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Bug #21915

Interstage fairings now hold on to decoupled parts

Added by dok_377 4 months ago. Updated about 2 months ago.

Status:
Confirmed
Priority:
Low
Assignee:
-
Category:
Parts
Target version:
-
Start date:
04/17/2019
% Done:

10%

Version:
Platform:
Windows
Expansion:
Core Game
Language:
English (US)
Votes:
Arrow u r green
Arrow d r red

Description

How to reproduce: take a fairing, attach either a heatshield with enabled staging or some decoupler with a part beneath it to the fairing. It can be the main fairing node or interstage node, doesn't matter. Then close the fairing on a heatshield or a part. Launch craft, then try to decouple. Parts that supposed to be decoupled stay attached as if they are still on the same vessel, but they are not. You can switch to them as shown in the second video, but they behave as if they are still attached. When you enable time warp, physics completely fail and decoupled parts just fall to the ground and explode.

Video #1: https://youtu.be/7JU48QKtN8Q
Video #2: https://youtu.be/wvLroh3tsSc

fairing.craft (21.1 KB) fairing.craft demonstration craft usable in 1.3.1 and 1.7.0 k-ohara5a5a@oco.net, 04/20/2019 08:22 PM
cylindricalFairing.jpg (75.5 KB) cylindricalFairing.jpg when pod is root part, separation works k-ohara5a5a@oco.net, 06/30/2019 12:23 AM
cylindricalFairing.craft (43.5 KB) cylindricalFairing.craft craft with lower tank as root part, fairing holds on k-ohara5a5a@oco.net, 06/30/2019 12:24 AM
47639

History

#1 Updated by dok_377 4 months ago

And apparently it doesn't work only in one direction. Only if you try to decouple something from the fairing. If you decoupling the fairing itself, it works as intended.

Video #3: https://youtu.be/cuT0zviOW2M

#2 Updated by dok_377 4 months ago

  • Description updated (diff)

#3 Updated by dok_377 4 months ago

Also, rcs doesn't work until you leave the render range of the fairing.

Video #4: https://youtu.be/PlzA5X7PfmQ

#4 Updated by dok_377 4 months ago

I think it has something to do with the root part of the vessel. If the fairing stays with the root part of the vessel, nothing is decoupling from it. If the fairing decouples from the root of the vessel (i.e. interstage of the rocket on the first stage with the root part on the second stage), then it's fine. See the attached video for demonstration.

Video #5: https://youtu.be/SgZHApejBs4

#5 Updated by k-ohara5a5a@oco.net 4 months ago

Before the fix to #20354, when a fairing spanned two parts of a craft, and those parts decoupled, the fairing would be dropped from the physics simulation.

Now, in version 1.7.0:
1) Such an interstage fairing remains physically active, and snugly holds the part on the detached craft that it was 'closed' onto (video 1 and 2 above)
if the fairing base is connected to the root part before decoupling.

2) The fairing continues to shield its contents from airflow, which in general is good because allows creative things like rescuing and recovering craft by re-entering them in cargo bays of other craft, and that shielding also generally prevents RCS from thrusting (video 4 above). Here, however, the fairing becomes open at one end, which generally turns off the shielding. KSP would preferably notice that the decoupling event has made the fairing ineffective.

Fairings do not have a decouple action---they never let go of attached parts---they only deploy their fairing shell. It looks like the designers' intention for using an interstage fairings was to deploy the shell before decoupling the craft that it joins.

Workarounds:
(1) if the fairing is closed on a part, probably we should be required to deploy it before it lets the part fly free. The workaround with putting root in the detached section depends on something that other players are likely to call a bug.
(2) after the craft are clear of each other, we can induce KSP to notice that the fairing no longer encloses the RCS thrusters by reloading physics (save/reload, or switch out of physics range and back). Alternatively, Module Manager can change the rules on shielded RCS
@PART[*]:HAS[@MODULE[ModuleRCSFX]] { @MODULE[ModuleRCSFX] { %shieldedCanThrust = True }}

#6 Updated by dok_377 4 months ago

wrote:

Before the fix to #20354, when a fairing spanned two parts of a craft, and those parts decoupled, the fairing would be dropped from the physics simulation.

