IIR, Carmack spent a lot of his own money on Armadillo Aerospace and most of the people who worked on it were volunteers. They had many ideas including custom d

IIR, Carmack spent a lot of his own money on Armadillo Aerospace and most of the people who worked on it were volunteers. They had many ideas including custom designed rocket engines and self contained composable pieces that could be built into large systems. It was very up Musk's "first principles" alley, but wildly underestimated the capital needed to be successful.