Final Report – Planetary Exploration Project

This post is from Fusion, my school's interdisciplinary STEM program.

This report documents the full arc of my Planetary Exploration Project (PEP): designing, building, and testing a six-wheeled rover prototype intended for surface exploration of Proxima Centauri B. The goal was to transform theoretical planetary science into a testable mechanical problem.

Design Phase

The rover uses a modular architecture with three independent motor units, each driving a pair of wheels. The two most important innovations were double-wishbone suspension systems and LEGO Technic universal joints, which together allow each wheel pair to flex independently over uneven terrain.

The suspension geometry came from studying actual planetary rover designs. Double-wishbone setups let the wheel travel vertically without changing its camber angle significantly, which matters when you're climbing rocks and can't afford to lose traction. The universal joints solved the problem of transmitting torque around corners without binding — critical when the chassis itself needs to twist to conform to rough ground.

Construction Challenges

CAD and reality disagreed more than I expected. Parts that fit perfectly in Onshape did not automatically fit when printed. I ran into two recurring issues:

Tolerance gaps: Printed parts needed slight oversizing in certain dimensions to account for material shrinkage and layer adhesion.
Grain direction: FDM printing creates anisotropic parts. Reorienting components so load paths ran along layer lines rather than across them prevented several stress fractures during testing.

Each failure during assembly was data. The prototype is supposed to produce constraints for the real design, and finding out where the model breaks down early is exactly the point.

Testing Results

I ran the rover on two terrain types and measured energy consumption per meter traveled:

| Terrain | Efficiency | |---|---| | Flat surface | 54.62 J/m | | 6.5° incline | 83.69 J/m |

The incline test also revealed something important: only 3.57% of the electrical energy input was converted into useful height gain. The rest was lost to drivetrain friction across the gearboxes, axles, and universal joints.

That number is brutal, but it makes sense. Every gear mesh, every bearing, every joint is a friction point. At scale, with a heavier vehicle and longer distances, those losses compound badly.

Mission Scaling

Extrapolating to a full-scale crewed rover over a 10-kilometer mixed-terrain mission suggested a total energy requirement of approximately 198 kWh. That's far beyond what battery chemistry can practically deliver for a vehicle that also needs to keep humans alive.

The conclusion: battery power alone is not viable. The realistic path is radioisotope thermoelectric generators (RTGs) — the same technology that has kept the Mars rovers running for years. RTGs convert heat from radioactive decay directly into electricity, with no moving parts and no dependence on sunlight (which matters on Proxima Centauri B, where the star is a dim red dwarf and the planet is likely tidally locked).

What the Prototype Actually Proved

The rover didn't need to be efficient. It needed to produce data that constrains the real design.

It did that. The friction measurements give us a realistic lower bound on drivetrain losses to design against. The construction failures gave us material and tolerance requirements. The suspension behavior under load told us where the geometry needs to change.

Engineering is mostly about learning what you got wrong and narrowing down the solution space. This prototype narrowed it considerably.

Originally published on ConnorK.