Investors looking for a stock to buy to get exposure to Elon Musk’s rocket company SpaceX have a handful of options on the London Stock Exchange. These include Baillie Gifford US Growth Trust and Edinburgh Worldwide Investment Trust, which are both in the FTSE 250, and the lesser-known Schiehallion Fund.

But there’s only one in the FTSE 100 index: Scottish Mortgage Investment Trust (LSE:SMT). Today, this £12.6bn trust has SpaceX as its top position.

But what’s so special about SpaceX? And why might investors want exposure to it?

Light years ahead of the competition

Put simply, SpaceX has totally transformed the global launch market by pioneering reusable rockets (its battle-hardened workhorse rocket is called Falcon 9).

Falcon has dramatically lowered the cost of accessing low Earth orbit, which is making space a rapidly developing commercial reality. And not just for other firms, but also for its own Starlink satellite business, which now delivers reliable high-speed internet to more than 10m customers.

As Scottish Mortgage points out: “Reusability is key. The old model of single use rockets was akin to buying an expensive car to make a single journey. Reusable cars allow mass transportation on the ground; reusable rockets allow mass transportation in space…Reusability places [SpaceX]years ahead of competitors.”

According to estimates, the global space economy could reach $1.8trn by 2040, up from around $613bn last year. Right at the centre of it, SpaceX is streets ahead of rivals due to relentless innovation, cost advantages, and Musk’s lifelong mission to make humans an interplanetary species.

A stacked portfolio

But SpaceX isn’t the only transformative private company in Scottish Mortgage’s portfolio. Two others that have become global juggernauts are TikTok owner ByteDance (the trust’s third-largest holding) and UK fintech Revolut (a smaller position, at 0.8% of assets).

Valued at around $550bn, ByteDance is an AI-powered company with vast scale (its platforms reach over 4bn monthly active users). And it’s aggressively moving into multiple markets, including gaming, education, and e-commerce, supported by surging digital ad revenues.

Meanwhile, Revolut finally received its full UK banking licence this week, allowing it to offer more lucrative products like mortgages, personal loans, and overdrafts.

Revolut co-founder and CEO Nik Storonsky commented: “This is a vital step in our mission to build the world’s first truly global bank.” It’s aiming to launch in 30 new markets by 2030.

While there’s no timeline for a ByteDance IPO, Revolut may go public later this year or in early 2027.

SpaceX mega-IPO

Scottish Mortgage first invested in SpaceX in 2018, at a valuation of $31bn. And Reuters recently reported that Musk is seeking a valuation of $1.75trn in an initial public offering, potentially as early as June.

Clearly then, the FTSE 100 trust is sitting on huge unrealised gains. Indeed, the holding has mushroomed to a meaty 15.4% weighting in the portfolio. Given this size, it’s very likely that Scottish Mortgage will crystallise profits upon IPO.

The big risk is that the IPO is a flop, which could cast doubt on the valuations of Scottish Mortgage’s other unlisted holdings. Volatility is also a given with Scottish Mortgage, especially when Nasdaq-listed growth stocks sell off.

But on balance, I continue to see this FTSE 100 trust as an excellent choice to consider for exposure to the world’s most transformative growth companies.