In his new book, New Space Capitalism: The Entrepreneurial Path to the Stars, Rainer Zitelmann presents the idea that private enterprise is the best way for space exploration to go forward, pointing out the ways in which public funding, since the days of the Moon landing, has been too uneven (and insufficient) to make the advances possible.

When reaching space initially was a political contest, the spirit was there, but since the end of the Cold War, it has been less of a priority.

Political commitment to space as an enterprise has fluctuated to the point that, as Zitelmann illustrates, for some years American astronauts were having to hitch a ride with the Russians to get to the International Space Station (the NASA engineers of the Cold War Mercury Program would have been appalled). The disasters of the space shuttles Challenger and Columbia reduced public enthusiasm for the enterprise, and it was harder to whip up excitement (and funding) for further missions.

But today, billionaires have become more involved, and the prospect of space tourism has also put more money into the enterprise. And this is, in its way, nothing new. In looking back to the earliest days of space as a pursuit, the building blocks, such as the building of big telescopes, were funded by the wealthy—and that it was by no means a natural fate that space exploration would become a government-funded enterprise.

It's easy for us to forget the philanthropists like James Lick, who left money to establish the observatory on Mount Hamilton in California. His bequest was $700,000—in 1874. A sum which, according to Zitelmann, "measured as an equivalent to US GDP, would be approximately $1.8 billion."

In a sense things have come full circle, as private individuals and companies are pushing the boundaries of space exploration and turning it into a range of commercial operations. One of the biggest growth areas is indeed for those who can afford it to go into space themselves. And this could be a huge market.

As Zitelmann puts it:

There are over 900 billionaires in the United States today. Their investable wealth dwarfs anything NASA ever dreamed of. Given the right tax and regulatory environment, a number of them will follow Jared Isaacman in traveling into space and investing in space.

Interestingly, he's a little more lukewarm about Martian exploration and travel, at least to the extent that Mars could be a popular tourist destination. Despite Elon Musk's Martian enthusiasm, it presents greater challenges to both tourist enterprises and those looking to exploit potential resources on the planet. In Zitelmann's words:

…I consider large-scale tourism on Mars unlikely, since not only does it take six to nine months to reach the planet, there's also only one launch window every twenty-six months. A tourist would need to commit several years of their life to such a journey, and that's something only a few wealthy retirees would realistically be able to do. Tourists are more likely to travel to the Moon, which would be worth a three-week trip.