8 ms·

CRS-7 Launch Update

67 points by chiachun 11y ago

dabeeeenster 11y ago
"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...
- mrfusion 11y ago
  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?
  - dabeeeenster 11y ago
    I think that might be a stretch but I don't think they care about that half as much.
  - lmm 11y ago
    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.
- dlgeek 11y ago
  The manned capsule has a powered abort system, and this one doesn't, so they really don't need to suggest anything (since a failure here would not be reflective of the surviviability of Dragon2). 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.
  - imglorp 11y ago
    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.
    - mikeash 11y ago
      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.
      - grecy 11y ago
        Can Dragon 1 have parachutes?
        mikeash 11y ago
        Yes, and it does on every flight since it's used to return things from the space station back to Earth. However an abort system also needs something to move the capsule away from the (probably exploding) rocket when something goes wrong, which is typically a strong and short-firing rocket on the capsule itself. In this particular case, it sounds like Dragon survived and probably could have been recovered using the parachutes, but they weren't armed since survival without an abort system isn't something they really try for. It would be interesting to make the attempt, but not informative for manned flights since those will have a proper abort system.
        grecy 11y ago
        Interesting, thanks. It would be interesting to know if they can remotely trigger the parachutes - i.e. in this case after it had fallen a ways they could have triggered them - even just to see what would happen.
dlgeek 11y ago
For those who are also having issues loading the site: Nothing that wasn't already released via Twitter or yesterday's press conference.
arianvanp 11y ago
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 sure if it would stand such forces of a jettison during such time.
- JshWright 11y ago
  No, Max-Q is much earlier in the flight. They were very close to the end of the first stage burn.
- deleted 11y ago
  [deleted]
- VLM 11y ago
  WRT max-Q its a meme that won't go away because the most "interesting" thing on the public PR timelines before the incident was max-q. However dynamic pressure drops off extremely quickly due to altitude (low air pressure) and max-Q was a good while before the incident, so it wasn't a direct issue. It could obviously be an indirect issue if something started to buckle a minute previous or shook loose and for whatever reason a minute later it burst, perhaps as pressure built up or something. 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.
beltex 11y ago
"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 https://twitter.com/elonmusk/status/615431934345216001
- colomon 11y ago
  Ugh, now imagining trying to debug a really sneaky bug that costs $100 million every time it triggers...
  - kabdib 11y ago
    I recommend Henry S.F. Cooper's book _The Morning Star_, which is about debugging hardware failures and OS race conditions on a spacecraft orbiting Venus. (There are similar stories about debugging stuff on the various Martian rovers, but Cooper's book is a very good treatment...).
    - twistedpair 11y ago
      It's actually "The Evening Star" Grab it used for $0.75 http://product.half.ebay.com/The-Evening-Star-Venus-Observed-by-Henry-S-Jr-Cooper-1993-Hardcover/145419 http://product.half.ebay.com/The-Evening-Star-Venus-Observed...
    - alphadevx 11y ago
      I think you mean The Evening Star, marvelous book: http://amzn.to/1Hq8TcX http://amzn.to/1Hq8TcX
    - kabdib 11y ago
      I stand corrected. Written in haste. Cooper is a wonderful writer, I've got all of his books :-)
  - drzaiusapelord 11y ago
    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.
sokrates 11y ago
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.
- DanielBMarkham 11y ago
  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.
  - rezistik 11y ago
    Implied pronouns, perhaps a trend from Facebook usage? On Facebook and Twitter you have an implied "I" that makes saying you did something redundant. This could transfer over to other formats of conversation.
    - nitrogen 11y ago
      Other languages are a bit ahead of English in that regard, but their conjugations make it clear who the subject is.
  - SeoxyS 11y ago
    > 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.
- termain 11y ago
  It's how engineers talk in this context.
chaostheory 11y ago
... and people think debugging pure software problems are hard.
phkahler 11y ago
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 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.
- JshWright 11y ago
  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 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_explosion
  - Serow225 11y ago
    Interpreting Musk's tweet about 'counter-intuitive' meaning BLEVE would make sense to me.
    - JshWright 11y ago

