What's required to shield parts?

[4x4cheesecake]

Hey there

While preparing my next entry for the Shuttle Challenge, I ran into a problem while aerobreaking in Eves atmosphere. Well, obviously the dense atmoshphere is a problem on it's own but my Shuttle would survive the aerobreak theoretically. The wings and MK3 parts are pretty heat resistant but two tanks, which are placed above the wings, will heat up as well, even though they should be shielded by the wings:

These are two Rockomax X200 fuel tanks. They are clipped inside the MK3 fueltanks and the wing:

For testing purposes, I alreaded moved the tanks upwards so they are no longer clipped into the wing but still, they are not shielded.

The wing parts below the tank are the parent part for the whole wing, which is connected to the MK3 fuselage, and a single wing element connected to this parent:

I also tried to place an additional wing element direct below the tanks, which is actually connected to the fuselage below the X200 tanks (the big wing is placed in the middle of the fuselage and moved downwards) but the tanks are still not shielded.

One more pic of the shuttle in general:

If anyone want to take a look at it ingame, here the craft file (stock parts only, KSP 1.4.5): https://www.dropbox.com/s/q8c20v61vm36wpt/EVE STS - 1.craft?dl=0

So, how can I shield these tanks? is it actually possible to shield parts without using a fairing, a cargo bay or a heat shield? The only solution so far seems to put a 10m heatshield on top of the MK3 cockpit and fly through the atmosphere while pointing the shuttle prograde but that's not the way I want to do it^^

 

[Rocket In My Pocket]

I often do the same thing with solar panels, placing them on the dorsal side so they are shielded during re-entry, typically works fine.

Heat, as I understand it, does bleed from nearby parts into other parts. This may be the issue? Do they start heating immediately, or is it somewhat delayed compared to the rest of the shuttle?

Have you tried surface attached radiators on the tanks themselves maybe? Or maybe mounting them on the dorsal side of the body in the first place, then translating them to where you want them?

Edited November 14, 2018 by Rocket In My Pocket

[4x4cheesecake]

7 minutes ago, Rocket In My Pocket said:

Heat, as I understand it, does bleed from nearby parts into other parts. This may be the issue? Do they start heating immediately, or is it somewhat delayed compared to the rest of the shuttle?

They are actually one of the first parts which will heat up to the point where the heat gauge becomes visible (well, they are also the parts with a heat resistance of just 2000K)

 

7 minutes ago, Rocket In My Pocket said:

Have you tried surface attached radiators on the tanks themselves maybe?

Haven't tried radiators yet, I have the gut feeling that they will not transfer the heat fast enough but I'll try it.

7 minutes ago, Rocket In My Pocket said:

Or maybe mounting them on the dorsal side of the body in the first place, then translating them to where you want them? 

Is there actually a difference when you place the parts differently and move them to the correct spot? Well, I placed a single wing element below the tanks because I thought it will be a difference but that was just a guess though.
I'll try that as well.

Edited November 14, 2018 by 4x4cheesecake

[Rocket In My Pocket]

1 minute ago, 4x4cheesecake said:

Is there actually a difference when you place the parts differently and move them to the correct spot?

There shouldn't be, but then again, your fuel tanks shouldn't be heating up lol.

I'm just throwing ideas out there, seems to me like the game is just not recognizing it for some reason.

Figured it was worth a shot.

[4x4cheesecake]

3 minutes ago, Rocket In My Pocket said:

There shouldn't be, but then again, your fuel tanks shouldn't be heating up lol.

I'm just throwing ideas out there, seems to me like the game is just not recognizing it for some reason.

Figured it was worth a shot.

Sure, I'm here to get ideas and I'll try all of them, so what ever comes into your mind, tell me about it^^

[4x4cheesecake]

Uhm...is it possible that radiators will just cool down the core temp but not the skin temp? They look quiet unimpressed from the heat (but they are more heat resistant, so I'll probably use them as a heat shield and clip them slightly into the bottom of the tanks xD). Even KER says that the radiators are the coolest part

 

[FleshJeb]

The only two places radiators work acceptably are in space or static on the ground.

Parts with high emissivity like precoolers and intakes work anywhere, but are best off attached directly to the problem part. Can you swap the 2.5m out for 1.25m tanks? Alternately, some wings or control surfaces mounted parallel to the airflow. I think they still have pretty high emissivity.

Heat occlusion is a funny beast with surface attached parts. You can also try attaching the front 1.25 to 2.5 adapter to the main tank and stringing the other parts behind it. I assume it’s the Rocko tank attached to the main tank now. Also, put some end caps on those things!

