1.2 Parachutes, round 2

[Loren Pechtel]

I really like how they function now but I've got one situation that is puzzling me.

I play with Stage Recovery and so I put chutes on anything that's going to fall onto Kerbin.  Once again, during re-entry I burned the last of my fuel and jettisoned the booster.  (Yeah, under 1.2 I could jettison the fuel rather than burn it.)  As the booster fell away I got a message about a parachute being destroyed by heat and aero forces.  Stage Recovery recovers the booster and gives me credit for the number of parachutes I attached, the chutes on my rocket look right.  In both cases the landing velocity is a bit below what Stage Recovery predicted in the VAB.  What got destroyed and how??  (I was at a completely unsafe speed for deployment but nothing should have deployed at that point.)  This is not the first time it's happened, either.

Is there perhaps a bug when you stage with armed parachutes?  And if so why isn't something going splat?  Could Stage Recovery have a bug that it doesn't check if a chute was destroyed?  I would think the stage would stay within physics range and actually land on it's chutes properly.  (Stage Recovery only acts on objects that go outside physics range, at which point it either picks it up off the ground or simulates a landing if it's still in flight--such simulated landings only require the proper resources, not that they actually work properly.  Chutes don't need staging, fuel doesn't need to be able to reach the engine.)

[Mystique]

You pushed stage button, chute on dropped part deployed and got ripped apart by aero forces/heat, but part itself ("unpacked") was still there, this is what SR checks for, it doesn't take into account deployment state of chute. To avoid these messaged, you may just jettison parts without deploying/arming chutes at same time, it'll still work in SR.

P.S. I get same minor problem, even though I use Realchute with arming when staging, so it should just arm, not get deployed immediately. It doesn't affect anything from recovery point of view, just doesn't look that cool.

Edited December 21, 2016 by Mystique

[bewing]

I'd like to create a bug report about this, but I don't think I can reproduce it without more info or (even better) a savegame.

Can you make it happen 100% of the time? What are the exact steps?

[Loren Pechtel]

5 hours ago, Mystique said:

You pushed stage button, chute on dropped part deployed and got ripped apart by aero forces/heat, but part itself ("unpacked") was still there, this is what SR checks for, it doesn't take into account deployment state of chute. To avoid these messaged, you may just jettison parts without deploying/arming chutes at same time, it'll still work in SR.

P.S. I get same minor problem, even though I use Realchute with arming when staging, so it should just arm, not get deployed immediately. It doesn't affect anything from recovery point of view, just doesn't look that cool.

How do you avoid arming the chutes?  At that point I'm down to a single stage, there's no place to put the chutes that they won't arm.  I'm also surprised the booster got outside physics range before going splat.  I think I was only about 20km up (This was a Kerbal-chasing mission, I always bring plenty of spare delta-v on those and all I had to burn it was a Terrier so the burn was long) and after the booster separated I should have followed a similar course until my drogues popped.

5 hours ago, bewing said:

I'd like to create a bug report about this, but I don't think I can reproduce it without more info or (even better) a savegame.

Can you make it happen 100% of the time? What are the exact steps?

I've seen it before but I haven't experimented to be sure what the trigger is.  I figured it was better to ask first in case it was something known.  Since it doesn't seem to be I'll try to reproduce it 100%.  I think the trigger is staging while the chutes are armed and the pressure requirements of the chutes are met but you are still going too fast.

I can't think of a reason for someone to do this unless they were using Stage Recovery and re-entered with the booster still attached in order to slow it enough to ensure recovery.  (If you jettison the booster as soon as you have done your de-orbit burn it will be at a dangerous speed and may not be recovered.)

[bewing]

5 hours ago, Loren Pechtel said:

How do you avoid arming the chutes?  At that point I'm down to a single stage, there's no place to put the chutes that they won't arm.

Since at that point you have multiple items in the stage, you can move the cursor over to the staging list, and a + sign will appear -- just like when you are building stages in the editor. Click on the + and you get a new stage. Move the decouplers or whatever into the new stage and stage it. (You may need to hit space twice, for some reason, to get the new stage to activate.) Alternately, of course, you can open the context menus of any decouplers you want to activate, and click the button to activate them by hand -- without using staging at all.

 

[Loren Pechtel]

19 minutes ago, bewing said:

Since at that point you have multiple items in the stage, you can move the cursor over to the staging list, and a + sign will appear -- just like when you are building stages in the editor. Click on the + and you get a new stage. Move the decouplers or whatever into the new stage and stage it. (You may need to hit space twice, for some reason, to get the new stage to activate.) Alternately, of course, you can open the context menus of any decouplers you want to activate, and click the button to activate them by hand -- without using staging at all.

 

Yeah, although the easier approach would be to put the offending chutes in a new stage 0.  Unfortunately that ensures it goes splat if it stays in physics range.  Maybe raising the trigger pressure on the chutes will solve it.

[Loren Pechtel]

More observations on this:  It can be triggered on the way up, also.

Furthermore, I'm even more puzzled.  This time every chute on my capsule streamed and was promptly destroyed.

I do not know all the trigger criteria but it appears that chutes that are staged while at their pre-deployment pressures deploy immediately without regard for safety.  Why I'm getting inconsistent behavior I have no idea.

[bewing]

Any chance you can turn off your mods temporarily and see if you can replicate any of this in stock?

 

[Loren Pechtel]

11 hours ago, bewing said:

Any chance you can turn off your mods temporarily and see if you can replicate any of this in stock?

 

I believe it's only stock parts involved and I have no physics mods installed.

 

Edit:  Oops--stock parts on the way down.  It's SpaceY SRBs I'm trying to land on the way up.

Edited December 22, 2016 by Loren Pechtel

[bewing]

Perhaps, but I have never once had a parachute pre-deploy, and I activate parachutes in space before reentry all the time. And I used to activate them a lot during atmospheric ascent -- but I haven't been doing that recently.

[Loren Pechtel]

10 hours ago, bewing said:

Perhaps, but I have never once had a parachute pre-deploy, and I activate parachutes in space before reentry all the time. And I used to activate them a lot during atmospheric ascent -- but I haven't been doing that recently.

The problem only seems to occur if you stage when the predeployment pressure is met.  Going up or down doesn't matter.  Unless you're using Stage Recovery there would be no reason for such chutes, though.

[Vanamonde]

Since this is not something which occurs in stock, the thread has been moved to modded support to avoid confusing people. 

[bewing]

I specifically tested again, and as Vanamonde says -- this issue does not happen in stock. So one of your mods is definitely causing it. You need to find out which one.