Reentry Heating (For Science!)

[Rylant]

45 minutes ago, Scarecrow71 said:

Check your TWR in the upper atmosphere.  Although I agree with you that this shouldn't happen, it does.  Pull back on the amount of thrust you are generating so that you aren't racing as fast as possible to orbit.  Stay < 2.0 on that ascent (TWR), and around 1.5 if you can.  That should help.

I dont think that is it. I always lock to prograde as I approach the upper atmosphere and reduce the throttle huge so that my apoapsis doesn't get away from me. I always ease into it so that my circuralization burn is really light. When it happened to me the first time, my apoapsis was around 75 and my periapsis was inside the atmosphere, but over zero. There was next to no throttle at all. 

This happened several times with more than one different ship. I finally turned off heating in order to resolve this. Seems like the wrong solution. 

Edited December 28, 2023 by Rylant

[18Watt]

14 minutes ago, Rylant said:

I dont think that is it.

I agree, that's not it.  I get stuff blowing up even when I'm coasting to orbit, seems to have nothing to do with thrust being produced or not.

[Audaylon]

I think something needs to changed is the probe core survival underneath its specific sized heat shield.  Every probe core will perish unless you oversize the heat shield 1 size.  But The expandable heat shield doesn't help.
My test setup of simple rockets and probe cores.  They do survive with oversized heat shield. 

XL probe underneath XL Heat Shield about to explode.  

[Vl3d]

There are definitely heating occlusion bugs.

[Scarecrow71]

I am simply turning heat off for the time being.  Although some of the issues I'm experiencing are a direct result of the craft I'm building, there is ZERO reason for things to explode in a fountain of hot lava at 60km when attempting to aerobrake in Kerbin's atmosphere.  If I'm trying a direct descent at 6 km/s?  Yes, I should explode.  Trying to use the upper atmosphere to slow down and reduce Ap, using multiple passes and not dipping closer than 60km?  Shouldn't happen.

[Kerbart]

7 minutes ago, Scarecrow71 said:

I am simply turning heat off for the time being.  Although some of the issues I'm experiencing are a direct result of the craft I'm building, there is ZERO reason for things to explode in a fountain of hot lava at 60km when attempting to aerobrake in Kerbin's atmosphere.  If I'm trying a direct descent at 6 km/s?  Yes, I should explode.  Trying to use the upper atmosphere to slow down and reduce Ap, using multiple passes and not dipping closer than 60km?  Shouldn't happen.

Would you mind posting a picture of saif craft during re-entry. On the off chance you're doing something to either design or orientation of the ship that the game doesn't like? At the very least we can learn from it.

[Scarecrow71]

23 minutes ago, Kerbart said:

Would you mind posting a picture of saif craft during re-entry. On the off chance you're doing something to either design or orientation of the ship that the game doesn't like? At the very least we can learn from it.

Nothing to see, really.  Standard craft (command module on top of a heat shield, with a tank and engine just below that to help slow down), pointed retrograde.  Ain't my first rodeo here.

[Mikki]

What i have seen now heat and occlusion work just fine, as expected. I made a few direct aerocapture maneuvers (with very high speeds) around Kerbin, Duna, Jool and Eve and i see no unfitting behaviour, it is quite realistic in my opinion.

I dipped into Eve three times in a row quite low (75-55km) to reduce my AP and land a rover. Works fine, i cannot imagine capturing into Eve`s atmosphere in one go, it will likely explode suddenly when reaching low altitudes.

Atmospheric densitys are very well pictured, even drag looks right to me...

People should consider how supersonic speeds (and multiples of them) increase heating drastically, when i compare the numbers on screen and the effects, it is sound all in all.

Remember, 340 m/s is Mach 1, - 680 m/s is Mach 2, - 1`020 m/s equals Mach 3  (Aluminium starts to get mushy)... and so on. Mach 5 and higher allready melts steel away by the way... ("Hypersonic Area*)

Entering Jool at a common 8`800 m/s orbital velocity is how fast? Yes, way over Mach 25, equals 31`680 km/h or imperial  19`685 Miles per hour.

Edited December 28, 2023 by Mikki
spell, format, stuff

[Kerbart]

9 minutes ago, Scarecrow71 said:

Nothing to see, really.  Standard craft (command module on top of a heat shield, with a tank and engine just below that to help slow down), pointed retrograde.  Ain't my first rodeo here.

• More mass, same cross section. That's not going to help you slowing down, It's going to help you maintain momentum
• From what I understand, engines are modeled as cones, I assume to reduce drag by "streamlining" the rear end of a rocket.  Not only are you maintaining your cross section, you're reducing your friction coefficient
• That stuff mounted underneath the heat shield will heat up. And from what I understand of the new heat model, transfer its heat a lot quicker to the rest of the ship
• Engine + tank have substantial mass, so IF they heat up, the capsule is going to be a lousy heat sink for them. Meaning that once heats starts flowing from them to the capsule, it's not substantially lowering their temperature so that flow will continue

A picture will at least give people a chance to see if they can reproduce the issue and elaborate on the problem. This not being your first rodeo might exacerbate the problem. This configuration might have worked in KSP1 but things have changed, so perhaps now it changed. Your design is likely solid, but the assumptions you based it on might be off.

