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#160
by
input~2
on 25 Dec, 2010 18:45
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#161
by
input~2
on 25 Dec, 2010 19:08
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So hypotheses I see talked about here are:
1) loss of command path between flight computer and TVC
2) loss of structural integrity on a strap-on, leading to asymmetric thrust - initial loss potentially due to turbopump letting go
3) loss of connection between core and strap-ons, structural or command
I'd like to see supporting or refuting evidence for these. And, valid additional hypotheses from established NSF members.
Where does your #2 come from?
Reply #137. Speculation about turbopump contribution comes from discussions among colleagues this morning.
You mean Reply #138, but I don't think this view has been backed up.
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#162
by
input~2
on 25 Dec, 2010 19:31
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#163
by
satlaunch
on 25 Dec, 2010 21:47
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Probably some GEO payloads will be moved to another commercial providers. There were rumours stating talks for launch Insat 3D with Ariane 5.
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#164
by
sanman
on 25 Dec, 2010 23:02
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Personally, I think that the GSLV-Mk2 should be abandoned, and that ISRO should simply move past this failure to the GSLV-Mk3, which is shorter and fatter.
The fact that GSLV-Mk2 was lengthened and made a little top-heavier for this flight with a larger faring (ie. to accommodate higher payload), makes these things look like they would have all contributed to the added stresses that could have tipped things past the failure point during that period of maximum aerodynamic stress.
I think shorter and fatter is okay for a rocket, since it's punching out of the atmosphere sooner rather than later. If you're making a hypersonic aircraft, let that be long and skinny, for prolonged atmospheric flight path.
I think ISRO should try to regain the initiative and move to directly flight test the GSLV-Mk3, albeit with a dummy payload rather than an expensive telecom satellite.
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#165
by
William Graham
on 25 Dec, 2010 23:07
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The fact that GSLV-Mk2 was lengthened and made a little top-heavier for this flight
This was a Mk.I
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#166
by
sanman
on 25 Dec, 2010 23:14
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This was a Mk.I
Alright, but the same difference applies. The GSLV-Mk3 is shorter and wider compared to this thing, and thus less likely to suffer from the same scenario. The fact that this rocket was lengthened and made to carry a heavier payload with a wider faring at the top would make it more unstable aerodynamically. I think that ISRO simply failed to gauge just how more unstable it would be.
Snapping of bolts and/or control cables - these all sound like things that could happen under excessive aerodynamic stress/vibration/shock.
Better to go with a design that lends itself towards more reliability. Shorter and fatter seems okay for something that's leaving the atmosphere soon anyway. Longer, thinner and more top-heavy seems inherently more problematic.
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#167
by
tu8ca
on 25 Dec, 2010 23:35
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Better to go with a design that lends itself towards more reliability. Shorter and fatter seems okay for something that's leaving the atmosphere soon anyway. Longer, thinner and more top-heavy seems inherently more problematic.
"Longer, thinner and more top-heavy" is actually more stable, since its COG is further ahead of its COP. Probably less stiff though.
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#168
by
Lars_J
on 25 Dec, 2010 23:55
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I'm curious - the configuration of this LV seems pretty unique (liquid boosters for a solid core) - or is this not so rare?
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#169
by
Skyrocket
on 26 Dec, 2010 00:13
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I'm curious - the configuration of this LV seems pretty unique (liquid boosters for a solid core) - or is this not so rare?
In fact, it is rare: GSLV Mk.1 and Mk.2 are the only launch vehicles to use a solid core with liquid boosters.
Even more strange, the boosters have a longer burn time than the core. Suboptimal, as the burned out core has to be carried further on and can not be jettisoned before the liquid boosters have burned out too.
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#170
by
kanaka
on 26 Dec, 2010 00:23
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Pals!!! Please let ISRO breath. I think ISRO was over ambitious in projecting themselves or rather say in their hurried show-put up with out bothering about their basic ground work which is very week. The basic ground work and rehearser should be made perfect (which was some what missing) before projection. Analysis of cause of failure should be done from the root in all aspects. Appropriate regress ground testing should be done with all parameters (including those that effect in flight) should have been done. I suggest ISRO should concentrate on Indigenous Cryogenic Engine and test it on PSLV first.
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#171
by
sanman
on 26 Dec, 2010 00:29
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In fact, it is rare: GSLV Mk.1 and Mk.2 are the only launch vehicles to use a solid core with liquid boosters.
