The IPO, due on June 12, is expected to raise up to $US80 billion for the company. Its only currently profitable sector is its telecommunications business (Starlink), but SpaceX’s long-haul potential is a near-monopoly on launches and other space services for American and other players in the burgeoning space business.
That doesn’t mean Musk is a confidence man: he really believes in his promises, and though he’s not actually an engineer he is deeply involved in the engineering aspects of everything he builds.
Musk does push hard at the boundaries of possibility, however, and with Starship he made two promises that are hard to keep: fully re-usable spaceships that deliver 100 tonnes of payload to Low Earth Orbit (LEO).
The ‘‘reusable’’ part of the promise is almost done; the ‘‘heavy lift’’ part not so much, because that brings him up against the Rocket Equation.
That’s Russian scientist Konstantin Tsiolkovsky’s classic ‘‘rocket equation’’ of 1903, which states that around 90% of a rocket’s launch weight has to be fuel if you want to put it into Earth orbit.
It has not been successfully challenged yet, which is why so many of Starship’s launches failed, and none has yet reached orbit.
Gadfly journalist Will Lockett, writing on the website Medium, said recently that ‘‘Musk ignorantly overstated how much thrust their rockets could generate (to comical levels) and grossly underestimated how much a rocket this giant would need to weigh.’’
A bit harsh, but probably true.
That is why every new version of Starship is lighter and more powerful than its predecessor: they simply got their original calculations wrong.
Version 3, which flew more or less successfully on 22 May, is much lighter, with much more powerful engines than Version 2, but the lower stage exploded shortly after separating from the upper stage.
The problem is that a lot of that lost weight comes from cutting the margins for safety: bigger and bigger engines on a lighter and weaker frame is a recipe for recurrent explosions. All space flight involves close margins for error, but Starship’s are getting tighter and tighter.
They can probably work most of the bugs out of Version 3, but it’s questionable whether it will ever lift the promised 100 tonnes into orbit or become reliable enough to carry human beings into orbit. That’s not a disaster for humanity, or even for Musk.
There are other heavy-lift vehicles coming out that can put 50-tonne payloads into orbit (Nasa’s SLS, China’s Long March 9, Blue Origin’s New Armstrong) but even at that carrying capacity Starship would win financially because of its reusability.
And if Starship never gets safe enough for people — well, there are lots of other vehicles that can do that job.
As for Musk’s more grandiose dreams of bases on the Moon and people on Mars, they are no more or less fantastical than they were before Tsiolkovsky’s equation turned out to apply even to him.
No rocket-propelled movement in space will ever impose one-tenth of the stress on his vehicles that is involved in struggling up out of Earth’s deep gravity well.
Elsewhere is different. No other planet or asteroid in the Solar System where human beings might one day want to land has even half of Earth’s gravity, and a fully debugged Starship is still a leading contender for those jobs.
The long-term solution (which would finally dethrone Tsiolkovsky) is to build a space elevator that remains always over the same spot (if you base it on the equator).
It requires a satellite in an orbit 35,000km high with a cable attaching it to the ground at one end and a counterweight in an even higher orbit that holds the whole system under tension.
Climbers would crawl up and down the cable to the satellite transporting cargoes and people. To get to further destinations, just transfer to real spaceships from the satellite.
All this could come to pass once we can build a cable strong enough to support 35,000km of its own weight.
Which may take some time, although carbon nanotubes, single crystal graphene and diamond nanothreads are all plausible candidates.
• Gwynne Dyer is an independent London journalist.
