Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 629361 times)

Offline Hooperball

  • Member
  • Posts: 42
  • Liked: 0
  • Likes Given: 0
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #660 on: 10/08/2012 06:53 pm »
For those who don't approve the use of the term "explosion" we may have a new acronym: EPR - Engine Pressure Release.

Not to be confused with this.


Obviously! Thanks!!


S

Online Chandonn

  • Extreme Veteran
  • Full Member
  • ****
  • Posts: 1240
  • "Pudding!!! UNLIMITED Rice Pudding!!!"
  • Lexington, Ky
  • Liked: 13
  • Likes Given: 17
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #661 on: 10/08/2012 06:54 pm »
For those who don't approve the use of the term "explosion" we may have a new acronym: EPR - Engine Pressure Release.

S

Official statement from SpaceX: "We know the engine did not explode, because we continued to receive data from it."  Did you even read it?
« Last Edit: 10/08/2012 06:55 pm by Chandonn »

Offline leetdan

  • Full Member
  • ***
  • Posts: 354
  • Space Coast
  • Liked: 298
  • Likes Given: 244
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #662 on: 10/08/2012 06:55 pm »
I've been reading this thread since launch, and it was mentioned that the Orbcomm timeline was completely absent from the F9 press kit and not public (though, of course, on L2).  Is there any chance that the Space Track data, facebook / forum speculation, and everything else about the supposed doom of the Orbcomm payload is once again due to lack of released information, as with the GNC door?

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4796
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 3339
  • Likes Given: 729
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #663 on: 10/08/2012 06:57 pm »

Quote
Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release


Could it mean that the loss of the thrust plume from engine 1 changed the flow/pressure gradient over the fairing?

Yes, a very high probability of what happened. The vehicle was still in atmosphere and there would have been a positive back pressure in the engine 1 compartment area. When engine 1 shuts down the back pressure from the plume would drop suddenly causing a rapid pressure drop, an almost explosive pressure event (here I mean a very rapid and large pressure change not an explosion) occurring on the outside of the faring as related to the pressure on the inside of the faring. All it would take is enough flexing in a a near max Q environment and the engine faring would shred.

As far as engine pressure loss it only means that a pressure sensor backed by a simultaneous reading from the backup pressure sensor detected a lower pressure than the limits allowed for the engine operation. Merlin engines are highly instrumented like the Shuttle's RS-25s because they were meant to be a man rated system. The engine controllers and system responses are also designed with that end goal in mind.


Maybe only a nit, but they didn't say engine pressure "loss," which I would expect them to say in case of low chamber pressure. They say pressure "release," which seems to me a euphemism for something breaking apart inside the engine and unleashing enough force to blow the fairing off.
« Last Edit: 10/08/2012 07:00 pm by Kabloona »

Online ugordan

  • Senior Member
  • *****
  • Posts: 8338
    • My mainly Cassini image gallery
  • Liked: 3163
  • Likes Given: 700
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #664 on: 10/08/2012 06:59 pm »
To what degree would this event be mitigated, or not, with the new engine configuration of F9 V1.1?  (at least with what we know thus far)

We know nothing much at this point other than:
1) engine #1 experienced a rapid pressure drop and was commanded to shut down
2) engine pressure release or EPR (TM), caused the fairing to blow off

Now, Occam's razor would suggest that the pressure loss is in the engine is directly responsible for the fairing. i.e. that by the time the engine was commanded to shut down, the fairing was already coming off.

Video shows everything happening virtually instantaneously, there is no visible engine plume decay before EPR that would suggest it was the lack of backpressure that caused the fairing to collapse. It looks to me the engine shutdown follows first visual indications of failure, not precedes it.

In either case, the root cause appears to be pressure loss in the engine and I don't see why a new engine arrangement alone would alleviate that.

Offline Avron

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 4930
  • Liked: 156
  • Likes Given: 159
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #665 on: 10/08/2012 06:59 pm »
I've been reading this thread since launch, and it was mentioned that the Orbcomm timeline was completely absent from the F9 press kit and not public (though, of course, on L2).  Is there any chance that the Space Track data, facebook / forum speculation, and everything else about the supposed doom of the Orbcomm payload is once again due to lack of released information, as with the GNC door?

been looking for Orbcomm FM44  .. don't see any data yet..

