Parachute parameters - altitude and pressure? What does it do?

[glorsh66]

All parachutes have two tweakable parametters
an altitude and pressure.

But what do they do? Is it an automatic system?
I tried different settings but didn't notice the difference

[Lewie]

2 hours ago, glorsh66 said:

All parachutes have two tweakable parametters
an altitude and pressure.

But what do they do? Is it an automatic system?
I tried different settings but didn't notice the difference

The altitude tweakable sets the altitude at which the parachute will deploy. You can stage your parachute before/during entry (or re-entry) and the chute will automatically deploy at the altitude you selected. Of course, many players just do it manually and stage the parachute when they want to.

The pressure tweakable sets the minimum pressure the atmosphere has to be at to deploy. It’s not that useful on Kerbin, but on places like Duna and Eve it really is. 

Hope that helps

[GuessingEveryDay]

2 hours ago, glorsh66 said:

All parachutes have two tweakable parametters
an altitude and pressure.

But what do they do? Is it an automatic system?
I tried different settings but didn't notice the difference

The altitude system tells to deploy completely by then.

The pressure setting tells the parachute when to open before then.

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions. 

[antipro]

7 hours ago, glorsh66 said:

But what do they do?

https://wiki.kerbalspaceprogram.com/wiki/Parachute#Deployment

"Parachutes semi-deploy at a specific atmospheric pressure. which is situated in different altitudes on different bodies (rough semi deployment altitudes are shown below).
Contrastingly, full deployment occurs depending on height above ground, not pressure."

[jimmymcgoochie]

The pressure parameter sets the minimum atmospheric pressure that the parachute needs in order to deploy- this will need to be adjusted depending on where you’re going- Duna has a really thin atmosphere with a maximum pressure of 0.06atm (6kPa), so you’ll need to set the minimum pressure on your parachutes as low as you can or they just won’t open before you hit the ground; in contrast, Eve’s maximum pressure is several atmospheres (either 400 or 500kPa, I can’t remember which) so you should set them to open as late as possible to reduce the strain on the chutes, and to reduce the time you spend floating down to the surface.

Once the parachute deploys, it’s only half open and won’t provide maximum drag until it fully opens. The altitude parameter sets the altitude above the surface that the parachute fully opens and provide full drag. Keep in mind that it takes about 5 seconds for the parachute to fully open up after it’s triggered so don’t set this number too low- anywhere from 650 to 1000m is suitable for Kerbin, I’d go as high as possible on Duna and really low on Eve (500m or maybe even less).

There’s a third option that I think is enabled with “advanced tweakables” switched on in the main menu settings, which has three options- deploy when safe, when risky or immediately: when safe is the default and will wait until you’re going slow enough that deploying the parachute won’t break it, when the parachute icon is white in the staging menu, but that also means that there’s a chance the parachute never deploys or deploys too late to slow you down; when risky is just that, opening the parachutes when the icon is orange, with a risk of breaking the parachutes but also a chance that they’ll be fine and will open early enough to slow you down; immediate is also self-explanatory, the chute will deploy at the pressure and altitude values you set regardless of whether it’ll survive or not, you’d need to be pretty desperate to use this option as odds are the parachute will just break.

In the staging menu the parachute icon can be white (safe to deploy but not armed), orange (risky) and red (unsafe), but will turn blue when it’s armed by staging. The background also changes colour, going orange or red when the conditions are too hostile to deploy the chutes e.g. during re-entry.

Drogue chutes can deploy faster and at lower pressures than mains and will help slow the craft down before the mains deploy, for high value craft (like crew pods) and larger craft it’s worth adding a drogue chute or two to make sure that the main chutes will work properly.

When landing a crew capsule on Kerbin I usually have the main parachutes set to 0.6atm pressure and 750m altitude, this is enough to open the parachutes well above the terrain unless it happens to be heading straight into some mountains- in which case I drag the pressure all the way down so the chutes open as soon as possible. I always leave the parachutes set to “deploy when safe”, it’s rare that the situation would require anything else.