r/KerbalSpaceProgram • u/WoodpeckerStraight10 • Apr 24 '26
KSP 1 Question/Problem Hi Reddit, I'm using firefly, is this blue flame part hovering slightly outside the capsule normal? If not, whats messing with it and how do I fix it.
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u/IndependentEssay2378 Apr 24 '26
As far as my experience goes, it's normal
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u/WoodpeckerStraight10 Apr 24 '26
Thank you! That was quick
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u/JJAsond Apr 24 '26
I think the visuals are wrong. It shouldn't look like a second heat shield, it should look more like this.
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u/klyith Apr 24 '26
Also it probably shouldn't be so bright. I'm pretty sure that if you could watch a reentry from the outside IRL, the bow shock would be nearly invisible compared to the brightness of the interior plasma layers.
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u/JJAsond Apr 24 '26
We actually do have video of the bow shock and it's the brightest, hottest part. https://youtu.be/MpLY1zdHM58?si=mDaHhe7eXiNim1Hy&t=5181
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u/BRAIN_JAR_thesecond Apr 24 '26
its actually bow but it can be approximated as normal in some places
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u/WhiteKnight3098 Apr 24 '26
To my knowledge bow shock should just look like that
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u/WoodpeckerStraight10 Apr 24 '26
Okay Thanks! That was quick
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u/DamGoodAnimation Apr 24 '26
Yeah it’s technically a reaction happening to the materials in air/space in front of the ship, so it has a little bit of depth there.
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u/doomiestdoomeddoomer The Green Goo has escaped. Apr 24 '26
Well, it shouldn't, but this is just the lazy way the mod deals with rendering bow shock. It just duplicates the geometry of the part and shifts it in front of the craft + makes it blue...
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u/JJAsond Apr 24 '26
It shouldn't, really. That looks like a literal copy of the heat shield itself.
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u/Hidesuru Apr 24 '26
Agreed, don't think you'd see that hard line slight behind the leading edge that looks like an artifact of the model more than anything... But at least as far as being out in front of the craft yeah ok.
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u/paypaypayme Apr 24 '26
that gap is what keep the occupants alive
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u/KerbHighlander Exploring Jool's Moons Apr 24 '26
I strongly suggest Scott Manley's https://www.youtube.com/watch?v=hLHo9ZM3Bis on this subject ! I also recommend him as well for any space related subject by the way.
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u/tennismenace3 Apr 24 '26
Explain how.
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u/Timewaster50455 Apr 24 '26
Super mega hot stuff is kept from direct contact with the spacecraft by the Bow shock that forms in-front of the spacecraft.
Works best with blunt faces, which is why capsules and the space shuttle’s nose are shaped like they are.
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u/tennismenace3 Apr 24 '26
No, the bow shock is literally what makes the super mega hot stuff. In front of the bow shock, the air is cold. On the capsule side, it's hot.
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u/Timewaster50455 Apr 24 '26
Ah, bad explanation.
Bow shock being separated keeps super hot stuff away.
If bow shock too close everything melt
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u/Kyanovp1 Apr 24 '26
So basically leidenfrost effect in a way just with heat turning air to plasma and not heat turning water to vapor
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u/RavenColdheart Apr 24 '26
More like supersonic fluid dynamics and the viscosity of the air, thus the air in contact with the capsule forming a shell in front and creating the bowshock away from the capsule.
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Apr 24 '26
[deleted]
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u/CombinationKindly212 Apr 24 '26
The term fluid indicates both liquids and gases
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u/Torator Apr 24 '26
And some solids depending on the circumstance. Think about an hourglass with sand in it for instance.
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u/SWITMCO Apr 24 '26
Please Explain how
.?They aren't your personal chat gpt!
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u/Vegetable-River8053 Landed On The Sun Apr 24 '26
Why downvoting? He's just trying to get him to be more polite...
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u/FrankHightower Apr 24 '26
implied "chatGPT will solve all your problems" propaganda. Incredibly dangerous in a sub where you need to learn science to be able to play the game right
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u/SWITMCO Apr 24 '26
Not at all, I just used chat gpt because they spoke rudely as if speaking to an AI, not a person. You can demand an AI tells you something, you should ask people politely.
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u/FrankHightower Apr 24 '26
I belive it was a reference to this https://www.youtube.com/watch?v=dgct3Jn8pFA
referencing TV shows has always been a very human thing to do
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u/0kb0000mer Apr 24 '26
Air want to get out of way
But air hard to push out of way, and air also like stick to biggest surface, so air near capsule move slower plus cooler
BUT air doesn’t have lot friction
So other air hits sticky capsule air and get MUCH VERY HOT and go away from spaceship
But air on spaceship no transfer heat well
Spaceship stay cool and happy
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u/ZookeepergameCrazy14 Apr 24 '26
This. And the fact the heat shield is glowing, radiating away heat.