Even more strange, the boosters have a longer burn time than the core. Suboptimal, as the burned out core has to be carried further on and can not be jettisoned before the liquid boosters have burned out too.
Gee, I wonder if the design could be modified to allow for jettison of the solid core while retaining the liquid boosters. Perhaps if there was a sheath around the solid core which it could slide out from when jettisoned?
Personally, I like the idea of the outer rockets being throttlable while the inner core has the greater main thrust due to solid fuel. That seems more steerable to me.
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#172
by
sanman
on 26 Dec, 2010 00:42
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"Longer, thinner and more top-heavy" is actually more stable, since its COG is further ahead of its COP. Probably less stiff though.
Hmm, this seems counter-intuitive to me. I would think that the longer a rocket is, the easier it is for torque forces to develop along that length to spin the rocket out of control.
http://en.wikipedia.org/wiki/Pendulum_rocket_fallacyI know about the "Pendulum Fallacy" but even if having more mass fartehr forward is better, still I'd think that the larger faring size (surface area) would catch more aerodynamic forces to tip the rocket into a bad orientation.
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#173
by
tu8ca
on 26 Dec, 2010 01:48
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Hmm, this seems counter-intuitive to me. I would think that the longer a rocket is, the easier it is for torque forces to develop along that length to spin the rocket out of control.
Interestingly, the boosters have fins. Not many modern rockets do.
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#174
by
gospacex
on 26 Dec, 2010 02:12
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Gee, I wonder if the design could be modified to allow for jettison of the solid core while retaining the liquid boosters. Perhaps if there was a sheath around the solid core which it could slide out from when jettisoned?
More mass and more failure modes. That would be a Frankenrocket, really.
Personally, I like the idea of the outer rockets being throttlable while the inner core has the greater main thrust due to solid fuel. That seems more steerable to me.
Booster steering is not achieved by differential thrust of main engines (this method would be too slow) - instead, engines are gimballed, or small vernier engines are used to steer (Soyuz).
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#175
by
sanman
on 26 Dec, 2010 02:44
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More mass and more failure modes. That would be a Frankenrocket, really.
Maybe if the composition of the solid fuel was changed to allow for longer burn?
Booster steering is not achieved by differential thrust of main engines (this method would be too slow) - instead, engines are gimballed, or small vernier engines are used to steer (Soyuz).
So then you'd benefit from having your engines farther away from the centerline axis to make it easier for them to apply corrective torque, whether it's due to differential thrust, gimbaling, etc. The wider design of the GSLV-Mk3 allows for this.
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#176
by
sanman
on 26 Dec, 2010 02:50
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Ares-1 was a solid booster design - how do they gimbal their thrust?
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#177
by
gospacex
on 26 Dec, 2010 02:54
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Ares-1 was a solid booster design - how do they gimbal their thrust?
In both axes
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#178
by
Jim
on 26 Dec, 2010 03:04
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"Longer, thinner and more top-heavy" is actually more stable, since its COG is further ahead of its COP. Probably less stiff though.
Hmm, this seems counter-intuitive to me. I would think that the longer a rocket is, the easier it is for torque forces to develop along that length to spin the rocket out of control.
http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy
I know about the "Pendulum Fallacy" but even if having more mass fartehr forward is better, still I'd think that the larger faring size (surface area) would catch more aerodynamic forces to tip the rocket into a bad orientation.
Most launch vehicles are statically unstable. Most of the mass is in the lower stages
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#179
by
MarsInMyLifetime
on 26 Dec, 2010 03:39
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Booster steering is not achieved by differential thrust of main engines (this method would be too slow) - instead, engines are gimballed, or small vernier engines are used to steer (Soyuz).
So then you'd benefit from having your engines farther away from the centerline axis to make it easier for them to apply corrective torque, whether it's due to differential thrust, gimbaling, etc. The wider design of the GSLV-Mk3 allows for this.
Greater torque for correction also implies greater torque for errors to propagate in the first place. If the control to the gimbals was indeed interrupted, that means that all errors were uncorrected and accumulating. Wider separation of the engines only magnifies the effect of imbalances (as in "give me a long enough lever and I shall move the world"). In short, if the brain isn't controlling the feet once out of the starting gate, this kind of race isn't going to end well.
