Elon Musk dropped a few further hints about his Hyperloops transit plan in London last night, saying it was "a cross between a Concorde and a rail gun" whose biggest hurdles included "right-of-way" issues.
And it seems that the ultimate destiny of the futuristic system would be to shift aging tech entrepreneurs around their retirement communities on Mars.
The sometime net-payments kingpin turned car designer turned rocketman told an audience at the Economist's Innovation Awards that he hoped to publish some actual details of the project before the end of the year.
The scheme was first hinted at earlier this year, sparking speculation that Musk was planning Futurama-style people tubes.
Last night, at the Huawei-sponsored event, Musk affirmed the goals of the system, and repeated his basic specs for a mass transit system that could reduce journey times between San Francisco and LA to 30 minutes.
These included that it should be "faster" than other methods, "ideally crash-proof" and "weather-proof".
Musk also made the not necessarily obvious point that it should cost "much less than other models of transportation".
It should also "leave when you arrive" he said, which presumably points to a more personal, taxi-like system, rather than the type of staggered trip schedule that would put him in competition with EasyJet or Ryanair.
As for potential blocks on the plan, he noted that we live in a "built up world" so there "can't be a right-of-way problem".
Addressing the inconvenient issue that previous generations tend to have already cluttered up most of the places where you might want to install your transit system with homes, offices, parks, etc, may be a bigger challenge than developing that cross-between-a-rail-gun-and-Concorde that would shoot people from one end of California at approaching 800 miles an hour.
It would of course be much easier, from a planning point of view, to build a Hyperloop system in a green field site... Mars, for example.
And Musk affirmed his intention last night to die on Mars, though "not at the point of impact".
Musk also said he'd like to "hit the retirement button before I get too senile".
Which leaves us with the prospect that if everything falls into place, Hyperloop will ultimately be the Martian equivalent of the retirement community golf cart. ®