The American company Space X has assembled the largest rocket so far, the BBC reports. The two rocket segments - the upper Starship and the lower powered Super Heavy - are fused at the Six X plant in Boca Chici, Texas.

Due to the height of about 120 meters, all previous rocket systems in relation to this one seem dwarfed.

When it finally takes off, it will produce twice the pressure of a rocket sent to Mars.

A massive crane was needed to connect the two segments. They are held in that position for an hour and then separated.

Starship Fully Stack pic.twitter.com/Fs88RNsmfH

- Elon Musk (@elonmusk) August 6

Space X has a few more weeks, ie months of testing before the first flight, possibly until the end of 2021. The company's chief executive, Elon Musk, called the rocket launch a "dream come true."

He says the Starship, when completed, will be able to take humans to the Moon and Mars. It could also quickly transport people around the world, and another obvious intention is to place satellites in orbit.

Currently the most powerful rocket in use is the Falcon Heavy, also developed by SpaceX. The Falcon Heavy produces 23 megawatts at launch, and the new Super Heavy rocket should reach around 70 megawatts.