Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 629233 times)

Offline Joel

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #700 on: 10/08/2012 07:57 pm »
Hi! You're both right. There are 45 possible pairs of engines. There are 72 possible ways in which to choose one engine, and then choose another engine.
No, there are 36 possible pairs (engine A and engine B is the same as engine B and engine A). And 9 ways to choose a single engine. 45 in total.

EDIT: I will stop here before being banned from the forum... It's getting a bit silly....
« Last Edit: 10/08/2012 08:00 pm by Joel »

Offline cscott

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #701 on: 10/08/2012 07:57 pm »
How can an engine "explode" and yet still send telemetry to SpaceX?
Electronics is placed (due to the high sensitivity of components [mechanical, dirt, water, ...]) into very rigid housings. I guess, that the nozzles of the neighbouring have a higher risk to be damaged by an explosion (if it was one). Also due to vibrations the pcb is typically mechanically seperated by vibration dampers (can be even some special type of foam).

If I could ask a question, it would be, what "telemetry was received" means exactly. Where all sensors/actors responding? It might be, that just the engine control computer responded to the guidance computer, but most of the s/a where damaged, not responding or responding of scale.

Although the exact data isn't included in the press release, SpaceX likely knows very precisely the extent of the damage based on which sensors did/did not continue returning valid data.  You are correct that the "big brain" of the telemetry system is sequestered away someplace safe far from the engine, but the actual sensors are placed in the engine bay itself at various locations.  If you'll recall, investigators were able to reconstruct Colombia's breakup in the atmosphere by following the millisecond-by-millisecond progress of sensors going silent or returning anomalous data, starting from "tire overpressure" readings as the landing gear wheel wells heated up.  When SpaceX reviews its telemetry data, it is also reconstructing the exact nature and progress of the "pressure release" by determining what other sensors were affected, and when.  So although it's true that just "continuing to return data" doesn't tell you much by itself, SpaceX stated unequivocally "no explosion"---which means they were able to determine that the pattern of sensor failure (or non-failure) indicated that there was not a large-scale destructive event.

Although it would be lovely to see an actual millisecond-level animation of the sensor data like the Columbia investigation eventually produced, it is likely that even describing the locations of the sensors involved would be way too much information for a press release less than 24 hours after the event.  The sensor locations may also be considered proprietary information.  So to some extent we have to take their word for it: there were lots of sensors, and the pattern of those that continued reporting data (perhaps all of them) indicated that there was "no explosion".

Offline mikegi

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #702 on: 10/08/2012 07:58 pm »
Am I late with this? - http://www.spacex.com/press.php?page=20121008

"Approximately one minute and 19 seconds into last night's launch, the Falcon 9 rocket detected an anomaly on one first stage engine. Initial data suggests that one of the rocket's nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued. We know the engine did not explode, because we continued to receive data from it. Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines. Our review of flight data indicates that neither the rocket stage nor any of the other eight engines were negatively affected by this event."
Facts aren't nearly as fun as biased speculation. SpaceX's reputation is doing a whole lot better than that of many posters on this thread, that's for sure.

Offline Maciej Olesinski

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #703 on: 10/08/2012 07:58 pm »
It takes too long for SpaceX. I bet they will give us complete report with solutions ready to apply. I belive that also Orbcomm mission is successful!

Offline Antares

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #704 on: 10/08/2012 07:59 pm »
Rocket pressure vessels don't develop nice, smooth, symmetrical holes in them, unless some sort of port or fitting that's part of the existing design comes loose.  They crack, which creates stress concentrations, which open the cracks quite quickly.  EPR and explosion, especially when heat + oxidizer without fuel yields burning metal, are essentially the same.

Oh, and the post about dumping fuel inside the stage during shutdown??  If that were the design, how would that work during static fire or an on-pad abort?
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline Joel

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #705 on: 10/08/2012 08:06 pm »
Just for my understanding. Does 30 seconds of extra burn roughly equate to 30 seconds of extra gravity losses, or around 300 m/s lost delta-v?

