Does the gaps between the different diameter matter?

[Paintprofreak]

So I just got the game last week and I was doing just fine until I started unlocking the bigger diameter parts. I'm wondering if I'm leaving tiny gaps between fuel tanks/engines/decouplers really matter all that much? Even attaching the science Jr to the second command module that holds 2 kerbals since it goes from bigger to small then big again? 

[Geonovast]

Hello, @Paintprofreak, and welcome to the forum!

It matters quite a bit in an atmosphere.  Generally you want to avoid a diameter change whenever possible.  There are adapter parts that let you transition from one size to another, so when you do transition to a different size, use those if you can.

[Snark]

2 hours ago, Paintprofreak said:

Even attaching the science Jr to the second command module that holds 2 kerbals since it goes from bigger to small then big again?

Yep, even that.

Note that when Geonovast says "adapter parts", we're talking about conical parts so that there's a smooth, "slanted" transition from one diameter to another.  This includes a reasonable selection of fuel tanks.  For example, if you want to mount a Science Jr. behind the Mk2 command pod, there's a short conical fuel tank that's 1.25m on top and 1.875m on the bottom.  So, you could put one of those upside-down under the command pod, then the Science Jr, then either you could have a 1.25m stack from that point, or you could use another conical fuel tank to go up to 1.875m or even 2.5m if you like.

Here's what the 1.25m-to-2.5m adapter fuel tank looks like:

...there are lots of others in various sizes and shapes.

[DeadJohn]

It matters in that it will cause extra drag, but in practice I find that I can just power through it with a slightly larger and more powerful lower stage than would otherwise be needed.

I generally avoid non-streamlined shapes because I like making pretty rockets. That's not always practical early in a science or contract mode game when limited parts are unlocked.

 

[Paintprofreak]

On 1/5/2020 at 4:39 PM, Geonovast said:

Hello, @Paintprofreak, and welcome to the forum!

It matters quite a bit in an atmosphere.  Generally you want to avoid a diameter change whenever possible.  There are adapter parts that let you transition from one size to another, so when you do transition to a different size, use those if you can.

Yes of course I try to use them as much as possible but I'm mainly talking like if I were to use the aerodynamic capsule that seats 2 then heatshield/decoupler then science jr/decoupler then adapter back up to width of the capsule? 

The reasoning behind the reason I need the 2 kerbal one is because  the Kerbal that landed on the mun the first time decided to use way two much fuel so getting back is impossible lol.. I unlocked only the 90 unlocks.  

 

Thank you for any and all information you can give me as i really enjoy space and rockets. 

[Jestersage]

23 hours ago, Paintprofreak said:

Yes of course I try to use them as much as possible but I'm mainly talking like if I were to use the aerodynamic capsule that seats 2 then heatshield/decoupler then science jr/decoupler then adapter back up to width of the capsule? 

The reasoning behind the reason I need the 2 kerbal one is because  the Kerbal that landed on the mun the first time decided to use way two much fuel so getting back is impossible lol.. I unlocked only the 90 unlocks.  

 

Thank you for any and all information you can give me as i really enjoy space and rockets. 

So we need a bit more precise name -- because the "aerodynamic capsule that seats 2" can be either Mk2 Command Pod, which have the diameter of 1.875, or Mk2 Cockpit, which have a diamter of "mk2".

And that affect atomospheric drag... which in turns matter if the performance of your craft depends on minimal drag. KSP drag modelling is simplified to the point that what diameter between the parts matter if and only if your craft depends on minimize drag to go to the orbit. So that means, if your craft is Horizontal takeoff, you better make sure there are no mismatch of diamter.

On the other hand, if your craft is vertical take off (aka using a rocket), just wrap it with a fairing and go.... or even spam as rocket engines as possible.

A perfect example are the numerous Orion clones (and in my case, Russian Federasiya), which is a 1.875m tank beneath a 2.5m capsule; and the Starliners  clones that modeled after the recent test (eg: https://kerbalx.com/The_ShadowZone/Starliner-K2). If there are fairing, then the thrusters does not need to counter the atmospheric drag induced. But if there is no fairing, the thrusters need to counter it by being powerful and/or having the extra fuel to have the capacity to do so (or as we say around here, "Moar boosters")

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The thing about this game -- just like in real world, is that there are no singular solution. There is a "relatively best solution", but may not be easy solution.