[DanielBMarkham]

There's another front-page article on HN right now about side projects.

If anybody has the time, many years ago I wrote a simulator for various launch concepts. It's a project that can start off quite simply -- and can get as complex as you'd like. I ended up with an earth-moon model that could handle various rocket/mass-driver/payload combinations.

It's both fun and educational. Great for trying out new languages.