OpenRocket... The Tutorial (A first time user's guide to creating OR (.ork) sims)

[K'Tesh]

Hi, K'Tesh here... I volunteered to help create an OpenRocket tutorial for NAR's Sports Rocketry magazine, but due to issues with time and trying to find the right subject, I missed my shot. But I did create the tutorial. Rather than let it go to waste, I've decided to post it here. And with that... Read the title of this thread in a Mel Brooks/Yogurt voice... On with the show.

If you follow these steps, you'll save yourself a lot of frustration, and even be able to create very accurate sims on your first attempt. And, unlike so many TV programs... I'm going to change the normal warning...

PLEASE TRY THIS AT HOME...​

(Here's a quick link to other tutorials I've done for openrocket...)

So, you've heard everyone talk about simming up rockets, and you're interested in learning how to use OpenRocket. You've downloaded/installed the program, and you've chosen your subject. Let's see how this is done... For this example, I'm going to use the classic Estes Renegade (1271) kit.

You've got the instructions (perhaps downloaded them from an online resource like JimZ's* site or plans.rocketshoppe). There's a list of parts on the instructions.

*This sim's instructions came from JimZ's site. (It has been updated to include a ruler for scaling the decals... I don't need that info anymore)



This should be easy... Let's get started.

First, open OpenRocket.



Over on the right we see "Add New Component"... Let's start with the body tube (it's the first thing on the list... ) So...



Wait... That's not the right size... It's supposed to be a BT-60 and 18" long. Now, you could go and hunt for the dimensions of a BT-60, or you could use the pull down menu just to the right of the component name (Select preset).




Click on that little blue box, and you get this:



Scroll down until you find the BT-60:



Click that and then "OK"



Ok, now the instructions call for the BT-60HE, and it conveniently has the length of the BT-60HE for us there (this time). But let's pretend it doesn't. There is a very useful resource out there for older kits that was created by John Brohm... His "Estes Body Tube/Kit Reference", last updated in 2008. Do a search for it and download it. It'll help greatly with vintage kits like this. A quick search, and you find the lengths of the body tubes, and perhaps find discrepancies which can be useful to know about.



Now, a lot of people don't know this, but Semroc has a lot of those old body tubes "cut to length". They're usually the same dimensions as the Estes parts... So, lets add the other body but, select the preset, and scroll down to Semroc's stuff...



Select the BT-60HE, and click ok...

 

[K'Tesh]

Oh... Let's add the nosecone now...



D'OH!!! Now we need to move the component up... Ok... You could click the "Nose cone" in the window on the left, and drag it to the correct position, or you could click the "Move up" button... Two clicks, and it'll be in the right position.



Now, let's select the right nosecone... Open the component window, "Select preset", from the database... Find it, click, then click "OK".



And... Uhmm... Wait... That doesn't look right...



Here's the rub... OpenRocket components are not always accurate when it comes to shapes of nosecones (I'd be willing to say it's nearly never accurate). So, what's wrong? The PNC-60AH has a rounded front that is actually quite wide, and relatively blunt. Not like the sharp point we see on this nosecone. We're going to need to break it down into its basic components. This is where transitions come into play. First, let's fix the front of the nosecone. With a search I found this nosecone someone (me) had posted online. I copy it and past it into the sim we're making.



From here, we add the aft transition, which will include the cylindrical section of the shoulder (The conic section behind that cannot be simmed and allow for the body tube to sit right. So, it's ignored.)

Here's the results pasting in the aft transition, and how OR will represent them...



That looks a lot more like what the actual nosecone does. Doesn't it?

Useful Links:
K'Tesh's OpenRocket Nosecone Tutorial
K'Tesh's OpenRocket Nosecone Library

Next, we'll add the engine mount... First an Internal tube, and from our references, we know it's dimensions. So, we click on the tube it's going to go into (or in this case the one it is glued into first), and select the appropriate part from the database. Here we find an error in the database. The instructions clearly say it's 15" long, the reference guide says it's 15" long, the Semroc part shows it as 15.5" long. I'll go with the instructions/guide info. Now, the instructions in the parts list just calls this a body tube, but in the steps, it's called a "Stuffer Tube"... So, let's change the name of it. While this is not necessary, this helps identifying the assemblies and parts as things are added in, and shows a level of attention to the details, reassuring anyone you share this with that it's an accurate sim.



