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I was going to put a whole back-story for this question here, but thought it'd be better as a Google+ post instead, for reasons that should be obvious to anyone who reads it.

So, during high velocity returns, is there a chance that a parachute will fail if the capsule is travelling too fast when it's deployed? If so, what's the optimal speed/altitude range for deployment?

If speed is not the cause of these failures, what is, and how can I mitigate it?

I should also say that I'm using Mechanical Jeb. For reasons explained in this question, I now always bring the MechJeb unit back with me. In the case of the most recent failure, the MechJeb unit was positioned between the capsule and the parachute, something that had worked for me before. But for my rendezvous mission, I used one of the radial mount options, keeping the (proper sized) parachute connected to the top of the capsule.

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  • Possibly related: kerbalspaceprogram.com/forum/showthread.php/…
    – kalina
    Sep 22, 2012 at 16:43
  • @MBraedley Have you looked at the flight log after impact? It won't (usually) tell you what caused a failure, but it should tell you where the failure is occurring, which might give some insight into your issue?
    – GnomeSlice
    Sep 22, 2012 at 16:58
  • indeed, you should get something along the lines of "Structural failure on linkage between Mk16 Parachute and Mk1-2 Command Pod"
    – kalina
    Sep 22, 2012 at 17:01
  • @pixel: Hmm, there is some useful information there that makes me think of another possibility. I've updated the question.
    – MBraedley
    Sep 22, 2012 at 17:38
  • in one of my ships everything below the command pod breaks away.. which is fine by me as I don't need a separator.
    – reto
    Jan 7, 2013 at 12:49

4 Answers 4

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TLDR: Yes, you will lose chutes from version 1.0.1

Kerbal Space Program has an advanced physics engine and while the planets of the Kerbol system are different to the Sol system, the mechanics are similar:

In real life a re-entering spacecraft is hitting air at huge speeds and that is heating the vessel. The chutes undergo huge stresses when deployed - both from aerodynamic pressure and heating. If these stresses are too great, the parachutes could simply tear off.

Version 1.0.1 of KSP brings this real life danger into the Kerbal universe. Now, if you're moving too fast when the chutes deploy, they can be "burned up". Or, even if you're not undergoing heating, the chutes can be destroyed due to aerodynamic pressures.

How can I avoid chute loss?

Not losing parachutes from heating is easy: Don't deploy them when your vessel is burning up. You can tell if the vessel is burning up by looking at it - is it on fire? Don't deploy chutes.

Not losing parachutes from aerodynamic stresses is also easy: Don't deploy (even partially) when you're going fast. How fast is "fast"? I've conducted some tests and it looks like 1000m/s is the magic number. Although it may change depending on atmospheric conditions.

Edit: After version 1.1 chutes can be destroyed going slower than 1000m/s. Look at the chute icon in the staging, it changes colour based on whether it's safe to deploy or not.

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    Thank you for posting this answer two years ago. But now with version 1.0 and the new aerodynamic system it seems to be quite outdated. Maybe you would like to revise it? I put a bounty of 50 points on this question.
    – Philipp
    May 1, 2015 at 16:31
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    Good edit to keep the answer actual.
    – Shadur
    May 8, 2015 at 10:28
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The rule of meassure I use is to only deploy the parachute when below the speed of sound (330 m/sec). I tend to wait until 250 m/sec, but I've never had a parachtute ripped off when under 330 m/sec.

The parachute doesn't do much anyway until you hit 500-1500m (Kerbin) altitude (most videos on Youtube show 500m, I'm playing 0.19.1 and it's usually roughly 1350m for me.). If at that point you're still going faster than 330 m/sec; may Kerbal God have mercy on your poor Kerbals' souls...

Edit: I do not use MechJeb, so I have no idea of its weight. The figures above are for a pod (doesn't matter how many Kerbals) and a parachute. If it's heavier, I'd scale those numbers accordingly.

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    parachutes will start stabilising the flight path as soon as deployed AFAIK as drogue chutes, but won't fully open until 500m above ground level (which can be a ways up if you're landing in a mountain region).
    – jwenting
    Apr 16, 2013 at 9:22
  • Yep, but if you're still going too fast when deploying, it'll be ripped off. I haven't landed on a celestial body with an atmosphere other than Kerbin, so I'm not sure if variations in atmosphere (pressure, density, ...) will have an effect on those numbers.
    – Flater
    Apr 16, 2013 at 12:45
  • +1 To jwenting regarding altitude. KSP's built-in altimeter shows ASL (above sea level - or, more precisely, above mean sea level) only. Parachute deployment happens based on AGL (above ground level) altitude except when over water (when "ground level" is effectively below sea level). I highly recommend getting MechJeb, which will help to show you the difference and makes a whole lot of other useful information and tools available.
    – Iszi
    Jul 25, 2014 at 18:39
  • Thank you for posting this answer two years ago. But now with version 1.0 and the new aerodynamic system it seems to be quite outdated. Maybe you would like to revise it? I put a bounty of 50 points on this question.
    – Philipp
    May 1, 2015 at 16:30
  • I've been anxious to play 1.0 (haven't had the chance), But I heard the latest update has made the lower atmosphere excessively soupy again. Might be some time, as I'd expect another patch to correct it in the near future. Generally speaking though, a dropping pod will be slowed down enough so you can deploy the parachute safely when close to the ground. There are currently some speed races towards the island off the coast that have people used parachutes as brakes at insane speeds, and they still don't rip off (plenty of them can be seen on reddit.com/r/kerbalspaceprogram )
    – Flater
    May 4, 2015 at 7:38
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Right clicking on the 'chute during flight it tells you if it is safe to deploy or not.

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In 1.0.5 up, the chute symbols in the staging turn different colors depending on speed and the state of the chute. When you are going around 273 m/s, it is about the perfect time to deploy the chutes, and the symbol will look normal. Once deployed, the chute icon will turn yellow, and then once fully deployed will turn green. If you cut the chute, it will turn red. Hope this helps!

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