comments SpaceX is ready for blast off. Elon Musk's soaraway rocket company is going public in a stock market flotation that values this mammoth US business at an astonishing $1.75trillion – £1.3trillion. And in an extremely rare opportunity, Britain’s small investors have the chance to take part in this blockbuster Initial Public Offering (IPO), which is the largest share sale in history. Act fast and apply before next Wednesday and you can take a bet on rocket man Musk's great adventure to infinity and beyond, backing his lunar missions and other ambitions on earth and in the heavens. SpaceX is seeking to raise about $75billion from investors, both private and professional money managers. Private investors are often excluded from this type of Wall Street bonanza, considered not worthy to be invited to the party. And British investors are almost never able to take part in US IPOs, due to regulations from America’s Securities and Exchange Commission (SEC). That’s not the case with SpaceX and Musk, who believes in ‘broad access’, is keen to have small investors on board for the thrill ride and so has included them in his huge retail book-building – which pulls together demand from individual investors for the stock. He is said to be reserving 20 to 30 per cent of the shares for ordinary people. And in an unusual move, it has been reported that as much as $2billion has been set aside for British private investors. Rocket man: If he pulls it off, Elon Musk's SpaceX stock market float will be the largest ever They can apply for shares from Friday 5 June, through platforms like AJ Bell, Barclays Private Bank, CMC Markets, eToro, Freetrade, Hargreaves Lansdown, IG, Interactive Brokers, Interactive Investor and Revolut. Some 555.6 million shares are on offer at $135 each and you have until next Wednesday June 10 to apply, although this deadline could be changed. The shares begin to trade at 2.30pm Friday, June 12. If you are considering it or just want to know more about an out-of-this-world stock market story, we explain what you need to know. SpaceX and the world’s biggest IPO SpaceX has grabbed the headlines by launching a world record IPO, which includes prospects such as space tourism, manufacturing capabilities on the Moon and Mars and asteroid mining. Anyone intrigued by the opportunity should, however, be aware of the risks in this extraterrestrial enterprise. Musk says that ‘we believe that space represents the largest economic frontier in human history.’ This may be inspiring. But the future direction of SpaceX shares could be influenced not just by the company's results, but by the behaviour of Musk, a controversial and mercurial figure. This 54-year-old executive divides opinion, even among those who pay tribute to his extraordinary intelligence and prodigious work ethic. This reinforces the message that, as always, you should not commit money that you cannot afford to lose, especially given the view in some quarters that SpaceX could be dangerously overvalued, with one analyst estimating that the business is worth $780billion, not $1.75trillion. Just five years ago, SpaceX was valued at $36billion. As Dan Boardman-Weston, chief executive of BRI Wealth Management, points out, anyone buying at the IPO is paying ‘a significant premium for future growth prospects.’ Buying the shares with a short or medium-term view could be a perilous escapade. This is a long-term investment of the kind backed by funds such as Scottish Mortgage that specialise in disruptive and highly ambitious ‘moonshot’ prospects. One for the future: Backing SpaceX should be a long-term investment in a wider portfolio The importance of doing research in SpaceX is underlined by indications of how the billions from the flotation will be spent. Some will go on artificial intelligence (AI) in which SpaceX is heavily involved. Like other US tech titans including the Google group Alphabet, SpaceX is determined to be a winner in this 21st century industrial revolution. This strategy has its hazards, however. AI requires vast computing power from data centres, buildings full of cabling and servers. Musk plans to address this shortage of such premises on earth by building them on satellites orbiting in space. This may sound a bit sci-fi, but experts say that this could become reality. Mark Boggett, manager of UK space fund, Seraphim Space Investment Trust, argues that data centres on earth could start to be barred because of the vast amounts of energy and water they use. Experts are less convinced by the feasibility of Mars colonisation, although this is Musk's fondest dream. For him the SpaceX mission is ‘to make life multiplanetary, understand the true nature of the universe and extend the light of consciousness to the stars.’ In the 200,000-word prospectus published last month, SpaceX revealed that its revenues for the first quarter of the year were $4.7billion, but that its net losses were $4.3billion. The company claims to have a potential market of $28trillion for its goods and services although this figure is not verifiable. Given such doubts, there can be no guarantee that the shares will perform in a stellar fashion. They could go to the moon and then onto Mars, or a dazzling ascent could be followed by a painful decline. What you need to know about investing in SpaceX SpaceX represents a gamble on innovation and future rewards for those who can look long into the future and beyond the confines of Earth. If this sounds like an opportunity you are happy to seize while still able to sleep at night, this is what you need to know. When you log onto a platform to apply for shares, you will be asked if you have read the 400-page prospectus. This is not obligatory. But it is useful. The pictures remind us that SpaceX – which designs, makes and launches rockets and spacecraft – is the world's leading launch provider. How to invest a £10,000 lump sum: Where you could earn returns of 75% in just five years