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#220
by
Jim
on 30 Dec, 2010 04:44
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May be a umbilical chord failed to unmate and somehow pulled at the cable assembly at launch.
That would be still be a connector failure
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#221
by
sanman
on 30 Dec, 2010 06:15
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This quad failure isn't credible to me, unless it was a progressive failure (1 then another then the other 2) and it was able to fly through 1 of them.
I suggest we wait for the investigation.
[Apollo13 nerdy Clint Howard voice]: "We're reading a quadruple failure! That can't happen!"
Clearly, if 4 control cables snapped, there had to be some major underlying cause. Either some big shock to break the 4 of them, or else repeated series of shocks to cause progressive failure. The latter case, due to extremely high turbulence forces caused by the enlarged faring, sound the most plausible to me.
Anyway, here's the latest from TIME:
http://www.time.com/time/world/article/0,8599,2040085,00.htmlThe article seems to mention a liquid core stage with solid strap-on boosters. Isn't it the opposite?
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#222
by
sanman
on 30 Dec, 2010 06:28
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So what are the speculative effects on turbulence forces / aerodynamic loads stemming from faring enlargement?
As a chemical engineer, I know what happens to a fluid at the interior of a pipe which suddenly transitions from a narrow diameter to a wider one - you get the pressure drop, vortices, etc, due to boundary layer separation. But that's at lower Reynolds number.
With a rocket traveling thru a slipstream with an enlarged faring at the front, you'd probably only care about boundary layer separation at lower Mach number. Once you're heavily hypersonic, then blunt-body behavior applies, and you shouldn't care about boundary layer, since the rocket is moving too fast for local pressure effects to matter much.
But Q-max is well below hypersonic velocities, isn't it?
We know the rocket broke up at ~47secs and 13km, but what was its velocity around the time of failure?
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#223
by
sdsds
on 30 Dec, 2010 06:49
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I believe indications of the Prandtl–Glauert singularity were visible in the launch telecast. Can anyone confirm that? It would imply that by the time of failure the vehicle was transonic.
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#224
by
kch
on 30 Dec, 2010 07:02
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Anyway, here's the latest from TIME:
http://www.time.com/time/world/article/0,8599,2040085,00.html
The article seems to mention a liquid core stage with solid strap-on boosters. Isn't it the opposite?
Indeed it is the opposite. It's an unusual arrangement, so the editor(s) may have thought it was a mistake and reversed it.
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#225
by
input~2
on 30 Dec, 2010 08:44
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#226
by
pradeep
on 30 Dec, 2010 08:52
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Snapping of 10 connectors led to GSLV failure: ISRO sources
Analysis of the data showed that snapping of connectors had led to the disintegration of the vehicle and it had nothing to do with the increase in the weight of the satellite, which was only marginal
from
http://netindian.in/news/2010/12/29/0009647/snapping-10-connectors-led-gslv-failure-isro-sources
I am also not a big fan of the weight causing the accident idea. GSAT-4 was 2180 kg. At 2310 kg, this satellite was only 130 kg heavier than GSAT-4. Also, adding weight does not matter as long as it is compensated by fuel or thrust.
My take is that the snapping of the connectors seem to be like an effect rather than the cause of the failure. The disintegration of the payload fairing could have led to this snapping. That could be a theory.
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#227
by
input~2
on 30 Dec, 2010 09:05
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The disintegration of the payload fairing could have led to this snapping. That could be a theory.
I don't think so: The loss of control of the boosters took place at +47s, the payload fairing disintegration took place after +50s
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#228
by
pradeep
on 30 Dec, 2010 11:33
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Do see this report-
http://mangalorean.com/news.php?newstype=local&newsid=214177"On the day of the failure it was announced the connectors relaying the command led to the rocket's failure. We have revisited and have confirmed that the connectors located between the cryogenic engine and the lower stage (engine) snapped. We have to find why the snapping happened," Nair said.
"As per the data there are no indications of any control command from the onboard computers to the rocket engines," he said.
