No warning parachute destruction (bug?)

[qoonpooka]

I have a lander on return from Mun.  The game is saved on the final approach. There is not enough dV left to abort the landing.  It's an aerobreaking maneuver directly from Munar ejection. Peri is 27km, I can bring that up to 32 or so.  Apo before atmo is 8M or something like that.  This is by far not the most aggressive aerobreaking I've ever done.

I've flown this mission before, and came in on basically this return trajectory from Mun once before.  I've taken this lander to minmus and come back home in a similar, more aggressive fashion.

Two things are different this time: 1) I'm using a nose-mounted basic chute instead of a pair of radial mounted chutes.  2) This rocket inexplicably decided to become unstable during liftoff and lean towards 270 (it did not do this on prior launches).  There are no additional asymmetries introduced, so I have no idea why that was other than, FNAR, the command capsule's reaction wheels toggled themselves off. (I discovered this after successfully wrestling the thing into orbit.)

On re-entry, however, around 20km altitude, well before I ever let my hand NEAR the spacebar, the parachute is mysteriously 'destroyed by aero forces and/or heat.'  At NO POINT does the part give me a heat bar. The housing for the parachute is still there, there is no explosion or anything, but the chute chamber vanishes.

This has never happened to me before EXCEPT if I were to deploy the chute while the indicator was red (which it is).  

Why is my chute suddenly destroyed?  The vehicle is just the pod, chute, and heat shield. SAS is off, the vehicle is stable and the heat shield is pointed in the right direction. I see no visual heat effect on the chute, nor is there any discoloration of the chute housing suggesting overheating is taking place. 

Valentina needs y'all's brains.

[Aegolius13]

When I've had this problem, it's because the parachutes were accidentally being deployed in an earlier stage.  If so, you can right click them and select "disarm" or something like that.  Then redeploy after it's safe.  You might have to right click again to redeploy; can't remember if the staging option comes back.

[DD_bwest]

have you accidentally armed your chutes while in space?  if so, they will open as soon as they reach the min atmo.  

you can double check by right click on them and see you they are, and if so you can just click disarm 

 

[qoonpooka]

7 minutes ago, Aegolius13 said:

When I've had this problem, it's because the parachutes were accidentally being deployed in an earlier stage.  If so, you can right click them and select "disarm" or something like that.  Then redeploy after it's safe.  You might have to right click again to redeploy; can't remember if the staging option comes back.

Yes. This was it. The rocket has also mysteriously re-ordered its own staging on me. Good grab!

[swjr-swis]

20 minutes ago, Aegolius13 said:

When I've had this problem, it's because the parachutes were accidentally being deployed in an earlier stage.  If so, you can right click them and select "disarm"

Alternatively, you can right click the chute and set the pressure (usually can slide it all the way to the right) and altitude (1000-1500m, but check your landing trajectory doesn't point to mountains) to something sane so it will wait to deploy until its low and slow enough. That way you do not even need to worry about staging manually.

[AlexanderB]

Depending on entry angle, mountains will certainly kill you, as its easily possible to go beyond parachute speeds, unless you fit airbrakes or drogues or some other way to slow down more.

[qoonpooka]

2 minutes ago, AlexanderB said:

Depending on entry angle, mountains will certainly kill you, as its easily possible to go beyond parachute speeds, unless you fit airbrakes or drogues or some other way to slow down more.

The problem was that my staging had re-ordered itself and the parachute was being erroneously deployed in orbit.  A collision with a mountain I would've been able to identify on my own... I have plenty of prior experience to draw from, on that. ;P

[AlexanderB]

My bad, I cut my post a little short.

I meant to say, depending on entry angle, speed and craft drag, its easily possible to stay above safe parachute speed all the way down to sea level. I try to build my entry-vehicles so they slow down to safe speeds at around 5k altitude, and set my parachutes to open at 0.34 (about 5k on kerbin), so even if I accidentally triger my parachutes in space, I should land safely. Should...

However, some mountains are taller than that. :X

Edited August 25, 2016 by AlexanderB
typo

[qoonpooka]

38 minutes ago, AlexanderB said:

My bad, I cut my post a little short.

I meant to say, depending on entry angle, speed and craft drag, its easily possible to stay above safe parachute speed all the way down to sea level. I try to build my entry-vehicles so they slow down to safe speeds at around 5k altitude, and set my parachutes to open at 0.34 (about 5k on kerbin), so even if I accidentally triger my parachutes in space, I should land safely. Should...

However, some mountains are taller than that. :X

If you trigger your parachutes in space, they will burn up on re-entry heating as you hit the atmospheric interface, which is what was happening to my chutes.  I wasn't deploying them at too high a speed, because I wasn't deploying them at all.  They were deployed automatically (and in error) because they were part of an earlier staging FNAR. But yes, the scenario you describe is definitely possible.

[Aegolius13]

I think the weird / confusing thing is that parachutes effectively have three phases: (1) armed (triggered via staging but not visibly deployed yet), (2) semi-deployed (chutes are out but not open all the way), and (3) fully deployed (chute has expanded and slows the craft dramatically).  As I understand it, arming is determined by staging, semi-deployment is determined by the pressure tweakable, and full deployment is determined by the altitude tweakable.  

I really don't get why the parachute gets destroyed by aero forces if it's been armed but has not yet even semi-deployed.  I.e., if the chute is still in its case, why is are the air and heat affecting it at all?  But at any rate, that's how the game does it.   EDIT: what may be happening is that the chute semi-deploys when it hits the (very low) default minimum pressure threshold, then is immediately destroyed before you can even see it.  

