How to stow landing legs (LT-2) aerodynamically in a service bay?

[antbin]

I'm working on a SSTO Minmus miner, it's looking good except for how to land it. Dropping down right on top of the RAPIERS is one option, but better would be some temporary retractable landing legs at the back of the plane.

Anyone seen a trick to stow big landing legs in a service bay? My attempt below doesn't work (the legs still pick up aero drag).

Edited August 3, 2015 by antbin

[Snark]

Yeah, the legs are pretty big-- I generally just abandon any attempt to stow them aerodynamically, and just eat the drag. They're pretty small compared with the rest of the ship, so in my experience the drag isn't too bad. A bonus is that since they're at the rear of the ship, the drag that they add helps with aero stability.

IIRC, components that are attached radially to something that's aerodynamically exposed (e.g. to the outside of a cylindrical fuel tank, that sort of thing) get drag added to them regardless of their actual physical positioning-- e.g. if you attach something to the outside of a tank, and use the editor's tweak-position tool to move them radially inwards so that they're physically inside the tank, they still get drag added; that is, moving them inside like that doesn't help. (Caveat: I'm not basing this statement on personal experience, just reporting secondhand on something I seem to recall reading on this forum a month or two ago.)

If that's the case, then I'd say what you're doing in the pic above wouldn't help-- it looks as though the legs are radially attached to the outside of the service bay, even if they've been physically nudged inwards. One idea might be to have a stack-mounted object that's truly physically inside the bay (i.e. it's mounted to one of the bay's interior nodes), and radially attach your legs to that thing, instead of to the service bay itself? Just something to try-- the idea being that things that are truly "inside" a service bay don't get drag, and things that are radially mounted to such an object ought not to get drag either. No idea if it actually would work in practice, but maybe worth a try.

Personally, I'd say just put 'em on the outside of the ship and let the drag fall where it may.

[Wolfox]

One idea might be to have a stack-mounted object that's truly physically inside the bay (i.e. it's mounted to one of the bay's interior nodes), and radially attach your legs to that thing, instead of to the service bay itself? Just something to try-- the idea being that things that are truly "inside" a service bay don't get drag, and things that are radially mounted to such an object ought not to get drag either. No idea if it actually would work in practice, but maybe worth a try.

Good idea, try to use cubic octagonal strut inside bay, attach legs to it and then move them physically out with positioning tool. If that logic is right, they should not cause the drag as their parent parts is occluded from drag by service bay.

[antbin]

Success... but only by turning the legs 90 degrees and landing on the sides of the feet. Ugly hack, but something for now.

I think the drag was because the legs clipped into the aft fuselage. It would make sense for drag to be calculated based on if the part's DragCube sticks out of the bay, perhaps? I've had some problems with Gigantor solar panels that appear (barely) stowed but still pick up heat and drag.

[Wolfox]

I think the drag was because the legs clipped into the aft fuselage. It would make sense for drag to be calculated based on if the part's DragCube sticks out of the bay, perhaps? I've had some problems with Gigantor solar panels that appear (barely) stowed but still pick up heat and drag.

I never did any proper research on this topic, although its very interesting. Only thing I know for sure, is that opened bay cause alot more drag than closed one. Problem is, I place into the bay mostly physics-less objects, like small experiments and batteries, which should not produce drag anyway (but get heated when exposed), so there is no real difference between closed and opened bay drag, except the drag caused by bay itself...

I personally believe that parts placed inside bay act the same as if they would be placed outside. I doubt that game distinguishes between in/out radial placement and portion of exposed part, its simply radial and adds drag to parent part. Correct me if I am wrong please.

[almagnus1]

Why not use Infernal Robotics to create something that will move the legs into the bay when you're not using them, yet deploy them to a stable position when you want to?

[Wolfox]

Found this:

Part occlusion is accomplished only through node connections. Parts that are connected to other parts via nodes have the size of that cube's face reduced by the size of the parent/child part. So surface mounted parts are not occluded from drag. (This is why stuff built with lots of things hanging off suffers a lot of drag.)

[Tazin]

I'm curious, how do you know if a certain part is generating drag or is occluded?

[Starhawk]

I'm curious, how do you know if a certain part is generating drag or is occluded?

If you hit mod+F12 (Alt+F12 in Windoze), you can turn on aero information in the action menus in-flight. This displays accurate drag info.

OT: From my experience it is harder to land a spaceplane on it's tail than it is to descend tail-first with your gear down and then just do a belly flop when you are a couple of metres off the deck. A vernor engine under the nose if needed to get it pointed upward when it's time to go and you're all set. Saves you the weight of a second set of landing gear as well.

Happy landings!

[Nich]

I just flop to the landing gear and drive up a mountain to get vertical

[Claw]

I think that's my quote. Something important to note though is that cargo/service bays act different than what that quote is referring to. Items inside a bay are checked for occlusion by the bay itself. If occluded, then it doesn't contribute drag. This id true even if some of it is sticking out of the bay due to clipping.

However, I don't believe the trick of "attach inside the bay and use gizmos to slide it out" works because the game is checking actual location of the part. So if you slide the part out of the bay using gizmos, it shouldn't be shielded anymore.

That being said, it's supposed to work that way, but I haven't verified. Sould be easy to verify with the aero overlay.

Cheers,

-Claw