Offline rklaehn

  • interplanetary telemetry plumber
  • Full Member
  • ****
  • Posts: 1259
  • germany
  • Liked: 191
  • Likes Given: 314
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #666 on: 10/08/2012 07:01 pm »
Official statement from SpaceX: "no explosion".  They continued to receive telemetry from the engine after the event.  Did you even read it?

Well, a very quick increase in pressure that leads to structural damage of rugged components that are meant to survive supersonic airflow (the fairing) could be called an explosion according to the definition of the word. http://en.wikipedia.org/wiki/Explosion.

Offline JustPassingThrough

  • Member
  • Posts: 2
  • Liked: 0
  • Likes Given: 0
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #667 on: 10/08/2012 07:10 pm »
  This may have been mentioned already but most likely the debris is just external fairing.  When you shut down an engine with a turbo pump you don't just slam the fuel valves shut.  You have to bypass the injector and do something with the fuel as the turbo pump spools down.

That fuel is dumped.  If it gets contained in the fairing you're going to have an overpressure event as seen at launch.   The fact that it happened around Max-Q just makes it more difficult for those trapped gasses to escape. If the engine shut down happened 60 seconds later it probably wouldn't have done anything.

Watch this test video of the Merlin 1C engine and go to about 2:53 second when they shut down the engine.. You can see just such an event occur as the dumped fuels cause a pressure pulse when the gases ignite outside of the chamber.  (external fuel dump igniting)

You can also see the fuel dump as the turbo pump spools down.  Which is clearly visible in the flight footage.. 



I think the events are probably just as they said.  An engine lost chamber pressure when something caused the combustor to fail.  This initial gas pulse from the leaking chamber is seen in the video.  The computer shut down the engine and the propellant was diverted to a dump line this dumped fuel built up in the fairing and ignited causing a pressure pulse that tore off a section of the fairing. 

A few seconds later the turbo pump spooled down and the fuel dumping stopped. The INU made the adjustments it needed to get the Delta-V required.

Eric

Offline peter-b

  • Dr. Peter Brett
  • Full Member
  • ****
  • Posts: 651
  • Oxford, UK
  • Liked: 18
  • Likes Given: 74
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #668 on: 10/08/2012 07:12 pm »
This thread has truly jumped the shark, now that people appear to be arguing over which misreading of SpaceX's press releases lets them complain most bitterly about how SpaceX is run by terribly irresponsible naifs who clearly don't know the first thing about anything and should be shut down for the safety of the public.

 :P

Seriously, though, insisting on an interpretation that "pressure release" really means "explosion" implies that you are also claiming that SpaceX are wilfully lying in press releases.
Research Scientist (Sensors), Sharp Laboratories of Europe, UK

Online JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10312
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1114
  • Likes Given: 656
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #669 on: 10/08/2012 07:13 pm »
We're going to have six pages of discussion about the definition of "explosion" now...

...or "detonated"...
Sometimes I just flat out don't get it.

Offline savuporo

  • Senior Member
  • *****
  • Posts: 5152
  • Liked: 1000
  • Likes Given: 342
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #670 on: 10/08/2012 07:14 pm »
It didn't explode, just blew itself to bits.
Briz-M market value recovered a little last night and CZ-4C is as strong as ever.
Orion - the first and only manned not-too-deep-space craft

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 14776
  • Liked: 7293
  • Likes Given: 1175
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #671 on: 10/08/2012 07:17 pm »
It didn't explode, just blew itself to bits.

This was clearly not the case.

 - Ed Kyle

Offline titanmiller

  • Member
  • Posts: 27
  • Liked: 4
  • Likes Given: 0
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #672 on: 10/08/2012 07:18 pm »
I've been reading this thread since launch, and it was mentioned that the Orbcomm timeline was completely absent from the F9 press kit and not public (though, of course, on L2).  Is there any chance that the Space Track data, facebook / forum speculation, and everything else about the supposed doom of the Orbcomm payload is once again due to lack of released information, as with the GNC door?

Is there any reason to assume that the second burn had to happen right away? What prevents the second stage from doing its second burn 24 hours later...battery power?

Online ugordan

  • Senior Member
  • *****
  • Posts: 8338
    • My mainly Cassini image gallery
  • Liked: 3163
  • Likes Given: 700
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #673 on: 10/08/2012 07:19 pm »
battery power?

... LOX boiloff, inertial platform drift...