Only if you're flying straight up. It's less of an issue if your velocity vector is more toward horizontal.

Well... divided by the square root of two if horizontal... But we are still talking about between 200 and 300 m/s lost delta-v?

What matters is how much extra time was spent flying up the vertical portion of the ascent vector.  The majority of the extra seconds of flight in this case were likely spent flying horizontally in space, during the second stage portion of the ascent.  Gravity losses in horizontal flight at orbital altitude are near-zero.  Some pitch up gravity losses likely did occur, but I wouldn't as much as expect 200 m/s.

 - Ed Kyle
But remember, that's 200m/s (or 50m/s, whathaveyou) pushing a full Dragon, etc... If the second stage was just pushing the Orbcomm bird, that 50m/s could be much more, perhaps even that whole 100-150m/s needed to push Orbcomm to the desired orbit plus margin.

Right. I forgot the changing mass. It all starts to make sense now. The engine out could have eaten up the whole second burn.

Offline cscott

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #706 on: 10/08/2012 08:13 pm »
Perhaps of interest: the SpaceX press release originally read:
"Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9’s other eight engines were impacted by this event."

Arstechnica (and my own memory) document this wording.

This was fairly quickly rewritten to:
"Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines. Our review of flight data indicates that neither the rocket stage nor any of the other eight engines were negatively affected by this event."

The rewrite makes sense, but knowing that two versions were floating around at different times might help mitigate some confusion among readers here.

Offline Chris Bergin

I'm trying to let this thread flow as freely as possible, as there are going to be a lot of differing opinions on this. I have removed a few rude posts.

Don't quote or respond to uncivil posts, report them and a moderator will remove the offending post (if it is a breach of rules).

I'll write a new article on this when we have enough info to hand. I'm working on that in L2.
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Offline JustPassingThrough

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #708 on: 10/08/2012 08:14 pm »
Rocket pressure vessels don't develop nice, smooth, symmetrical holes in them, unless some sort of port or fitting that's part of the existing design comes loose.  They crack, which creates stress concentrations, which open the cracks quite quickly.  EPR and explosion, especially when heat + oxidizer without fuel yields burning metal, are essentially the same.

Oh, and the post about dumping fuel inside the stage during shutdown??  If that were the design, how would that work during static fire or an on-pad abort?

Rocket combustors can and do develop nice round holes in them; If you have a burn through.  They normally start as a hot spot then as the wall fails the combustion gas pushes through the hole.  You end up with a hole that looks like someone took a cutting torch and cut a hole out.

Static tests for the merlin engines don't include a fairing.  On pad aborts and tests have water suppression systems running prior to shutdown. 


Offline simonbp

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #709 on: 10/08/2012 08:22 pm »
How many permutations of combinations can produce an explosion that is not an explosion but which dumps fuel maybe, and enough to cause a second stage to not restart, unless it did, but where would it go?

;)

Offline Antares

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #710 on: 10/08/2012 08:24 pm »
I still say something with unstable stress concentrations is more likely, be it pointy or with degraded material properties from heat.  Water inside the heat shield for this posited dumping?
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline cscott

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #711 on: 10/08/2012 08:26 pm »
Rocket pressure vessels don't develop nice, smooth, symmetrical holes in them, unless some sort of port or fitting that's part of the existing design comes loose.  They crack, which creates stress concentrations, which open the cracks quite quickly.  EPR and explosion, especially when heat + oxidizer without fuel yields burning metal, are essentially the same.

Sure, and the internal combustion engine in your car undergoes thousands of explosions per minute.

Containment is the significant difference.  When an "explosion" occurs in a space designed to contain it, and the containment works, it is a "pressure release".  We usually refer to the event as an "explosion" only when it is not contained and causes unexpected damage.  A boiler that pops a safety valve and vents did not "explode".  Similarly, the SpaceX event occurred within a fairing that was designed for a pressure release and behaved as expected (ie, the fairing redirected the pressure away from neighboring engines by popping off).

