Before settling on the 2018 Starship design, SpaceX successively presented a number of reusable super-heavy lift vehicle proposals. These preliminary spacecraft designs were known under various names.
2016 artist's concept of the ITS booster returning to the launch pad
2016 artist concept of the ITS Interplanetary Spaceship, in orbit near the rings of Saturn
2018 artist's conception of the redesigned BFR/Starship at stage separation
SpaceX Merlin
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Merlin is a family of rocket engines developed by SpaceX for use on its Falcon 1, Falcon 9 and Falcon Heavy launch vehicles. Merlin engines use RP-1 and liquid oxygen as rocket propellants in a gas-generator power cycle. The Merlin engine was originally designed for sea recovery and reuse, but since 2016 the entire Falcon 9 booster is recovered for reuse by landing vertically on a landing pad using one of its nine Merlin engines.
Test firing of the Merlin 1D at SpaceX’s McGregor test stand
Merlin 1C under construction at SpaceX
Merlin 1C Vacuum engine at Hawthorne factory in 2008