Offline Joel

  • Full Member
  • ****
  • Posts: 532
  • Wisconsin
  • Liked: 44
  • Likes Given: 42
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #674 on: 10/08/2012 07:24 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?

Offline Remes

  • Full Member
  • ***
  • Posts: 377
  • Germany
  • Liked: 176
  • Likes Given: 130
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #675 on: 10/08/2012 07:25 pm »
You have 9 engines. There are a few hundred of combinations of 1-2 engines out before shutdown
72


(before shutdown-> n(n-1)

9 possibilities for the first engine out,  8 remaining for the second:

1-2, 1-3, 1-4, ..., 1-9   (8 possibilities)

2-1, 2-3, ...

3-1, 3-2, ...

...

9-1, 9-2, ... , 9-8

total of 9*(9-1). Even less, if the sw-developers take symmetries into acount.)


Quote
and a couple more out after it. [shutdown]
Right, it increases the number of scenarios to be handled.

For sure they would shut down (in a planned way) two opposing engines. Things gets a little bit more difficult, if the center engine was shut down early. As the thrust vector needs to go through the center of gravity, they would need to change the angle of the rocket to the flight path. As it is happening after 160 seconds, it shouldn't matter any more (I guess)?



Edit: n*(n-1)+9

if you take single engine shutdowns into account.
« Last Edit: 10/08/2012 07:29 pm by Remes »

Offline Herb Schaltegger


Well, a very quick increase in pressure that leads to structural damage of rugged components that are meant to survive supersonic airflow (the fairing) could be called an explosion according to the definition of the word. http://en.wikipedia.org/wiki/Explosion.

Nit (maybe not so minor, actually): Having not seen supersonic wind tunnel imagery of the F9 configuration at all, let alone throughout the entire flight regime, the fairing itself may not even have been experiencing supersonic flow at the time of the incident, depending on where the closest shock has attached itself to the vehicle. Flow behind the shock is, of course, subsonic.  And even if the shock was attached at the leading edge of the fairing at the time, the flow behind it would be subsonic and certainly fairly turbulent as well; any significant pressure surges next to or immediately aft of the fairing will (and quite probably did) cause a change in structural loading of the fairing and resultant failure.
« Last Edit: 10/08/2012 07:26 pm by Herb Schaltegger »
Ad astra per aspirin ...

Offline rcoppola

  • Senior Member
  • *****
  • Posts: 2327
  • USA
  • Liked: 1883
  • Likes Given: 832
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #677 on: 10/08/2012 07:25 pm »
To what degree would this event be mitigated, or not, with the new engine configuration of F9 V1.1?  (at least with what we know thus far)

We know nothing much at this point other than:
1) engine #1 experienced a rapid pressure drop and was commanded to shut down
2) engine pressure release or EPR (TM), caused the fairing to blow off

Now, Occam's razor would suggest that the pressure loss is in the engine is directly responsible for the fairing. i.e. that by the time the engine was commanded to shut down, the fairing was already coming off.

Video shows everything happening virtually instantaneously, there is no visible engine plume decay before EPR that would suggest it was the lack of backpressure that caused the fairing to collapse. It looks to me the engine shutdown follows first visual indications of failure, not precedes it.

In either case, the root cause appears to be pressure loss in the engine and I don't see why a new engine arrangement alone would alleviate that.
Pardon, let me be more specific.
We do know that the fairing was blown out due to some pressure release scenario. The F9 V1.1 has a new faring design to accommodate the new engine configuration. I am curious as to what would happen if this event occurred within the context of the new faring design and engine configuration. Either way, I'm sure some additional dynamic load tests among others will be cycled into V1.1 simulations.
Sail the oceans of space and set foot upon new lands!
http://www.stormsurgemedia.com

Online ugordan

  • Senior Member
  • *****
  • Posts: 8338
    • My mainly Cassini image gallery
  • Liked: 3163
  • Likes Given: 700
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #678 on: 10/08/2012 07:26 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.

Offline happyflower

  • Full Member
  • **
  • Posts: 202
  • Earth
  • Liked: 53
  • Likes Given: 51
Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #679 on: 10/08/2012 07:27 pm »
How can an engine "explode" and yet still send telemetry to SpaceX? To me "explode" is very specific. After an engine explodes, its non functional in every aspect of that word.

Tags:
 

Advertisement NovaTech
Advertisement SkyTale Software GmbH
Advertisement Northrop Grumman
Advertisement
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1