[glzone1]

Does anyone know how important hot staging is?

It seems to give the booster a real kick - what's that do to turbo's and fuel movement?

You've got hot exhaust onto cold cryo fuel tank header?

You've got to carry more mass in terms of protection for the tank?

Is doing MECO and then push and then get 100 yards apart or something before second stage / ship engines kick on a big enough penalty to justify all the extra complexity?

[rogerrogerr]

All the velocity you lose in any kind of throttle back is velocity you never get back. It hurts you the entire rest of the flight.

[syncsynchalt]

aka "gravity losses". Every second you're not (yet) in orbit you're losing dv / cargo capability.

[cwillu]

IIRC, it basically removes the need to do a handoff between the relatively tiny tanks that can reliably pump fuel and oxidizer in zero-g from the main tanks that struggle with that in starship, and completely removes the need for any of that on the booster.

[jdranczewski]

They were originally planning to not do hot staging, aiming instead for a somewhat funny approach where they spin the ship and booster slightly so they are passively separated by centrifugal forces. A bunch of things went wrong in the first test flight, so this was never attempted, and they switched to the "simpler" hot staging in flight 2.

[numpad0]

eliminates the need for ullage thrusters to force the blobby propellants in the tank onto pump intakes