mikegarrison

This is the default, unless you are intentionally making only a very limited production run. I personally think SpaceX is overboard with the "build it before we even know what the design will be" thing, but maybe that's just because they are so far out of their previous experience that they feel like the lessons learned for the production process are worth the wasted production. Traditionally the process for airplanes was to build mockups, then flight test prototypes, then the initial versions of the vehicle, and then start implementing design improvements. And of course you also have to design the tooling, the factories, and all the other parts of the production stream at the same time. Starting in about the 1990s, companies started trying to eliminate mockups by using CAD models instead, and also tried to eliminate building prototypes and dedicated flight test vehicles. However, this has a hit or miss record, really. It worked quite well for the 777. But there have been some spectacular failures of this technique, most notably the 787 and A380, both of which had huge delays and cost overruns stemming from trying to cut too much out of the prototyping process.

Of course they were serious. I'm sure they had trade studies and considered hot staging, ullage motors, and this flip thing. They chose the crazy, risky one just in case it actually worked. The flip failed pretty spectacularly, so then they went with one of the safer options. It's a pattern with them. Also, there is a huge difference between pushing the boundaries of the envelope in flight test with the cost of occasional failure versus intentionally failing the test. "Test to destruction" is of course a real thing, and commonly done, but when you do it, you state in the test plan that you are doing it. SpaceX didn't try to explain away their test failure after the test flight, so I don't really understand why their fans seem to now be trying to do so.

Um. What was that? Japan is a very different place, I guess.

How can space be "deep" if I have to go up to get to it?

That's a wildly generous take on it. "No, we didn't lose directional control -- we WANTED our spacecraft to wildly tumble during re-entry." However, it is contradicted by what SpaceX themselves said during and after the flight, where they said they lost control of the vehicle.

Vaguely? There is always going to be some water in solution with the jet fuel, and it can freeze up. The specific issue (I think) was the ice freezing onto the walls of the fuel lines at low fuel flows, and then being knocked loose when the fuel flows were increased when the engine was commanded to go to higher power. The soft, slushy ice then clogged the intake to the fuel/oil heat exchanger, which starved the engine of fuel. The plane had flown through unusually cold air. The design had met all certification requirements, but this incident revealed that the certification requirements were not completely adequate, and so both the design and the certification requirements were changed. It only affected the RR Trent engines. https://en.wikipedia.org/wiki/British_Airways_Flight_38

Right now Boeing has all 10 fingers burned on "probably good enough". I suspect they will be really, really reluctant to launch with a system they don't think is working perfectly.

An issue specifically with hydrogen is that it is just difficult to store hydrogen at all. Not only does liquid hydrogen need to be kept at 20-30 Kelvin, but hydrogen is of course the smallest of all atoms, and it really likes to escape straight through the walls it is being contained in. Not only that, but it loves to nestle into the crystal structure of metals, causing hydrogen embrittlement.

I decided to remove this post.

Water does freeze in vacuum. What happens is that it evaporates (due to the extremely low pressure), which causes it to drop in temperature due to the phase change. The issue with a leak is whether the ice would plug the leak or not. If the ice does not plug the leak, then this boiling/freezing thing would just continue as all the water fountained out into space. But if the ice plugs the leak, it should be pretty stable.

I went outside on my front lawn and saw nothing but some wispy clouds. Then I realized the clouds were flickering. Other people around me have pictures of sheets of color, but apparently these were taken with "night mode" on their cameras. To the naked eye it was dim enough that there was little or no color. Still, most of the time these storms hit, it is cloudy in Seattle. This was the first one that happened that I could see with the naked eye.

Sort of. The real problem here is not the Second Law. The real problem here is that cooling the Earth below the ground is not the goal. The issue is that the atmosphere and oceans (which are thermally connected) are too warm and only getting warmer. Bringing more heat from underground into the atmosphere would not help at all. Yes, it would increase radiation into space, but increasing radiation into space is not the real goal. That would be like heating up metal to be red hot in order to cool it, because you know that red hot metal radiates more heat away from itself. But for obvious reasons this would not actually cool the metal, but instead make it warmer. If we could pump the heat outside of the atmosphere, then the idea would have some possible merit (theoretically, not practically, because of the scales involved). But pumping the heat *inside* the greenhouse will only make the greenhouse hotter.

Consider a spacecraft cooling system. It moves heat from inside the spacecraft to the radiators, and due to the Second Law, you end up with more heat in the radiators than you removed. Sounds like a net loss, right? Except having hot radiators is actually good, because then the heat radiates out into the rest of the universe. That seems to be the idea the OP is going for, except the issue is that it would be as if your radiators were covered by insulating blankets. In that case all you would be doing is getting the radiators hot to no good effect. (The atmosphere is the insulating blanket.)

Supposed to be a 95% chance of acceptable launch weather.