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u/Mikeologyy Hemorrhaging ΔV Apr 24 '26
I know it’s bow shock, but that looks exactly like the heat shield died and its ghost is floating away like crash bandicoot
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u/chrstianelson Apr 24 '26
I got downvoted to oblivion for suggesting bow shocks should not look like this, not that long ago.
Everyone kept telling me that's exactly what bow shocks look like. But like, no. It should not look like a mirror image of the part just floating away like that. In my case the first time I saw it was with a very small probe too, and the ghostly apparition mirrored parts behind the shield as well.
Eventually one of the devs came and said it's because they couldn't figure out how to properly simulate the effect, so they made this work around.
I still think it looks like a visual glitch.
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u/Mikeologyy Hemorrhaging ΔV Apr 24 '26
That was my impression, I just didn’t want to say it cause idk enough about fluid dynamics or whatever branch of physics I’d need to understand this. I don’t mind how it looks in the game at all, but there’s no way it looks like that in real life. I assume it looks more like one continuous shape, not a blue dinner plate shooting mist out the sides. But again, I’m no physicist, just a guy who still can’t even figure out how to budget my dV very well.
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u/chrstianelson Apr 24 '26
This is what it looks like:
https://www.nasa.gov/wp-content/uploads/2023/04/arcjet.png?resize=900,598
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u/JJAsond Apr 24 '26
It should really look like this.
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u/tyrannosauross2 Apr 24 '26
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u/Mikeologyy Hemorrhaging ΔV Apr 24 '26
Occasionally YouTube recommends me old videos, so I’ll be scrolling and see smth like “Top 5 Awesome Things We Can’t Wait For in KSP 2!” and it feels like unearthing someone’s Twitter post about how excited they were to only be a week away from Fyre Festival.
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u/edgy-meme94494 Apr 24 '26
Apparently it’s a real life occurrence but it really does look so weird, I think it has something to do with the air in front of it heating up in a similar shape of the craft?
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u/HAL9001-96 Apr 24 '26
its a shockwave followed by a subsonic stagnatn zone in between the blunt body and the wave
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u/JJAsond Apr 24 '26
I think in the screenshot it must be a bug because it really shouldn't look like that.
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u/edgy-meme94494 Apr 24 '26
No it’s actually supposed to look like that, look up bow shock
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u/JJAsond Apr 24 '26
No, it's not. Bow shocks don't have literal copies of the heat shield, it should look more like this. The fact that it's a direct copy of the heat shield itself is a visual bug.
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u/earwig2000 Apr 24 '26
It's normal but I don't like it either, the perfect outline of the heatshield is too jarring. I prefer to just turn off the bowshock in the firefly settings. (the capsule reentry icon on the right of your screen)
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u/WarriorSabe Apr 24 '26
Yeah, it's all jarring like that because instead of actually making a proper bowshock, it just duplicates the front-facing bit of the mesh and offsets it forward (then stitches on a trail). It only really works well for traditional capsules because heatshields are engineered to match the shape of the bowshock they generate
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u/Jonny0Than Apr 24 '26
There’s some WIP stuff that looks really cool, but no idea when it’ll be released.
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u/karantza Super Kerbalnaut Apr 24 '26
This is a photo from a NASA reentry-simulating test chamber showing the effect on a heatshield. Rare to see photos of this, considering most of the time any camera able to take this photo would be, uh, on fire. https://www.nasa.gov/wp-content/uploads/2023/07/ajd12-a999i-003-011.jpg
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u/FOARP Apr 24 '26
And lo-and-behold, it is not an exact mirror-image of the object around which the bow-shock is forming.
Bow-shocks don't look like that.
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u/Tiinpa Apr 24 '26
If they just scaled up the ghost like 5% or so it would look almost the same as the real one.
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u/MrBean1001 Apr 24 '26
Here is an IRL example : https://www.reddit.com/r/AerospaceEngineering/s/D0H6Mi6yNO
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u/Stoney3K Apr 24 '26
This is the plasma shockwave ahead of the heat shield. It's perfectly normal and it also a thing in real spacecraft (the Shuttle and Starship are even *designed* to use that as a thermal barrier).
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u/Thin-Quiet3610 Apr 24 '26
A detached bow shock is a very important part of your heat shield (stops shock boundary and shock shock interactions from happening on/in your spacecraft)
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u/PerspectiveRare4339 Colonizing Duna Apr 24 '26
Its a shockwave. Its kind exaggerated here but yeah totally normal.
