Troubleshooting my aircraft

[PolecatEZ]

My issue with most SSTOs I make is that they tend to "level out" at around 30,000 meters and refuse to nose up when I pop the rockets on. No amount of RCS or lift surfaces seems to break them out when they're going around 1200-1500 m/s. Every once in a while I get lucky and hit the right approach angle before the high speeds and can rocket them that way, but I want to know how you pull your nose up and down at those speeds and how can I work my designs so I don't have that issue so badly?

[CalculusWarrior]

Hmm, I'm not exactly an expert on spaceplanes myself, but maybe you could try playing around with the centres of mass & lift? Ideally you want the centre of lift slightly behind the CoM.

Alternatively, add a SAS unit or two, if you can find room.

Hope I could help.

[Neodyme]

I have the exact opposite issue, my plane decides it wants to be a bike and do a wheelie when it hits ahout 23km and have my rockets on, causing me to plummet, as its unrecoverable, not eve asas can fix it, dunno why it does it though

[PolecatEZ]

Hmm, I'm not exactly an expert on spaceplanes myself, but maybe you could try playing around with the centres of mass & lift? Ideally you want the centre of lift slightly behind the CoM.

Alternatively, add a SAS unit or two, if you can find room.

Hope I could help.

I follow that rule religiously and it works well at lower altitudes, but does behind mean exactly straight behind or is it better to have it slightly above or below also? SAS is also a standard feature, but it doesn't help much when neither I nor the SAS can make my nose budge a fraction of a degree upwards at speed. Down is usually no problem, pulling up is ridiculously hard.

I have the exact opposite issue, my plane decides it wants to be a bike and do a wheelie when it hits ahout 23km and have my rockets on, causing me to plummet, as its unrecoverable, not eve asas can fix it, dunno why it does it though

Can you give me an idea exactly how your CoM and CoL interact? Are they on exactly the same plane and directly in front, behind, or touching each other? Or is there variation? How about thrust? Does that play into this?

[Jason Patterson]

At 30km, you generally want to be going substantially faster than 1200-1500 m/s. If you're limited to that speed at 30km, then I would suggest trying to cut some mass, which will also help your maneuverability. At that altitude you're barely in the atmosphere anymore, so your control surfaces won't work very well. Vectoring engines are helpful, but really, control pod torque should be enough to change the attitude of your plane.

Are you turning off avionics at that point? If not, you should try doing so, since it will dampen any changes you try to make.

Is your rocket engine(s) off axis vertically? If the thrust vector for the rockets doesn't go through the center of mass, then it's going to cause a torque toward the opposite side, which might be what's keeping you from going up.

[Jason Patterson]

You might have better luck posting a picture of the craft and/or the craft file itself. It's hard to give general advice about specific problems.

[CalculusWarrior]

I had an issue with my plane suddenly wanting to pitch up at high altitudes. Turns out it was just that I had installed extra engines below the centre of mass of the craft and the resulting torque was quite annoying. I found that adding RCS helped out quite a bit, as at high altitudes control surfaces become suggestion surfaces, they just suggest which direction your plane should point, and it goes where it will.