What the heck is going on in here?

[I_Killed_Jeb]

Not sure what the hell is going on here with my current experimental spaceplane design -

As you can see, the jet engines are sucking up fuel and generating measurable thrust, but the force is not transferred to the plane for some strange reason. Just to see what would happen, I swapped out the engines to aerospikes with the exact same result!

Now, if I take this exact same design, and just place the side engine-wing assembly right by the tail of the craft, thrust is generated normally. (Of course, it doesn't fly particularly well that way but just as a proof of principle) What gives? In the SPH the center of thrust is still behind CoM even without the tail aerospike

[TechnicalK3rbal]

Two things:

1. If you left they brakes on, they can stay locked for a looooooooooooooooong time.

2. The wings behind the engines are probably blocking the thrust.

3. The jet engines take a while to get to full thrust, so if you didn't wait long enough...

[I_Killed_Jeb]

Two things:

1. If you left they brakes on, they can stay locked for a looooooooooooooooong time.

2. The wings behind the engines are probably blocking the thrust.

3. The jet engines take a while to get to full thrust, so if you didn't wait long enough...

1. You can tell by the screencaps that the brakes are unlocked

2. Awesome, didn't consider that, although in terms of physics that doesn't make any sense

3. Not it, you can wait forever and will not budge

[TechnicalK3rbal]

I meant after the brakes are turned off, they'll still function as if they ere on.

[Specialist290]

Did you have the brakes locked at any point before you activated the engines, though? Sometimes the brakes on the landing gear like to "stick" for a few seconds.

[I_Killed_Jeb]

Nope, the brakes were never turned on, and in the original design if I switch on the tail aerospike the thing will be accelerated down the runway. I guess I should've explained I'm not a total n00b, I've made lots of SSTOs before with no problem but they've always been of the the delta-wing, all engines in the back configurations, and I'm trying to branch out a bit with my designs but now, this. Very odd

[austin4050]

I can almost guarantee it is because of the rear wings.

[RocketPilot573]

Yep, I'm 99% sure that it's those wings...

[I_Killed_Jeb]

Thanks guys, will give it a shot later. Very very odd that the game takes that, of all things, into account

[austin4050]

Yeah the game is still an alpha, so physics sometimes forgets itself and goes wonky. But if you move the engines up on the fuselage about 10* degrees or so it should be fine. if not I would strongly suggest posting it in bugs.

[Hodo]

I have had this issue before.

I had to restart my career mode. It was broken bad. No matter what I did it was like the planes were glued to the runway.

Even when I did get them off the ground, by building a VTOL they wouldn't move forward even when full thrust.

[Kasuha]

When you aim an engine at another part of your ship, it will stop generating thrust and concentrate only on trying to overheat and destroy that part. Only after that part has exploded it will start generating thrust.

[FoxKit]

I had a similar problem with a spaceplane design. The engines are too close to the fusalage, and the collision mesh of the body of the plane is blocking the engines. :/ You need to move them out a little further (throw in an octagonal strut). The game requires the whole circular area of the engine be clear for it to thrust. It's silly that it looks like it's just a pixel or two off, but... Yea.

[Tidus Klein]

If it is your wings do what I do to save weight and be-rid of the vertical stabilizer all together and just angle your two horizontal stabilizers up in a Y fashion, saves weight, functions no different, and looks cool.

[I_Killed_Jeb]

Thanks guys, as most of you pointed out it was the tail elevators somehow blocking the exhaust which negated the thrust. Now a new problem - for some reason the ailerons on my wings deflect in the opposite of intended direction (i.e. pitch up control input makes them deflect downwards), and flipping them in the SPH makes no difference. What's up with that?

[Kasuha]

Action of control surfaces depends on whether they are ahead of center of mass (or lift? not sure) or behind it. Maybe you think they're ailerons and game thinks they're canards.