My favorite videos of his are not the ones where he shows off new video games, but the ones where he delves into space history and engineering and astrophysics. He's taught me so much!
From twitter:
@IridiumComm: Iridium is excited to share we're planned to launch on Monday, Jan 9 at 10:22am PST weather permitting. http://bit.ly/2iZ7mCE #IridiumNEXT
Elon said they're shooting for next week, rumor is that it'll be Monday. (Edit: I forgot that it was confirmed by Iridium, the customer, so it's beyond a rumor at this point.)
Falcon Heavy is said to be scheduled for a launch in about six months. However, it's been six months away for several years now.
Big planes have an order of magnitude lower complexity than a rocket of the Falcon 9's caliber. That's a somewhat subjective statement, I'm sure, but even if it weren't the case there's so much variation between each Falcon 9 I'd be surprised if they could crank that many out with any reasonable amount of QA.
The Soviet Union managed to produce their Soyuz-U rockets at a higher pace than that some four decades ago [1] while achieving a success rate of > 97%. Sure, it's a different rocket with different capabilities, but it was also a long time ago.
...one only has to make a similar comparison between Tesla and a variety of auto manufacturing firms to note there is a distinct whiff of under-performance and delays that, by outward appearances, appear to be top-down culturally.
It's mildly interesting that this is only for 7 Iridium-NEXT launches. An eight was recently added, but it will also have a pair of German GRACE-FO satellites attached to it, so it probably makes sense that the FAA would want to approve that one separately.
They weren't grounded. They have to get an FAA license for every launch (or, in this case, a bulk license for all of their Iridium launches over the next 18 months).
The FAA _could_ have denied them a license, but that's pretty unlikely, as the AMOS-6 event was a 'test anomaly', not something related to flight.
They were grounded, the FAA was a party to the AMOS-6 investigation. I don't think they would have been given a license until the FAA were satisfied with the results of that investigation.
Maybe, maybe not. They got the license when they applied for it. They obviously didn't bother applying for the license until they were satisfied with their investigation of AMOS-6.
Charcoal has a surface area of a few acres per teaspoon (which makes sense when you look at a micrograph, since all the woody cell walls are preserved https://www.youtube.com/watch?v=kF10i39VQ4w), whereas carbon fiber composites are impregnated with resin. Obviously all it takes is one oxygen/carbon interface to cause an explosion, as we saw.
Similar to explosives, the more thoroughly mixed it is the more energetic the reaction. Pouring LOX over charcoal and soaking charcoal in LOX are very different (the first ignites vigorously, the latter explodes like a stick of dynamite). http://www.popsci.com/diy/article/2009-09/most-dangerous-way...
On a similar note, all kinds of materials that you wouldn't expect become very flammable with high surface area and/or pure oxygen environments. See e.g. the thermal lance, which is a very powerful cutting tool that works by running oxygen over iron (rust at high speed!). Or the very serious risk of explosions in flour mills due to high amounts of dust suspended in the air.
Yup. Growing up on a farm, it wasn't uncommon to hear of explosions in grain silos from a spark in the dust or barn fires from undried hay bales.
That's right, wet hay bales can and will spontaneously combust. It sounds counter-intuitive, but wet hay bales are more dangerous than dry hay bales, because hay actually heats up as it dries. As the hay gets hotter, it starts giving off flammable gas. The heat it is generating combined with the gas it is giving off means they could light on fire at any moment if they've been stored before fully drying.
And where is hay commonly stored? In a barn, with an attached grain silo. And that grain silo is sometimes full of fine dust. Which, like flour, can easily explode at the smallest spark or flame.
The main ingredient is bacteria feeding on the hay, which causes an exothermic reaction. Above a certain temperature the thermophilic bacteria get happy and a runaway reaction occurs. These bacteria need moisture to survive.
Essentially you're creating a compost pile unintentionally.
This phenomenon is easy to exploit actually. Laying out "sheet mulch" with 9-12" of hay on top of an opaque layer (typically newspaper or cardboard) can greatly accelerate the production rate of soil and repair degraded soils. No tilling or digging required, the mulch retains water and cuts down evaporation, and weeds are smothered by the opaque layer. This yields high quality produce without fertilizer and with a minimum of labor. The late Bill Mollison of permaculture design describes it here (@21m): https://vimeo.com/142711756
As noted earlier by schiffern, charcoal has a huge surface area, and carbon fiber has a different structure with much less surface area.
But, I'd still expect it to burn very nicely in the presence of concentrated oxygen.
Carbon fiber, is solid fibers about 5-7 microns thick and of arbitrary length. The fiber is embedded in a matrix, typically of epoxy. A typical ratio for a high-performance part would be about 64% carbon fiber and 36% epoxy. If built properly, the epoxy or other matrix material will completely encapsulate the carbon, including a thin coating on the surfaces.
That said, the first thing I'd want to do in the presence of 100% liquid oxygen is to coat the entire carbon composite to ensure that the composite and the oxygen stay apart. The epoxy itself is an organic compound, and the thickness of the coating is at most a few hundred microns (you have to be very careful sanding the surface to prep it for a more durable coating, or you'll get into the carbon).
Source: I'm a carbon fiber designer and fabricator.
https://www.youtube.com/watch?v=mBcoTqhAM_g