Thread: SpaceX - On to Mars

Originally Posted by Dragonfly

that's a lot of MegaWatts

It really is. It takes that much power. Several MW for each of up to 36 or 37 engines.

Originally Posted by OhOh

Am I right in assuming the turbo pumps spin unpowered initially and allow enough oxygen and fuel into the engines to start the rocket engines, because the oxygen and fuel tanks are sufficiently pre-pressurised?

They use a reservoir of high pressure gas to spin up the turbopumps. That gas also precools the turbopumps so they don't get damaged by cold shock when the super cold liquid oxygen and liquid methane comes to the intake.

For pressurizing the tank on their Falcon rockets they use helium. Elon Musk once stated the helium costs more than the kerosene and LOX propellant. For Starship they use a different method. They boil some of the LOX for the LOX tank and some methane for the methane tank. In flight that hot gas comes from the engines. Two reasons for that. Using helium may double their launch cost, if they get their cost as low as they intend. Second they want to produce the fuel on Mars. They won't have helium there.