Re-entry Heating setting recommendations; ?

[GarrisonChisholm]

I have been digesting some of what I have seen recently discussed about re-entry heating, and a question occurred to me; what type of re-entry "should" fail? Irrespective of attempting to simulate a more dangerous atmosphere than is appropriate for the planetary body, what type of entry profile (angle/velocity) is just so filled with Tom-Foolery that it Should result in dramatic failure? Does it purely boil down to m/sec, or are other factors involved in such a decision?

[annallia]

Suicide drops if I understand your question correctly.

I could be wrong but I do believe the game takes into account not just your speed but how much atmosphere you are going through at that speed so a plane at 10km moving at 1500 m/s will generate way more heat than the same plane at the same speed at 40km.

And m/s alone seems to be enough if you get it high enough, I had one vessel hit at 14,000 m/s and exploded instantly... well at 68km but since it was coming straight in with no angle that is pretty much instant.

[Guest]

Heating is a product of V^3, IIRC, so a large part of it does come down to speed.

[GarrisonChisholm]

Suicide drops if I understand your question correctly.

I could be wrong but I do believe the game takes into account not just your speed but how much atmosphere you are going through at that speed so a plane at 10km moving at 1500 m/s will generate way more heat than the same plane at the same speed at 40km.

And m/s alone seems to be enough if you get it high enough, I had one vessel hit at 14,000 m/s and exploded instantly... well at 68km but since it was coming straight in with no angle that is pretty much instant.

Jeepers. 14 km/sec? Was that a test, or was it actually trying to land- and where was it coming from? :?

[eddiew]

Well I just raged and dialled the heat scale back to 70%. Had a little MK1 rocket/glider that came back from Minmus and overheated 55km up. Even at 70% it took three passes to land safely, so I may bring it down more.

I've stopped caring whether it's "cheaty" - right now the atmo heating is causing the game to not be fun for me because I can't fly the sort of ship I like to fly. Since I can make the game fun again with one minor edit to the save file, I shall do so

Also I'm dialling down the conductivity to avoid that thing where small parts like reaction wheels get used as heatsinks for the rest of the vessel and detonate immediately. That at least is a conspicuous bug and I don't feel bad for fixing it with the debug tools provided.

[LethalShade]

Going in straight, without any angle, will probably result in your demise.

[Jouni]

Kerbin reentry is a 3000+ m/s maneuver. Designing a craft for it should have gameplay challenges and require some effort, just like other maneuvers of similar magnitude.

[uglyduckling81]

Well I just raged and dialled the heat scale back to 70%. Had a little MK1 rocket/glider that came back from Minmus and overheated 55km up. Even at 70% it took three passes to land safely, so I may bring it down more.

I've stopped caring whether it's "cheaty" - right now the atmo heating is causing the game to not be fun for me because I can't fly the sort of ship I like to fly. Since I can make the game fun again with one minor edit to the save file, I shall do so

Also I'm dialling down the conductivity to avoid that thing where small parts like reaction wheels get used as heatsinks for the rest of the vessel and detonate immediately. That at least is a conspicuous bug and I don't feel bad for fixing it with the debug tools provided.

Can't say I have had any problems with heating at all. I was wondering if it's even working. 3000m/sec aim for Peri of about 25-30km lands every time unless I mess up something like not deploying chutes or attempt a powered landing and botch it.

[Geschosskopf]

I have been digesting some of what I have seen recently discussed about re-entry heating, and a question occurred to me; what type of re-entry "should" fail? Irrespective of attempting to simulate a more dangerous atmosphere than is appropriate for the planetary body, what type of entry profile (angle/velocity) is just so filled with Tom-Foolery that it Should result in dramatic failure? Does it purely boil down to m/sec, or are other factors involved in such a decision?

Your thread title and your text question are 2 different things so I'll try to answer both, starting with the text above.

The Text Question

I find it very hard to think of any situation in the normal course of sane-and-sober KSP gameplay where reentry/aerocapture/aerobraking should be really and truly deadly. This is because KSP is set in a toy-sized solar system where ship speeds are an order of magnitude less than in real life. If we assume that you're trying to fly realistic, sensible mission profiles and (a huge and obviously false assumption) that the heat and aero models are not borked and/or bugged, then you should never find yourself in a position to fry, at least if you take reasonable precautions. Now, if you try to land center mass on Kerbin when returning from Jool, or something similarly mad, then you should have a problem.

Consider that in real life, Apollo landed directly on Earth when coming back from the Moon (although it came in rather tangentially instead of going center mass). This should, therefore, be quite possible in KSP. And because of the tiny size of KSP, the velocities involved when returning from Minmus, Duna, and Eve aren't significantly higher, so direct, Apollo-style landings from those places should also be quite possible, even normal. Furthermore, the other planets with significant atmospheres (Eve, Jool, and Laythe) should have wide upper regions where the air is thin enough to aerobrake/capture in without much concern, again because speeds in KSP are really not that high, although I wouldn't want to land directly on any of them.

Unfortunately, at present the aero model is rather borked. Kerbin's atmosphere is the only one that realistically fades out over a long distance, thereby providing a nice aerobraking zone. All other atmospheric densities drop off very steeply so they are in effect more like oceans than atmospheres. This is what makes just barely touching the top layer of air at Eve, Jool, and Laythe pretty much instantly fatal from heat without slowing you down at all. And there are also related problems with the heat model, although those are harder to pin down because of all the complex interactions in the heat system.

Reentry Heat Setting

This IMHO is a matter of personal taste because regardless of what you do with it, you'll make something either impossible or super easy. Using a relatively high setting only produces realistc results at Kerbin, while turning it down to allow realistic interplanetary aerocaptures makes things at Kerbin a doddle. But realize that this inconsistent result is a product of the inconsistencies in the underlying aero model (and some issues with the heat model), so things will never be to your liking everywhere no matter what you do.

Some recommendations for different play styles:

* High Settings (100% or more):

Do this if you never venture out of Kerbin's SOI, or if you believe interplanetary aerocaptures should be impossible (or require extreme engineering) based on the speeds of the real solar system, ignoring the fact that nothing goes anywhere near that fast in toy-sized KSP. And also ignoring the undeniably borked aero model at other planets.

* Low Settings (20% or less):

Do this if you're big into interplanetary bases and colonies. 20% is about the highest you can go and still have useful interplanetary aerocaptures. In effect, this changes the non-solid surroundings of Eve, Jool, and Laythe from being oceans to proper atmospheres. It does, however, make futzing around within Kerbin's SOI rather harmless. But given that your attention is focused on other planets, you're not going to be doing much of that anyway.

* Medium Settings (20-100%):

Don't do this as it produces bad results everywhere. Kerbin becomes a doddle while interplanetary stuff is still too deadly.

Edited July 26, 2015 by Geschosskopf

[eddiew]

Can't say I have had any problems with heating at all. I was wondering if it's even working. 3000m/sec aim for Peri of about 25-30km lands every time unless I mess up something like not deploying chutes or attempt a powered landing and botch it.

Strange :S I've been flying these little guys...

...for the last 4 hours, because I had so many rescue missions within 2km/s range that I started sending up clusters of return vehicles.

From LKO, they do just fine, but coming in at Minmus velocities with 100% heating, they die a horrible death, usually with the cockpit exploding first

[GarrisonChisholm]

Your thread title and your text question are 2 different things so I'll try to answer both...

Thank you kindly! I am just at the point in my first play where I am sending my first probes to Eve & Duna, and given the difficulty of getting encounters I am in no hurry to be a colonizing player. It sounds like the default (I presume) 100% is for me.