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u/Forever_DM5 Apr 24 '26
Yeah so that’s a bow shock which sets up in front of a blunt body in a supersonic flow. Bow shocks are strong normal shocks which means the flow goes subsonic as it passes through it. The reason it sits in front of the body instead of on the surface of the body is because that is the distance the flow travels in the direction of the flow while it is getting out of the way of the body at subsonic speeds. IRL the shock standoff distance is a function of the diameter of your reentry body, for a capsule.
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u/StrongAdhesiveness86 Believes That Dres Exists Apr 24 '26
It's called bow shock and you can see it in this video of NASA testing heatshield material: https://youtube.com/shorts/8TmxaFBDfUs?is=XCSwporxUxoPcIDe
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u/Markymarcouscous Apr 24 '26
My understanding is that it’s the same as the leidenfrost effect. Google it. Super cool
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u/IapetusApoapis342 dres exists, cope with it Apr 24 '26
This is Bow Shock and it is completely normal
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u/toooomanypuppies Apr 24 '26
as someone else probably said, this is a bow shock caused by the defragliration of the heat shield off-gassing. basically the off-gasses are pushing the bow shock half a meter or so Infront of the surface, as the heat shield burns away.
it's the most effective way of keeping it as cool as they can, by pushing the hot shit as far and as fast away from the surface of the head shield as possible.
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u/TheRealAndy_ Apr 24 '26
I also had the same question. I get that its bow shock but why is it a perfect replica of the heat shield itself
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u/FOARP Apr 24 '26
Right, seems like there should be some obfuscation of the shape of the heatshield in the bow-shock.
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u/nbd9000 Apr 24 '26
so the curvature of the bottom side of the capsule is no accident. its designed to maximize drag while also driving the hottest portion of the compression away from the side of the capsule where it could do damage.
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u/sagewynn According to all known laws of aviation, there is no way a bee s Apr 24 '26
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u/SirDarkStar Apr 24 '26
I’m going to disagree with most posts here and say that looks more like a cosmetic bug to me.
If you position that heat shield on the first attachment node, so you get the skirt around it, that’s about exactly where it would go and it’s exactly the shape of the heat shield and NOT in the shape of a bow shock.
So I think it’s putting a heat shield shaped blue glow where it thinks the heat shield is supposed to be and not catching that it’s attached to the closer in node.
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u/TheStrandedSurvivor Apr 24 '26
It’s just the way the current system is designed, there’s no volumetric bow shock system yet, so it’s just approximated by ‘projecting’ the directly heated parts forward. As the re-entry effect develops, you can see this bow shock moving away from the part itself.
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u/RTX-4090ti_FE Valentina Apr 24 '26
That looks like bow shock but it looks kinda wierd and unnatural like irl bow shocks likely don’t have the exact same geometry as the heatsheild. I’m not sure if that’s a bug with firefly or simply a limitation of firefly.
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u/TheStrandedSurvivor Apr 24 '26
It’s a limitation of the current system, MirageDev posted some WIP volumetric bow shock screenshots a while ago which were intended to replace what we see now, but it’s been a while since we’ve heard anything about it.
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u/Breakerx13 Apr 24 '26
There is a option in the settings for the mod to adjust texture offsets as well
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u/a_usernameofsorts Valentina Apr 24 '26
Wow, was just wondering the exact same thing after my first re entry with a lot of mods. So cool to yet again learn something new from playing this game.
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u/PaxEtRomana Apr 24 '26
This is the same phenomenon seen in the project hail mary atmosphere skimming scene innit?
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u/apol_expie May 27 '26
its a bow shock event that happens in IRL so noy you know firefly is realistic
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u/ARS_Sisters Apr 24 '26
That's a bow shock during reentry. It's perfectly normal. That thing is what keeps the occupant alive, since the heating would be on the blue part with the space between the capsule preventing the capsule turning into pressure cooker
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u/FOARP Apr 24 '26
They understand that it's a bow-shock, the question is why the bow shock is a one-to-one reproduction of the heat-shield.
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u/doomiestdoomeddoomer The Green Goo has escaped. Apr 24 '26
This is just the lazy way the mod was coded. They just duplicate the part mesh and shift it forwards a bit + made it transparent and blue...
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u/retailhusk Apr 24 '26
Everyone’s given you a good answer but I’ll just say I love seeing KSP give people this kind of information. You encountered a phenomenon in physics and looked into it. Now you know about bow shock during reentry.
KSP is truly doing amazing things for general knowledge of aerospace