Now, in version 1.7.0:
1) Such an interstage fairing remains physically active, and snugly holds the part on the detached craft that it was 'closed' onto (video 1 and 2 above)
if the fairing base is connected to the root part before decoupling.

2) The fairing continues to shield its contents from airflow, which in general is good because allows creative things like rescuing and recovering craft by re-entering them in cargo bays of other craft, and that shielding also generally prevents RCS from thrusting (video 4 above). Here, however, the fairing becomes open at one end, which generally turns off the shielding. KSP would preferably notice that the decoupling event has made the fairing ineffective.

Fairings do not have a decouple action---they never let go of attached parts---they only deploy their fairing shell. It looks like the designers' intention for using an interstage fairings was to deploy the shell before decoupling the craft that it joins.

Workarounds:
(1) if the fairing is closed on a part, probably we should be required to deploy it before it lets the part fly free. The workaround with putting root in the detached section depends on something that other players are likely to call a bug.
(2) after the craft are clear of each other, we can induce KSP to notice that the fairing no longer encloses the RCS thrusters by reloading physics (save/reload, or switch out of physics range and back). Alternatively, Module Manager can change the rules on shielded RCS
@PART[*]:HAS[@MODULE[ModuleRCSFX]] { @MODULE[ModuleRCSFX] { %shieldedCanThrust = True }}

So you saying that it's not a bug or...?

I would prefer the fairing behavior from pre 1.7 than this (not only me, I imagine), because this change severely cripples the usual usability of the fairing. Deploying the shell before decoupling is highly undesirable from a design standpoint. Reloading the game or physics simulation just to turn on the rcs is definitely not a normal behaviour and should be considered a bug regardless, in my opinion.

Fairings do not have a decouple action---they never let go of attached parts

Even if a fairing and a part have a decoupler in between? That's extremely odd and shouldn't be like this.

#7 Updated by k-ohara5a5a@oco.net 4 months ago

  • File cylindricalFairing.craft added
  • Status changed from New to Confirmed
  • % Done changed from 0 to 10

I was confused by the posts above with "If you decouple the fairing itself..". I see now that the situation there is "if the decoupler separates the fairing from the root part..."
By "fairings do not have a decoupler action" I only meant that there is no button to push on a fairing to say "let-go", only the button to say "open".

If the interstage fairing is a simple cylinder, appearing to go from the flat end of one stage to the flat end of the next (attached craft) it certainly looks like the fairing should allow separation, and usually it does. But, if the root part is on the side with the fairing base, after decoupling some strong force hold the two separate craft in position, until the fairing is deployed. Maybe a fairing has a function like struts between the base an part it is closed on, that is meant to auto-release when the parts are separated, and that auto-releasing no longer happens in some cases.

#8 Updated by dok_377 4 months ago

wrote:

I was confused by the posts above with "If you decouple the fairing itself..". I see now that the situation there is "if the decoupler separates the fairing from the root part..."
By "fairings do not have a decoupler action" I only meant that there is no button to push on a fairing to say "let-go", only the button to say "open".

If the interstage fairing is a simple cylinder, appearing to go from the flat end of one stage to the flat end of the next (attached craft) it certainly looks like the fairing should allow separation, and usually it does. But, if the root part is on the side with the fairing base, after decoupling some strong force hold the two separate craft in position, until the fairing is deployed. Maybe a fairing has a function like struts between the base an part it is closed on, that is meant to auto-release when the parts are separated, and that auto-releasing no longer happens in some cases.

Sorry, i should have been more clear with my explanation. English is not my main language. I did show separation of the fairing with the decouplers in my videos, that should be sufficient enough for figuring out the bug.

#9 Updated by dok_377 3 months ago

1.7.1 and the bug is still present.

#10 Updated by k-ohara5a5a@oco.net about 2 months ago

47639

The way fairings hold on, to the part on which they were closed, will cause difficulty if anyone makes a traditional inter-stage fairing on a rocket with the root part below the fairing (as cylindrical Fairing attached) because the discarded stage has no control with which to deploy the fairing as is now needed.

The problem with enclosed parts being considered stowed (which is resolved after a quicksave/quickload) came up recently on the forum https://forum.kerbalspaceprogram.com/index.php?/topic/185821-parachutes-not-deploying-while-stowed/

#11 Updated by k-ohara5a5a@oco.net about 2 months ago

  • File deleted (cylindricalFairing.craft)

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