Lastly, that shuttle looks amazing. I love it.

[4x4cheesecake]

8 minutes ago, FleshJeb said:

The only two places radiators work acceptably are in space or static on the ground

Ok, thanks...the 'static' part is new to me.

13 minutes ago, FleshJeb said:

Can you swap the 2.5m out for 1.25m tanks? Alternately, some wings or control surfaces mounted parallel to the airflow. I think they still have pretty high emissivity.

Actually I can remove these tanks, since this mission doesn't require so much fuel...I already removed some fuel from tanks to reduce the weight^^
But I want to keep the 'remove tanks' option as my 'Plan B' if everything else fails....I would prefer a way to make this design work as intended than changing too much on the craft.

Can you be a bit more specific about the wings/control surfaces parallel to the airflow? I'm not quiet sure what you mean. Where am I supposed to place them? Below or in front of the tanks?

 

25 minutes ago, FleshJeb said:

You can also try attaching the front 1.25 to 2.5 adapter to the main tank and stringing the other parts behind it. I assume it’s the Rocko tank attached to the main tank now. Also, put some end caps on those things!

Yes, the rocko is attached to the body. I'll put some caps on the adapters and attach the adapters to the body instead

25 minutes ago, FleshJeb said:

Lastly, that shuttle looks amazing. I love it.

Thanks

[bewing]

I agree that reentry heating is a funny beast -- odd things happen with it, and I've never figured it out myself. My personal guess for an experiment would be to place 1.25m heatshields with no ablative just in front of those tanks.

We could try summoning a dev to try to explain the algorithm, but honestly, I'm not even sure that they quite know how it works.

 

[Tyko]

20 minutes ago, bewing said:

We could try summoning a dev to try to explain the algorithm, but honestly, I'm not even sure that they quite know how it works.

Visualizing @Snark lighting candles and sacrificing a Kerbal to summon a dev   

[4x4cheesecake]

*burns some myrrh*

[FleshJeb]

58 minutes ago, 4x4cheesecake said:

Ok, thanks...the 'static' part is new to me.

Can you be a bit more specific about the wings/control surfaces parallel to the airflow? I'm not quiet sure what you mean. Where am I supposed to place them? Below or in front of the tanks?

Static/unmoving isn’t as important as low altitude/dense air. They just really thermally inefficient and draggy in the thin hot stuff. Also, I think they only affect core temp directly.

Wings: Since you’are entering belly-down, I was thinking on the dorsal surface with the rear of the wing pointing up. Any orientation that minimizes their drag should do. As long as they stay cooler than the tank.

FYI, in the .cfg files “emissiveConstant” is the thing you’re looking for. 0.95 is really good. I think the default if unlisted is 0.6, but i’d have to look in physics.cfg. Your slant adapters are 0.8. Example: https://wiki.kerbalspaceprogram.com/wiki/Parts/Aero/circularIntake/intakeShockCone.cfg

Likewise, there are parts that make really good insulators when placed in-line. Service Bays are my go-to. My default 1.25m spaceplane stack is nose cone - svc bay - cockpit - precooler.

As usual, I agree with everything @bewing said. Thermal occlusion is mostly voodoo.

Since you’re already invested in RCS Build Aid and EdEx, consider CorrectCoL—If only for the more accurate CoL indicator.

Please ping me when you get this thing working. I’m sure it will be educational and awesome.

[4x4cheesecake]

1 hour ago, 4x4cheesecake said:

I'll probably use them [radiators] as a heat shield and clip them slightly into the bottom of the tanks

 

2 hours ago, Rocket In My Pocket said:

mounting them on the dorsal side of the body in the first place, then translating them to where you want them

 

1 hour ago, FleshJeb said:

try attaching the front 1.25 to 2.5 adapter to the main tank and stringing the other parts behind it. I assume it’s the Rocko tank attached to the main tank now. Also, put some end caps on those things!

Tried these ideas and failed

 

35 minutes ago, bewing said:

My personal guess for an experiment would be to place 1.25m heatshields with no ablative just in front of those tanks.

In front of the tanks even though I have to keep a pretty steep AoA while aerobreaking? Well, I'll try it and see what will happen

15 minutes ago, FleshJeb said:

Wings: Since you’are entering belly-down, I was thinking on the dorsal surface with the rear of the wing pointing up. Any orientation that minimizes their drag should do. As long as they stay cooler than the tank.

