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So I built this giant spaceplane with huge wing system, about 19 Rapier engines, and 1 NERV nuclear engine. It keeps on flipping out after it lifts from the runway, and it takes the full runway. can anyone help me?

 

 

 

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16 minutes ago, HerobrineLiu said:

Maybe the center of lift is in front of the center of mass?

Most likely.  It's also possible that they're really close on launch, but the fuel burned during takeoff moves the CoM too much.

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3 minutes ago, mrhexed said:

wait, the center of lift is supposed to be behind the center of mass?

 

Yes.  Not too much, though.  Too far back and you won't be able to fight the dive.

You also want to try to build your plane in a way that the fuel draining doesn't move the CoM too much.  You can manually empty the tanks in the SPH to see where it moves, but I believe there's a mod (Better CoM maybe?) that shows you empty and full at the same time.

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3 minutes ago, Geonovast said:

Yes.  Not too much, though.  Too far back and you won't be able to fight the dive.

You also want to try to build your plane in a way that the fuel draining doesn't move the CoM too much.  You can manually empty the tanks in the SPH to see where it moves, but I believe there's a mod (Better CoM maybe?) that shows you empty and full at the same time.

Thank you! I'll try this immedieately

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It looks like the flip starts when you turned on timewarp, which is known to give such effects on occasion.  Also, you may want to use bigger wing parts/control surfaces near the back, which should give more authority there as well as pull the center of lift further back.

 

Prior to that, though, your speed was really dropping off, so you may need more engines or less mass...

Edited by 1101
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Flipping high up generally means that you have too much drag up front, or that your CoT is too far off your CoM.  Once you start running out of air, your flaps can't compensate for it anymore.


Also, as @1101 said, don't timewarp a spaceplane ascent.  Physics timewarp is far from perfect.

You may also want to get some gimble capable engines.

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When you have SAS set to stability for a plane, your nose will rise over time as you traverse the curve of the planet.

The drag that your plane experiences rises exponentially as your nose rises above prograde. For the first few degrees it isn't too bad. Once it goes above 5 degrees, you are experiencing a lot of extra drag. Once your nose is 10 degrees above prograde, the excess drag on your fuselage is immense -- and your nose is going way beyond 10 degrees in your video.

This is the main reason why rotating your wings so that they have positive incidence even when your plane's nose is locked to prograde is so useful.

 

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15 hours ago, bewing said:

When you have SAS set to stability for a plane, your nose will rise over time as you traverse the curve of the planet.

The drag that your plane experiences rises exponentially as your nose rises above prograde. For the first few degrees it isn't too bad. Once it goes above 5 degrees, you are experiencing a lot of extra drag. Once your nose is 10 degrees above prograde, the excess drag on your fuselage is immense -- and your nose is going way beyond 10 degrees in your video.

This is the main reason why rotating your wings so that they have positive incidence even when your plane's nose is locked to prograde is so useful.

 

You're right!

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