NOTHING declares world-changing ambition like a space rocket. This week’s spectacular test confirmed the Falcon Heavy as the planet’s most powerful operational launch vehicle. It also testified to the outsized vision of Elon Musk, its creator. To ensure humanity’s long-term survival he wants both to colonise Mars and to wean the Earth off fossil fuels.

Mr Musk is not the only billionaire entrepreneur with grand ambitions to improve the future of mankind. Mark Zuckerberg, the founder of Facebook, wants to “cure, prevent or manage” all diseases by the end of the century. Bill Gates, having made his fortune at Microsoft, wants to eradicate polio and malaria, as part of a broader goal of improving health and alleviating poverty. Both are among a number of philanthropists who plan to remake education—Mr Zuckerberg’s other goal is for children to “learn 100 times more than we learn today”.

As the Falcon Heavy soared above the Kennedy Space Centre in Florida, one question was over what Mr Musk’s dreams mean for business (see Briefing). The other was what to make of this desire to save humanity, in pursuit of which Mr Musk and his fellow billionaires have been strikingly innovative.

A century ago John D. Rockefeller, Andrew Carnegie and Henry Ford ruthlessly made fortunes and then established foundations to enlighten the masses and ensure world peace long after their death. Mr Gates and others, having seen how foundations can eventually become cautious and conventional, favour a “sunset philanthropy” model, aiming to spend their riches before they die. (Warren Buffett, now 87, is donating most of his fortune to Mr Gates’s foundation, to dispense on his behalf.) Such tycoons also pride themselves on measuring impacts and outcomes, applying the same rigorous scrutiny to their charitable activities as they did in their business.

From Rockefeller to Rocket-fella

In the latest twist younger billionaires like Mr Zuckerberg, who made their fortunes in their 20s or 30s, have switched from a serial model of philanthropy, in which you make money first and then retire and give it away, to a parallel one, where you start giving the money away while it is still coming in. Mr Musk has gone further still. Rather than using his business wealth to support philanthropy in an unrelated area, he runs two giant companies, Tesla (a clean-energy firm that sells electric cars) and SpaceX (which builds the Falcon rockets), that further his ambitious goals directly. Both companies sell something that people happen to want now—cars and satellite launches—as a way of hastening Mr Musk’s dreams.

The grand schemes of the mega-rich provoke excitement in some quarters and unease in others. One complaint involves accountability. Billionaire philanthropists do not answer to voters. Their spending power gives them the ability to do great good, but what if they prefer to act more like Blofeld-style Bond villains than Iron Man-style superheroes? Wealth also grants the mega-rich special access to policymakers and elected officials. Shovelling your fortune into a charitable foundation has the happy side-effect of reducing tax bills, too—meaning that billionaires’ schemes can leave poorer taxpayers to fill in the gaps in public spending.

Given that so many of today’s billionaires are geeks, there is also a danger of techno-solutionism. The idea that problems in health, education and so on can be solved with whatever technology is in vogue (today’s favourite is the blockchain) has usually proved naive. Deep change generally requires co-operation with governments and social mobilisation. Recognising such things is hard for techies used to seeing politicians as clueless and regulation as something to be innovated around.

And yet these reservations are surely outweighed by the billionaires’ scope for good. The would-be world-changers are applying innovative and evidence-based approaches in clinics and classrooms, where elected politicians are often too timid to risk failure, captured by entrenched interests or unwilling to spend public money on experimentation. For all their wealth, the billionaires would struggle to force change upon society. Although today’s philanthropists are more visible than those of previous generations, they account for less than a quarter of all charitable giving in America—which has remained roughly constant, at around 2% of GDP, for decades, according to David Callahan of Inside Philanthropy, a specialist website.

The billionaires’ most useful function, then, is not to bring about change themselves, but to explore and test new models and methods for others to emulate. Using their access to policymakers, they encourage the adoption of the ideas that work. Even an Avengers-style coalition of billionaires, like the one assembled by Mr Gates and Mr Buffett under the “Giving Pledge” banner, could not solve really big problems like infectious diseases, colonising Mars and climate change without the co-operation of governments, industry and voters.

So, as the Tesla car sent skywards by the Falcon Heavy begins its trip around the sun, salute the billionaires for their ambition. Raise your eyebrows, in some cases, at their hubris and political naivety. But applaud their role as public-policy trailblazers, opening up paths to a better future.