ADELAIDE • American futurist and inventor Elon Musk has unveiled ambitious plans to send cargo ships to Mars in five years and use rockets to carry people between Earth's major cities in under half an hour.

The founder of SpaceX said a planned interplanetary transport system would be downsized so it could carry out a range of tasks that would then pay for future Mars missions.

"The most important thing... is that I think we have figured out how to pay for (the system)," Mr Musk told a packed auditorium at a global gathering of space experts in Adelaide yesterday.

"Which is to have a smaller vehicle, it's still pretty big, but one that can... do everything that's needed in the greater Earth orbit activity."

Mr Musk said his firm had starting building the system, with the construction of the first ship to start between six and nine months.

"I feel fairly confident that we can complete the ship and launch in about five years," he added.

At least two cargo ships would land on the Red Planet in 2022, with the key mission of finding the best source of water - mooted as a way to power rockets, he said.

The rockets would place power, mining and life-support infrastructure on Mars to support future missions, with four ships set to take people, equipment and supplies to the planet in 2024. The trips would be funded by a range of activities, including launching satellites, servicing the space station and lunar missions.

Mr Musk said the rockets should also cater to Earth's inhabitants by reducing the travel time between major cities to less than half an hour. A trip from Bangkok to Dubai would take 27 minutes, and from Tokyo to New Delhi, 30 minutes, according to his calculations.

"Once you are out of the atmosphere, it would be as smooth as silk, no turbulence, nothing," he said.

AGENCE FRANCE-PRESSE