Quote
Oh, and the post about dumping fuel inside the stage during shutdown??  If that were the design, how would that work during static fire or an on-pad abort?

Did you watch the video on that post?  It shows exactly that.  There is a fireball and rise of pressure but usually (for the static fire or pad abort case) the pressure is redirected by the fairing but does not require a safety release.  At Max-Q the loads are different and the response is different.  It's still working as designed.

Obviously, we'd all be happier if that particular design feature didn't need to be demonstrated in flight.  But lets try to keep our heads on: the pressure drop was unexpected and an anomaly.  The various visible responses to the pressure drop (fuel venting, engine shutdown, fairing separation) were, as far as we can tell, designed features of the spacecraft performing nominally.

Offline Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #712 on: 10/08/2012 08:28 pm »
Just for my understanding. Does 30 seconds of extra burn roughly equate to 30 seconds of extra gravity losses, or around 300 m/s lost delta-v?

Only if you're flying straight up. It's less of an issue if your velocity vector is more toward horizontal.

Well... divided by the square root of two if horizontal... But we are still talking about between 200 and 300 m/s lost delta-v?

What matters is how much extra time was spent flying up the vertical portion of the ascent vector.  The majority of the extra seconds of flight in this case were likely spent flying horizontally in space, during the second stage portion of the ascent.  Gravity losses in horizontal flight at orbital altitude are near-zero.  Some pitch up gravity losses likely did occur, but I wouldn't as much as expect 200 m/s.

 - Ed Kyle
But remember, that's 200m/s (or 50m/s, whathaveyou) pushing a full Dragon, etc... If the second stage was just pushing the Orbcomm bird, that 50m/s could be much more, perhaps even that whole 100-150m/s needed to push Orbcomm to the desired orbit plus margin.

Right. I forgot the changing mass. It all starts to make sense now. The engine out could have eaten up the whole second burn.
That's what I think happened, based on the very limited information we have now. Still, I think the Orbcomm bird is in a usable orbit, if far from ideal.
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Offline sdsds

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #713 on: 10/08/2012 08:30 pm »
http://www.spacex.com/press.php?page=20121008

On net I give this release 7 out of 10 possible stars. Because it is essentially complete it gets a base score of 5 stars. It gets 1 bonus point for timeliness. It gets 3 bonus points for the sentence, "We will continue to review all flight data in order to understand the cause of the anomaly, and will devote the resources necessary to identify the problem and apply those lessons to future flights." It loses 1 point for each of the sentences, "It is worth noting that Falcon 9 shuts down two of its engines to limit acceleration to 5 g's even on a fully nominal flight. The rocket could therefore have lost another engine and still completed its mission." 5+1+3-1-1=7.
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Offline Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #714 on: 10/08/2012 08:31 pm »
http://www.spacex.com/press.php?page=20121008

On net I give this release 7 out of 10 possible stars. Because it is essentially complete it gets a base score of 5 stars. It gets 1 bonus point for timeliness. It gets 3 bonus points for the sentence, "We will continue to review all flight data in order to understand the cause of the anomaly, and will devote the resources necessary to identify the problem and apply those lessons to future flights." It loses 1 point for each of the sentences, "It is worth noting that Falcon 9 shuts down two of its engines to limit acceleration to 5 g's even on a fully nominal flight. The rocket could therefore have lost another engine and still completed its mission." 5+1+3-1-1=7.
Why does it lose a point for those? It's technically correct, isn't it?
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Offline peter-b

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #715 on: 10/08/2012 08:32 pm »
http://www.spacex.com/press.php?page=20121008

On net I give this release 7 out of 10 possible stars. Because it is essentially complete it gets a base score of 5 stars. It gets 1 bonus point for timeliness. It gets 3 bonus points for the sentence, "We will continue to review all flight data in order to understand the cause of the anomaly, and will devote the resources necessary to identify the problem and apply those lessons to future flights." It loses 1 point for each of the sentences, "It is worth noting that Falcon 9 shuts down two of its engines to limit acceleration to 5 g's even on a fully nominal flight. The rocket could therefore have lost another engine and still completed its mission." 5+1+3-1-1=7.

