Time to get Geeky in space! Carl and Richard talk about what it takes to make a truly reusable spacecraft. First up is the venerable space shuttle, which wasn't so much reusable as rebuildable. It never really made economic sense, but it definitely drove the technology forward. SpaceX has been able to recover four first stage rockets from Falcon 9 flights, but hasn't reused any yet, and Richard gets into the nitty gritty details of the challenges of reusing rocket engines. It may require a different engine design to be truly reusable. And what about the rest of the rocket? Reusability is hard, and the economics may not make sense - it's important to understand the trade-offs!