OpenRocket tutorial: Achieving perfect(-ish) rounded nose cones

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neil_w

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Some folks like to get the appearance of their OR models to be as close to perfect as possible. Sometimes this means nose cones with rounded tips, which OpenRocket does not yet natively support. I have seen many attempts at rounded nose cones around here, but few that have gotten it right. Here's a quick tutorial on getting rounded nose cones as close to perfect as possible within the current constraints of OpenRocket 22.02.

Please note: this will have little to no effect on the sim results, it's just for appearance's sake. It also means you won't be able to use nose cones from the parts library, and will need to set a lot of parameters yourself (especially the shoulder). If you're still determined to go ahead with this, read on.

Recently I was modeling the Odd'l Break-Away, which has a classic rounded ogive balsa nose of the following dimensions:
  • Length: 3.2"
  • Base diameter: 0.99"
Here's what the profile looks like (it's currently in filler/primer, please ignore the ugliness):
IMG_3456.jpg

1: Enter the rough components

Every rounded nose consists of a nose cone and a transition. Initially, we'll just rough them in and then tweak until we achieve the desired result.

First the nose cone. Here are the important parameters:
1685025007714.png

Shape must be "Power series".

The next three parameters are just starting points; we'll tweak them later. 0.4 is a good first guess for Shape parameter; for length and base diameter, start with a value of about 1/5 the base diameter. Here's what it looks like:
1685025158136.png
That already looks pretty good.

Next add a transition of the same shape as your nose cone, in this case ogive. As previously mentioned, you'll need to manually set all the parameters. I won't worry about the shoulder for now:
1685025460350.png

This nose cone is Ogive with Shape parameter 1. Length is set to actual nose cone length minus whatever you used as the length of the nose cone component above, in this case 3.2" - 0.2" = 3". Fore diameter is set to "Automatic", and aft diameter is that of the actual nose cone.

Here's what we have so far:
1685025630044.png
Close but not quite there; the tip doesn't quite match up with the rest of the nose. Let's fix it: back into the config edit for the nose cone. It looks like the tip should be shorter, so let's fiddle until it looks like the slopes match up correctly. Reducing the length to about 0.14" seems about right:
1685025919975.png
Here's what the whole thing looks like:
1685025931447.png
That's pretty good, and we could stop there. But it seems like, for this nose cone, that's still a bit too pointy. The actual nose is blunter than that. So let's increase the size of the nose tip. I'll bump it up to 0.3", and keep the length at about 0.7 times the length:
1685026409536.png 1685026439196.png

Now it's looking very good. At this point, you can try very small tweaks of the length, diameter, and Shape parameter values to get it to look exactly like you want. Changing one of the parameters will frequently require changing others to keep the joint between the nose and transition smooth. The only change I made to the above is to bump the shape parameter down to 0.35. Finally, adjust the length of the transition so that the total length (nose + transition) equals that of the real nose cone.

Here's my final result. ORK file is attached. This is, as far as I'm concerned, as good as you're gonna get with the current version of OR.
1685026693514.png
In general, for longer/skinnier nose cones, the nose tip will have longer length relative to diameter, and a lower Shape parameter value. For stubbier nose cones, the opposite.

This approach works fine for conical noses as well.

Enjoy!
 

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Just needed this and found it with the search. Thanks! My nosecone for my DARE 101 didn't really match the LOC Precision parts library and I'm trying to tweak things to see if my SIM will match actuals more closely.
 
...so of course we need, at some point, for OR to support nose cones that look like this in the actual simulation results. I have no sense of how easy or hard that will be, though.

It's kind of too bad that we can't properly simulate one of the most ubiquitous nose cones there is, the rounded tip ogive of the Estes Alpha III/IV/VI and related models.
 
...so of course we need, at some point, for OR to support nose cones that look like this in the actual simulation results. I have no sense of how easy or hard that will be, though.

It's kind of too bad that we can't properly simulate one of the most ubiquitous nose cones there is, the rounded tip ogive of the Estes Alpha III/IV/VI and related models

I keep trying to get them to make a "Freeform nosecone" where you import 1/2 of the profile of the NC (lengthwise) and it then multiplies it until it creates a completely round NC with the perfect shape.
 

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