Mercury reentry sometimes is too hard to keep aiming for retrograde surface velocity.

[pack7df]

Sometimes (almost always), when i reentry, i tried to aim to retrograde surface, the RCS are trying hard to keep the ship in that orientation, but in some points is not enough and the angle of attack become too big and the ship explode due overheating. Some times, it does not happen. I don't know what is happening.

[siimav]

Try the ROHeatshields procedural heatshield part with Stock (not restock!) shape.

[pack7df]

There is a rare behaviour, if you close the game and flight this Mercury Capsule, the effect is very low, the RCS could handle it. But if you make any other flight then the error appears. With the procedural heatshield you suggest, is the same.

[siimav]

RCS isn't the issue. IRL Mercury didn't use any during re entry and instead opted for a slow BBQ roll. The real problem is that HS occlusion has close to zero error margin. Sometimes even negative margin.

[ezsnackeur]

But there is totally an issue with crafts having different aerodynamic behavior every time a save is reloaded, he's onto something in my opinion.

[njits23]

I know for a fact that a bug exists where your CoM will shift from where it's supposed to be. If this happens to you in a Mercury capsule, you burn up and die as the RCS isn't strong enough to keep you surface retro.

What I have not figured out regarding the bug is what causes it. I do know that once it shows up for a craft, it'll persist for the rest of the flight. The only way to fix it was to reload an earlier save. I also think I've only had it happen to crewed craft, but that might just be randomness. I don't think all capsules get the OffsetCoM feature if they can't actually use it (like Mercury and the lander cans), so I don't think that's to blame.

[siimav]

So what's the AoA with disabled RCS when that issue happens?

[njits23]

With the matching Mercury heatshield it's enough to burn you up even from a suborbital trajectory. IIRC it was somewhere around 5-10 degrees. I sadly don't have any of the actual AoA figures from when it most recently happened to me: https://discord.com/channels/319857228905447436/1312475979418964038/1314230793182117928

Edit: on second thought, the 5-10 degrees might have been with a 45N RCS thruster firing.

[ezsnackeur]

ive seen procedural shields with the restock model produce lift even at 0 aoa, also the direction of the lift vector would shift at every reload, even with constant attitude

[pack7df]

After review the ship, i discover i used old parts that were deprecated, it looks that i copied some old ship in previous saves. And the it was loaded in this new version. So i was using deprecated parts, now it works fine. I think a message warning should appear if a user is using a deprecated part.

[Capkirk123]

Probably resolved by adding a small amount of ablator to Mercury in #192