I've also gone through and added the info from the parts list into the other components, including the "Rocket", and save the file for the first time. In doing this, I discovered an assumption (and we all know how to spell assume) I had was wrong. I assumed that this had a blow molded PNC-60AH... NOPE!!! It's an injection molded PNC-60AH with a base (a check online shows one in bag, with a black (not white) version). Fortunately for me, I have a sample. The injection molded nosecones and the blow molded nosecones are not the same (exposed) length. So, I found another sim with the correct version (in this case the original Estes Citation Patriot (KC-3)) and pasted it in. As an added bonus, I got the part number for the Nosecone Base, and a screw eye as well... But, it's like the wrong screw eye... The correct part is the SE-1, which my measurement has as 3/8" OD, so I fixed it.

Note: In my image searches on this kit, I found that there's a version of it with a blow molded (in white) nosecone. However, I don't have the instructions for that one, nor any scans of the flat parts (e.g. fins) of it. So, I'll make a note of this by renaming the kit to reflect which version it is. Oh, and the NC Base Piece (detail) is actually sealed on the upper end, but I opted not to do that as I was tired and couldn't figure out how deep the hole was. Later, I figured out how to do it, and it'll be capped in the final .ork file.



Now you'll see the advantages of using the zoom function of OR's Side view. Sadly, however, when we switch to 3D view, we don't have the ability to zoom in (but we CAN rotate the rocket around the horizontal axis (and roll the rocket over)).

Back to the Engine Mount... Let's add the centering rings, the engine hook retainer, and the engine hook. By making the centering rings part of the engine tube (in this case the stuffer tube). If/when it becomes necessary to move the tube in following the instructions (hint: in this case it does), All the components will move together and stay in the proper location relative to each other. The engine hook has been simulated by a fin made from steel, and has been attached to a Phantom Body Tube* (PBT) to get it in the correct location. The instructions also state that the aftmost centering ring has a notch, so I've simulated that as well with a fin (made from a custom material that I've created and labeled "Air" with zero mass and density) attached to the same PBT as the engine hook.

*PBTs are an invention to allow parts to be mounted to transitions, or internally, when they normally cannot be. They're body tube segments that have 0.0" length, 0.0" thickness, a diameter that matches the needed diameter of the part that will be mounted to it, and in my case, composed of a custom material "Air" which has zero mass or density.



Next the other internal components... The parachute, shock cord, and the tube coupler.. Now these parts get themselves put into the wrong place... Let's move the coupler into the correct location. It's added to the rear body tube, and when added, is located at the back end of the parent component (the rear body tube). In the component window, changing the "Location relative to" to the top of the parent component, along with a negative value (in this case 3/4") it's put into the correct location.

 

[K'Tesh]

As I learn more about this kit, I found the engine block, and a BT-52AG were missing from the sim. So, I've added them, and moved the engine mount into its correct location... This is where attaching those subcomponents to the stuffer tube pays off. Once they were in place relative to it, when it moved, they moved with it. Oh... And we need to designate the stuffer tube as the motor tube... Open the Stuffer Tube's component window, and click on the "Motor" tab. Then check the "This component is a motor mount" box, and add the overhang.

Confession time: When it comes to the engine block... Estes has two thicknesses of the spiral wound versions... .197" and .25". I don't have a physical sample to measure from, so I had to make a best guess. I went with .25, as this is a D powered rocket, and it's my guess they'd have gone with the heavier/stronger part.





And with this, the internal components of this simulation is done... Now it's time to work on the outside. To do this, I like to switch to "View Type: 3D Unfinished" or "3D Finished". Let's look at the unfinished first.



Then with "3D Finished".


Now that's been twisted around the center point, and rotated slightly. I wanted to look and see that everything on the back end looked right, and it does. I've also changed the color of the nosecone and the centering ring in their respective appearance tabs.



Note: When I was doing the parts search for the centering rings I couldn't find the Estes parts in the database, so I went with the Semroc equivalents.

 

[K'Tesh]

Now, it's on to the external parts, the launch lugs, and the fins... Here we're also concerned about the surface finish, as it'll affect the altitude predictions. I like to go with "smooth paint", and so I selected it for the finish of the launch lugs. I'll also do this for the other external components.



With multiple components that are made from the same part, you can copy and paste them. Click the part, then go to the edit menu, and hit copy (or you could do Control +C for PCs (I have no idea what you'd use for Apple computers)).



Next you click the component you want to paste it to, and paste it (Control+ V)



After it's pasted, I'll rename it (from "Aft" to "Fwd"), and re-position it to its correct location, based on the instructions. I'll eventually want to change the color of it, the aft one, and the nosecone based on the finished colors called for in the instructions.

Next, we add the fins. Click on the aft body tube in the viewing window, then the free-form fins component from the add component window.



