How three into one will go
Three rockets take off in a “sandwich” configuration, whereby the outer two vehicles boost the inner vehicle until they run out of fuel, at which time all three separate. The inner vehicle then fires its engines and continues up into orbit, while the two booster vehicles are guided by remote control back to a runway landing.
The design is similar to one used in the long-defunct Mustard project, which was established by the British Aircraft Corporation. It was started in 1964 but cancelled the following year