Why do people complain about the rocket plumes in KSP2?

[BowlerHatGuy3]

Ever since we first got footage of KSP2 people have been complaining that the vacuum plumes don’t look realistic enough, and that they are expanding too much.

I disagree with this because 1: most of the photo/video evidence that is used to argue this has the rocket in the upper atmosphere, not in vacuum. And 2: there are photos and videos of rockets in a vacuum where the plumes look similar to the ones we see in KSP2.

There were some good ones posted by a fellow in the latest dev update:

And there is a video from a SpaceX fairing showing an engine plume similar to the ones we see in the game as well:

I am by no means an aerospace engineer or rocket scientist so I am open to being corrected if I’m wrong.

[PDCWolf]

The plumes are wrong, period. We have the visuals of low energy plumes applied to high energy ones. I just don't know how many more actually authoritative sources people need on this. There's actual reports, mathematical simulations, and image evidence. Concave plumes are only found on low pressure systems where particle collisions are more relevant to the final shape than the pressure those particles are ejected from the chamber at. How's this been so badly misinterpreted to implement a concave curve on rocket engine exhausts is beyond me.

https://arc.aiaa.org/doi/10.2514/1.A33058

https://www.sciencedirect.com/science/article/pii/S2214914720303846

https://www.semanticscholar.org/paper/Rocket-Exhaust-Plume-Phenomenology-Simmons/bf208d7438098f37b4937e2095379034db003559

https://www.researchgate.net/figure/Number-density-distribution-of-plume-species_fig4_253683878

 

 

[Spicat]

 

Reminder of the book devs have base their conclusion on (page 713/709 seems to be the interesting stuff): 

https://ftp.idu.ac.id/wp-content/uploads/ebook/tdg/DESIGN SISTEM DAYA GERAK/Rocket Propulsion Elements.pdf

From what I can see, the second stage of the falcon 9 seems to always have a plume like we have in the game (When in vacuum). The OP video of Scott Manley is probably the better one to show this.

https://www.youtube.com/watch?v=3saCf6xJ2gk

https://i.imgur.com/x2w5ixV.mp4

Obviously it depends on a lot of factors. Sometimes the shockwave is less visible like in the above video.

What we have in vacuum seems to be accurate, but maybe the transitional effect is what needs work. We have somewhat what the falcon 9 is offering. 

The LEM also show the vacuum thingy:

https://www.youtube.com/watch?v=9HQfauGJaTs

Edited May 28, 2023 by Spicat

[Pat20999]

I can also hear them in space!

[PDCWolf]

18 hours ago, Spicat said:

 

 

That's the overexpanded mach diamond, encircled in the actual complete plume. This is much easier to visualize when you watch a launch.

 

[Wheehaw Kerman]

On 5/27/2023 at 5:00 PM, BowlerHatGuy3 said:

Ever since we first got footage of KSP2 people have been complaining that the vacuum plumes don’t look realistic enough, and that they are expanding too much.

I disagree with this because 1: most of the photo/video evidence that is used to argue this has the rocket in the upper atmosphere, not in vacuum. And 2: there are photos and videos of rockets in a vacuum where the plumes look similar to the ones we see in KSP2.

There were some good ones posted by a fellow in the latest dev update:

And there is a video from a SpaceX fairing showing an engine plume similar to the ones we see in the game as well:

I am by no means an aerospace engineer or rocket scientist so I am open to being corrected if I’m wrong.

Because realism matters in our game about little green space frogs, basically.   Lack of it breaks immersion for those of us who understand plume behaviour.  I am not one of those people, but I’m one of the people who find the abstraction of life support a bit immersion-breaking, and can relate.

[MarcAbaddon]

I haven't played in a month or so (waiting for next patch) and while I am not that miffed about it not being super realistic (would be better if it was obviously) I remember what I disliked what the interaction between air vortices at high speed and the rocket plumes, with the air vortices basically overriding the rocket plumes. Not sure if this has been fixed since, need to check once of these days.

[BowlerHatGuy3]

On 5/28/2023 at 4:41 PM, PDCWolf said:

That's the overexpanded mach diamond, encircled in the actual complete plume. This is much easier to visualize when you watch a launch.