He said simulated experiments will have to be carried out to find out why the connectors got disconnected from the rocket.
"Whether vibrations or external forces led to the snapping of connectors has to be found out. We will have to conduct simulation experiments to find that out," Nair said.
To a query as to why the ISRO was taking a long time to come out with a preliminary report, he said: "The preliminary data runs into more than 100 pages even though the flight is of around 50 seconds."
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#229
by
seshagirib
on 30 Dec, 2010 14:53
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^
quote
"
"As per the data there are no indications of any control command from the onboard computers to the rocket engines," he said.
"
At the time of failure would one expect steering commands or just commands to compensate for perturbations?
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#230
by
ugordan
on 30 Dec, 2010 16:32
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At the time of failure would one expect steering commands or just commands to compensate for perturbations?
They're one and the same. Steering commands are meant to correct for any attitude disturbances and keep the vehicle on the proper flight profile - pitch, yaw, roll for that phase of flight.
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#231
by
Targeteer
on 30 Dec, 2010 22:31
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^
quote
"
"As per the data there are no indications of any control command from the onboard computers to the rocket engines," he said.
If there were in fact NO commands from the computers to the engines as implied by the statement, the vehicle would/could not have pitched over after launch--correct? No commands would seem to have resulted in a much earlier loss of control... A loss of commands later in the launch would seem more likely, belying the quote above.
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#232
by
sanman
on 31 Dec, 2010 01:29
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Let's look more closely at this:
http://netindian.in/news/2010/12/29/0009647/snapping-10-connectors-led-gslv-failure-isro-sources"The take-off was smooth and the flight was normal till 47 seconds. But trouble arose in the next three seconds, when 10 connectors located between the second and third stage (cryogenic stage) got separated, leading to the vehicle losing controllability," the sources said.
So that sounds like something could have happened with the cryogenic upper stage (CUS), that could have caused a major problem to the connectors below it. Could a propellant tank have ruptured/leaked due to aerodynamic stresses, and then disabled those connectors/cables?
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#233
by
seshagirib
on 31 Dec, 2010 02:32
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^
quote
"
"As per the data there are no indications of any control command from the onboard computers to the rocket engines," he said.
If there were in fact NO commands from the computers to the engines as implied by the statement, the vehicle would/could not have pitched over after launch--correct? No commands would seem to have resulted in a much earlier loss of control... A loss of commands later in the launch would seem more likely, belying the quote above.
On a second reading may be we should interpret the statement as:
"....no indications fo any control command from the oboard computers (reaching) to the rocket engines" - (word in italics mine).
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#234
by
Danderman
on 31 Dec, 2010 03:15
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So that sounds like something could have happened with the cryogenic upper stage (CUS), that could have caused a major problem to the connectors below it. Could a propellant tank have ruptured/leaked due to aerodynamic stresses, and then disabled those connectors/cables?
It looks like its time to remind everyone that the third stage was experiencing a leak on the launch stand a few days before the launch. That leaking propellant had to go somewhere.
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#235
by
sanman
on 31 Dec, 2010 03:47
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Yeah, but it sounded like it was just a tiny cryo leak, or otherwise they would've aborted the launch.
The rocket lifted off fine, so it seems the connectors were working fine for those first 47 seconds. But maybe that small leak could have turned into a big leak or even a rupture as the aerodynamic stresses built up?
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#236
by
pradeep
on 31 Dec, 2010 04:23
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#237
by
seshagirib
on 31 Dec, 2010 09:47
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It looks like its time to remind everyone that the third stage was experiencing a leak on the launch stand a few days before the launch. That leaking propellant had to go somewhere.
Maybe some access panel was opened on the pad allowing moisture/dust to get into the connectors? Worse still some one forgot a wrench in the innards of the vehicle.
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#238
by
pradeep
on 31 Dec, 2010 11:05
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#239
by
input~2
on 31 Dec, 2010 12:24
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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..
