Best place to put RCS thrusters

[ineon]

(I think this is a general question and not particularly related to any specific craft - but if a specific example would be useful then I can upload one later.)

I recall reading that attaching items radially are affected by drag, and that items attached in a stack are not. What happens if you attach an RCS thruster behind a wing (where you would usually attach control surfaces)? Is that radial or stacked, and (more importantly) is it affected by drag? 

I think that I also recall reading that it doesn't matter how it has been offset and rotated, the item still behaves the same as if it were not offset or rotated. I assume that this means that I can make a RCS thruster look like it is attached on the body just behind the wing, when it is actually attached to the wing just next to the body?

Final questing: do RCS thrusters work inside cargo bays? IRL that would not work, but I wonder if the game engine is simplified enough to get away with it.

Edited January 19, 2016 by ineon

[Champ]

7 minutes ago, ineon said:

(I think this is a general question and not particularly related to any specific craft - but if a specific example would be useful then I can upload one later.)

I recall reading that attaching items radially are affected by drag, and that items attached in a stack are not. What happens if you attach an RCS thruster behind a wing (where you would usually attach control surfaces)? Is that radial or stacked, and (more importantly) is it affected by drag? 

This is considered radial, and will be affected by drag. By the way, i think objects in a stack are affected by drag. It's far less drag if it's occulted, but it still cause drag.

 

9 minutes ago, ineon said:

(I think this is a general question and not particularly related to any specific craft - but if a specific example would be useful then I can upload one later.)

I think that I also recall reading that it doesn't matter how it has been offset and rotated, the item still behaves the same as if it were not offset or rotated. I assume that this means that I can make a RCS thruster look like it is attached on the body just behind the wing, when it is actually attached to the wing just next to the body?

Yes, you can, but it would change nothing : they would still be considered as radially attached.

10 minutes ago, ineon said:

Final questing: do RCS thrusters work inside cargo bays? IRL that would not work, but I wonder if the game engine is simplified enough to get away with it.

I think they work, if the cargo bay is opened. May be better to check it.

If you are building a rocket, sincerely, forget the drag for RCS thrusters. If you are building a spaceplane, then you would better use the place-anywhere-linear-RCS

[Val]

6 hours ago, ineon said:

I recall reading that attaching items radially are affected by drag, and that items attached in a stack are not. What happens if you attach an RCS thruster behind a wing (where you would usually attach control surfaces)? Is that radial or stacked, and (more importantly) is it affected by drag?

If it's not attached using attachment nodes (the green balls), then it counts as surface attachment and will experience drag, unless it's inside a bay. Occluding a part behind another only works against ascent and re-entry heating.

6 hours ago, ineon said:

I think that I also recall reading that it doesn't matter how it has been offset and rotated, the item still behaves the same as if it were not offset or rotated. I assume that this means that I can make a RCS thruster look like it is attached on the body just behind the wing, when it is actually attached to the wing just next to the body?

Offset doesn't matter, but rotation does. Parts have different drag depending on which side is facing the airflow, regardless of how it is attached.

6 hours ago, ineon said:

Final questing: do RCS thrusters work inside cargo bays? IRL that would not work, but I wonder if the game engine is simplified enough to get away with it.

They do work in cargo bays, if the bay is open and the exhaust isn't too close to the walls or other parts.

Edited January 19, 2016 by Val
Now with spelling and grammar

[ineon]

7 minutes ago, Val said:

If it's not attached using attachment nodes (the green balls), then it counts as surface attachment and will experience drag

Ohhh... that makes a huge amount of sense. That does sounds like a very consistent way of defining surface-attached and non-surface-attached parts.

 

[Snark]

57 minutes ago, ineon said:

Ohhh... that makes a huge amount of sense. That does sounds like a very consistent way of defining surface-attached and non-surface-attached parts.

Also, bear in mind that some parts (like RCS thrusters) are always radially attached, they're radial parts.  There's no way to attach them on a node.

7 hours ago, ineon said:

I think that I also recall reading that it doesn't matter how it has been offset and rotated, the item still behaves the same as if it were not offset or rotated. I assume that this means that I can make a RCS thruster look like it is attached on the body just behind the wing, when it is actually attached to the wing just next to the body?

The orientation of the RCS thruster does matter.  It can only thrust in certain directions.

Whether it matters how you use the offset-and-rotate widgets (as opposed to how it's just "naturally" oriented and positioned, based on where you put it):  that, I don't know.  But if you're correct, i.e. if you can tinker with the orientation and positioning with the widgets and it doesn't make any difference to the RCS function, then I would be surprised.

[gilflo]

Just use RCS Build aid to place them near COM or DCOM

http://forum.kerbalspaceprogram.com/index.php?/topic/33124-105-rcs-build-aid-v076/

[RizzoTheRat]

On ‎19‎/‎01‎/‎2016 at 4:15 PM, Val said:

They do work in cargo bays, if the bay is open and the exhaust isn't too close to the walls or other parts

Anyone know how close their exhaust can be to another part without causing issues?  I sometimes find it a squeeze fitting them in where I want them.

[Evanitis]

I'd say closer than you'd think. I wouldn't risk stating without testing that (unlike engines) RCS exhausts doesn't get blocked by other parts... But it definately was my impression when I positioned those too close to stuff.

[Snark]

1 hour ago, Evanitis said:

I'd say closer than you'd think. I wouldn't risk stating without testing that (unlike engines) RCS exhausts doesn't get blocked by other parts... But it definately was my impression when I positioned those too close to stuff.

+1 to this.  Doesn't appear to make any difference, the "exhaust" you see from the RCS thrusters is just eye candy with no physical effect on anything, as far as I can tell.  Aside from not exerting physical force, it also doesn't have any heat, so you don't have to worry about blowing things up (the way you do with, for example, sepratrons).

[FancyMouse]

My old test in 1.0.4. Summary: you should always put RCS port parallel to your control axes (i.e. + setup), never x setup (45 degree rotated). Disclamer: haven't run the same test in 1.0.5 yet.

[Snark]

1 hour ago, FancyMouse said:

My old test in 1.0.4. Summary: you should always put RCS port parallel to your control axes (i.e. + setup), never x setup (45 degree rotated). Disclamer: haven't run the same test in 1.0.5 yet.

I'm sure it still applies.

This, and also turn on fine control mode when using RCS for lateral thrust.