[Mikki]

6 minutes ago, Kerbart said:

• More mass, same cross section. That's not going to help you slowing down, It's going to help you maintain momentum
• From what I understand, engines are modeled as cones, I assume to reduce drag by "streamlining" the rear end of a rocket.  Not only are you maintaining your cross section, you're reducing your friction coefficient
• That stuff mounted underneath the heat shield will heat up. And from what I understand of the new heat model, transfer its heat a lot quicker to the rest of the ship
• Engine + tank have substantial mass, so IF they heat up, the capsule is going to be a lousy heat sink for them. Meaning that once heats starts flowing from them to the capsule, it's not substantially lowering their temperature so that flow will continue

A picture will at least give people a chance to see if they can reproduce the issue and elaborate on the problem. This not being your first rodeo might exacerbate the problem. This configuration might have worked in KSP1 but things have changed, so perhaps now it changed. Your design is likely solid, but the assumptions you based it on might be off.

And this is how we can "cheese" reality: Eve, Mach 11, 13`363 km/h. It just works. 

Spoiler

 

[Scarecrow71]

31 minutes ago, Kerbart said:

• More mass, same cross section. That's not going to help you slowing down, It's going to help you maintain momentum
• From what I understand, engines are modeled as cones, I assume to reduce drag by "streamlining" the rear end of a rocket.  Not only are you maintaining your cross section, you're reducing your friction coefficient
• That stuff mounted underneath the heat shield will heat up. And from what I understand of the new heat model, transfer its heat a lot quicker to the rest of the ship
• Engine + tank have substantial mass, so IF they heat up, the capsule is going to be a lousy heat sink for them. Meaning that once heats starts flowing from them to the capsule, it's not substantially lowering their temperature so that flow will continue

A picture will at least give people a chance to see if they can reproduce the issue and elaborate on the problem. This not being your first rodeo might exacerbate the problem. This configuration might have worked in KSP1 but things have changed, so perhaps now it changed. Your design is likely solid, but the assumptions you based it on might be off.

Thanks for assuming I don't know what I'm doing here.  I told you:  Nothing to see.  Standard craft, standard entry, standard parts.  I'm not the only one who has stated this doesn't work; all you need to do is read through the thread to see that.  I'm not sharing an image of a standard craft that everyone builds.

[Kerbart]

21 minutes ago, Scarecrow71 said:

Thanks for assuming I don't know what I'm doing here.  I told you:  Nothing to see.  Standard craft, standard entry, standard parts.  I'm not the only one who has stated this doesn't work; all you need to do is read through the thread to see that.  I'm not sharing an image of a standard craft that everyone builds.

Don't be rude. If I have to assume anything it's because you're not sharing anything. Don't yell at people for "assuming" when they're trying to help but are working blind and you refuse to elaborate.

[Scarecrow71]

12 minutes ago, Kerbart said:

Don't be rude. If I have to assume anything it's because you're not sharing anything. Don't yell at people for "assuming" when they're trying to help but are working blind and you refuse to elaborate.

What elaboration are you looking for?  I literally stated:

• Command pod, on top of a heat shield, on top of coupling, on top of a tank, on top of an engine
• Standard re-entry profile
• Attempting to aerobrake to reduce Ap before landing
• Burning up at 60km
• I'm not the only one who has reported this happening in the upper atmosphere

I'm not trying to be rude, but I fail to see why you are asking for an image of the simplest craft EVERYONE BUILDS.  Literally, everyone builds this craft.  And >90% of the people have used this tactic in KSP1 to aerobrake to return to Kerbin.  Exactly what part of all of this are you not understanding?  What elaboration beyond simply reading the rest of this thread - which I have to assume you haven't done because you aren't asking anyone else to provide screenshots - do you need here?

[Periple]

1 hour ago, Kerbart said:

Engine + tank have substantial mass, so IF they heat up, the capsule is going to be a lousy heat sink for them. Meaning that once heats starts flowing from them to the capsule, it's not substantially lowering their temperature so that flow will

The KSP2 thermal model doesn't include heat transfer between parts.

[Vl3d]

17 minutes ago, Scarecrow71 said:

• Command pod, on top of a heat shield, on top of coupling, on top of a tank, on top of an engine
• Standard re-entry profile
• Attempting to aerobrake to reduce Ap before landing
• Burning up at 60km

What do you mean you're trying to do aerobraking in Kerbin's upper atmosphere engine first at interplanetary speed? Of course you're exploding!

