# 3D-Printed Solar System

Here is project #2 with the new 3D printer, just like the Berlin Wall it’s an artsy one: the eight planets of our Solar System scaled down by a factor of about 109. This post contains a photo gallery of the planets, and further down the details of design, creation, and painting.

### Details of the Creation Process

#### Scaling and Planning

This project started off with the idea of creating a to-scale version of the Solar System where both object size and object distances are at the same scale. Naively I assume that would be possible, so I created a spreadsheet and did the math on it. Turned out it was not possible at all, so two different scaling factors needed to be found: one for the planet size and one for their distances from the Sun.

The wall in my apartment is about 4.5 m long so the distance of the furthest planet, Neptune, had to be scaled down from 4,530,000,000,000 km to 4.5 m. The object diameters were constrained by the 3D printer’s print bed and my personal preference so I defined the miniature version of Jupiter to be around 15 cm in diameter. That resulted in Mercury (the smallest) to be 5 mm large which was not too small to print.

I decided against including moons into the artwork because they fit neither into the solar-system scale (Earth’s moon would stick on the Earth half sphere) nor into the object-size scale (the Moon would be far beyond Mars). Likewise, the Sun is problematic to add because it is enormously large in comparison to the other objects. Besides being hard to paint, it would be almost 1.5 m in diameter when printed to-scale.

Below is a table of the planet sizes and distances:

Object Solar System Miniature
Distance to Sun
[M km]
Diameter
[k km]
Distance
[m]
Diameter
[mm]
Sun 0 1392 0 1450.00
Mercury 57 4.8 0.050 5.00
Venus 108 12.2 0.095 12.71
Earth 149 12.8 0.131 13.33
Mars 228 6.8 0.201 7.08
Jupiter 780 140 0.689 145.83
Saturn 1437 116 1.269 120.83
Uranus 2871 50 2.535 52.08
Neptune 4530 48 4 50.00

#### Modeling and Printing of the Half Spheres

The modeling of the 3D objects was fairly straightforward. I created half spheres in Blender and used the slicer software Cura to convert them into a format that the 3D printer can work with. The specific printer is a Ender 3 Pro and the filament is PLA. All prints were smoothed using sand paper with grit 60 and 180 to hide the bumpy seams of the layer-wise printing.

The reasoning behind half spheres is that I reckoned they would look nice when attached to a wall. On top of that they are easier to position than full spheres which would probably require some string attachment or something comparable. Also, half spheres use less material and can be painted faster.

#### Painting

While being by far the most time-consuming sub-task, there is little to report about the painting. After sanding, the it starts with two layers of white primer.

Then acrylic colors need to be mixed to best match the color tone of the respective planet. This was a rather difficult task and (as can be seen above) for some planets the color tone does not match particularly well. I used almost exclusively matt colors with few exceptions e.g. for Earth’s oceans.

The last layer of paint is a varnish. While I didn’t take the exact time I’d estimate the paint job to have consumed about 10 man hours in total.

I also want to give a shout-out to a friend who helped me significantly with the painting and color mixing! Jupiter and Saturn we worked on jointly and the other planets half-half.

#### Saturn’s Rings

Saturn’s rings posed a special challenge: They are supposed to be as thin as possible (the real rings are estimated to be around 10 m thick – so forget about a to-scale miniature here) and still needed to have the structural integrity to look stiff when attached to the wall.

For sizing and accurate information on gaps this webpage by Scott S. Sheppard was very helpful.

#### Closing Remarks

I first marked all planet positions on the wall and then glued the small ones on there. For the larger ones I used double-sided adhesive tape. The project was a lot of fun. I am also happy to have a nice decoration which is not too aggressive and yet filling an entire, large piece of white wall.

I honestly find the beauty of our Solar System really touching. While there is no objective definition of beauty, humans still share similar opinions on basic things like flowers, fire, or the sky being beautiful, perhaps simply because it is in our genes. For the Solar System this argument cannot be made, as we have only recently acquired high-resolution images of the objects out there. It is a little bit of an underappreciated circumstance that our seven other planets are not just gray dusty rocks, but such marvelous and diverse objects.

(82 Posts)
Zürich-based Software Engineer with Google; opinions are my own. I am interested in data science, software engineering, 3d-printing, arts, music, microcontrollers, and sports.
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