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#240
by
edkyle99
on 01 Jan, 2011 03:06
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ISRO has posted the preliminary findings report on the GSLV failure today.
Report: #GSLV Preliminary Failure Report is out - http://isro.gov.in/pressrelease/scripts/pressreleasein.aspx?Dec31_2010
The exact cause of snapping of the set of connectors, whether due to external forces like vibration, dynamic pressure is to be analysed further and pin-pointed.
So apparently no clues yet on the cause(s) of the famous connectors snapping..
The report says: "These connectors are intended to be separated only on issue of a separation command at 292 seconds after lift-off. The premature snapping of these connectors has led to stoppage of continuous flow of control commands to the First Stage control electronics, consequently leading to loss of control and break-up of the vehicle."
So how are these connectors separated at 292 seconds? Is this "snapping" actually a separation process that usually only happens at staging, but that somehow happened prematurely? The phrase "premature snapping" seems to indicate that "snapping" might be a standard procedure when it is not "premature".
- Ed Kyle
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#241
by
seshagirib
on 01 Jan, 2011 04:00
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^
Looking at the flight profile of GSLV the the 292s time mark corresponds roughly to the Stage 2 seperation.
Does any one know if (speaking generically) the electrical connectors are demated prior to pyro seperation of stages or it happens automatically due to the seperation of stages?
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#242
by
seshagirib
on 01 Jan, 2011 05:36
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ISRO has posted the preliminary findings report on the GSLV failure today.
Report: #GSLV Preliminary Failure Report is out - http://isro.gov.in/pressrelease/scripts/pressreleasein.aspx?Dec31_2010
The exact cause of snapping of the set of connectors, whether due to external forces like vibration, dynamic pressure is to be analysed further and pin-pointed.
So apparently no clues yet on the cause(s) of the famous connectors snapping..
The report says: "These connectors are intended to be separated only on issue of a separation command at 292 seconds after lift-off. The premature snapping of these connectors has led to stoppage of continuous flow of control commands to the First Stage control electronics, consequently leading to loss of control and break-up of the vehicle."
So how are these connectors separated at 292 seconds? Is this "snapping" actually a separation process that usually only happens at staging, but that somehow happened prematurely? The phrase "premature snapping" seems to indicate that "snapping" might be a standard procedure when it is not "premature".
- Ed Kyle
This could be a software error - issue of a connector separation command too early in the flight....But difficult to imagine,why the software would be messed with to that extent, for this particular flight.
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#243
by
Art LeBrun
on 01 Jan, 2011 05:47
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Short circuit anyone? Voltage spike?
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#244
by
sanman
on 01 Jan, 2011 08:57
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Read this:
http://www.hindu.com/2011/01/01/stories/2011010157991800.htmSnapping of connectors caused GSLV failure: ISRO
Staff Reporter
Programme Review and Strategy Committee set up to look into the future of the programme
The precise cause of the snapping of conductors is to be analysed further
Failure analysis panel will recommend corrective action on GSLV vehicle
BANGALORE: A Preliminary Failure Analysis Team constituted to study the flight data of GSLV-F06, which crashed seconds after its launch on December 25, said that the primary cause of the failure was “the untimely and inadvertent” snapping of a group of 10 connectors located at the base of the Russian Cryogenic stage.
The fact that all of those connectors are located at the base of the cryogenic stage can't be a coincidence. They must have been weakened by exposure to cryogenic temperatures. At those temperatures, anything will crack like glass.
I'm thinking that the aerodynamic stresses caused a cryo fuel leak in that Cryogenic Upper Stage. Otherwise, how else do you explain all 10 connectors failing nearly simultaneously?
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#245
by
Jim
on 01 Jan, 2011 12:00
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The fact that all of those connectors are located at the base of the cryogenic stage can't be a coincidence.
No, where else would they be? And no, not all of them would react the same way if exposed to cryo temps.
It could be a structural failure.
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#246
by
ugordan
on 01 Jan, 2011 15:30
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Didn't they say the cryo stage was lengthened to increase propellant load? Maybe this is a snafu with longer cables - improperly fastened, flapping around, etc.
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#247
by
input~2
on 01 Jan, 2011 17:51
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These connectors are intended to be separated only on issue of a separation command at 292 seconds after lift-off.
