Cosmic Girl is a mother ship that can carry at least one LauncherOnelaunch vehicles. (The picture shows a LauncherOne under the left wing of the mother ship - between the fuselage and a jet engine.)
Cosmic Girl is a Boeing 747-400 aircraft. After the bankruptcy (2023) of Virgin Orbit, the airplane was sold to Stratolaunch. It is used as part of the Roc launch platform.
When a LauncherOne launches from Cosmic Girl at high altitude, then that rocket can put a small satellite up to 300 kg (660 lb) (see satellite) payload into orbit.