Uhm... It looks like the launch lugs are in the way of the fins (or vice versa). I'll move the fins... Click on one of them, and rotate them 60° from the component window that opens. I'll also change the Component material to "Balsa", and set the Thickness to 1/8". In the image below, I've yet to change the fin cross section to "Rounded" as the instructions clearly call for that, and change the surface finish to "Smooth paint".



Now those fins are the wrong shape. Fortunately, JimZ's site includes a scan of the fins with a ruler. I'll first open the image, and get working on it in my editor. I use MS Paint. I have Gimp, but anyone who has a PC has Paint included, and not everyone knows how to use other editors (including me).



I need to get that fin rotated in a way that is usable to OR. OR requires it to be upright (root edge on the bottom edge of the image), facing left and the fin must be black. Based on this image, I'll flip it vertically, then I'll need to get it rotated. Flipping can be done in Paint. Gimp is the program I use to rotate images. I don't know anything more about how to use that program. As this is not a tutorial about graphics programs, I'll outline steps involved.

After flipping the image in Paint and rotating it using Gimp, due to the requirements for importing images into OR, I have to get the image down to black and white. I'll start by taking the image back to paint and outline the fin in a high contrast color (in this case red).



I've discovered that the scan is 300 DPI (by measuring the length of an inch on the ruler in the scan). Next, I eliminate all the non-red colors first by saving it as a 16 color .bmp image. Then eliminating all the other colors... I only want the fin outline and the rest white... Then once I get there, I fill the fin with the red color, and swap it to black. Finally, I save the file again, getting it ready for OR to access.

 

[K'Tesh]

From here, it's back to OR. Open the fin component window, and click on "Shape". Then "Import from image".



Select the file you created for the fin... then "Open"... And you get this...



Ok... The shape is good, but the fins are a TAD too big... See the black thing where the fins meet? That's the nosecone. We need to scale this. Now we know that its 300 DPI, so we find out how long the image's root edge is in pixels, and divide by 300. My measurements have it as 820 pixels, which tells us that the fin is actually 2.73333 inches. Now click on "Scale fin" and change the root edge (32.244") value to 2.7333" and then click "Scale".




And here's the results... That looks much better... But...



Those fins look pretty thin, and sure enough, the thickness got scaled too. So, we need to fix it. Back to the "General" tab, and "Fin thickness"... Change it from .011" to .125". Let's also place the fins in the correct place (5/16" from the bottom of the parent component), and rename the part.



Save this... and you're done with what is needed for simulating the rocket for flight performance. After this, it's on to the graphics (if you want). Of course. I want... But it's after 3:30 am local... So the rest will have to come later. In the meantime... Here's some...

Useful Links:

OpenRocket... The Tutorial (A first time user's guide to creating OR (.ork) sims)
Cabernut's OpenRocket files thread
K'Tesh's OpenRocket Files Thread
K'Tesh's OpenRocket Files Feedback Thread
K'Tesh's OpenRocket Tutorials
K'Tesh's OpenRocket Nosecone Tutorial
K'Tesh's OpenRocket Nosecone Library
K'Tesh's OpenRocket Parts Library
neil_w's Decals in OpenRocket: a not-so-quick and fairly complete tutorial
Plans.rocketshoppe
JimZ

 

[K'Tesh]

Now it's on to the appearance. This is TOTALLY not needed for flight simulation... However, if you want a rocket that looks like it's going fast even while standing perfectly still, you do. If anything, this is where much of the hard work in OR comes from... Pulling graphics out of background colors. Let's look into how it's done.

First, in OR click on a component, in this case, I've gone with the aft body tube, and click on the appearance tab.




Uncheck the "Use default" box, and change the "Shine" (aka gloss) to a level you like... Me, I like 100% shine.


To get the shine to show, right click and hold the button down on your mouse (no idea what Apple users do), and move it until the shine appears and looks good to you and release the button. I like this...



Now do this with the other external parts you want "painted" black (some people will want to do the engine hook (which is reasonable, it quite likely would be painted). Don't forget the launch lugs will need it too.

Once that's done, it's time to turn to the Florescent Red Paint that the instructions call out. From my experience, and the fact that Estes sells it, I'm looking for Testor's Florescent Red, and I find an image of it that is not showing shine... I'll save that image for the color.



But being a .jpg, it has artificial artifacts in the color. So, using my graphics editor (Paint). I'll take a sample that seems to have the fewest artifacts. Then do a search to get the "average color of an image". I like what I get from this site: https://matkl.github.io/average-color/.

I'll click the button, find my sample of the color, and I get this result:



So, my red will be red 219, green 87, and blue 64... Let's enter this into OR.

Clicking on my forward launch lug, I notice that I forgot to fix the name of it (from when I copied and pasted it). So, I fixed that. Then on the "Appearance" tab. Now click on the "Color:" block (currently showing black).




