Elon Musk is already dreaming of a gigantic spacecraft of the next generation. If it was built, the body of the rocket would be wider than an NBA basketball court.

• SpaceX is working on building a completely reusable spacecraft system called Starship.

• According to a presentation given by the founder of the company Elon Musk in September 2018, the finished rocket can reach a height of about 387 feet (118 meters) and a width of 9 meters (30 feet).

• But Musk tweeted on Wednesday that he was already considering a "next generation" spacecraft 18 meters in diameter. It's wider than an NBA basketball court.

• This doubled diameter could give the "new generation" Starship about eight times more volume than the first version, allowing ambitious journeys to Mars – but one or the other vehicle has not yet been built.

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A day after StarXper's last SpaceX flight – a truncated prototype of a massive planned launch system, called Starship – the company's founder, Elon Musk, has let slip a clue about its huge plans for the future.

Musk tweeted On Wednesday, he will present SpaceX's latest thoughts on the Starship system on September 28th. The date marks the 11th anniversary of the company's first launch with its Falcon 1 rocket.

Until then, most of what we know about Starship comes from Musk's last presentation in September 2018. At that time, the vehicle was still called "Big Falcon Rocket" and was supposed to be made from composite materials made of carbon fiber. SpaceX now uses stainless steel, but seems to retain similar dimensions, based on several renditions published by Musk (including one of the spacecraft on the surface of the moon).

Read more: Elon Musk says SpaceX could land on the moon in 2 years. A NASA official said, "We will work in partnership with them, and we will get there faster" if the company can succeed.

These dimensions suggest that the first operational version of Starship would be a vehicle about 9 meters wide and 118 meters high. Yet Musk is already imagining an even bigger version of Starship.

He revealed part of his ambitious plan when a Twitter user asked for a version of Starship 39 feet wide (12 meters). Musk responded that a "next-gen" version of Starship would probably double this diameter: a width of 18 meters, or almost 60 feet.

It's wider than an NBA basketball court.

The graph below shows how the first Starship system would be compared to its prototypes, such as Starhopper and Starship Mark 1. The Apollo-era Saturn rocket and NASA's upcoming Space Launch System lunar rocket are also included.

However, performing some basic calculations helps reveal the magnitude of what Musk is proposing to do with SpaceX in the very distant future.

A "next gen" ship can have 8 times the volume of the first operational ship

By simplifying the dimensions of the first-generation spacecraft into a cylinder (and ignoring its aerodynamic nose), a final volume of about 7.5 million liters is achieved. The same calculation on the new generation spacecraft – assuming that its height also doubles, at about 236 meters (775 feet) – gives an approximate volume of 60 million liters.

In fact, if you double the width and height, the launcher will be about eight times larger. Even if the new generation Starship was not bigger than many skyscrapers, it would still have been several times bigger than its predecessor, still hypothetical.

Potentially tweaking the volume does not say much about the payload or the number of people that a new-generation spacecraft could carry into orbit, nor about the depth that such a gigantic spacecraft could reach. But it's hard not to imagine that the answers are "more numerous, bigger, faster and further" because they could carry a lot more fuel and carry more Roquor engines.

Read more: SpaceX has launched a giant rocket engine with 'crazy power' for lunar and martian missions. The future of Elon Musk could depend on its unmatched performance.

Admittedly, a nose as wide as a basketball court is larger than any other rocket, and could accommodate space telescopes that astronomers can only dream of at the moment. For example, NASA's next James Webb Space Telescope (JWST) will be upgraded to an Ariane 5 rocket with a width of 4.5 meters (20 meters) in 2021. If a new-generation spacecraft is built it could have at least six space observatories of $ 10 billion in its refit at a time.

However, Musk plans to build a city on Mars that will be self-sustaining in the 2050s (and eventually will have pizza joints). If he hopes to see this mission accomplished before his stay on Earth, SpaceX may need the largest rocket his leader can imagine.

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