An operations plan released by the agency indicates a four-hour launch window opening at 3.33am local time on Friday from Nasa’s Kennedy Space Center, with backup opportunities on Saturday and Sunday. Elon Musk’s company has not yet commented on the new launch window.

Organised by billionaire entrepreneur Jared Isaacman, the Polaris Dawn mission aims to reach a peak altitude of 1,400km — the highest for any crewed mission in over half a century, since Nasa’s Apollo programme.

The highlight of the mission is set to be the first spacewalk by a four-member crew composed entirely of non-professional astronauts, who will be wearing sleek, newly developed SpaceX extravehicular activity (EVA) suits.

The launch was delayed twice last week, initially due to a technical issue with the launch tower and subsequently because of weather constraints affecting the splashdown phase.

Complicating matters further, a separate SpaceX Falcon 9 mission lost its first stage booster, which typically performs a precision upright landing on a drone ship.

This incident led to a temporary grounding, since lifted, of the prolific launch vehicle heavily relied upon by Nasa and private companies for deploying astronauts and satellites into orbit.