Efficiency of aerodynamic cones

[gilflo]

I do not see any DV gain when mounting aerodynamic cones on my rockets.

I thought I saw somewhere about KSP 0.22 that they were taking in account when building a rocket.

The best gain I saw was 3DV on a total of 13350 DV.....!!!

[FellipeC]

AFAIK they make the rocket more stable, just that

[sal_vager]

You aren't in the atmosphere that long, is it long enough to really notice a difference?

And as FellipeC says, they help with stability, less drag up front means you are less likely to flip over.

[gilflo]

Up to now I made very stable rockets without aerodynamic cones.

It looks prettier, but more pieces that slow down the game...

Not worthy..

[Kasuha]

I ran a short test and in my opinion they are only useful to straighten up the descent stage. On ascent their effect is negligible.

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[stupid_chris]

I don't think it slows them down. I think what it's doing is that it pushes the CoD on the other side of the craft. So the CoD ends up on the side with the boosters without nose cones. When drag compiles up, the CoM and CoD aren't aligned and it creates a rotation point at the CoD, which pushes the side with the nose cones down.

You should redo that test with a copy who has four nose cones and one who doesn't and see which is the most stable on ascent without SAS.

[Kasuha]

Center of drag to the left of the center of mass with everything else balanced will make your ship lean to the left. In other words, if your theory was true, the ship would lean to the other side.

But two factors are in the play in this case - center of drag pushed to one side, and center of mass pushed to the other side of center of thrust. Apparently the center of mass being off center of thrust is the stronger factor here.

Also you can see that angles under which the device steered off course differed wildly. When I started just one SRB vertically, it did not go off course a bit even with no nose cone and without SAS. So I don't think I'd get any conclusive results. If you want, do that experiment yourself.

Edited October 27, 2013 by Kasuha

[stupid_chris]

Sigh, reason #6789504 why I shouldn't get up before noon. You're right But yeah, thrust asymmetry might be playing here. Maybe try putting an object of the same mass and with drag of 0.2 on the other side?

[numerobis]

Both center of mass and drag will be moved towards the stack with nose cones. Drag will move less than mass. Drag will also move up less than mass, which is why they stabilize.

On descent, stacks with nose cones have 2% more mass but only 0.67% more drag, so terminal velocity is about 0.065% faster.

[Kasuha]

I have added some tests to the original album, you may take a look starting at image 15. Yes, nose cones add some stability. But it's very small however much of integrated difference may be in those pictures. Actually I had to make the test very sensitive to see any differences and I had to skip many tests which were way less conclusive than those I posted.

[Wallace]

They supposedly have low drag, but high 'directional drag' whatever that means, they are supposed to help stability rather than DV, and also to look all cute and pointy like a proper rocket should.

[p1t1o]

The effect is much more pronounced on tall, heavy rockets with a CoM more towards the bottom.

You wouldn't expect to see much of a difference by just sticking it onto an SRB as they are already quite stable - stabilising a stable object just make it...behave the same.

[Kasuha]

The effect is much more pronounced on tall, heavy rockets with a CoM more towards the bottom.

You wouldn't expect to see much of a difference by just sticking it onto an SRB as they are already quite stable - stabilising a stable object just make it...behave the same.

I'm looking forward your set of experiments.

[numerobis]

They supposedly have low drag, but high 'directional drag' whatever that means, they are supposed to help stability rather than DV, and also to look all cute and pointy like a proper rocket should.

They have low angular drag compared to other parts. That said, I can't figure out exactly what angular drag *is*, other than that bigger values mean more drag. Seems to just be a non-physical hack to make things stop spinning.

[Tank Buddy]

I don't know what machine you're running this game on, but I don't know how a few nosecones could possibly make a difference.

[gilflo]

30 or 40 cones on a 800 pieces rocket can make a small difference.

[numerobis]

Half a dozen control surfaces would make a bigger difference.

[kurja]

Engineer redux mod shows a small dv increase when adding nosecones. There's a mass increase that goes with it so I guess the net result depends on your how and where you fly it.

I played a bit with this and it looks like rockets with cones on them fly a bit straighter and further, but like said it's not a big difference.

On the other hand, we can finally prettify our rockets with them without increasing aerodynamix drag, yay =D

edit - I take that back, engineer redux is actually showing dv reduction as nosecones are added.

Edited October 27, 2013 by kurja

[p1t1o]

I'm looking forward your set of experiments.

Indeed, touche. I'll see what I can do.

[Dispatcher]

When there was no(t much) advantage to using nose cones, I made fueled nose cones and adapters for use with rockets and jets. I also reduced their drag in an effort to compensate for a lack of aerodynamic advantage. You might be interested in my sig line.

(Edit: while all two star ratings are rather lack lustre, I've read nice things about the combo in forum posts, so give them a try and see what you think.)

Edited October 28, 2013 by Dispatcher
More.

[gilflo]

Where are your nose cones in spaceport ?

[KerbMav]

Were these test with or without FAR?

[Kasuha]

Were these test with or without FAR?

Without FAR. I don't have any mods.

[KerbMav]

With FAR:

Test setting one reveals similar behaviour, booster assembly leans towards the side with nose cones and finally spirals out of control.

With SAS firing 2-2-1 boosters in stages the control body reached Kerbin escape velocity.

Firing all four boosters lead to flip-over even with SAS on and built in reaction wheels.

Decoupling and descend test was rather inconclusive, yet coned booster seemed to drop faster.

Test setting two was equally similar, coned boosters flew a bit longer before dancing to the ground.

Conclusion:

Weight seems to matter more than slightly reduced drag.

Even with FAR's updated aerodynamics.

[JoCRaM]

They work by moving your center of drag down in relation to your center of mass (if you put them at the top of your rocket), which SRBs also do (assuming you put them at the bottom of your rocket)

which is why the .22 drag of a stowed cone parachute is a bad thing.