SpaceX founder Elon Musk said Saturday the first orbital stack of the Starship rocket should be ready for flight in the coming weeks, taking the unorthodox billionaire a step closer to his dream of orbital and then interplanetary travel.

SpaceX in May successfully landed its Starship prototype, SN15, a reusable heavy-lift launch vehicle that could eventually carry astronauts and large cargo payloads to the moon and Mars.

The touchdown came after four prototype landing attempts had ended in explosions.

"First orbital stack of Starship should be ready for flight in a few weeks, pending only regulatory approval," Musk tweeted.

The complete Starship rocket, SpaceX's next-generation launch vehicle, stands 120 meters (394 feet) tall when coupled with its super-heavy first-stage booster.

It is at the center of the Tesla Inc. CEO's ambitions to make human space travel more affordable and routine.

An orbital Starship flight is planned for the year's end, and Musk has said he intends to fly Japanese billionaire entrepreneur Yusaku Maezawa around the moon in the Starship in 2023.