I tend to just avoid using the air pressure tweakable, and manually hit the staging on my parachutes once they're reached safe deployment speeds.  Since you have to wait to stage the parachutes until you're safe anyway, the pressure thing just adds more confusion.  The altitude tweakable is generally fine at 1km (it does take into account surface elevation), though you can modify it a little bit if you get sick of waiting for the slowed craft to land.   

Anyone else remember the old reentry tutorial, where the default altitude setting was 500m, which made it impossible for the chutes to open in time?  Good times.  I kept re-trying the scenario, thinking I was doing something wrong.  

 

Edited August 25, 2016 by Aegolius13

[DD_bwest]

12 minutes ago, qoonpooka said:

If you trigger your parachutes in space, they will burn up on re-entry heating as you hit the atmospheric interface, which is what was happening to my chutes.  I wasn't deploying them at too high a speed, because I wasn't deploying them at all.  They were deployed automatically (and in error) because they were part of an earlier staging FNAR. But yes, the scenario you describe is definitely possible.

They only do that if they are still on default settings, you need to change it by right clicking on them after you place them in the vab,  or in flight.

When you turn up the min pressure, they wont deploy until you reach an altitude that has that much atmospheric pressure or the Min altitude has been reached.  Its good to get into a habbit of doing this, because if you set it to .69 min pressure,   even if you arm them in space, they wont deploy until the last 2000meters,  which should have you going slow enough.  

 

  Used right, you can simply set a PE at around 30km,  walk away for a bit and you will come back to a safely landed pod.

[qoonpooka]

1 minute ago, DD_bwest said:

They only do that if they are still on default settings, you need to change it by right clicking on them after you place them in the vab,  or in flight.

When you turn up the min pressure, they wont deploy until you reach an altitude that has that much atmospheric pressure or the Min altitude has been reached.  Its good to get into a habbit of doing this, because if you set it to .69 min pressure,   even if you arm them in space, they wont deploy until the last 2000meters,  which should have you going slow enough.  

 

  Used right, you can simply set a PE at around 30km,  walk away for a bit and you will come back to a safely landed pod.

Unless there's a mountain.

[DD_bwest]

1 minute ago, qoonpooka said:

Unless there's a mountain.

I find it rather uncommon for a mountain to cause problems when you plan ahead and Use drogue chutes.    even if the min pressure is far off, the min altitude will deploy them.    with your drogues at 2500m and your mains at 1000m,  you should still be safe.

and dont come in so steep lol i did that alot early on and it isnt needed lol  i find a 30km PE to be the money spot

[qoonpooka]

Just now, DD_bwest said:

I find it rather uncommon for a mountain to cause problems when you plan ahead and Use drogue chutes.    even if the min pressure is far off, the min altitude will deploy them.    with your drogues at 2500m and your mains at 1000m,  you should still be safe.

and dont come in so steep lol i did that alot early on and it isnt needed lol  i find a 30km PE to be the money spot

I also use a 30km PE.

 

[DD_bwest]

2 minutes ago, qoonpooka said:

I also use a 30km PE.

 

ah good so you found it lol  its a good number to have,  as ive even used it for getting back safely even from outside kerbins SOI.  as long as you have heat sheilds that is lol

[pincushionman]

42 minutes ago, qoonpooka said:

If you trigger your parachutes in space, they will burn up on re-entry heating as you hit the atmospheric interface, which is what was happening to my chutes.  I wasn't deploying them at too high a speed, because I wasn't deploying them at all.  They were deployed automatically (and in error) because they were part of an earlier staging FNAR. But yes, the scenario you describe is definitely possible.

No. He's saying you can set the chutes so thst they "arm" when you hit the staging button, but don't "deploy" until pressure conditions are met. That's kind of what had already happened to you; they "armed" while still in space, and their "deploy" pressure was set too low so it happened while you were still too high and going too fast. That's why they didn't tear off before you got to 20 km or so.

[DD_bwest]

30 minutes ago, Aegolius13 said:

I think the weird / confusing thing is that parachutes effectively have three phases: (1) armed (triggered via staging but not visibly deployed yet), (2) semi-deployed (chutes are out but not open all the way), and (3) fully deployed (chute has expanded and slows the craft dramatically).  As I understand it, arming is determined by staging, semi-deployment is determined by the pressure tweakable, and full deployment is determined by the altitude tweakable.  

I really don't get why the parachute gets destroyed by aero forces if it's been armed but has not yet even semi-deployed.  I.e., if the chute is still in its case, why is are the air and heat affecting it at all?  But at any rate, that's how the game does it.   EDIT: what may be happening is that the chute semi-deploys when it hits the (very low) default minimum pressure threshold, then is immediately destroyed before you can even see it.  

I tend to just avoid using the air pressure tweakable, and manually hit the staging on my parachutes once they're reached safe deployment speeds.  Since you have to wait to stage the parachutes until you're safe anyway, the pressure thing just adds more confusion.  The altitude tweakable is generally fine at 1km (it does take into account surface elevation), though you can modify it a little bit if you get sick of waiting for the slowed craft to land.   

Anyone else remember the old reentry tutorial, where the default altitude setting was 500m, which made it impossible for the chutes to open in time?  Good times.  I kept re-trying the scenario, thinking I was doing something wrong.  

 

thats exactly what would be happening to you,   its default is so low it deploys really high and is instantly destroyed,  i change it to atleast .69 from the default of .02