1,000 Starships and 20 Years Are Needed to Build Sustainable City on Mars, Says Elon Musk

So it will take about 20 years to transfer a million tons to Mars Base Alpha, which is hopefully enough to make it sustainable

— Elon Musk (@elonmusk) November 7, 2019

Musk said that the launch cost per Starship flight would be as low as $2 million if they stick to their current goal of creating sustainable cities on Mars. In order to make these cities self-sustainable, around 1,000 Starships would be required to fly up to space. 

These Starships need to transport cargo, infrastructure, as well as crews to the planet over a time span of 20 years. The reason for the two-decade span is that the planets only align every two years, so a realistic flight approach would take a while. 

Musk also went into more detail about the Starship. According to Musk, Starship's design is meant to enable it to fly up to three times a day and is built for re-usability.

As the planets align only once every two years

— Elon Musk (@elonmusk) November 7, 2019

So if we consider that amount, that means that over 1,000 launches would occur each year for each Starship. If the company builds as many Starships as they currently have of Falcon rockets (approximately 100), bearing in mind that each of these can transport around 100 tons to orbit, that means that SpaceX would launch more than 10 million tons to orbit every year. 

That's a hefty amount of payload. However, it is in line with Musk's dream of a busier orbital space.

When all is said and done, we first have to send a crewed mission to Mars. At this stage, the focus, in fact, is on sending astronauts back to the Moon.

NASA and SpaceX have been working hand in hand to push forward with these missions. The plan is to land on the Moon by 2022, with the goal of sending a crewed mission by 2024. 

After that, we can focus on sending people to Mars.