4:09 AM - 29 Jun 2015
(There are similar stories about debugging stuff on the various Martian rovers, but Cooper's book is a very good treatment...).
I'm curious as to the QA system used here. I imagine with proper simulation this should have been catchable. I wonder if SpaceX's low cost approach means cutting certain corners and situations like these where catchable issues make it into the wild because of the difficulty of rocketry in general with the added difficulty of cheap spaceflight tacked on.
I really hope they didn't just find themselves in a STS-51-L moment where it'll take months to truly iron out the root issues. Thank goodness there was no loss of life and SpaceX's stack isn't man rated yet.
I'm seeing a lot of folks dropping articles. It's also becoming quite common to eliminate pronouns at the beginning of sentences, i.e., instead of "I went down to the store" you write "Went to the store"
I use this purposefully to jar the reader. I have no idea what the underlying linguistic reasons are.
You're probably demonstrating this on purpose: your very first sentence is itself an example of dropping a pronoun + verb.
It's considered standard to write in formal, passive, third-person tone. [2]
During undergrad, I was constantly drilled to make my writings as concise as possible.
[1] http://www2.aje.com/en/education/other-resources/articles/ed... [2] http://writingcenter.unc.edu/handouts/passive-voice/
They almost feel like "uncountable" nouns, but I'm not sure. "Flight" can be countable, but as a generalized state/phase, I think it wouldn't be. It doesn't sound strange to me (a native speaker).
It would not be wrong to use "the" for many/all of these cases, but it would have changed the meaning, somewhat.
[1] http://www.edufind.com/english-grammar/definite-article/
Sounds like they are trying to suggest that if there had been people in the capsule they would have survived...
They intentionally disable ("safe") the parachute system during the launch phase, but from the rumors I'm hearing coming out of SpaceX, if they had been enabled, this capsule would have survived.
I wonder if the launch abort mechanism on the Dragon V2 would've been of any help here too to jettison it safely away from the rocket.
I read the rocket was around maximum dynamic pressure during the event (Or just after?) and I'm not sure if it would stand such forces of a jettison during such time.
The other meme is there are or have been rockets or overall systems with flight profiles and designs that have unsurvivable portions of the flight. Or only extremely theoretically survivable. Think of the old shuttle system, for example. A RTLS abort was theoretically survivable, but lets be realistic here... However the space-x guys are extremely proud that they designed an overall system that has no unsurvivable by design flight portions, and also very proud that they did a test flight with a separation near max-q specifically to prove it would work just fine even at max-q...
One interesting problem with a structural failure at that speed is it could be hard computationally to tell the difference between some irrelevant pogo-ing or vibration vs 50 ms later half the rocket is flying sideways, at which point it might be unsurvivable. Bad car analogy is I can jump out of an airplane with a parachute at 100 MPH and all turns out just fine, but randomly getting tossed out of a 100 MPH car isn't going to likely end very well even if under ideal conditions its no big deal.
The in-flight abort test for Dragon v2 is scheduled to occur later this year. It hasn't occurred yet. https://en.wikipedia.org/wiki/Dragon_V2#Flight_testing
Also note that Dragon v2 was not on this mission and won't fly to space for a while. This was a Dragon v1 mission. Dragon v1 is unmanned and has no launch abort capability.
As I understand it, the primary payload (the new international docking adaptor for the ISS) wasn't in the Dragon capsule itself, so it wouldn't have been saved even if the Dragon was recovered (sadly).
Option 1 is based on the fact that it's constantly evaporating and needs to vent. This seems really unlikely given that it passed all test on the pad 2 minutes before. It also sounds like this was likely ruled out based on Elon's tweet about a "counter intuitive cause".
Option 2 sounds like fire or flames due to fuel leakage or something, but then realize that this is the second stage and all the action is going on 100 or more feet down in the first stage. They also have a camera on the 2nd stage engine which was shown shortly before the incident and nothing was going on in there. I wonder what the in-tank camera showed.
It seem that to get the extra energy into the tank, something must have fired up early. But if there's one thing Spacex seems to have a lot of it's data. Aside from a breech letting external air in (like the last shuttle accident), how do you get enough added energy into a tank to build pressure to the breaking point? In 2 minutes.
The IDA is the heaviest thing they have ever carried in the trunk, AFAIK. Maybe its mounting bracket failed and it impacted the top of the second stage, buckling the LOX tank. A suddenly induced crack allowed some LOX to escape (the initial 'puff'), and the suddenly reduced pressure allowed the rest of the LOX to boil off and the tank to BLEVE, causing the catastrophic failure of the second stage.
Obviously this is a completely theoretical scenario, but it's one of many I could dream up...
EDIT: While is is a fairly technical discussion, I realize I got a little heavy handed with the acronyms there...
IDA: https://en.wikipedia.org/wiki/International_Docking_Adapter
LOX: https://en.wikipedia.org/wiki/Liquid_oxygen
BLEVE: https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosionExample footage here: https://youtu.be/p7x-SumbynI?t=25m45s