67 points by chiachun 11y ago

"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...

mrfusion 11y ago
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?
- dabeeeenster 11y ago
  I think that might be a stretch but I don't think they care about that half as much.
- lmm 11y ago
  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.
dlgeek 11y ago
The manned capsule has a powered abort system, and this one doesn't, so they really don't need to suggest anything (since a failure here would not be reflective of the surviviability of Dragon2). 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.
- imglorp 11y ago
  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.
  - mikeash 11y ago
    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.
    - grecy 11y ago
      Can Dragon 1 have parachutes?
      - mikeash 11y ago
        Yes, and it does on every flight since it's used to return things from the space station back to Earth. However an abort system also needs something to move the capsule away from the (probably exploding) rocket when something goes wrong, which is typically a strong and short-firing rocket on the capsule itself. In this particular case, it sounds like Dragon survived and probably could have been recovered using the parachutes, but they weren't armed since survival without an abort system isn't something they really try for. It would be interesting to make the attempt, but not informative for manned flights since those will have a proper abort system.
        grecy 11y ago
        Interesting, thanks. It would be interesting to know if they can remotely trigger the parachutes - i.e. in this case after it had fallen a ways they could have triggered them - even just to see what would happen.

dlgeek 11y ago

For those who are also having issues loading the site: Nothing that wasn't already released via Twitter or yesterday's press conference.

arianvanp 11y ago

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 sure if it would stand such forces of a jettison during such time.

JshWright 11y ago
No, Max-Q is much earlier in the flight. They were very close to the end of the first stage burn.
deleted 11y ago
[deleted]
VLM 11y ago
WRT max-Q its a meme that won't go away because the most "interesting" thing on the public PR timelines before the incident was max-q. However dynamic pressure drops off extremely quickly due to altitude (low air pressure) and max-Q was a good while before the incident, so it wasn't a direct issue. It could obviously be an indirect issue if something started to buckle a minute previous or shook loose and for whatever reason a minute later it burst, perhaps as pressure built up or something. 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.

beltex 11y ago

"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 https://twitter.com/elonmusk/status/615431934345216001

colomon 11y ago
Ugh, now imagining trying to debug a really sneaky bug that costs $100 million every time it triggers...
- kabdib 11y ago
  I recommend Henry S.F. Cooper's book _The Morning Star_, which is about debugging hardware failures and OS race conditions on a spacecraft orbiting Venus. (There are similar stories about debugging stuff on the various Martian rovers, but Cooper's book is a very good treatment...).
  - twistedpair 11y ago
    It's actually "The Evening Star" Grab it used for $0.75 http://product.half.ebay.com/The-Evening-Star-Venus-Observed-by-Henry-S-Jr-Cooper-1993-Hardcover/145419 http://product.half.ebay.com/The-Evening-Star-Venus-Observed...
  - alphadevx 11y ago
    I think you mean The Evening Star, marvelous book: http://amzn.to/1Hq8TcX http://amzn.to/1Hq8TcX
  - kabdib 11y ago
    I stand corrected. Written in haste. Cooper is a wonderful writer, I've got all of his books :-)
- drzaiusapelord 11y ago
  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.

sokrates 11y ago

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.

DanielBMarkham 11y ago
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.
- rezistik 11y ago
  Implied pronouns, perhaps a trend from Facebook usage? On Facebook and Twitter you have an implied "I" that makes saying you did something redundant. This could transfer over to other formats of conversation.
  - nitrogen 11y ago
    Other languages are a bit ahead of English in that regard, but their conjugations make it clear who the subject is.
- SeoxyS 11y ago
  > 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.
termain 11y ago
It's how engineers talk in this context.

chaostheory 11y ago

... and people think debugging pure software problems are hard.

phkahler 11y ago

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 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.

JshWright 11y ago
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 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_explosion
- Serow225 11y ago
  Interpreting Musk's tweet about 'counter-intuitive' meaning BLEVE would make sense to me.
  - JshWright 11y ago