SpaceX: “Close, but no cigar. This time”

One example of his being polite doesn't mean he doesn't also make fun of competition publicly. Look at the interview where the interviewer asks him about a competitor's electric car (BMW I think) and he just laughs for a not-insignificant amount of time followed by something like "have you seen the thing?"

The question is, without Musk, would all of those amazing engineers have spontaneously ordered themselves into a company to build a rocket that will eventually take humanity to mars?

Musk's function isn't to design the rockets, it's to believe so totally in the idea, to commit so much of his own time and money to it, to overflow with passion, that a generation of engineers are willing to follow him down a path to either greatness or ruin. History is littered with failed rocket startups.

You have to be a little bit crazy to believe you're going to do that kind of stuff. Hell, even the smallest startups face impossible odds for success.

NASA could have a charismatic front man. I'd nominate Neil deGrasse Tyson. But here's the problem: NASA is ultimately run by Congress and the executive branch, not Neil deGrasse Tyson. Ultimately, his words would mean nothing because he can't back them up.

Musk, when he says he's going to build a Raptor engine, has the authority to make it happen.

I think you're getting downvoted for the perceived negative tone, which I'm not sure if you intended. It's true, but I don't see anything wrong or sinister about it. If I was in charge of SpaceX, I would have done the same thing.

Even without the video, several news sources jumped into calling the mission a failure, even though the actual mission of resupplying the ISS went perfectly, and the landing was a long-shot experiment. Those calls would only be louder with a flashy explosion video with no backing explanation on hand, ready to go out with the news of the landing failure. By the time more info was available, the story would be gone, and the explanation would be ignored. This would damage SpaceX's brand, ability to get Government missions and private contracts, etc.

It's also entirely plausible that they didn't bother to install a high-speed data link from the barge to the mainland for the purpose of getting the video instantly. It would probably be an expensive and finicky way for them to instantly distribute video that would more likely than not be damaging to their brand.

We'll just have to see on that - it depends a lot on how many times the 1st stage can be reused, how much the refurbishment costs, and what the risk involved is. The first launch is pretty low-risk at this point, but how risky is the tenth launch on the same 1st stage?

IIRC, they are on record as wanting to eventually recover the 2nd stage as well. It's a much tougher problem though - the 2nd stage has much higher velocity at engine cutoff, its engine is a variant designed to operate in vacuum and reportedly can't be made to operate in the atmosphere easily, and any additional hardware added to the 2nd stage has a much higher penalty on the rocket's performance than on the 1st.

Sure, let's go over it together. Tlb is many things, but "rarely wrong" is probably near the top of the list. He certainly read those sections before making that comment, so there must be something here which made him as an engineering expert say that it doesn't properly address thermal expansion. I'll try to run an emulator of tlb's mind, but mine is far less sharp.

The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling. These minimally constrained pillars to tube joints will also allow a smoother ride. Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion. This is an ideal location for the thermal expansion joints as the speed is much lower nearby the stations. It thus allows the tube to be smooth and welded along the high speed gliding middle section.

This seems like the key sentence:

Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion.

There are two stations, one in SF and one in LA: http://i.imgur.com/3TavjCY.png

(For simplicity, let's assume it's just the main route.)

That would mean each station needs to absorb 150 meters of thermal expansion. (Would anyone mind double-checking that tlb's calculation is correct?)

So it looks like the tube is resting on these things: http://i.imgur.com/srQjmps.png

and the plan is for the tube to expand due to heat, and the expansion will be absorbed at the two stations at the end.

Is that really feasible, especially given that different points along the route could have temperature differences? I drove along Highway 1 and saw how incredibly different the weather can get, and while that's south of where the route is planned, it's easy to imagine that part of the tube could be roasting in direct sunlight while the other is cooled by rain. Something like 90 degrees F at one part vs 70F at another part. That's a difference of 32.22C to 21.11C, or a total temperature difference of 11.11C.

The route from SF to LA is about 350 miles. If a tube of that length expands 300 meters, then we can divide 300 meters by 350 miles to get the total expansion over a single mile. So a variation of 40C would give an expansion of 0.85 meters within a single mile.

Since the variation in that scenario would be ~11C, multiplying the expansion by 11C/40C equals an expansion of 0.235 meters.

So I suppose the question is: Is it feasible for those things the tube is resting on to absorb a quarter meter of expansion without that expansion being pushed all the way up to the station? It's the temperature differential along the route that seems to matter, not necessarily the difference from summer to winter.

Judging by this screenshot: http://i.imgur.com/wgUJqWr.png

... it seems like an expansion of 0.25 meters might be a big deal.

But I don't know what I'm talking about. Is all of that about right so far?

I'd also be curious whether the thermal expansion results in the tube becoming bigger in the circular direction, like a bigger "O", or if it expands parallel to the tube, like becoming a longer tube. Or even both.

It seems like the plan addresses this with the first part of that paragraph:

The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling.

But again, where precisely does 0.25m of steel go? I'm having trouble visualizing how the pillars could "allow for 0.25m of longitudinal slip over 1 mile."

I realize that a temperature variation of about 10C over 1 mile is a little extreme, but we should examine how the system handles extreme situations.