Ablator is used even when staged

[tomf]

I think this is a bug in the heatshield configuration

To reproduce build a ship with radiators and a staged heatshield, put it in orbit of the sun somewhere around the orbit of Moho.

The ship will heat up to around 600K. The radiators are able to stabilize the ship at that temperature. However this temperature is hot enough to make the ablator slowly evaporate despite the fact that it is currently staged and the ablator is going to be required later to re-eter on Kerbin.

[Starwaster]

I think this is a bug in the heatshield configuration

To reproduce build a ship with radiators and a staged heatshield, put it in orbit of the sun somewhere around the orbit of Moho.

The ship will heat up to around 600K. The radiators are able to stabilize the ship at that temperature. However this temperature is hot enough to make the ablator slowly evaporate despite the fact that it is currently staged and the ablator is going to be required later to re-eter on Kerbin.

http://i.imgur.com/WKl3Z9Z.png

That's not a bug. Heat shield ablation starts at 500K. If it gets that hot it will ablate. Staging is irrelevant.

[tomf]

Perhaps it isn't a bug but a feature request, the ablator shouldn't evaporate when it is staged and perhaps the temperature at which it ablates should be considerably higher. I realise it won't be trivial to distinguish between ship that is hot but whose temperature is being controlled by the radiators and a ship that is undergoing re-entry and heating up rapidly.

[micha]

The heat shields' ablation shouldn't trigger just on temperature, but on temperature plus being exposed to an air stream.

[cantab]

Yeah I had this issue, my heatshield slowly boiled away on my Moho mission and I was left with only a tiny amount remaining. It doesn't seem realistic or desirable I don't think.

[Padishar]

It doesn't seem realistic or desirable I don't think.

Neither is a vessel whose equilibrium temperature is over 600K...

[BudgetHedgehog]

So then we have the question of how to send a craft to Moho and back while ensuring the heatshield doesn't evaporate before we return?

[sal_vager]

Don't bring it with you? It's redundant mass all the way there and back, and can be left in orbit of Kerbin.

[seyss]

I have the same issue.. I'll just Hyperedit the ablator back.. this is a bug in my opinion.

[Superfluous J]

I think this is a reasonable thing to expect to be "realistic." Not the actual temperatures involved, but how the ablator acts.

If we (Humans) sent a returnable probe to Mercury and it had a heat shield for the return trip to Earth, would it ablate away just for being so close to the Sun? I don't know. If it would, then we're fine. If it wouldn't (and I'd like to know why ) then we have a problem.

[sal_vager]

Trouble is we don't have a heat shield that's intended for such high temperatures, the current stock heat shields will boil away if they go over a fixed temperature, whether this is by aerobraking, heating via engine thrust or via ambient heat doesn't matter, nor does being staged or not.

I'm not sure if there's a real need for such heat shields yet, Moho lacks an atmosphere and you'll be destroyed by the Sun before you get that close, the only use would be to re-enter at Kerbin but this could be worked around by not using the Moho or Sun vessel to re-enter directly, or by providing for the installation (docking) of a heat shield later.

Fairings also make good heat shields, arguably better than the stock heat shields as they don't have ablator, just be careful not to stage them, it's also worth checking if a heat shield inside a fairing counts as "stowed" and becomes immune to heat.

What we need is a new heat shield, not to make existing heat shields immune to boil-off.

Edit:

Well this is disappointing...

Okay I'm going to ask that this is changed, I can put a feedback report in QA when that starts but if you guys also add feedback to the public tracker the exp guys can flag it and it'll help.

Edited September 6, 2015 by sal_vager