### Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 630111 times)

#### Hooperball

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #680 on: 10/08/2012 07:27 pm »
The order of events as stated in the press release:

1. The engine lost pressure suddenly.
2. The engine was commanded to shut down.
3. They continued to receive data from the engine.

They then go on to say the EPR is the cause of the fairing rupture.

That's all we know and this thread does appear to be going in circles. Perhaps we should start a Merlin failure and damage mitigation techniques thread.

S

« Last Edit: 10/08/2012 07:32 pm by Hooperball »

#### Joel

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #681 on: 10/08/2012 07:30 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?

#### ugordan

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #682 on: 10/08/2012 07:31 pm »
After an engine explodes, its non functional in every aspect of that word.

Well, generaly the part that does the exploding and the part that sends telemetry are physically separated so if the explosion/rupture is not big, it's not unreasonable to have it be left alive from a telemetry standpoint. Engine controllers have to withstand pretty rough conditions in normal operation, anyway.

#### john smith 19

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #683 on: 10/08/2012 07:33 pm »
Lucky that they had performance margin on this flight
You've used the word "luck" on several occasions and commented that Spacex would not be so lucky on "performance critical" missions.

But as for "performance critical" missions I'd guess they'd start by not carrying any *secondary* payloads (which, if the payload was that heavy or the orbit that difficult the primary customer would not agree to anyway). So the question becomes are there parts of the F9 payload/orbit operating envelope that are marginal with *all* engines operating normally and standard margins on propellants?

Do you have any *specific* examples where their indicated payload/orbit parameters are pushing the limits of the vehicles capabilities? If you don't then is there *any* reason to expect the results of such a mission to be any worse than the ones today?
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#### rklaehn

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #684 on: 10/08/2012 07:33 pm »
One other thing: losing an "edge" engine very near max-q is probably almost a worst case scenario from a control point of view. The vehicle seemed to handle that sudden loss of thrust very gracefully.

#### mduncan36

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #685 on: 10/08/2012 07:37 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."
« Last Edit: 10/08/2012 07:37 pm by mduncan36 »

#### Remes

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #686 on: 10/08/2012 07:37 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.

Quote
To me "explode" is very specific.
Depending on where it happens, what energies were released, ... to me it is not specific at all.

#### Robotbeat

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #687 on: 10/08/2012 07:38 pm »
"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, or

"engine pressure release" sounds synonymous to "explosion" to me. Maybe it wasn't a catastrophic explosion, but it definitely went out with a bang.

Think about it, if you were SpaceX, would you want to say that one of your engines "exploded"?

We're going to have six pages of discussion about the definition of "explosion" now...

In my opinion, mission-wise, a second stage restart failure, if that turns out to be the case, is more significant to potential SpaceX customers than the first stage engine shutdown, because a restart issue would be a flat out launch failure.

- Ed Kyle
BTW, I think that there's a good chance that the reason the second stage didn't restart wasn't that there was some sort of problem with the second stage but that the second stage had eaten up the delta-v losses caused by losing an engine, ensuring primary mission full success (i.e. putting Dragon at the exact right orbit) at the expense of putting the secondary payload in a lower than planned orbit.

Also, BTW, the Orbcomm secondary payload was never to be put in a regular operational orbit anyway*. It is a prototype and a test payload for the operational next-gen Orbcomm constellation. So, a lower than planned orbit should still be almost as useful to Orbcomm as the full orbit, from what I can see so far. Disappointing, of course, but should be still useful for testing out the next-gen Orbcomm constellation (a constellation of one, until the next one goes up sometime).

They probably got a really good deal on this flight.

*(This is based on the assumption that the operational constellation will be put at something other than 52 degrees... The current operational Orbcomm constellation is at mostly 45 degrees.)
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#### modemeagle

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #688 on: 10/08/2012 07:40 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?
My simulator calculated almost zero increase in gravity losses if the 1st stage compensated at 90 seconds into the flight (10 seconds after event).  I determined this would not be the best time to increase the angle of attack since your still in the atmosphere and dynamic pressure is still high.  If it waited until 160 seconds to transition from a gravity turn to a guided compensation profile then the dynamic pressure would be nearly zero and the total increase was only 100 m/s.

This is simulated data and not based on an actual Falcon 9 trajectory.  This is using a guidance system I wrote.

#### edkyle99

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #689 on: 10/08/2012 07:41 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 expect as much as 200 m/s.  Note that the pitch angle is probably within 5-15 degrees of horizontal during the latter portions of first stage flight.

- Ed Kyle
« Last Edit: 10/08/2012 07:47 pm by edkyle99 »

#### Jim

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #690 on: 10/08/2012 07:42 pm »
Do you have any *specific* examples where their indicated payload/orbit parameters are pushing the limits of the vehicles capabilities? If you don't then is there *any* reason to expect the results of such a mission to be any worse than the ones today?

Most GTO/GSO and all planetary missions
« Last Edit: 10/08/2012 07:42 pm by Jim »

#### Joel

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #691 on: 10/08/2012 07:42 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72
45

9 (9-choose-1) combinations of one engine-out. 36 (9-choose-2) combinations of two engines-out.
« Last Edit: 10/08/2012 07:48 pm by Joel »

#### mrmandias

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #692 on: 10/08/2012 07:43 pm »
Overall maybe this will calm down some of this Space X good ULA & everyone else bad I have noted about.

Certainly not, because it takes two sides to quarrel, and the anti-SpaceX side (they protest they aren't, but they protest too much) will  make hay.  Eliciting a response.

The funny thing is that everybody more or less agrees on the facts and that the engine failure is bad while the rocket continuing on is good.  All that's left is arguing about entirely subjective over-all emotional responses.  Which isn't non-partisan.  If you subtract out the partisanship, there's nothing left.

#### peter-b

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #693 on: 10/08/2012 07:46 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."

Well, now we know why there appeared to be debris.

I still think that some people in this thread are massively over-reacting to this incident.
Research Scientist (Sensors), Sharp Laboratories of Europe, UK

#### Hooperball

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #694 on: 10/08/2012 07:47 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72
45

9 (9-take-1) combinations of one engine-out. 36 (9-take-2) combinations of two engines-out.

72

9 possibilities for the first engine times 8 possibilities (8 remaining) for the second. = 72

S

#### peter-b

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #695 on: 10/08/2012 07:51 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72
45

9 (9-take-1) combinations of one engine-out. 36 (9-take-2) combinations of two engines-out.

72

9 possibilities for the first engine times 8 possibilities (8 remaining) for the second. = 72

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.
Research Scientist (Sensors), Sharp Laboratories of Europe, UK

#### Joel

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #696 on: 10/08/2012 07:51 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72
45
72
45

Math is fun! And OT. You forget that A and B is the same as B and A.

#### mrmandias

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #697 on: 10/08/2012 07:52 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.

#### Robotbeat

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #698 on: 10/08/2012 07:53 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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

#### Remes

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##### Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #699 on: 10/08/2012 07:53 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72
45

9 (9-choose-1) combinations of one engine-out. 36 (9-choose-2) combinations of two engines-out.

I respectfully disagree.

(I guess, 9-choose-2 are the binomial coefficients). That was my first guess too, but then I thought that engine 1 shutdown, followed by an engine two shutdown is not the same as the reverse, so you have to take into account the different orders, too. These are negelected by the binomial coefficients.

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