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MunsterIII

EVA kerbals die on re-entry

Question

I have three kerbals hanging on to the back of a heat shield during reentry.  The heat shield is 2.5m, so more than enough room for all three to fit.  Yet they still overheat and explode even after many tries.  Do they actually have to be in a pod for the heat shield to work properly?  Here is the scenario: https://imgur.com/a/Q2FAfSp

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8 minutes ago, MunsterIII said:

I have three kerbals hanging on to the back of a heat shield during reentry.  The heat shield is 2.5m, so more than enough room for all three to fit.  Yet they still overheat and explode even after many tries.  Do they actually have to be in a pod for the heat shield to work properly?  Here is the scenario: https://imgur.com/a/Q2FAfSp

I think they overheat because of regular heat transfer from the hot heat shield. Try putting something else between the heat shield and the ladders. Maybe a girder or a structural panel or something like that.

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1 hour ago, sh1pman said:

I think they overheat because of regular heat transfer from the hot heat shield

That's probably the case. Kerbals can reenter even without a heat shield (at least they used to in 1.7.3, haven't tested in 1.8.1). The thermal debug window can show details.

Here's a trick I learned: To land at KSC, start from equatorial low orbit just above the desert peninsula before KSC. Burn the jetpack retrograde towards the horizon mostly to depletion, keeping some spare fuel for attitude conrol. Then turn sideways into the wind and enjoy the plasma grill. After the fireworks, deploy chute and you should be coming in for a soft landing in front of the astronaut complex. I use this method to recover rescued pilots. Zero-star engineers and scientists don't have their parachutes, yet.

1 hour ago, sh1pman said:

Maybe a girder or a structural panel or something like that.

Parts with large thermal mass would be best. But those often have large mass, too.

Edited by HansAcker

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29 minutes ago, sh1pman said:

I think they overheat because of regular heat transfer from the hot heat shield. Try putting something else between the heat shield and the ladders. Maybe a girder or a structural panel or something like that.

Yeah, maybe having a red hot hunk of ceramic 6 inches from their faces isn't too great.  I will try this and see what the results are.

Edited by MunsterIII

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Mine enjoy reentries with their head outside the service bay, so it is not a problem in general. But heat transfer and rotational stability are important to watch, otherwise they get grilled :o

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On 10/29/2019 at 5:04 PM, sh1pman said:

I think they overheat because of regular heat transfer from the hot heat shield. Try putting something else between the heat shield and the ladders. Maybe a girder or a structural panel or something like that.

I tried sticking a battery in there, but they still exploded.  Also, I added a radiator to cool things down during re-entry and they still exploded.

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Just now, MunsterIII said:

I tried sticking a battery in there, but they still exploded.  Also, I added a radiator to cool things down during re-entry and they still exploded.

Radiators don’t work like that, they only dissipate core heat from things like drills and ISRU parts, not reentry heat. 
Battery is very light, which means very low thermal mass, which makes it heat up or cool down very quickly. Try sticking something a bit heavier in there.

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2 minutes ago, sh1pman said:

Radiators don’t work like that, they only dissipate core heat from things like drills and ISRU parts, not reentry heat. 
Battery is very light, which means very low thermal mass, which makes it heat up or cool down very quickly. Try sticking something a bit heavier in there.

How heavy does it need to be?  The kerbals blow up at 67km moving at 3km/s (I just realized that the ui was hidden so most of the info was hidden).

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18 minutes ago, MunsterIII said:

How heavy does it need to be?  The kerbals blow up at 67km moving at 3km/s (I just realized that the ui was hidden so most of the info was hidden).

Hard to tell. I’ve never done anything like that, so you’ll have to experiment a bit more.

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On 10/30/2019 at 11:38 AM, HansAcker said:

Kerbals can reenter even without a heat shield

ive landed plenty of kerbals like this! just need some EVA propellant (though its monopropellant now isnt it?) and a parachute! before the days of kerbals having their own chutes KIS was what i used for eva chutes

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6 hours ago, MunsterIII said:

The kerbals blow up at 67km moving at 3km/s

Heat transfer is not your problem, but piloting or design: The Kerbals must get direct heat.

67km alt is just 1-2 seconds into the atmosphere, if your PE is low enough (and it should be since you are very draggy and very light). 3km/s is roughly Minimus return, it should take a lot more time until Kerbals suits crit temp is reached. Try to enable heat info in debug menu for each part, open all Kerbals and seats and heatshields in space, pin them and use pause to have time to study the readouts.

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Hmm what could be more fun to try ? So I asked in my astronaut complex if there any voluntar for a crazy idea: no problem !

Note: 160 Ablator are enough, but 800 do not make you too heavy...

 

Check 1: Entry speed

floAU9N.png

well above 3000 m/s

Check 2: Heating during entry

anA5Gte.png

just cosy ;)

Check 3: Proof all Kerbals still alive as flames die

YiAUkLt.png

 

Note on Piloting: Do NOT go retrograde as seats are unlikely in that position (at least mine have been not). I had to turn 90° to bottom until heatshield was in true front.

Edited by CBase

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6 hours ago, CBase said:

Note on Piloting: Do NOT go retrograde as seats are unlikely in that position (at least mine have been not). I had to turn 90° to bottom until heatshield was in true front.

I am not using seats; that is not the kerbal way :P.  These guys only have some ladders to grab onto if that makes a difference.  Also I'm pretty sure I'm aimed perfectly retrograde because I have an octo2 w/ reaction wheel clipped into the shield.

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That might be the problem, if they just grab the ladder, they might be still treated as individual vessel. I am pretty sure KSP does heat calculation including shielding per vessel, therefore non of your Kerbals actually is protected by the heatshield. 

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2 minutes ago, CBase said:

That might be the problem, if they just grab the ladder, they might be still treated as individual vessel. I am pretty sure KSP does heat calculation including shielding per vessel, therefore non of your Kerbals actually is protected by the heatshield.

Yeah I was kind of concerned that that might be the case.

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