Inconsistent physics or controls glitch?

[twilite20K]

I was just working on this hateful SSTO spaceplane... And a few flights ago I was able to successfully get it up to a 30,000m orbit. Great.

So then I try a radical redesign, without saving, moving some fuel tanks around, radial connecting, semi-clipping but no console clipping or anything non-stock. move the ram engines above the wing instead of below the wing a few other things. Try to fly...it lifts, and then promptly nosedives like a steel pigeon. Ok, that didn't work.

So I reload my spaceplane design, and in an effort to save weight, remove the Rockomax Radial engines from the bottom of the leading forward delta wings.

original plane here:

http://i.imgur.com/fL9L7g5.jpg?1

Ok so it should fly like it did before, after such a minor change, right? No. Won't stay in the air unless I jam on the pitch button. Like the thing has no lift of it's own anymore. So has anyone else seen anything like this before?

Edited August 30, 2013 by twilite20K

[Dewm]

I've had this problem.

I had a plane that flew like a dream, cruised around in it and what not.. then I decided to switch the direction of the landing gear.. and she wouldn't even take off. Weird...but whatever.. I'll just switch em back. all it is, is a simple rotation. SO I switch em back..and she still flies like crap. I messed around for a good hour trying to get that thing to fly again.. no go. and all I did was rotate landing gear 180, and then back. no other changes.

[Thomas Cook]

Could you, maybe upload the image of the plane with the center of mass and center of thrust enabled?

My planes always seems to fail at that point. I've also had lots of trouble when fuel got consumed. It seems that if you consume fuel, the center of mass could change, tipping planes in directions you don't want.

[Johnno]

So I reload my spaceplane design, and in an effort to save weight, remove the Rockomax Radial engines from the bottom of the leading forward delta wings.

Ok so it should fly like it did before, after such a minor change, right? No. Won't stay in the air unless I jam on the pitch button. Like the thing has no lift of it's own anymore. So has anyone else seen anything like this before?

Well first of all, those radial engines are 0.9 tons each. Removing them likely changed your center of mass enough that the plane became unstable. Did you put the engines back and do another flight to confirm that it was the change that did it, rather than a bug being introduced?

Removing nearly 2 tons from the middle of a spaceplane is rarely a "minor change". Even the slightest of changes can upset the balance, this is why a lot of people (myself included) have trouble once they get up to lighting their rocket engines, because mass has shifted from the jet fuel being burned that the CoM no longer is where you'd need it to be.

SSTOs are hard, I think you're underestimating the change you did. Try putting the engines back and see if it flies like it did before.

[krenshala]

It would be nice if we had a toggle to switch fuel tanks from full to empty and back in the hangar/VAB. That would make some of the design process easier for these kinds of things.

[numerobis]

It would be nice if we had a toggle to switch fuel tanks from full to empty and back in the hangar/VAB. That would make some of the design process easier for these kinds of things.

I bet this would be trivial to code up.

However, in my experience, I'm headed for disaster if I break the rule that fuel tanks must be centered on the center of mass. Sometimes I can build something that can handle a moving center of mass, but it's going to require a few more test "flights".

[twilite20K]

Actually once I removed the joystick and restarted the game, the controls went back to normal. Strange thing is I disconnected the stick during flight to see if that was the culprit and my plane still flew like a lead duck. Not that the controls were unresponsive, but the plane would just gradually lose lift. I'm strictly keyboard now, and this aluminum goose is now stuck in orbit!!