This is a guide to show you how to print your ships from Kerbal Space Program, the game where you launch overenthusiastic little green men into space on rockets of your own design. We'll be using Dasoccerguy's excellent KSPBlender add on to import the .craft file into Blender, where we will clean it up and generate a .stl for printing. This guide was written with MatterControl in mind, but it is applicable to any 3D printing software. KSP has evolved as a game quite a bit since this article was published, some of the steps may no longer be accurate to the current state of the game.

Software

• Kerbal Space Program
• Blender
• MatterControl
• io_kspblender
• io_object_mu

Step 1 - Build a Ship

• In this guide, we're going to use one of the stock ships from the game, the Kerbal X. We also printed the Stearwing D45.
• You may want to remove some of those struts. They are very thin, so they don't print well, and KSPBlender has trouble with them.
  • You can have as many boosters as you want, though.

Step 2 - Install Blender Addons

• Open the blender User Preferences by pressing CTRL + ALT + U or going to File > User Preferences
• Go to the Addons page
• Install both addons by clicking the Install From File button and choosing the zip file that you downloaded
• After you install each addon, enable it by clicking the check box to the right of its listing.
• Save User Settings

Step 3 - Set Your KSP Directory

• KSPBlender needs to know where the game assets are in order to get the models and textures.
  • Because it is pulling the data directly from your game folder, it will work with any addons you have installed as well.
• If you are using Steam, you can find out where the game data is by right clicking and going to Properties, then hitting Browse Local Files under the Local Files tab
• Put the location of your game folder into kspdir.txt
  • On Linux this file will be in ~/.config/blender/2.75/scripts/addons/io_kspblender-master/
  • On Windows it will be in C:\Users\{user}\AppData\Roaming\Blender Foundation\Blender\2.75\scripts\addons\io_kspblender-master\
  • On the Mac its in the Blender application bundle

Step 4 - Import Your Ship into Blender

• Delete the default cube from the scene by pressing A until all objects are selected, then X.
• Import the .craft file
  • Go to File > Import > KSP Craft (.craft)
  • Browse to the game folder, then you will find your ships in the Ships folder.

Step 5 - Remove Parts You Don't Want Printed

• Your ship will be imported with all possible parts, including things like parachutes and launch stability enhancers.
• Actually, you might want to keep the launch stability enhancers, since they will help support the ship during printing.
• To delete an object, right click to select it. Then press K to bring up the KSPBlender menu and choose Delete Part.
• You can also delete a part by finding it in the Outliner, right clicking, and choosing Delete Hierarchy.

Step 6 - Configure Moving Parts for Printing

• Moving parts may not be imported in the configuration you want to print. These include landing gear, cargo bays, solar panels, etc.
• Select the object, then bring up the K menu and choose Toggle Deploy.

Step 7 - Scale and Rotate for Printing

• The dimensions of the model are given in Kerbal meters, however the slicer will interpret the units as millimeters, resulting in a very small print.
• Some parts are extremely thin. For instance the interstage fairing and engine bells. Make sure you scale the model large enough so that these things will actually be printed.
  • You can check whether or not a part will be printed correctly by viewing the G-Code in MatterControl.
• Scaling can be done either in Blender or after you have imported the model into MatterControl.
  • To scale in Blender, press A until everything is selected, then press S. Either drag the mouse to the scale you want or enter values in the pane on the left.
    • In order for the pane on the left to work, you may need to enable Global Undo in the Editing page of the User Preferences.
  • You can also scale the model in MatterControl using the edit function.
• If your ship is a spaceplane, you may want to rotate it so it prints vertically. Press R in Blender to rotate.

Step 8 - Make 3D Printable

• This function unifies all parts of the ship into a single manifold mesh.
• This is especially important to use if your ship has part clipping. The slicer will not fill in the spaces where objects intersect.
• Select a part of the ship, then bring up the K menu and choose Make 3D Printable.
• You may get an error regarding multi-user content. You can fix this by selecting everything then pressing U to make everything single user. Select object & Data from the menu.
• An alternative to this step would be to run the exported STL through a service like NetFabb or MakePrintable.

Step 9 - Export STL

• Press A to select all.
• Go to File > Export > Stl (.stl)
• Drag and drop the STL file into the MatterControl Queue.

Step 10 - Recommended Slice Settings

• Some of the engine bells are very thin on the end. To deal with this, we just used bottom clipping, so it would skip the first few layers which are too thin to print.
  • Remember to turn off bottom clipping before your next print.
• Support material will almost undoubtedly be required. Our standard recommended support material settings are...
  • Overhang Threshhold: 30 degrees
  • Pattern Spacing: 2.5 mm
  • Interface Layers: 0
  • Z Gap: 1 layer
• Detailed models like this are prone to stringing. To minimize this, have a look at our guide on optimizing retractions.

Step 11 - Check the G-Code

• The Layer View in MatterControl will let you preview the print so you can make sure it will turn out how you like.
• The print will have all the features of the actual in-game ship, including engines inside of stage fairings and things inside cargo bays.
  • It won't have the insides of cockpits or the Kerbals themselves, though.
• There is a bug in MatterControl 1.3. If your print looks like a giant mess, try turning off Display Extrusions.
• Check to make sure that thin parts will actually be printed. If not, you may need to scale up the model more or print it in multiple parts.
  • If you can't or don't want to scale up the model, the only other thing you can do is edit the mesh for that part in Blender.
• Many slicers have trouble generating support structures under the fins. This is because they are thin and pointy on the bottom. You can either try a different slicing engine, or print the fins separately and glue them on.

Step 12 - Print!