SpaceX went public at $1.75 trillion in June. Yesterday it committed $16.8 billion to a chip fab in Grimes County, Texas. Follow the chain connecting those two numbers and you end at a light source that doesn't exist yet. Start from the top. SpaceX has filed for up to 1 million data-center satellites, targeting hundreds of gigawatts of compute in orbit. Musk says current global chip output covers about 3% of what his companies will eventually need. So Terafab exists to print over 1 terawatt of…