Oh, I just understood the idea behind this. Yeah, that's clever, I'm curious if it will work

[bewing]

25 minutes ago, 4x4cheesecake said:

In front of the tanks even though I have to keep a pretty steep AoA while aerobreaking?

See, I've never noticed the angle making any real difference. Have you ever tried this experiment? Have a long thin single-stack rocket reenter, with an almost exact 90 degree AoA (held with a good strong reaction wheel or ten and infinite EC). Which parts get hot? Answer: the part on the nose, or the part on the tail. One or the other, not both. And nothing in between. Why? Because it seems to think that one of those parts is the "front" and all the rest is occluded.

And I guess I meant a 2.5m heatshield.

[4x4cheesecake]

1 minute ago, bewing said:

See, I've never noticed the angle making any real difference. Have you ever tried this experiment? Have a long thin single-stack rocket reenter, with an almost exact 90 degree AoA (held with a good strong reaction wheel or ten and infinite EC). Which parts get hot? Answer: the part on the nose, or the part on the tail. One or the other, not both. And nothing in between. Why? Because it seems to think that one of those parts is the "front" and all the rest is occluded.

And I guess I meant a 2.5m heatshield.

Nope, I haven't done this experiment before but I just tried it on my ship (of course I took the 2.5m heatshield) and it doesn't help. While holing a AoA of ~45°, the tanks still heat up and explode. Just for fun I also tried it with the ship pointed prograde and, as expected, the tanks are fine (lost the docking port an the cockpit and a few RCS thrusters).

Well, I'm curious now and repeat the experiment with a rocket shaped thingy^^

[FleshJeb]

29 minutes ago, 4x4cheesecake said:

Tried these ideas and failed

In front of the tanks even though I have to keep a pretty steep AoA while aerobreaking? Well, I'll try it and see what will happen

Oh, I just understood the idea behind this. Yeah, that's clever, I'm curious if it will work

On phone, quoting hard.

Again, what @bewing just said.

Fooey!

I think ultimately what we’re going to discover is that those tanks are crap. Rebuilding the body with an additional, partially full Mk3 tank segment may be your best bet. The other bonus to this is lower overall drag.

I was going to suggest changing your reentry profile, but you already did.

As to the other stuff going boom: Stick a precooler between the nose docking port and the cockpit, and offset it into the cockpit. The RCS thrusters should do better attached to the coolest wing, even if you have to cheat and offset them where they need to go.

[4x4cheesecake]

10 minutes ago, FleshJeb said:

I think ultimately what we’re going to discover is that those tanks are crap. Rebuilding the body with an additional, partially full Mk3 tank segment may be your best bet. The other bonus to this is lower overall drag.

In terms of heat restistence, the tank is crap

But luckily, we have a brilliant mind around because

THIS:

1 hour ago, FleshJeb said:

Wings: Since you’are entering belly-down, I was thinking on the dorsal surface with the rear of the wing pointing up. Any orientation that minimizes their drag should do. As long as they stay cooler than the tank.

WORKS!!

I have attached a few wing connector typ D sideways, in a 45° angle (clipped into the body) and during the testflight, the tanks heated up 'just' to 1965K/2000K. Still a close call but at least, this is a freaking nice workaround and as usual, the Kerbal way of adding 'moar' will help to keep the temp even lower

Maybe I'll look for a different part which doesn't mess around with my CoL but for the moment, this should do the trick

[FleshJeb]

35 minutes ago, 4x4cheesecake said:

WORKS!!

I have attached a few wing connector typ D sideways, in a 45° angle (clipped into the body) and during the testflight, the tanks heated up 'just' to 1965K/2000K. Still a close call but at least, this is a freaking nice workaround and as usual, the Kerbal way of adding 'moar' will help to keep the temp even lower

Looks like the power of the educated guess paid off!

The fun thing about thermal is that radiated heat is proportional to T^4, so the closer you ride the edge, the more efficient it is. Boy, were you riding the edge there!

I'm curious about the orientation— I was thinking like a vertical tailfin, which shouldn’t impact CoL much at all. Got any screenies for your loyal and hardworking assistants?

[4x4cheesecake]

@bewing

I've done the experiment and the result is quiet confusing^^

90° AoA in respect to the prograde vector:

Hottest & critical part: Rocko Tank
Hottest skin temp: 1953K/2000K
Coolest part: Heat shield
Coolest skin temp: 1246K/3300K

 

90° in respect to the ground:

Critical Part: Rocko Tank
Critical skin temp: 2013K/2000K
Hottest part: heat shield
Hottest skin temp: 2095K/3300K
Coolest part: heat shield (the same...there is just one heat shield xD)
Coolest skin temp: 2095/3300K

Even KER is confused but still not the result I've expected from what you've said since the heat shield is def. not the hottest part. Did I perform the experiment incorrect?

