Heatshields and spinning

[martinborgen]

Most obvious on the inflatable one. That this is spawned from the Kraken itself! My eve lander have one below, and then three on strut segments on the top, to keep it pointing retrograde on the descent. But it starts spinning like mad, sometimes even breaking apart. And detatching the shields from any payload is a giant hazzle, they tend to hit parts of the rocket and break things. 

But the issue is also seen on another eve lander I made, avoiding the inflatable heatshield. How do you counter these spinning effects? 

[natsirt721]

I have never experienced uncontrollable rotation with any of the shields, perhaps your design is in err? Pictures would go a long way.

[Rath]

Don't clip them.

[Daniel Prates]

Are you sure the CoM is in the right place? In an atmosphere entry, your object has to have low CoM that is situated in the front (movement wise, it must be prograde-placed). Also, the whole thing also needs radial simetry. If it is not thus designed, it will start to spin, and armosphere may keep feeding that speed with more torque in each turn. Eventually it  becomes uncontrolable.

If your project is correct, then think about some extra reaction wheels to keep it alligned.

[martinborgen]

Clarification. It spins along it's own axis, it basically rolls. The correct end points towards the ground and space respectively. 

[Snark]

1 hour ago, martinborgen said:

Clarification. It spins along it's own axis, it basically rolls. The correct end points towards the ground and space respectively. 

Screenshot, please.  It matters a lot how your ship is designed.

Out of curiosity, do you have any aero control surfaces (e.g. steerable fins like the AV-R8) on your lander?  And are they facing "backwards" during reentry with the heat shield?  And they're forward of the CoM during reentry?

One thing I've noticed is that SAS can get kinda confused with aero control surfaces in pointing-backwards situations, so that it induces a leftward roll when it's trying to correct rightwards.  That can cause an out-of-control spin.  I'm not saying that's your problem, just something to check for.  If you turn off SAS, does that make the problem go away?

[martinborgen]

The winglets are disabled in all axis of control, ant not deployed. 

 

Here's the lander: 

http://imgur.com/79teBwD

http://imgur.com/g8psFAs

Edited February 27, 2017 by martinborgen

[VincentThacker]

On 2/27/2017 at 11:01 AM, Snark said:

Screenshot, please.  It matters a lot how your ship is designed.

Out of curiosity, do you have any aero control surfaces (e.g. steerable fins like the AV-R8) on your lander?  And are they facing "backwards" during reentry with the heat shield?  And they're forward of the CoM during reentry?

One thing I've noticed is that SAS can get kinda confused with aero control surfaces in pointing-backwards situations, so that it induces a leftward roll when it's trying to correct rightwards.  That can cause an out-of-control spin.  I'm not saying that's your problem, just something to check for.  If you turn off SAS, does that make the problem go away?

Thanks a lot!

I could not understand why my Eve lander suddenly started rolling uncontrollably at a certain point during atmospheric entry. I even edited the craft file to make sure that all the identical parts (such as multiple groups of legs and parachutes placed with symmetry) were placed at exactly the same height along the vertical axis, ensuring that the craft had complete cylindrical symmetry. I was at my wit's end until I found your solution. I turned off SAS and it stopped. You made my day. +1

Edited May 20, 2018 by 100055