The evolution of a Lego Mindstorms Mars Rover

Last weekend I (oh, and about 9000 other people) participated in NASA's International Space Apps Challenge. My team worked on the Curiosity at Home challenge, split in three parts: translating NASA's SPICE data format to a more readable form, parsing that into commands to the rover, and building a representation of the Curiosity Mars rover itself.

The code is available on Github. It still needs some work, but, you know, hackathon.

I worked on building the rover, using Lego Mindstorms, and it proved to be trickier than I had anticipated. Most times it would look great, but then refuse to steer or even move at all, as soon as some weight was put onto it. And by weight I mean the NXT brick, which we felt was an indispensable component of the rover.

I'm in the process of disassembling the rover and taking photos of it, so that I can then rebuild it and document the build steps. But, in the meantime, a quick recap of how it evolved throughout the (mostly sleepless) weekend. Unfortunately, I don't have pictures of every intermediate version.

Iteration 2

By this point, we had an initial, flimsier version. But I wanted more robustness, as well as proper front-wheel steering. At this point, the motor powered 4 wheels. Here it is (with Frits, as a bonus):

Lego rover, iteration 2

Iteration 6. Probably

Yeah, I don't remember exactly which iteration these pictures correspond to. Have I mentioned "sleepless"?

Anyway, you'll notice this version is shorter, meaning less strain on the middle section, better distribution of weight and, we hoped, better steering. By then, we had already moved to a motor powering only two wheels, and now we have finally started using two separate motors, one for each rear wheel.

Lego rover, iteration 6

Iteration 8, I think

Shorter, sturdier, and uses different rotations of the the back wheels for steering, as well as the front wheel gears.

I was disappointed with the middle wheels, by this point they were mostly just for show. But the deadline approached, and we had to make decisions.

Lego rover, iteration 8

Iteration 10, final version

Not too many changes from the previous iteration, mostly some incremental adjustments. This is what we presented, and worked reasonably well (all things considered).

Lego rover, iteration 10 (final)

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