[Scarecrow71]

Just now, Vl3d said:

What do you mean you're trying to do aerobraking in Kerbin's upper atmosphere engine first at interplanetary speed? Of course you're exploding!

Not interplanetary; I have yet to do that in For Science.  Munar return.

[The Aziz]

How is going engine first into atmosphere a standard procedure 

[Wheehaw Kerman]

5 minutes ago, The Aziz said:

How is going engine first into atmosphere a standard procedure 

I try to avoid that.  Not sure whether this is standard, but on approach to Kerbin, I’ll burn any remaining fuel at an angle between retrograde and radial out, to slow myself down while retaining a nice comfy safe periapsis of at least 30 kilometres, and jettison the last stage as soon as I hit 70 kilometres or when it runs dry.  I never really liked this - NASA wouldn’t have built that much margin for error into a craft, but at least it makes for a gentler re-entry for the crews.

[The Aziz]

1 minute ago, Wheehaw Kerman said:

jettison the last stage as soon as I hit 70 kilometres

Exactly. Anything deeper and you're guaranteed to run into trouble.

[Kerbart]

1 hour ago, Periple said:

The KSP2 thermal model doesn't include heat transfer between parts.

Doesn't it just heat up the entire craft? Which could be also be interpreted as instant heat transfer.

Edited December 28, 2023 by Kerbart
Typo

[Mikki]

I just whipped up an immersive recreation of the Apollo Moon program return mission profile as close as possible.

Wall of pictures and comments ahead, everyone can make his own picture of what happens.

Mun orbit is retrograde and we will hit the ocean east of the KSC, no problem. Clearly heating is on, i checked it for you all.

Tighten your seatbelts:
 

Spoiler

...15 km x 15.5 km retrograde mun orbit, departure trajectory hits Kerbin at around 35 km PE, the famous "envelope to the mailbox slit" maneuver...

... Separation from transfer stage... three Kerbals, monoprop is close to full...

... ablator has been reduced to 0.24 tons before launch...

...Bob Kerman notices how his crewmates start singing "Allways look on the bright side of life", and an uncomfy feeling creeps up his neck...

...back to our investigation, note that SAS is disabled and the reentry capsule starts orienting itself with the heatshield facing prograde... 60`000m above sealevel, 3185 m/s or Mach 9.3, equaling 11`465 km/h... 

...heating up, 52`000 meters above sea... same speed...

...drag is slowing down, 35`000 meters above sea, 2`803 m/s, Mach 8.25, or 10`090 km/h, PE starts to drop, AP is still close to mun orbit...

...AP starts to drop fast and the Mk3 pod goes Mach 7.5...

...ablator is... ablating, 40 kg melted away until now...



...27`500 meters above sea, 1475 m/s, Mach 4.3, still 5`310 km/h fast, plasma keeps dissappearing as expected, leaving hypersonic regime... 

...at the height of 26`600 meters above sea level plasma is gone and the capsule still travels at 1370 m/s, or Mach 4 respectivly 4`950 km/h...

..my Kerbals slapped some parachutes to the capsule, i knew i forgot something, phew...

...I hope you liked this test, the ablator was down to 0.19 tons from 0.24 tons, so 50 kg of resin and other nasty stuff has been evaporated during this reentry. I haven`t noticed once any heatbars appearing on this trajectory and heating is on for sure, first descent was horribly too low and bars went up fast before explosive actions took over the screen...

 

 

 

Edited December 28, 2023 by Mikki
you guess it typo

[Scarecrow71]

27 minutes ago, The Aziz said:

How is going engine first into atmosphere a standard procedure 

I always go engine first (retrograde) so I can burn off any fuel I have remaining as I get near Pe.  This helps reduce speed AND decreases Ap.  Once fuel is burned, I jettison the engine and tank, letting the ablator do its job.

[Periple]

19 minutes ago, Kerbart said:

Doesn't it just heat up the entire craft? Which could be also be interpreted as instant heat transfer.

Nope, heat fluxes are modeled individually for each part. Just not conduction between parts.

[mcdjfp]

I might be mistaken, but I suspect that the heating "model" works just fine if you stick to the expected heat shield/capsule/parachute configuration. Once you start getting fancy ( start trying to copy Space X, or anything else not anticipated by the programmers), and start trying to use non-heat shield high heat tolerant parts to shield more vulnerable parts, the less complex heating model starts showing undesired behaviors.

[Wheehaw Kerman]

16 minutes ago, Scarecrow71 said:

I always go engine first (retrograde) so I can burn off any fuel I have remaining as I get near Pe.  This helps reduce speed AND decreases Ap.  Once fuel is burned, I jettison the engine and tank, letting the ablator do its job.

Hm.  Frankly not surprised to read this - I would have been surprised if you’d been doing something whacky.  Maybe you’re running into some sort of bug?  I’ve got less than a dozen re-entries from the Mun and Minmus so far, but aside from some broken parachutes have not had any issues.