18 minutes ago, FleshJeb said:

I'm curious about the orientation— I was thinking like a vertical tailfin, which shouldn’t impact CoL much at all. Got any screenies for your loyal and hardworking assistants?

Sure

Like you said, I've oriented them with the tail pointing up (45°):

Works like a selfmade radiator

I haven't done any screenshots during the testflight but if you want to see it in action as well, I'll repeat the flight

edit: Well, you deserve a screenshot during flight^^

1957K/2000K while crossing the Pe at 75800m with a speed of 4434m/s.
In previous flights, I wasn't able to go below 80000m and even than there was no guaranty to survive^^
 

Edited November 14, 2018 by 4x4cheesecake

[FleshJeb]

13 minutes ago, 4x4cheesecake said:

Sure

Like you said, I've oriented them with the tail pointing up (45°):

Works like a selfmade radiator

I haven't done any screenshots during the testflight but if you want to see it in action as well, I'll repeat the flight

Ah ok. I was thinking in an orientation that doesn’t resist anything but sideslip. Long edges up and down, and short edges forward and back. I think you can still clip them into the Rockos completely, and they’ll be treated thermally as if they’re fully exposed. What you’ve got now makes for a nasty airbrake. Wings always work, even if clipped. I think they even work in cargo bays still.

No need to repeat the test, but I’d love to see the eventual mission.

Nice job on bewing’s experiment. Results are always going to be inconsistent. Sometimes with the same craft on different runs. I bet if that were pointed 85deg up and slightly retrograde, instead of 90, you’d get very different results. Heat shields have a “safer” zone behind them that I think is cone-shaped. I have no idea how much this depends on AoA. It would be nice if the SPH had a visualizer for this, so we didn’t have to guess.

[4x4cheesecake]

5 minutes ago, FleshJeb said:

Ah ok. I was thinking in an orientation that doesn’t resist anything but sideslip. Long edges up and down, and short edges forward and back. I think you can still clip them into the Rockos completely, and they’ll be treated thermally as if they’re fully exposed. What you’ve got now makes for a nasty airbrake. Wings always work, even if clipped. I think they even work in cargo bays still.

I'll do some finetuning on the weekend, so far I'm just happy to have a solution to work with. There are still several tests to do, for example the impact on the atmospheric flight stability or how many wing parts can be added to increase the effect on the temp or removed without having any differences (part count is already pretty high...), this will also include different orientation of the parts.
On the other hand, orientating the parts like tail fins will definitly result in a better stability and less drag but somehow I think I have to sacrefice something in order to justify the heavy use of part clipping and to keep a peace of conscience.

14 minutes ago, FleshJeb said:

No need to repeat the test, but I’d love to see the eventual mission.

I'll ping you in my mission report

[bewing]

OK, so I guess my experiment was out of date.

[FleshJeb]

12 hours ago, 4x4cheesecake said:

I'll do some finetuning on the weekend, ... [snip] somehow I think I have to sacrefice something in order to justify the heavy use of part clipping and to keep a peace of conscience.

I'll ping you in my mission report

Awesome!

Given the limitations of LEGO-style building, I’d justify the wing clipping as adding mass and drag to the tank as radiator fins embedded into the surface. Functionally, the tank and the wings are one “unit”. Now, if you want to see KSP abuse, go look at Brad Whitstance’s SSTO to Tylo and back. I would have sworn he was editing config files until I figured out how he did all the drag reduction.

[Foxster]

I think in the OP's situation of getting this thing down on Eve I'd be tempted to use a couple of inflatable heat shields instead of the naked plane body. Or would the challenge not permit that?

[4x4cheesecake]

5 minutes ago, Foxster said:

I think in the OP's situation of getting this thing down on Eve I'd be tempted to use a couple of inflatable heat shields instead of the naked plane body. Or would the challenge not permit that?

Like this?

Yep, I had this idea already and the challenge will allow such a design but it is not require to land on Eve, I just need to get captured in an orbit. Even though it might be possible to use heatshields, a 'simple' aerobreak should be possible without these and in this case, it is more about to trick the game mechanic to work as expected. Since this doesn't seem to be possible (and summoning a dev takes quiet some time), the selfmade radiator is a really nice workaround

Anyway, if someone can find an reasonable explanation for this behaviour, I'm still interested^^
(No, 'heating is a funny beast' is not a reasonable explanation )