What do the parachute settings do?

[Annushka]

Parachutes have two settings -- "Min Pressure" and "Altitude". Can someone please explain the effect of these two settings?

[adinfinitum]

Minimum pressure is the pressure the chutes first deploy, as a fraction of the air pressure at Kerbin's sea level. So if you have that set to 0.5 and a barometer on your ship, you'll see that it deploys at ~50 kilopascals. The altitude setting is the height above ground the chute fully opens.

[Annushka]

Thank you.

[moogoob]

The only one I ever touch is the open height one. Particularly if I'm trying to use chutes on Duna. Open HIGH.

[Reactordrone]

In terms of practical application the pressure switch can be set up to deploy the parachutes at a specific altitude range (0.34 gives about 5km) regardless of whether there's a crew or probe core left on the vehicle to open them. Opening altitude may need to be increased in thin atmosphere's such as on Duna to give time for the fully deployed chute to straighten you up for a vertical landing.

[mcirish3]

Also worth noting you probably don't want them burning up while in reentry. So you do not want the initial deployment to happen until your are below heating threshold. In Other words below 10km.

[klevi]

I wasn't deploying my chute, but it would be destroyed at about 20km. Changing my Min Pressure to 0.3 solved this issue.

What I don't understand, is why that works, and that's bothering me...

Will the chute always deploy at the min pressure regardless of whether or not you actually deploy it manually?

Any chance anyone could explain?

[mekasha]

No matter what your deployment settings, parachutes must always be activated manually first (either by staging or right-click).

Once you have activated them, they will not "pop out" until the minimum pressure is met. With the default values, falling from orbit to kerbin will mostly guarantee your parachutes will burn up if you deploy them while still in orbit. Increasing the pressure trigger means that the chutes open at a lower altitude (pressure increases as you get closer to sea level). Opening lower means you have more time to cool down/lose speed due to drag forces, which is why your parachutes would survive.

It's also possible that depending on your design and descent, you're coming in so hot that the parachutes are being melted off without even being deployed. If you're seeing heat bars show up on parts as you de-orbit, you're probably coming in too fast.

[adinfinitum]

I wasn't deploying my chute, but it would be destroyed at about 20km. Changing my Min Pressure to 0.3 solved this issue.

What I don't understand, is why that works, and that's bothering me...

Will the chute always deploy at the min pressure regardless of whether or not you actually deploy it manually?

Any chance anyone could explain?

If you were using the default deployment pressure then it's almost a guarantee that your parachutes are gonna come out and burn up on reentry, 0.04 atmospheres is pretty high up in Kerbin's atmosphere.

The parachutes have to be activated to deploy, but they don't have to deploy at the moment you activate them. Think of it as arming the trigger on the chute instead of deploying the chute. Perhaps they were in a stage that you activated before reentry? Because they shouldn't deploy if you haven't activated them.

[klevi]

I must have just messed up my staging, and didn't realize that I had already "armed" the chute.

Regardless, seems to be working splendidly now with min pressure at 0.3. Thank you very much for the responses.

[matthomas7]

On 5/19/2015 at 9:45 AM, mekasha said:

No matter what your deployment settings, parachutes must always be activated manually first (either by staging or right-click).

Once you have activated them, they will not "pop out" until the minimum pressure is met. With the default values, falling from orbit to kerbin will mostly guarantee your parachutes will burn up if you deploy them while still in orbit. Increasing the pressure trigger means that the chutes open at a lower altitude (pressure increases as you get closer to sea level). Opening lower means you have more time to cool down/lose speed due to drag forces, which is why your parachutes would survive.

It's also possible that depending on your design and descent, you're coming in so hot that the parachutes are being melted off without even being deployed. If you're seeing heat bars show up on parts as you de-orbit, you're probably coming in too fast.

This, for whatever reason, isn't true for me. I have vanilla 1.05 and when returning from from anywhere outside of near orbit, my chutes auto deploy around 20k and eventually burn up. They are staged alone, as the last stage, as they always are, and yet, I always have this problem when doing anything outside of near orbit.  These are the first two chutes you gain access too, mk16 and the radial one. Haven't unlocked any others. I can confirm that changing the pressure, as the gentleman above did, resolved the issue. 

Edited January 29, 2016 by matthomas7
Confirmed comment

[Snark]

Welcome to the forums, matthomas7!

1 hour ago, matthomas7 said:

This, for whatever reason, isn't true for me.

From reading your description, actually it sounds exactly like it's true for you.  What mekasha said was:

On 5/19/2015 at 7:45 AM, mekasha said:

Once you have activated them, they will not "pop out" until the minimum pressure is met. With the default values, falling from orbit to kerbin will mostly guarantee your parachutes will burn up if you deploy them while still in orbit.

And that's exactly what you're experiencing:

1 hour ago, matthomas7 said:

when returning from from anywhere outside of near orbit, my chutes auto deploy around 20k and eventually burn up.

20K is the altitude at which you hit the default minimum pressure that mekasha refers to.  Your chutes then semi-deploy there (because you already staged them), and then they burn up, exactly as mekasha said they would.

Parachutes never automatically deploy themselves.  They only deploy when staged.  They're deploying in your case because you did, in fact, deploy them before hitting atmosphere.

My impression as to where the confusion is coming from is that you're under the impression that you didn't stage them, and that they're deploying anyway.  Correct?

Therefore, the real question here is "how are the parachutes getting staged, when I didn't intend them to be?"

Some potential explanations that come to mind:

• The parachutes are grouped together with something else (like a decoupler) in the staging sequence, without your realizing or intending that.  (This is easy to happen in KSP; the editor tends to bung them in with other components, and you need to manually sort it out.)  So they're getting activated when you do that last stage, and you're not realizing it because nothing happens at that time.  (Yes, I know you mentioned that "they're in a final stage by themselves", but maybe something went off the rails somewhere and you didn't notice something.  I'm just raising it as a possibility; it's something to double-check.)
• You do in fact have the parachutes off in a final stage by themselves, as you say, but you've accidentally hit the space bar (without noticing it) before you begin reentry.
• You've accidentally gotten the parachutes lumped into some action group for the rocket that got activated while you were in orbit.
• You're running some mod that's automatically deploying the parachutes for you.  (You said "vanilla", so I'll assume this isn't the case.  Just mentioning it for the sake of completeness.)

Here's an easy way to tell that you've already staged your parachutes before reentry:  What color is their icon in the staging UI?  A truly unstaged parachute should be the normal default white color.  If you're seeing a cyan-colored icon, it means that they have already been "armed" (i.e. activated via staging) and are just waiting for the pressure to climb high enough to deploy.  So, if you see cyan when you think you haven't staged them yet, it means you have staged them at some point, somehow.

So, let's say you're in that position:  how do you fix it?  One way is to adjust the minimum-pressure setting, as the previous posters describe.  However, this is an old thread (you necro'd it, the last post was back in May, long before 1.0.5).  Now that we're running 1.0.5, however, you have an additional option.

1.0.5 added a new feature that allows you to "disarm" a parachute that has already been staged, as long as it hasn't deployed yet.  Just right-click on the parachute and choose "Disarm".  This restores it to its original, pre-staged state.  Then you can just fiddle the staging UI to put it back into a not-yet-activated stage, so that you can set it off via spacebar when you're down to where it's safe.