On the moon, an electric rail launcher with 5-10G only needs to be a few km long.
(Iirc, 1G acceleration of four minutes is the launch velocity of the moon? ~ 2.4 km/s.)
Edit: This assumes local materials for the electric launcher. If everything is skipped from Earth, it might be different. But, consider -- if you need to launch so much stuff from the moon, you must already have the infrastructure to build things there.
On the moon, an electric rail launcher with 5-10G only needs to be a few km long.
(Iirc, 1G acceleration of four minutes is the launch velocity of the moon? ~ 2.4 km/s.)
Edit: This assumes local materials for the electric launcher. If everything is skipped from Earth, it might be different. But, consider -- if you need to launch so much stuff from the moon, you must already have the infrastructure to build things there.