objects in a cargo bay should be removed from aerodynamics, except they are not

[king of nowhere]

i tried putting the propellers of my space plane inside cargo bays so that when i close the cargo bay, they would not screw up aerodynamics. i've seen it done on a youtube video, and while i feel bad copying ideas, my eve ssto project was going nowhere and i decided to make an exception.

except, it does not stop aerodynamics from affecting my propellers. aerodinamic overlay shows no difference with closing the cargo bays

experimenting with it, i confirmed the lack of difference by flying with the cargo bays closed. it keeps flying, propelled by the propellers

https://imgur.com/ja85Sjz

i discovered that the way to keep aerodinamics out of the cargo bay is to keep it closed before starting. in this last experiment, i closed the cargo bays before moving the plane, then i used rocket propulsion. the cargo bay, is, correctly, isolated from aerodinamic disturbances

https://imgur.com/tU2804y

 

unfortunately, this does not solve my issue, as i need to use both the propellers and the rockets in the same flight.

is this a bug? what can i do about it?

[Spricigo]

14 minutes ago, king of nowhere said:

i feel bad copying ideas

Just my opinion, but I don't think is smart to pretend to not know a good way to do things just because someone thought of it before you.

 

20 minutes ago, king of nowhere said:

is this a bug? what can i do about it?

It may be. Cargo bays are know to have been doing strange things before (e.g. shielding things while open and not shielding while closed). It may also be he case that your propeller are clipping through the bay's walls, for what the game is concerned the propellers are outside, thus exposed to drag.

Try to open and close the cargo bays and look if that change something, use the debug menu to display drag on part window and check if the other parts inside the cargo bay are also exposed or if it is only the propellers (you may also check parts in different part of the vessel causing disproportionate drag). If is just the propeller see if is possible to use the move gizmo tool to bring it closer inside. If anything else fail, try make the propellers align with the airflow to minimize the drag but remember to bind deployment angle with something you are not using to control something else, remember that you have 180º of deflection to work with since you can invert the deployment direction  (supposing you are using the part named propeller. I read somewhere that normal control surfaces works fine too if not better in some circumstances, but since aerospikes/vectors+stagging + FMRS mod also works (and can make the whole process a lot faster too, which I consider more important than reusability* in the stock sense. Of course, that is personal preference)  I didn't bother to check this propeller thing myself)

BTW, grabbing units and shielded docking ports are also know to have acted funny with aerodynamics at some point. Keep in mind that it may also be something to solve or exploit at some point.

 

*my concept of reusability in KSP often envolves recycling the entire craft and building something else with Extra Planetary Launchpads.    ...and often I don't even bother to recycle since I already have more than enough materials from ISRU *shrugs* 

 

[king of nowhere]

11 hours ago, Spricigo said:

It may be. Cargo bays are know to have been doing strange things before (e.g. shielding things while open and not shielding while closed). It may also be he case that your propeller are clipping through the bay's walls, for what the game is concerned the propellers are outside, thus exposed to drag.

 

i checked, they are not.

closing and reopening the cargo bay also does not work. i found out, though, that closing the bay, saving the game and reloading it, that works. not ideal, as reloading a game with the airplane in midair will make it lose some momentum but, lacking anything better, it can be dealt with.

 

Quote

Just my opinion, but I don't think is smart to pretend to not know a good way to do things just because someone thought of it before you.

my purpose is to invent an eve ssto. if i just wanted to use one, i'd go on kerbalx and look for it. if i was doing this for a job, that would be the best solution, but in this case "fun" requires me to figure stuff out.

Edited September 9, 2020 by king of nowhere

[Spricigo]

39 minutes ago, king of nowhere said:

in this case "fun" requires me to figure stuff out.

I get it. Still, forgetting what you leaned from a video to figure it yourself is not an option. 

[Linkageless]

I don't know about actually having props still propelling from inside a closed service bay, I've not experienced that.  I could only guess they are seen as not shielded.  If it's possible, perhaps only temporarily.

What I have definitely seen a lot of is prop blades continuing to be shown by the F12 aero forces visualisation, when the bay doors are closed and it seems they're not doing anything.  Worse still, those forces keep being shown even if I turn off F12, leaving the vessel with a permanent pink halo while it stays in focus.

I don't recall if I'd actually checked the aero debug in the part action menu of those blades for drag.  It being a problem with the service bay calculations wouldn't surprise me.

I'd found that if I turn off the F12 display, disable the motor and close the doors, then enable F12, the blade forces aren't shown.  I've been happy enough to do that ever since, just so I don't get stuck visualising (seemingly) irrelevant forces.

I wonder if, like a tree falling in the forest making no sound, just because one can't see it, it isn't there?

[Lt_Duckweed]

I'm fairly certain this s a visual UI only bug.  Stratz and I saw something very similar with our Jool craft, where the blades still had drag listed in their part windows, even though the bay was closed.  But it was purely visual, the blades were actually producing no drag, but when you closed the bay it didn't update the UI correctly.

[Linkageless]

Yes, that sounds very like what I've experienced.

It would be interesting if anyone was able to get screenshot evidence of a PAW showing a blade with any significant lift/drag/etc inside a closed bay.

I have seen, for example, -0.1kN forward lift on an un-powered yet still rotating blade in a closed bay mid way on an Eve ascent.  I did wonder if that was fractionally slowing me down or if it was just a rounding error and could be ignored.  I chose to ignore it.

[king of nowhere]

On 9/12/2020 at 1:22 AM, Lt_Duckweed said:

I'm fairly certain this s a visual UI only bug.  Stratz and I saw something very similar with our Jool craft, where the blades still had drag listed in their part windows, even though the bay was closed.  But it was purely visual, the blades were actually producing no drag, but when you closed the bay it didn't update the UI correctly.

I can sort of confirm this. i did check in controlled circumstances, and indeed i found that the propellers stop producing thrust. the reason i didn't realize this is that i was around top speed the previous time i checked, and the plane without propulsion started moving downward, getting speed and giving the illusion that propulsion was staying the same.

i cannot be sure that there isn't any residual drag, but if there is, it must be minor

[Draalo]

Are the parts inducing drag mounted to the node inside the cargo bays or attached to the surface inside?

As far as i now KSP considers parts mounted to the surface as mounted outside.

 

Test it. mount a small tank inside the bay to the node. attach 8 Batteries radial to that tank. Does it still produce drag?

[Lt_Duckweed]

6 hours ago, Draalo said:

Are the parts inducing drag mounted to the node inside the cargo bays or attached to the surface inside?

As far as i now KSP considers parts mounted to the surface as mounted outside.

 

Test it. mount a small tank inside the bay to the node. attach 8 Batteries radial to that tank. Does it still produce drag?

For cargo bay occlusion, ksp does not care about where you attached the part, only that it is physically inside the bay.  You can attach parts anywhere on a craft and offset them into a bay and the bay will shield them.

[Spricigo]

2 hours ago, Lt_Duckweed said:

For cargo bay occlusion, ksp does not care about where you attached the part, only that it is physically inside the bay.  You can attach parts anywhere on a craft and offset them into a bay and the bay will shield them.

However, a part may not be shielded because of a tiny bit clipping through the wall. That is more often the case(but still rare occurrence) with parts attached to the wall than to the nodes.