Eve lander gets completely destroyed

[RoninFrog]

I am planning to rescue Jeb, Val, and Bill off of Eve with this lander:

https://imgur.com/a/MSKREIv

https://kerbalx.com/MunsterIII/Mona-Lisa-III-Lander

I am testing it out, and it seems to work great until 1100 meters.  Most of the parachutes are deployed by then and everything is going smoothly until the game freezes.  The next thing that happens is the entire lander is fairly evenly distributed over an area of about 10 km.  I have no clue what is happening.  Any ideas?

 

Lander description:  Double layer asparagus pancake for ascent.  Heat shield on top and bottom for stable descent.  SRB on the bottom to deorbit (use cheats to get there).  First stage deploys drogues, second deploys main chutes, third releases probe.

Edited December 19, 2019 by RoninFrog

[OHara]

If I understand, the trouble happens 1100 meters above sea level during descent.

There was a problem with 1.8.0, fixed in 1.8.1, that would allow you to be falling faster than intended through the atmosphere.  If the problem is 20meter off the surface, there is still a problem in 1.8.1 with terrier engines having their 'collider' too large, about 20meters long.  Other than that, I might suspect you've discovered a new bug with KSP on the new Unity engine, or old mods newly having problems with KSP on that new engine.

Your kerbalx link points to your editing session and won't work for others. There should be a link like https://kerbalx.com/MunsterIII/Mona-Lisa-III-Lander but it looks like you might not have made it visible yet (?).

(Not your question, but double-pancake asparagus might be too draggy for Eve ascent. I'm sure you work out something after getting around the landing problem.)

[Dafni]

36 minutes ago, OHara said:

... If the problem is 20meter off the surface, there is still a problem in 1.8.1 with terrier engines having their 'collider' too large, about 20meters long...

Wait, what?? I never heard of that one. Must have missed it.

Thanks for the heads up. That sounds like a nasty bug there.

[AHHans]

4 hours ago, MunsterIII said:

I am testing it out, and it seems to work great until 1100 meters.  Most of the parachutes are deployed by then and everything is going smoothly until the game freezes.  The next thing that happens is the entire lander is fairly evenly distributed over an area of about 10 km.

It looks to me like you have all the parachutes on the upper stage, and the only connection to the lower stage goes only through the parts in the center. So if one single part in the center gets destroyed your craft will fracture into many small-ish pieces, even without destroying any more parts.(*) And all the forces of holding the lower stage in the air are going through this one single piece. I don't know how KSP models this kind of problem, but in one of my Eve crafts (it's always Eve, isn't it) I also had all the parachutes on the top, and all the rest of the craft hanging from one part (a mk1 capsule, the root part). During descend this part tended to spontaneously disintegrate (I think when the chutes went from partly deployed to fully deployed, but I don't really remember anymore). My solution was to spread out the parachutes over more than one part, so that not all the forces go through one single part. You could try with struts between the lower stage and the upper stage parts with the parachutes.

(*) See: this report for a somewhat role-played description of a similar event.

 

[Foxster]

I'd say there is just too much mass hanging off a few decouplers. Its a very draggy craft and when the atmos gets real thick I think it's just pulling itself apart. 

That craft could be a fraction of the size if you did some proper streamlining. At the moment you are throwing huge amounts of dV away to drag. Drag being the no.1 consideration for an Eve ascent craft. 

It would be OK for Kerbin's thinner atmosphere but not for Eve. You need a few thin stacks, not the dozen of fat, non-tapered  ones you have.