[RO] how thin a rocket should be?

[Kesa]

Using Realism OverHaul, Thiner rockets produce less drag, but thiner tanks have a worse dry : wet ratio.

Since the effect of drag is not easy to figure out, I'm searching for empirical tips about how thin a rocket should be. Is it a sensitive parameter, is it worth optimizing, or does a rocket twice fater or thinner than optimal will still perform well?

I've seen video where Mechjeb displays drag losses, but I'm a bit confused with all the different windows Mechjeb proposes (I'm more used to KER), but I think I could use it to do some trials (compare difference in drag loss with difference in dV).

[Red Iron Crown]

Moving this mod-related question to General Add-on Affairs.

[regex]

According to this post, the Saturn V lost some 40m/s to drag losses IRL. So I would say that your rockets should be 10.1m thin.

[NathanKell]

Square-cube rule, though. The heavier the rocket, the lower the drag losses (mass, and thus the force->acceleration conversion in drag, goes by cube, but wetted area, and thus the force of drag, goes by square). For smaller rockets drag will matter more.

Also, Saturn V had a horrific ignition TWR, so it paid for low drag losses with gravity losses.

That said, unless you're doing something insanely squat you probably don't have to worry.

[Astrofox]

Well, you could try my N-prize Challenge, and see, I guess (yes there is an RSS version of the challenge) I love the Idea of a "Thin Rocket" in any rocketry program, whether it be in KSP, or Real Life.

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I would love to see what you come up with.

[Astrofox]

Today i built a rocket that is extremely thin, but only works with stock, it just barely makes it to orbit, using up some of the satellite's fuel of course.

[Astrofox]

Here is the link to this amazingly thin rocket that barely does it (in stock), it requires Mechjeb for the launcher and satellite.

Tinylaunch Mk1

[Taki117]

As long as your rocket is decidedly aerodynamic (no pancakes!) then losses due to drag will be negligible. (40m/s for the Saturn V is a drop in the bucket compared to how much it actually had)

[PB666]

Using Realism OverHaul, Thiner rockets produce less drag, but thiner tanks have a worse dry : wet ratio.

Since the effect of drag is not easy to figure out, I'm searching for empirical tips about how thin a rocket should be. Is it a sensitive parameter, is it worth optimizing, or does a rocket twice fater or thinner than optimal will still perform well?

I've seen video where Mechjeb displays drag losses, but I'm a bit confused with all the different windows Mechjeb proposes (I'm more used to KER), but I think I could use it to do some trials (compare difference in drag loss with difference in dV).

Surface area/mass drag has no bearing since drag is based on total mass not weight. I can say this. The MechJeb losses are not do to drag, they are due to lower engine ISP in lower atmosphere. I can't explain the science but the atmosphere rolling around the nozzles outlet causes a loss of ejection force. Toroidal Aerospike rocket avoids this by thrusting at a conic using momentum induced turbulence in the atmosphere to dissociate the atmosphere momentarily from the ejection resulting in high takeoff ISP.

1. If you are going to make a tall ship, do it with tall starting parts, there is segmental flexibility as each node, and lots of short part stacked causes bending particularly in lower atmosphere. If you are doing a 20 stage rocket from scale mods, (I do 1.414x from 0.5 to 3, 0.625, .85, 1.25, 1.7, 2.5, 3.75) you prolly should avoid very tall engines like LV-N unless u use struts to stabilize. dV is something like 23000

2. There are better ways, ION drives can get very high dV without all the stages.

3. Tall ships should be shaped like an inverted cone, very tall sections will tend to be less stable.

[NathanKell]

You...really should have looked at the [RO] tag before posting that. This is not stock KSP we're talking about here, and you can bet your bottom dollar that drag in FAR is based on surface area * Cd. And that's just the start of what doesn't apply in RO land.