Why didn't the heatshield do anything?

[KerbolExplorer 991]

So I builded a small probe to land on Eve, everything was going great untill re-entry, now I knew that Eve's atmosphere is quite brutal so I added the big shield. I knew it didn't have ablator but it should have resisted the re-entry(it did work last time i tried), but this time the thing blew up instantly, it was like if the shield wasn't even there.

Video:

Better look at the probe:

Is it normal for this to happen? if so what could i do to fix it?

[RealKerbal3x 5,790]

@KerbolExplorer If you're entering Eve's atmosphere at nearly 5km/s, the inflatable heatshield just isn't gonna cut it, because it doesn't have ablator. This means it doesn't have thermal conductivity as low as the ablative heat shields, so it's transferring heat to the decoupler behind it (as @overkill13 said) and causing it to overheat.

For a probe of that size a 2.5m ablative heatshield will probably be large enough, anyway. Try using that

Edited May 30, 2020 by RealKerbal3x

[AHHans 975]

Do I spy a Terrier engine in there? If so, then have a look at bug #23924. (In short: something is wrong with the definition of the Terrier so that it isn't protected by heat-shields closer than 21m to it.)

Edited May 30, 2020 by AHHans
fixed typo

[N_Danger 880]

You shouldn't need an engine to land. The parachutes will slow you down enough.

[overkill13 240]

Hit F3 and figure out what overheated.  It wasn't the heatshield, because the shield still exists after the explosion, it's just disconnected from the probe.  It looks like the large heat shield was shedding heat to the smaller parts and they were unable to deal with it because they are so small.  The engine probably has decent heat handling, so I'm banking on that decoupler. 

What did your first attempt, the one that worked, look like?  It might be worth oversizing the probe a bit (1.25m parts), at least a decoupler, but maybe an LV-909 and 1.25m fuel tank too, even if only partially fueled.  Another option would be to use the 1.25m to 0.625m adapter tank, either empty or with fuel if you can get it to transfer through the shield to the transfer stage, and put the rest of the rocket on top of it.

Edit:  For some reason I thought the heat shield had a 1.25m base...  Anyhow most of the things still apply, making the parts larger might allow better heat handling.  You can actually eliminate the decoupler since that inflatable heatshield has a decoupler built in.

Edited May 30, 2020 by overkill13

[AHHans 975]

P.S. You do realize that the terrier is a pure vacuum engine and has an extremely poor atmospheric Isp? Already at Kerbin sea level it has lower thrust than the spark, not to talk about the soup that surrounds Eve.

[KerbolExplorer 991]

I'm not sure if it was the engine bug or that the heatshield wasn't enough, I'm going to go with the heatshield option since I retried the mision this time with an ablative heatshield and I changed the engine.

Eitherway I managed to land it on Eve, the parachutes were more than enought to stop the fall. And yes the engine choice was terrible, it was more there to make the probe look good and incase that the transfer stage didn't managed to get to Eve, to atleast try to get a fly-by or with luck an orbit.

 

Thanks for the help!

Edited May 30, 2020 by KerbolExplorer

[AHHans 975]

41 minutes ago, KerbolExplorer said:

I'm not sure if it was the engine bug or that the heatshield wasn't enough, I'm going to go with the heatshield option since I retried the mision this time with an ablative heatshield and I changed the engine.

Feel free to try it with another heatshield but the same engine.

[jimmymcgoochie 1,709]

On a related note: engines are no use on Eve, the atmospheric pressure will make most of them function poorly and a vacuum engine like the Terrier will be essentially useless. If the heat shield alone doesn’t slow you down enough, a couple of parachutes certainly will, but rockets are dead weight and jets don’t work either as there’s no oxygen in the air.

[Gargamel 6,345]

4 hours ago, KerbolExplorer said:

and incase that the transfer stage didn't managed to get to Eve, to atleast try to get a fly-by or with luck an orbit.

But If you ran out of fuel...... maybe the payload was too much mass due to an extra engine and it's fuel?  Betcha that is a significant amount of the lander's mass right there.  

[peteletroll 667]

It's definitely the Terrier aerodynamics bug. You can fix it with a ModuleManager patch, read the linked bug report to find it.