[Video Tutorial] Stop that Spin! - Mitigating spin in Onion/Asparagus designs

[NecroBones]

I put this together tonight to show one of the main causes of spin during launch, and a reasonable solution.

[xcorps]

Great video.

Clearly spoken, precise diction, to the point and informative.

[The Destroyer]

Or, if you're lazy, just add fins, usually the first stage/atmo is where the main "spin stage" is

[NecroBones]

I've seen them spin, even with fins and several SAS modules...

But yeah, there are multiple ways to deal with it. The point here is to show what the cause is, and a possible solution to address the root cause, not the symptom.

[Pecan]

Nice one! You're really pumping these videos out at quite a rate now, aren't you :-) Hope you're enjoying making them, they make their points very clearly.

[NecroBones]

Yeah, I made a bunch and then had other things come up. I need to get back to it soon.

[Dispatcher]

Very good video. I've recently encountered such rotation for the first time. I thought it might have something to do with my using the new NASA parts but now I understand how to fix this. Thanks!

[AlexisBV]

For the cool factor, I usually augment the spin before staging, that way the spent stages go flying out quasi-radially when they decouple (useful especially with heavy stuff that the decouplers can't really push away, and when I don't want to bother with separatrons). And it looks cool too

Naturally, this only works if there's nothing in the way, and if you're not in the middle of a turn. That really kills your maneuverability.

I just wouldn't want to be in the module, I never was much a fan of spinning rides in theme parks...

Edited June 11, 2014 by AlexisBV

[jBeta]

NecroBones: just curious what mod(s) are used in that video for the the clouds? Is that EVE?

[NecroBones]

NecroBones: just curious what mod(s) are used in that video for the the clouds? Is that EVE?

Yup, Environmental Visual Enhancements.

[LethalDose]

0.o the fuel lines act as struts!?

Well, I learned something.

[Red Iron Crown]

This problem has plagued me for a long time, your video laid out the problem and solution nicely. I never realized that fuel lines behaved as struts.

You've got a great voice, Necro, very clear and little hesitation.

[NecroBones]

Thanks, glad I could help!

[rkman]

As far as i know all that a strut does is make the two connected parts move less relative to one another, and strut location does not matter.

I think the cause of rotation is due to a bug:

Surface attachment connection flexibility and strength affected by order of creation of the attached parts http://bugs.kerbalspaceprogram.com/issues/290

And the solution is not because of strut symmetry but because of there being twice as many struts, reducing torque down to a level where SAS can cope with it a lot better.

[Temeter]

Interesting. I was aware of irregular struts and to much burden on decoupler causing this behavior, but never factored in fuel lines, even though i knew of their function as strut.

Edited July 17, 2014 by Temeter

[Red Iron Crown]

As far as i know all that a strut does is make the two connected parts move less relative to one another, and strut location does not matter.

That has not been my observation. The strut has two connection points and you can see parts flex around those points in less structurally sound designs. Strut location on radial boosters has a big effect on how they behave when they separate. Triangulated strut structures work really well, too; I suspect that wouldn't be the case if location didn't matter.

[NecroBones]

That has not been my observation. The strut has two connection points and you can see parts flex around those points in less structurally sound designs. Strut location on radial boosters has a big effect on how they behave when they separate. Triangulated strut structures work really well, too; I suspect that wouldn't be the case if location didn't matter.

This is my experience as well. Strut placement matters a lot, particularly under high stress.

When I was building the spacecraft for the video, I did several test-launches with each configuration before filming, and I was able to tune them to be better and worse with placement, quite a bit.

[Red Iron Crown]

I wonder if this problem is somewhat mitigated in 0.24+ now that engine gimbals can be used for roll authority. Need to do some testing.

[NecroBones]

I wonder if this problem is somewhat mitigated in 0.24+ now that engine gimbals can be used for roll authority. Need to do some testing.

I had the same thought. It obviously won't help with non-gimbal engines, such as SRBs or the LV-T30. If nothing else, it should at least help.