Devlog 3: Kerbal Gravity Program (KGRP)

KGP—well, actually let’s call it KGRP now because apparently “kgp” is already taken by some Kubernetes stuff, and I don’t want stuff breaking anyone’s cloud infrastructure—is a mission planning tool I’m building for KSP players and actual aerospace engineers to map out complex trajectories. It’s loosely based on libraries like Skyfield, Poliastro, and Trajectorize. The ultimate goal is to make it easy to plot out massive interplanetary trips, whether you’re trying to reach Jool and Sarnus (with the Outer Planets Mod) or calculating a real-world journey out to Neptune.

What I did today

Well, today was mostly chill on the numerical part. I got the RKF(4)5 adaptive step solver fully up and running, and the burns produced by the Lambert solver are perfect and insanely accurate. The physics side of things is feeling really solid.

But then came the C++ transition, which immediately humbled me.

For hours, this was only working in Python because CMake seriously hates me. Seriously, why does a plain text file have so much attitude? Even though I explicitly gave it the include paths in VS Code, the thing still refused to find where Eigen was. I was getting so incredibly frustrated that I was genuinely on the verge of ragequitting, deleting the whole directory, and typing sudo rm -rf out of pure spite.

And then I realized what a complete idiot I was being.

CMake wasn’t failing to compile the library. It had actually built the thing perfectly. The issue was that I was stubbornly typing ./build/kgrvs like a caveman, completely missing the fact that the compiled binary was sitting right there inside ./build/Release/kgrvs.

Once I actually typed the right path, the C++ code ran flawlessly and matched my Python results perfectly down to the decimal point. The engine is officially alive, and I need to go look at a wall for a few minutes to recover from the self-inflicted psychological damage.

(BTW here is me almost bricking my computer)