Elon Musk’s SpaceX is building floating spaceports at sea to launch rockets into space and hypersonic flights around Earth.

In a tweet, Musk confirmed that the development of “floating, superheavy-class” spaceports was underway on offshore sites, in preparation for “hypersonic travel” as well as trips to the moon and Mars.

It follows the posting of  job advert for an offshore operations engineer position in Brownsville, Texas.

The job ad, which reinforces the company’s ultimate mission to enable “human life on Mars”, notes that applicants must be “willing to work significant overtime”.

The company currently launches its rockets from Cape Canaveral in Florida, where Nasa’s Kennedy Space Centre is based, though Musk has expressed his desire to create offshore launchpads near Florida and the Dominican Republic.

Musk has previously proposed a hypersonic flight system that could ferry passengers across major cities in the world. In a conference in Australia in 2017, he claimed a potential spacecraft could take passengers from New York to Shanghai within 39 minutes. The aircraft could travel between 4,000 to 6,000mph.

The company has also advanced plans for landing sites for its reusable rockets which promise to bring down the cost of space travel by billions of dollars. It first landed a first-stage booster of a rocket on a landing pad near the coast of Florida in 2016.

It comes just weeks after SpaceX marked the historic launch of its Crew Dragon spacecraft, becoming the first private company to send humans to the International Space Station, and the first to launch from US soil since 2011.

The SpaceX boss has made it his goal to commercialise spaceflight, but faces stiff competition from a number of other tech billionaires, including Amazon boss Jeff Bezos and Sir Richard Branson.