Jet engine J-20 applies thrust in wrong direction and switching from Cruise to Reverse ignites an afterburner instead of switching thrust direction.

[Zwartekop]

I build a plane in the VAB and put the J-20 jet engine at the back of the plane. I did not activate the reverse mode.  It is in cruise mode. After launching the craft the thrust goes in the wrong direction. When I click on the engine and apply the reverse mode the thrust just increases but in the wrong direction.  The sound changes too. Because of this I think it's an after burner mode that isn't supposed to be there. Reverting to launch or VAB does nothing. Even restarting the game doesn't help. It used to work but it suddenly bugged itself. I tried putting the engine on the front but then it suddenly starts pushing and I'm going backwards again. 

Here's a video to show what I mean: 

 

I'm using KSP2 without mods. 

PC Info: 

• Windows 11
• GPU: RTX 3060
• CPU: AMD Ryzen 5 5600
• RAM: 32 GB

Edited February 26, 2023 by Zwartekop

[Razor235]

It's because your horizontal stabilizer is directly in line with the exhaust plume and occluding it, blocking all thrust.  There's some force pushing back on the tail so it moves backwards as a whole.  Yes it's unrealistic.  Yes it's annoying.  Yes, it will require you to redesign (or raise or lower the tail).

 

The sound is fine and matches with jet blast being redirected on a metal plate.

[Zwartekop]

That's one mystery solved. That still doesn't explain however why setting the thrust to reverse instead of cruise turns it into a jet in afterburner mode. Suddenly the backwards thrust gets 5x as strong.

 

[jimmymcgoochie]

9 minutes ago, Zwartekop said:

That still doesn't explain however why setting the thrust to reverse instead of cruise turns it into a jet in afterburner mode. Suddenly the backwards thrust gets 5x as strong.

The plane is just rolling backwards at first, no thrust is being applied. Switching it to reverse thrust makes it actually produce reverse thrust and the plane responds appropriately. The sound effect is a little hard to hear under the music but it doesn’t sound that dissimilar to a real jet engine with thrust reversers deployed. Try a different plane design with the same engine and see what happens then.

[Zwartekop]

On 2/28/2023 at 12:43 PM, jimmymcgoochie said:

The plane is just rolling backwards at first, no thrust is being applied. Switching it to reverse thrust makes it actually produce reverse thrust and the plane responds appropriately. The sound effect is a little hard to hear under the music but it doesn’t sound that dissimilar to a real jet engine with thrust reversers deployed. Try a different plane design with the same engine and see what happens then.

That's not true I remember it going up to 20m/s pretty quickly. I solved my particular problem by just moving the tail wing up a lot but there's definitely some kraken drive stuff going on. I think this player used the same effect to multiply engine power massively: 

 

Just now, Zwartekop said:

That's not true I remember it going up to 20m/s pretty quickly. I solved my particular problem by just moving the tail wing up a lot but there's definitely some kraken drive stuff going on. I think this player used the same effect to multiply engine power massively: 

 

I'll do more testing later this evening.