Author Topic: FAILURE: GSLV - GSAT-5P - December 25, 2010  (Read 152926 times)

Offline edkyle99

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #240 on: 01/01/2011 03:06 am »
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

Quote from:  GSLV Preliminary Failure Report
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
« Last Edit: 01/01/2011 03:07 am by edkyle99 »

Offline seshagirib

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #241 on: 01/01/2011 04:00 am »
^

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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Offline seshagirib

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #242 on: 01/01/2011 05:36 am »
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

Quote from:  GSLV Preliminary Failure Report
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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Offline Art LeBrun

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #243 on: 01/01/2011 05:47 am »
Short circuit anyone? Voltage spike?
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Offline sanman

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #244 on: 01/01/2011 08:57 am »
Read this:

http://www.hindu.com/2011/01/01/stories/2011010157991800.htm

Quote
Snapping 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?

Offline Jim

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #245 on: 01/01/2011 12:00 pm »

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.
« Last Edit: 01/01/2011 12:00 pm by Jim »

Offline ugordan

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #246 on: 01/01/2011 03:30 pm »
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.

Offline input~2

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #247 on: 01/01/2011 05:51 pm »
Quote from:  ISRO GSLV Preliminary failure report
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 ?

Offline sanman

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #248 on: 01/01/2011 06:16 pm »
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?

Offline Jim

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #249 on: 01/01/2011 11:47 pm »
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

Offline pradeep

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #250 on: 01/02/2011 05:50 pm »
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

Offline seshagirib

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #251 on: 01/03/2011 02:59 am »
Found this to be a informative article on stage seperation techniques:

http://daretodreamsid.blogspot.com/2010/07/stage-separation-of-space-launch.html
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Offline sanman

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #252 on: 01/03/2011 07:52 am »
ISRO seems to be constituting panels of "Eminent Experts" to go over the recent GSLV failure and to review the upcoming challenges ahead:

http://www.brahmand.com/news/ISRO-forms-eminent-panels-to-study-GSLV-F06-failure/5942/1/21.html

Heh, well it's not exactly India's Augustine Commission, but hopefully some good comes out of it.

Offline starsalor

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #253 on: 01/03/2011 10:25 am »
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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Offline cd-slam

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #254 on: 01/03/2011 11:02 am »
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.

Offline Jim

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #255 on: 01/03/2011 01:59 pm »
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. 

Offline sanman

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Offline robertross

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Re: FAILURE: GSLV - GSAT-5P - December 25, 2010
« Reply #258 on: 01/05/2011 01:58 am »

Online Salo

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« Last Edit: 01/05/2011 07:58 pm by Salo »

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