The "Choose Color" pallet opens up.



Now click on the "RGB" tab



And enter your RGB values, and click "OK".

 

[K'Tesh]

Now the launch lug is "florescent red". Repeat for the other parts that are going to be painted that color.



And the results...



Now your rocket is painted... But a couple of things bother me... The joint where the fins meet the body tube, and the decals... Doesn't this thing have decals?

Let's tackle the fins issue first. The problem is that the color is the same. A little tweaking from black to a VERY dark grey will work. In the past, I've found RGB 40, 40, 40 works well... Black enough to be "black" but grey enough to show up against the body tube without calling out that it's not really black. I'll do the same to the aft launch lug.



Now, about those decals... Dang... No ruler. No indication of scale. Time to make a call to the hive mind. Anyone? Anyone? Anyone? (Please send me a PM if you can help with the scale of the decals) [EDIT] Got the info needed We're good... [/EDIT]

 

[K'Tesh]

But I can still work a little. I can get the decals ready for the rocket when I get my answer from the hive. [EDIT] Got the info...[/EDIT]

Let's get busy with them... Here's the image from JimZ's site. [EDIT] JimZ updated the image to include a ruler[/EDIT]



Black and white... EASY!!! (normally, it's a lot harder than this will be).

I saved the image as a 16 color .bmp



Then I changed the color of what is supposed to be white, to yellow (I have to make it not-white for the cleanup, and I wanted a good contrasting color to the red, white, and black of the paint scheme)...



Then I changed the background to white



And outlined the fin decals in boxes of RGB 40, 40, 40. Then flood filled the boxes with the 40, 40, 40 color...



Next, I changed the white background to the florescent red color, and the yellow back to white, and cleaned up the edges of the black decal's colors... Finally ending up with this:



Once I learn what the width of those white bars are, I can finish this up. [EDIT] I got the info I needed...

 

[K'Tesh]

Ok... I've got some feedback from the hive mind... looks like the image was 300 DPI, it's consistent with the scan of the fins, so I'm going to go on that presumption until I get better information.

For the body tube, I'm back in the appearance tab... I click on the "Texture" and pull down to "From file..."




I've created a series of "templates" that I use for my paint and decals... Called "Body Tube Paint and Decals". Lets open that up.



And the results...



Now we need to edit this... So, from the same "Texture" menu, click the "Edit" box, and my default (MS Paint) image editor opens up with the "Body Tube Paint and Decal" image. Let's scale this... As my images are 300 DPI, I'm going to make the graphic 300 pixels to the inch. 18" x 300 = 5400 (for the length), by Pi x 1.637" x 300 = 1542.8 ( for the circumference/width). Now, there is no such thing as a .8 pixel, so I'm going to round to the nearest whole number (pixel) and I get an image that is 5400 long x 1543 wide and change it to the florescent red color.



If I save that image, the .ork file's 3D image will look just like it did before adding the image. But I need to get the decal on it... So no need to save the image quite yet. Now, according to the instructions, they give the positioning of the name decal exactly in the instructions, and that's 1" from the bottom... Again... EASY!!! That's like... 300 pixels... I can do that.

In the image I've created of the actual decals, I'll trim it down to right at the edge of the name decal.



Next, I'll rotate the body tube image and mark it at 300 pixels for dropping this image in place.



Rotating that CCW, and saving it gives us this in OR...



Let's give the image a spin...

 

[K'Tesh]

Ok... looking good... but in looking at the instructions, the decal is supposed to be centered between the fins (it clearly states that in the finishing steps)... Hmm... let's let OR rotate the image for us... But FIRST... New FINS!!! (trust me)

I'm adding 3 fins 18" long, .25" high, and 0.0" thick. This allows me to center the decal image.



Back to the appearance tab... On the "Offset:" menu, changing the x: value rotates the image in the direction I want... And with a rotation of x: 0.15, it looks perfect to me...



Now to delete the temporary fins...



Now... On with the fin decals... OR can be tricky with decals on fins, but this one is going to be.... You guessed it... EASY!!! No weird writing. No need to mirror and flip decals to make them readable (when applied). It's nice to have such an easy kit to sim up (for once).

Let's open the fin's component window, and the shape tab... let's look at the maximums of this fin... The Maximum length (not the root edge) is 3.938", the highest point is 3.184", so the image would usually be 394 x 318 pixels (remember, you can't have a fraction of a pixel). However, the decals are 300 DPI. So, lets make this 300% larger and thus easier on us (and less grainy at the same time). 3.938 x 300 = 1181.4 (rounded down to 1181) pixels x 3.184 x 300 = 955.2 (rounded to 955) pixels.