Is there a possibility that a modification to the software reproduced inadvertently such a separation command encoding sequence at 47.8s after lift-off ?
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#248
by
sanman
on 01 Jan, 2011 18:16
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Exactly how does stage separation occur? Through explosive bolts?
Premature stage separation is a specific type of structural failure which seems to have more possible causes associated with it than other types.
Whether the connectors failed due to premature stage separation, or whether premature stage separation occurred due to connector failure, there should be some way to discern cause from effect.
How is stage separation recorded/registered? Hopefully, there would be something in the telemetry logs which shows whether the stage separated an instant before the control signals were lost, or whether the control signals were lost before the stage separation occurred.
What are the main ways through which aerodynamic loads and turbulence are detected - purely through the inertial guidance system?
If so, then the frequency and magnitude of correction commands would be an indicator to the buildup of such forces.
But how are sheer forces detected or monitored?
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#249
by
Jim
on 01 Jan, 2011 23:47
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Exactly how does stage separation occur? Through explosive bolts?
Premature stage separation is a specific type of structural failure which seems to have more possible causes associated with it than other types.
Whether the connectors failed due to premature stage separation, or whether premature stage separation occurred due to connector failure, there should be some way to discern cause from effect.
1. How is stage separation recorded/registered? Hopefully, there would be something in the telemetry logs which shows whether the stage separated an instant before the control signals were lost, or whether the control signals were lost before the stage separation occurred.
2. What are the main ways through which aerodynamic loads and turbulence are detected - purely through the inertial guidance system?
If so, then the frequency and magnitude of correction commands would be an indicator to the buildup of such forces.
3.But how are sheer forces detected or monitored?
1. Break wires
2. Correct
3. See # 2
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#250
by
pradeep
on 02 Jan, 2011 17:50
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The report says: "These connectors are intended to be separated only on issue of a separation command at 292 seconds after lift-off. The premature snapping of these connectors has led to stoppage of continuous flow of control commands to the First Stage control electronics, consequently leading to loss of control and break-up of the vehicle."
So how are these connectors separated at 292 seconds? Is this "snapping" actually a separation process that usually only happens at staging, but that somehow happened prematurely? The phrase "premature snapping" seems to indicate that "snapping" might be a standard procedure when it is not "premature".
- Ed Kyle
As per the launch manifest for GSLV-F06, second stage burn out is at 289 seconds. So, perhaps this separation should have taken place after GS2 burnout and GS3 ignition, which makes sense since this separator is below the cryo engine and the computer is on the top.
Exactly how does stage separation occur? Through explosive bolts?
Each stage separation occurs using different methods. For GSLV-F06, it uses Flexible Linear Shaped Charge for first stage, Pyro Actuated Collet Release Mechanism for the second stage, Merman Band Bolt Cutter Mechanism for the third stage and spring thrusters for spacecraft separation.
Pradeep
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#251
by
seshagirib
on 03 Jan, 2011 02:59
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#252
by
sanman
on 03 Jan, 2011 07:52
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#253
by
starsalor
on 03 Jan, 2011 10:25
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Looks to me the rocket was not properly balanced.......then the snaps occurred. Since the rocket was stretched, it seems to be nose-heavy,thus breaking apart at maximum dynamic pressures.
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#254
by
cd-slam
on 03 Jan, 2011 11:02
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Looks to me the rocket was not properly balanced.......then the snaps occurred. Since the rocket was stretched, it seems to be nose-heavy,thus breaking apart at maximum dynamic pressures.
That's a fairly big leap of faith. Until there is evidence to the contrary, I would tend to believe the official word, premature snapping of connectors.
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#255
by
Jim
on 03 Jan, 2011 13:59
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Looks to me the rocket was not properly balanced.......then the snaps occurred. Since the rocket was stretched, it seems to be nose-heavy,thus breaking apart at maximum dynamic pressures.
No such thing as not "not properly balanced" in this case. LV's are not "balanced" fore and aft.
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#256
by
sanman
on 03 Jan, 2011 15:34
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#257
by
sanman
on 04 Jan, 2011 04:40
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#258
by
robertross
on 05 Jan, 2011 01:58
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#259
by
Salo
on 05 Jan, 2011 19:51
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