
SpaceX receives FAA approval for return to flight [pdf] - mhandley
https://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/SpaceX%20LLS%2017-096%20License%20and%20Orders_01_06_2017.pdf
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jxcl
This is a great video that explains the current thinking behind the cause of
the explosion:

[https://www.youtube.com/watch?v=mBcoTqhAM_g](https://www.youtube.com/watch?v=mBcoTqhAM_g)

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artursapek
Ah Scott Manley, my favorite KSPer. That guy has a talent for explaining
things.

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flexie
What is a KSPer?

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bpicolo
[https://kerbalspaceprogram.com/en/](https://kerbalspaceprogram.com/en/)

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trose
Great news! Anyone know when we can expect the next launch? I heard they're
going to test the falcon heavy this year.

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Shank
The /r/SpaceX subreddit has a good launch manifest here:
[https://www.reddit.com/r/SpaceX/wiki/launches/manifest](https://www.reddit.com/r/SpaceX/wiki/launches/manifest)

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milansuk
I can not wait for Q2 2017: Falcon Heavy "demo flight"!

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tdy721
I can! Wait, I mean... I have... been waiting... since... late 2015?

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JshWright
It's been 'next year' for ~5 years now.

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gozur88
But now it's 'this year'.

Actually, wasn't it 'this year' last year? I thought they were saying Q4 2016
early 2016.

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JshWright
Yeah, the time between 'now' and 'how far out FH is' has been slowly
converging for the past 18 months or so.

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searine
The next few months are going to be back to back launches.

Let's hope Spacex can keep the pace.

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londons_explore
I hope they have the whole thing super-practiced and can do one per week like
a big production line.

Big planes, which are of similar complexity, have production lines rolling off
one per day, so it's doable with the right processes.

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thelambentonion
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.

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msl
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.

[1]
[https://en.wikipedia.org/wiki/Soyuz-U](https://en.wikipedia.org/wiki/Soyuz-U)

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trothamel
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.

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ge96
Damn I didn't know that they were grounded. Glad to hear that they'll be
flying again.

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JshWright
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.

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robryan
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.

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JshWright
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.

They were never denied a license.

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ge96
Iridium like those Iridium flash satellites with the door-sized solar panels?
Ha

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VanillaCafe
How wrong is it to think of "carbon composite" as "charcoal"?

Because with that conceptualization, it seems like an inherent risk to store
liquid oxygen in a charcoal container on a rocket ship.

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schiffern
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](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...](http://www.popsci.com/diy/article/2009-09/most-dangerous-way-light-
grill)

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azernik
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.

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freehunter
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.

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slededit
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.

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schiffern
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](https://vimeo.com/142711756)