I'm sure SpaceX will be excited to hear how their press release scored on sdsds's arbitrary and incomprehensible press release scoring system. I on the other hand don't have a clue what you're talking about...
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Offline sdsds

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #716 on: 10/08/2012 08:34 pm »
Why does it lose a point for those? It's technically correct, isn't it?

Perhaps. But the first sentence is purely marketing spin; the second involves a hypothetical scenario which did not take place on this mission. "It's worth noting the glacier freezer could have delivered Ben and Jerry's. In which case we would have sent them "Coffee Coffee Buzz Buzz Buzz" flavor.
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Offline kniklas

It is the first F9 launch with engine failure. How problematic it is for the mission we will see....

If I were astronaut to fly with F9 with consciousness that every fourth flight there might be engine failure it would me feel very uneasy (I fully appreciate engine-out capability). Therefore SpaceX must do better then this.

If I remember correctly previous F9 launch attempt had problem with pressure drop caused by faulty check valve (?). Launch was aborted. I'm not sure if recent and previous pressure drop events in engine chamber share the same root cause.
Kamil N.

Offline Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #718 on: 10/08/2012 08:42 pm »
Why does it lose a point for those? It's technically correct, isn't it?

Perhaps. But the first sentence is purely marketing spin; the second involves a hypothetical scenario which did not take place on this mission. "It's worth noting the glacier freezer could have delivered Ben and Jerry's. In which case we would have sent them "Coffee Coffee Buzz Buzz Buzz" flavor.
It is worth noting because the first thing someone might wonder if they see that SpaceX has engine-out capability is what they would do if they lost another, and that engine-out is kind of done anyway as part of a normal launch, so it is a relatively well-exercised "feature," i.e. that it wasn't just a stroke of luck that they succeeded in spite of losing an engine but that it was due to careful engineering. And that's true, because it DOES take a lot of work to make sure engine-out is a useful capability... It doesn't come for free with all multi-engine rockets.

(That said, there is a period of time that Falcon 9 v1 can't lose an engine and still make orbit... though, presumably, that's well before Max-Q and presumably there is enough warning that they can shut down before release if the problem shows hints at ignition.)
« Last Edit: 10/08/2012 08:42 pm by Robotbeat »
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Offline iamlucky13

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #719 on: 10/08/2012 08:47 pm »
Am I late with this? - http://www.spacex.com/press.php?page=20121008

"Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines. "

Oh, that's interesting.  Are they saying that the deliberate ejection of panels is somehow part of their engine protection scheme?  I'm having a hard time visualizing how that would work.

Keep in mind, this almost certainly refers to the overall engine bay, not blowouts on the failed engine itself.

The engine bay is the space above the nozzles, which mostly-encloses the combustion chambers with the aerodynamic fairings and the debris shields between the engines, etc. See a photo with covers in place here:
http://www.wired.com/autopia/2012/05/spacex-launch-aborted-as-engine-ignition-begins/

If you have a combustion chamber or turbopump failure, that means combustion gasses or possibly even fuel and oxidizer in an enclosed space. Hot gas + nowhere to go equals increasing pressure and heat.

(the engine bay isn't even close to sealed as far as I know, but the pressure may rise faster than whatever is leaking into the bay can leak out)

That could potentially damage the other engines, or their fuel lines, actuators, and instrumentation, or even the rocket structure.

So you can design some of those panels to deliberately be the weak point in all the structure that encloses the engine bay. When the pressure reaches a certain point, the panels burst or tear off instead of the pressure reaching the point where something more important fails.

Anybody started the betting yet? My money is on turbopump RUD.

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