And, speaking of Elon Musk... and claims, about other things than Maglev trains in a vacuum tube......like Mars rockets in the vacuum of space.

I went to the monthly JPL Von Karmen series lecture tonight in Pasadena, on the upcoming Mars 2020 Rover Mission......

Which is really cool, and will learn a lot more about Mars.....And, it was a lecture filled with all kinds of facts about how difficult Mars is to get to, and the atmosphere, and the radiation, and lack of magnetic field, and how they wanted to bring rocks back, and how difficult that is.

To bring back a few pounds of Mars rocks samples would take sending an unused rocket to the surface, loading the samples, and using that first rocket just to get them off of the surface into orbit around Mars, where a second rocket would need to rendezvous with the first rocket, to pick the samples up, and take them back to earth, and how none of that is yet funded for picking up samples from the next Rover we are sending in 2020....

It's all about those same three factors affecting transportation efficiency and costs we all deal with on earth, applied to transporting rocks back from Mars, overcoming time, distance, gravity.....

At the end of the lecture there are always good questions from the audience. And, a lot of these folks are pretty smart, and ask pretty smart questions about the physics, chemistry, engineering, and the like involved in these missions, and the doing the science. And, I was sitting among a group of retired JPL "lab rats" my age. And, one of them asked how much credibility folks at JPL and NASA actually put in Musk's recent claim that Spacex would be unmanned on Mars by 2023, and manned maybe 3 years later (which he has since already backpedaled on). And, in response to that question, a good sized segment of this audience actually started laughing.

As the speaker diplomatically noted in reply, Spacex has done some really cool engineering, but that they have a different "focus" on this, and we'd just have to see........