Oh, and you guessed it, I've got a template for the fins paint... So, let's stop off at the Appearance tab again... Click the "Texture" menu, and "From file", then pick the appropriate file, and finally click "Open"



And the results...



Looks like changes are needed... In the immortal words of Robin Williams (as Adrian Cronauer) "Oh... It's an order... In that case gentlemen... Let's edit" "https://www.101soundboards.com/sounds/286195-in-that-case-gentlemen-lets-edit".

Click the edit button, and your editor will open with this image:



We'll need to resize, and change the colors to our 40, 40, 40 dark grey (don't forget to change "By:" from "Percentage" to "Pixels" (and uncheck the "Maintain aspect ratio" box.



Now the instructions clearly say that the edge of the decal should be 5/16" from the fin tip... 5/16 = .3125" or 31.25 (pixels)... .3125 x 300 gives us 93.75 pixels (rounding up to 94 pixels). So I dropped the decal in with the edge at 94 pixels from the edge... And I get this:



Oh... I forgot to mention... Fin decals need to be pointed "down (so the bottom edge is the fin tip), and the "front" is pointed to the right.

 

[K'Tesh]

Once I've saved the image, I get this...




And with that, I'm happy with this sim... The only thing left is to get a pretty picture.... That Blue CG mark is kinda in the way, so let's move it by adding some weight to the nose. Click on the nosecone, and once the configuration window opens, select "Override".



Check "Override mass" and enter a value (any value can do) for the mass of the object. Here, I selected 10 oz., then click "Close"



And the results. Take a snapshot of this image (for my computer it's "Windows +prt sc")



Now, go back to the "Edit" menu, and click on "Undo (Modify Nosecone)", or you could click "Control + Z" to undo it.



And take a snapshot of the results...



Now with the snapshot with the additional mass, copy a section of the image that includes the area that the blue was on for the regular image.



and paste into the other image, taking care to get the body tubes and fins aligned properly...

 

[K'Tesh]

And now it's time to crop the image out... I like to use a color that isn't one of the colors of the rocket, or any of the print in the window, then I flood fill that color into the window with the rocket, and crop that area out...



After I trim the unwanted border... I get...



Change the background color back to white...



And get rid of that red spot...



And we're left with this image...


Don't forget to save it...



And don't forget to save the .ork file too...



And you're done...




Useful Links:

OpenRocket... The Tutorial (A first time user's guide to creating OR (.ork) sims)
Cabernut's OpenRocket files thread
K'Tesh's OpenRocket Files Thread
K'Tesh's OpenRocket Files Feedback Thread
K'Tesh's OpenRocket Tutorials
K'Tesh's OpenRocket Nosecone Tutorial
K'Tesh's OpenRocket Nosecone Library
K'Tesh's OpenRocket Parts Library
neil_w's Decals in OpenRocket: a not-so-quick and fairly complete tutorial
Plans.rocketshoppe
JimZ

Special thanks to JimZ, Tim Smith, Saverio Prato and Rich DeAngelis II for their help with this sim. All The Best Guys!!!

 

[K'Tesh]

I should have put in a little something about selecting motors... Let's fix that... So, you've got your sim, and you can do this at *ANY* point after you add your engine mount's tube, whether it's the body tube, or an inner tube.

Click on the tube that will be holding your motor, and open the component window.



Click on the "Motor" tab, and check the "This component is a motor mount" box, and set your motor's overhang. Ignition can be changed for staged motors here, but for a single stage rocket, I don't mess with this at all.



Once you close that window, you can add your motors by selecting the "Motor & Configuration" tab.



Next you'll see this at the top of your sim's window...



Click on "New Configuration" and you'll see this...



Then click the "Select motor" button and this window opens...



Now from here you can set different filters (by motor's total impulse, or motor's OD, or motor's length)... Typically I don't mess with these. I just scroll down until I find a motor that the instructions call for (FYI old motors might not be in the database). Click on it, then click on the "Ejection charge delay" drop down menu, and select your delay, then click "OK"



Here's your resulting configuration...



Repeat as often as necessary to get the various motors recommended by the manufacturer, or you'd like to sim with. Once you're done with that, click back on your "Rocket design" tab.



You can then select whatever motor you want from the "Flight configuration" drop down menu and run your sim. Once you save the .ork, the configurations you created will be saved.

 

[K'Tesh]

Buffer post... JIC I need one.

 

[K'Tesh]

Buffer post... JIC I need one.

 

[K'Tesh]

Ok Folks... Let's see what you were able to do with OR, after following this. I want to see your sims.