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CRS-7 Launch Update

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Re: CRS-7 Launch Update

#51

Post by SeoxyS »

DanielBMarkham wrote: post #15
sokrates wrote: post #14

As a non-native English speaker, I find the omissions of "the" very prominent and interesting in SpaceX speech. "shortly before first stage shutdown", "resulting in loss of mission", "139 seconds into flight", "some period of time following separation", "data to determine root cause" -- is this a general theme in engineering or journalism? I wonder what linguists have to say about this.

Not a linguist but a writer here who loves language. 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.

> Not a linguist but a writer here who loves language.

You're probably demonstrating this on purpose: your very first sentence is itself an example of dropping a pronoun + verb.

Re: CRS-7 Launch Update

#52

Post by jacquesm »

drzaiusapelord wrote: post #45
makmanalp wrote: post #37

Earlier quoted context omitted.

I don't think we have the ability to 100% simulate anything - I don't doubt for a second that a lot of this stuff is being simulated already, and I think you may be severely overestimating just how useful any doable simulation is in terms of catching a bug like this one. You have literally hundreds of systems working in concert and tied to more hundreds of physical components coming under extreme temperature and pres…

>You have literally hundreds of systems working in concert and tied to more hundreds of physical components coming under extreme temperature and pressure conditions This is exactly what computers are for: doing hard stuff we can't do on paper or just by real world prototype testing. I imagine this is a hard problem, but it may be so because from a time/budget perspective it may just make financial sense to let stuff…

Faster computers do not equate to magically better programs and/or programmer capabilities. The computers from Feynmans days could do finite element analysis and structural simulation on grids fine enough for just about all engineering work. It's the execution details that get you (such as an O-ring...). And nobody simulates the execution in a meaningful way simply because there isn't enough data to start your simulations with. These are human failures first, process failures second.

Re: CRS-7 Launch Update

#53

Post by Symmetry »

sokrates wrote: post #14

As a non-native English speaker, I find the omissions of "the" very prominent and interesting in SpaceX speech. "shortly before first stage shutdown", "resulting in loss of mission", "139 seconds into flight", "some period of time following separation", "data to determine root cause" -- is this a general theme in engineering or journalism? I wonder what linguists have to say about this.

In these cases the phrases are being used as proper nouns for preexisting events on the timeline. For example, I wouldn't say that I went for a walk "five minutes before the noon," I'd say "five minutes before noon." They're speaking in a jargon that treats these events the same way that you or I would talk about Monday or midnight and which also gives them precise meanings. If the main engine shut down on its own at an unexpected time then you could say "shortly before the main engine shut down." This lets you say things like "The main engine lost power 30 seconds before main engine shutdown" and be only slightly confusing rather than nonsensical.

Re: CRS-7 Launch Update

#54

Post by JshWright »

Serow225 wrote: post #49
JshWright wrote: post #29

Earlier quoted context omitted.

There are plenty of other scenarios... 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 o…

Interpreting Musk's tweet about 'counter-intuitive' meaning BLEVE would make sense to me.

Hmm... perhaps, but that seems pretty 'intuitive' to me.

Re: CRS-7 Launch Update

#55

Post by lmm »

drzaiusapelord wrote: post #32
colomon wrote: post #16

Earlier quoted context omitted.

Ugh, now imagining trying to debug a really sneaky bug that costs $100 million every time it triggers...

Stupid question perhaps, but don't we have the ability to 100% simulate the rocket physics and the code it runs on in a simulation environment? Or are they just punching out code, shoving it onto rocket controllers, and testing in the real world? 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 cor…

Fluid dynamics is still very hard to simulate, and that's where rockets go wrong.

Re: CRS-7 Launch Update

#56

Post by Symmetry »

drzaiusapelord wrote: post #32
colomon wrote: post #16

Earlier quoted context omitted.

Ugh, now imagining trying to debug a really sneaky bug that costs $100 million every time it triggers...

Stupid question perhaps, but don't we have the ability to 100% simulate the rocket physics and the code it runs on in a simulation environment? Or are they just punching out code, shoving it onto rocket controllers, and testing in the real world? 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 cor…

Science has yet to discover the ultimate physical laws that govern the universe so 100% simulation is still impossible even in theory. In practice high fidelity simulation is still hard. Here's a video about the state of the art in combustion chamber simulation and what it's current state is:

https://www.youtube.com/watch?v=txk-VO1hzBY

Re: CRS-7 Launch Update

#57

Post by ahelwer »

drzaiusapelord wrote: post #41
nkoren wrote: post #34

Earlier quoted context omitted.

Rocket physics are actually relatively trivial and, yes, can be fully simulated (and are). Rocket plumbing is always the hard part. Perhaps the threads on some connector got stripped as it was screwed together. Perhaps there was a manufacturing flaw or unexpected bit of corrosion in a particularly vital bolt. Perhaps a bit of contamination in a fuel line caused something catalytic to happen. Perhaps a bit of excess H…

I guess my point is, can we do a full simulation of every screw, material, plumbing, liquid dynamics, weather dynamics, etc and augment those with known fail scenarios and other fuzzy data to build out a real world KSP that predicts fails reliably? We should understand how things like corrosion and condensation work on a rocket engine. Considering the low cost of incredible amounts of CPU power, granular level simula…

The radar technique is possible because of the trivially-parallizable finite-difference time domain method, which most certainly does not simulate every photon (this may have been a rhetorical flourish on the part of wherever you learned this; FDTD curiously has zero error term). Nor would it simulate a wave hitting from every direction; each of those would be a separate run of the simulation.

Re: CRS-7 Launch Update

#58

Post by chromaton »

drzaiusapelord wrote: post #32
colomon wrote: post #16

Earlier quoted context omitted.

Ugh, now imagining trying to debug a really sneaky bug that costs $100 million every time it triggers...

Stupid question perhaps, but don't we have the ability to 100% simulate the rocket physics and the code it runs on in a simulation environment? Or are they just punching out code, shoving it onto rocket controllers, and testing in the real world? 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 cor…

I recall John Carmack mentioning that they tried fluid dynamic simulation with their rocket motors. It got them a general idea of how the motor would perform, but in real life the performance of the motor was significantly affected by small changes in e.g. the quality of the welds in the combustion chamber.

Re: CRS-7 Launch Update

#59

Post by grecy »

mikeash wrote: post #48
imglorp wrote: post #46

Earlier quoted context omitted.

Maybe all the cargo shots should have these systems enabled to further exercise them. It would have been nice to demonstrate capsule survival in yesterday's event.

It's not something you merely "enable." These cargo missions are using Dragon 1 capsules, whereas the manned system is Dragon 2. The abort system in Dragon 2 is integral to the capsule (it doubles as the landing system used after a normal flight) and isn't something you can just retrofit to a different vehicle.

Can Dragon 1 have parachutes?

Re: CRS-7 Launch Update

#60

Post by grecy »

Osmium wrote: post #13
arianvanp wrote: post #5

Just after the pressure event you see Dragon being slung off the rocket... If only it was possible to deploy the parachutes during launch we could've hypothetically saved the payload. 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 s…

> we could've hypothetically saved the payload. 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).

If it wasn't in dragon, how was it going to get to the ISS?
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