While working on the Jupiter ACE project I was amazed, over and over again, by the power of the available free software tools.
First there is DesignSpark Mechnical. An extremely powerful 3D CAD program from RS Components. It's a trimmed down version of SpaceClaim Engineer, a truly high-end CAD package. Which also means it misses some features, like directly placing texts, the option to mirror 3D objects, and the possibility to export to STEP files. Which sometimes makes makes it harder to get some things done, but usually there is a workaround. It does however support import of images or photo's. Which can be place and rotated in 3D space. Something that was tremendously helpful when drawing the Housing.
Second, of course, there is KiCAD. The free, open source, multi platform, Electronics Design package. With the release of version 5 it has really become a serious piece of software. It works flawless, and I've not seen it crash anywhere during my whole design process. The work flow has significantly improved since the previous version, and the available libraries are extensive. OK, you still cannot drag a component on your PCB while keeping the traces connected, but that's my only (minor) complaint. Tools like 3D view and STEP export on the other hand are truly amazing, and the only reason I could make an image as shown above.
And last, the PrusaSlicer. A fork of the (already pretty good) Slic3R. Since Prusa Printers forked it, and put a (full time) team of software engineers on it it has grown to be awesome. Adaptive layering, advanced move and align tools, customizable support, 3MF project support, its got it all.