Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

CRS-7 Launch Update

spacex.com

Post reply on HN
Print view View original

31–40 of 83 posts

Re: CRS-7 Launch Update

#31

Post by Serow225 »

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.

It's standard in military debriefings (aerospace at least), especially for flight test debriefings. The flight test pilots I've worked with, mostly former U.S. Navy test pilots, all spoke like this during their debriefings and wrote in the same way for their flight logs, report-outs, etc.

Re: CRS-7 Launch Update

#32

Post by drzaiusapelord »

colomon wrote: post #16
beltex wrote: post #12

"Cause still unknown after several thousand engineering-hours of review. Now parsing data with a hex editor to recover final milliseconds." 4:09 AM - 29 Jun 2015 https://twitter.com/elonmusk/status/615431934345216001

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 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.

Re: CRS-7 Launch Update

#33

Post by nkoren »

rwhitman wrote: post #30
beltex wrote: post #12

"Cause still unknown after several thousand engineering-hours of review. Now parsing data with a hex editor to recover final milliseconds." 4:09 AM - 29 Jun 2015 https://twitter.com/elonmusk/status/615431934345216001

After watching the press conference yesterday I got the sense that Musk's tweets aren't particularly helpful for SpaceX press relations

The thing is -- despite all the "Iron Man" winks and glamour of being a billionaire who wants to colonise Mars, etc. -- Elon is truly, deep down, a nerd's nerd. Which means that his respect for the PR department is probably roughly proportional to how much duct tape they've wrapped around his head.

Re: CRS-7 Launch Update

#34

Post by nkoren »

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…

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 H20 condensation in a LOX valve caused an ice dam to form and the supply line to over-pressurise. These are the sort of problems which bring rockets down: really damned complicated plumbing problems.

Re: CRS-7 Launch Update

#36

Post by fche »

phkahler wrote: post #21

My thoughts on this. Overpressure in the LOX tank could be due to 1) failure to vent properly or 2) something heating it up. 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 fir…

Did Jack Swigert stowaway on board to do a cryo-stir?

Re: CRS-7 Launch Update

#37

Post by makmanalp »

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 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 pressure conditions, some of which can interact in the weirdest and most unexpected ways - certainly not ones you'd always think to model. The chances that any one of those does something unexpected is not low, and the chances that it cascades into a much larger failure is non-significant.

edit: It's also sometimes a human problem - thousands of people working on this together, and all sorts of different incentives. Here's a famous example of a failure, and the PR kerfuffle that ensued: https://en.wikipedia.org/wiki/Rogers_Commission_Report

Quoth Feynman:

"It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management. What are the causes and consequences of this lack of agreement? Since 1 part in 100,000 would imply that one could put a Shuttle up each day for 300 years expecting to lose only one, we could properly ask "What is the cause of management's fantastic faith in the machinery? .. It would appear that, for whatever purpose, be it for internal or external consumption, the management of NASA exaggerates the reliability of its product, to the point of fantasy."

Re: CRS-7 Launch Update

#38

Post by timsally »

anotherangrydev wrote: post #35
beltex wrote: post #12

"Cause still unknown after several thousand engineering-hours of review. Now parsing data with a hex editor to recover final milliseconds." 4:09 AM - 29 Jun 2015 https://twitter.com/elonmusk/status/615431934345216001

TBH, that hex editor thing sounds like bs.

Can you be more specific? If you have a partial piece of data (say because the data was streaming and a rocket exploded), the parser for that data is unlikely to work out of the box. Hence the use of a hex editor.

Re: CRS-7 Launch Update

#39

Post by lmm »

mrfusion wrote: post #4
dabeeeenster wrote: post #2

"Preliminary analysis suggests the vehicle experienced an overpressure event in the upper stage liquid oxygen tank approximately 139 seconds into flight. Telemetry indicates first stage flight was nominal and that Dragon remained healthy for some period of time following separation." Sounds like they are trying to suggest that if there had been people in the capsule they would have survived...

Also the first stage might have survived and returned to landing if it had known about the trouble and detached earlier? Or am I misunderstanding?

If the second stage just hadn't been there then the first stage might have survived and landed. But I'm not sure there is any way to "detach early", and you'd have the problem of having too much fuel left over in the first stage. I doubt it's designed to land in those circumstances (why would it be?), so it probably couldn't.

Re: CRS-7 Launch Update

#40

Post by anotherangrydev »

timsally wrote: post #38
anotherangrydev wrote: post #35

Earlier quoted context omitted.

TBH, that hex editor thing sounds like bs.

Can you be more specific? If you have a partial piece of data (say because the data was streaming and a rocket exploded), the parser for that data is unlikely to work out of the box. Hence the use of a hex editor.

Yeah, but why not write your own temporary parser or whatever. They (should) have top-class software engineers in there, why they don't just make a quick and dirty script to sort out whatever they're looking for?

IDK, that tweet felt like when you're watching a movie and then the 'hacker' comes around and you see a lot of props on the screen that are designed to excite 'geeks'. Like, right now, a lot of guys should be like: "OMG OMG! They are looking at the hex code directly! Damn, that is so looooooow-level, they call it rocket science for a reason!"

Anyway, hopefully they find the problem; whether with hex editors or not SpaceX is really doing cool stuff.

Post reply on HN