever configuration gets you up there also has to work on the way down, so test it both on powered ascent and unpowered descent.

[Extraneous]

I can't wait until 0.17 and us getting a centre of mass indicator when making spaceplanes - will make designing them so much easier.

Think of it in this way - look at your plane from the side and draw a line from the centre of your main wing perpendicular to the wing's surface. If the majority of your spaceplane's weight is behind this line, it will pitch nose-up under thrust. If the majority of your plane's weight is in front of it, it will pitch nose-down. The further away from the line, the stronger the effect is.

[cookiedamage]

Thanks to all, I'll try removing some weight in the back among other things.

[Volt]

Your wings are also quite far forward, considering you don't have a proper tail-plane. If the centre of lift is too far in front of the centre of gravity, that can also have an effect. Trial and error is the only way to fix this without visual cues.