Laythe "re"-entry?

[strider3]

So far, I have had no luck at all getting any type of vessel to maintain some form of control when trying to make it through Laythe's atmosphere . I have tried space planes from other people who state they work on Laythe and capsules that re-enter Kerbin's atmosphere without issue...but refuse to do so on Laythe. Invariably, at some point when temperatures and speeds are starting to taper off very nicely, any craft I have will lose attitude control and tumble through the rest of the decent (space plane) or  lose "hold" on SAS / Surface / retrograde and come in sideways until parachutes open (capsules). It does not matter how many control surfaces or reaction wheels I add, they all lose their SAS "hold", in all modes, with lots of electrical power available.

I'm not at all experienced with space planes...and only trying them at this point to see if I can land on Laythe's water biomes and collect science.

One thing I do not understand at all...why does a simple capsule that re-enters and lands or splashes down on Kerbin, without ever losing it's attitude control, lose control in the thinner atmosphere and lower gravity of Laythe? Even Duna never caused these issues, with several different types of landing craft.

[king of nowhere]

this is very strange. the atmosphere should not matter if the capsule is aerodinamically stable. and personally i found that laythe's atmosphere is not bad, if you come equipped with thermal resistant stuff

try to post some pictures maybe?

[18Watt]

My experience has been whatever works on Kerbin will work on Laythe also.   So if you have a ship that works good on Kerbin, but not Laythe, try to figure out what's different.

Without pictures, we are just guessing here.   

One thing to look at is your entry speed.   Are you testing at Kerbin from a 100X100km circular orbit, but arriving at Laythe from a hyperbolic trajectory, at 4,000+m/s?

Another difference might be your fuel balance, or where your COM (center of mass) is.   If your COM moved too far back when you burned fuel, it will become unstable.   Try moving fuel to more forward fuel tanks before entry.   

Based on your description, I'd say the COM balance issue is the most likely culprit.   Again, try moving as much fuel to forward tanks as you can, and see what happens.

Pictures would help.

 

[strider3]

I will get back to you with some pictures, hopefully today.

[LineOfRahl]

22 hours ago, 18Watt said:

My experience has been whatever works on Kerbin will work on Laythe also.   So if you have a ship that works good on Kerbin, but not Laythe, try to figure out what's different.

Without pictures, we are just guessing here.   

One thing to look at is your entry speed.   Are you testing at Kerbin from a 100X100km circular orbit, but arriving at Laythe from a hyperbolic trajectory, at 4,000+m/s?

Another difference might be your fuel balance, or where your COM (center of mass) is.   If your COM moved too far back when you burned fuel, it will become unstable.   Try moving fuel to more forward fuel tanks before entry.   

Based on your description, I'd say the COM balance issue is the most likely culprit.   Again, try moving as much fuel to forward tanks as you can, and see what happens.

Pictures would help.

 

COM is everything with aerodynamic stability. The center of mass MUST be ahead of the aerodynamic center.  Moving fuel will make or break a stable entry.

It's a fine line between burning up, and overshooting when aerobraking. The high velocities make it very touchy when adjusting the altitude for entry, the difference between 30km and 40 km is huge. Some of my return encounters even from Duna can be pretty fun lol Especially if I have very little dV to work with and have to rely entirely on aerobraking to kill of velocity.

[Vanamonde]

Laythe's atmosphere is thinner so if your craft is depending on control surfaces to hold attitude, they might not be sufficient for the air there. 

[strider3]

I'm entering the Laythe atmosphere from a very low, circular orbit. My speed as I hit the atmosphere is 1,700 M/S, or less, for all craft. I've given up on keeping "capsules" or other "vertical" craft from tumbling in the atmosphere...they never overheat so, who cares? Parachutes, when deployed, will get the vertical types back into a proper surface alignment for landing. The problem with verticals is having them float in Laythe's water biomes and getting the science back into orbit.  Space planes continue to be a problem...I don't know how you can add more control surfaces than I already have, but they all refuse to "nose up" and just crash into the surface at high speed.

Laythe is shelved, along with Eve, for possible future exploration.