Musk: SpaceX has begun developing “super heavy” rocket boosters for its trip to Mars.

Elon Musk’s latest prototype of the Starship has reached a recent test altitude of about 150 meters,media CNET reported. But the SpaceX CEO said Monday that his rocket company could begin building a prototype of the booster paired with the Starship this week.

“It’s going to be really cool,” Musk said in an interview at the Humans To Mars Virtual Summit.

The Starship is SpaceX’s platform for bringing humans to the moon, Mars and beyond, but to reach these deep space destinations, the company plans to pair the Starship with a powerful first-stage booster called Super Heavy. So far, we’ve only seen short test flights or “jumps” of early prototypes of the Starship.

Musk added that the number of “super-heavy” boosters could be smaller than originally planned — probably 28 Raptor engines, not 31. It’s still a lot of engines, and we’re going to increase the thrust of those engines. “

In addition, Musk said the next “jump” test of the Starship prototype “could take place next year” and aim to lower expectations a little. “The first batch may not succeed,” he said. “It’s an unknown territory. No one has ever built a fully reusable orbital rocket… And then there’s something twice as big as Saturn V (the rocket carrying astronauts to the moon) that’s completely reusable… It’s really another thing, it’s profound. That’s the gateway to the Milky Way, or at least the solar system. “