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#180
by
sanman
on 26 Dec, 2010 03:39
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Ares-1 was a solid booster design - how do they gimbal their thrust?
In both axes 
So it is possible to gimbal a solid booster then?
Gee, maybe one day someone will come up with a hybrid liquid-solid design for a launch vehicle. I've heard of colloidal rockets, but I'm not sure what their performance characteristics are. I'd assume more thrust than liquid, but less than that of pure solid.
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#181
by
sanman
on 26 Dec, 2010 03:42
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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.
Not necessarily - corrective torque is applied through the engines or thrusters, so a design can give them distance from COG/COM for corrective torque purposes. At the same time the design would try to minimize the development of torque forces farther away from COG/COM.
I don't see that opportunity for maximizing corrective torque has to automatically result in simultaneous increase in destabilizing torque, which would arise mainly due to aerodynamic factors.
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#182
by
butters
on 26 Dec, 2010 03:53
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So it is possible to gimbal a solid booster then?
Gee, maybe one day someone will come up with a hybrid liquid-solid design for a launch vehicle. I've heard of colloidal rockets, but I'm not sure what their performance characteristics are. I'd assume more thrust than liquid, but less than that of pure solid.
Most solid strap-on boosters are gimbaled, and so are solid-fueled missiles.
Virgin Galactic SpaceShipOne used a hybrid rocket burning solid HTPB rubber in liquid nitrous oxide. SpaceShipTwo will use a larger version of the same, and so would the SNC Dream Chaser spaceplane.
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#183
by
sanman
on 26 Dec, 2010 04:43
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Another comment I'd like to make is that I think the Indian govt should seek to have ISRO spin off its already successful proven workhorse PSLV to the private sector, preferably to at least 2 competing service providers.
That would allow ISRO to focus more purely on engineering and proving newer launch vehicles like the GSLV that would push the envelope.
Since PSLV is already proven in its reliability, it would be for private sector companies to then show they can provide the same level of reliability in their operations, while they gradually seek cost efficiencies. They could also gradually evolve the design in their own distinctive ways, according to market forces/demands.
As painful as today's setback is, I think that taken in the right perspective, it could also create political opportunities for a shift in how things are done.
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#184
by
edkyle99
on 26 Dec, 2010 15:53
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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.
I don't see a problem with the basic GSLV layout in terms of control authority. GSLV clearly is a controllable configuration, based on its past successes. During this flight, something appears to have happened to the control system itself. Any rocket, even short-fat ones, would have turned and burned as a result.
I wonder if the real problem might be associated with the constant changes ISRO has made to GSLV. I'm not sure any two have been identical. Both that flew this year were different configurations. It can't be easy to certify that many configurations at once.
Then there was that leak business. It will be interesting to see if that had anything to do with the final result.
- Ed Kyle
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#185
by
Ronsmytheiii
on 26 Dec, 2010 17:27
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First of all, is the GSLV Mk.I roughly equivalent to the Delta II class? If so, this failure might lead to a small window of opportunity for Soyuz, SpaceX and OSC to establish themselves in this class and could prove disastrous for future orders for ISRO. Seems like there will be quite a bit of competition in this SLV category in the future, should be interesting to see how it plays out and with such competition things like this failure could have large market repercussions.
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#186
by
input~2
on 26 Dec, 2010 17:34
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#187
by
edkyle99
on 26 Dec, 2010 18:05
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#188
by
Jim
on 26 Dec, 2010 20:49
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Another comment I'd like to make is that I think the Indian govt should seek to have ISRO spin off its already successful proven workhorse PSLV to the private sector, preferably to at least 2 competing service providers.
That is not viable. Not only can't the market support the production of the same vehicle by the different contractors, the differences in engineering by different orgs would cause issues.
Not knowing the Indian conops, but PSLV maybe produced by the private sector for ISRO already.
Your posts seem to be of one who doesn't understand launch vehicles.
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#189
by
sanman
on 27 Dec, 2010 01:15
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Okay, well how about spinning off to a single private contractor then?
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#190
by
Jim
on 27 Dec, 2010 01:30
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Okay, well how about spinning off to a single private contractor then?
Arent private contractors already involved?
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#191
by
jcm
on 27 Dec, 2010 02:13
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Okay, well how about spinning off to a single private contractor then?
Arent private contractors already involved?
Only at the subcontractor level, I think. except for the Russian stage. For the most part VSSC (ISRO's version of NASA-Marshall, also in the Deep South :-)) is the main contractor, stage integrator and launch vehicle integrator. Hindustan Aeronautics Ltd in Bangalore does a lot of the structures but my impression is (please correct me if you know better) ISRO still holds most of the high level reins - in the US context, more like Ares I than Atlas V.
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#192
by
butters
on 27 Dec, 2010 02:33
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Experts analysing the voluminous data are of the view that a hardware problem or defect has led to the snapping of the four connectors
from: http://economictimes.indiatimes.com/news/politics/nation/hardware-defect-suspected-for-rocket-failure/articleshow/7169237.cms
Four data lines snapped simultaneously? That sounds rather like a design flaw or at best a systemic flaw in the assembly process. If it were a manufacturing defect, then one would not expect all four lines to fail at once.
Is it possible that the loss of just one booster TVC system could have caused the pitch-up anomaly observed in the launch footage? I wonder what evidence they have to suggest that all four booster TVC systems were lost.
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#193
by
seshagirib
on 27 Dec, 2010 03:29
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^If loss of TVC command lines is true and is the root cause, this happened for the first time in seven flights. QC issues rather than design looks to be most likely.
Added Later: On second thoughts could be a design issue also if vibration or resonance modes not fully accounted for - more so in light of the newer launch vehicle configuration ( taller, heavier,larger payload fairing...)
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#194
by
input~2
on 27 Dec, 2010 08:14
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http://www.hindu.com/2010/12/27/stories/2010122756631000.htm"There is disappointment among ISRO's rocket technologists that the GSLV mission on December 25 failed because of “a very, very trivial issue.” They said it failed because the signal from the equipment bay, which houses the electronic brain of the vehicle and is housed atop the rocket, to control the vehicle, did not reach the first stage. A bunch of wires, running to more than 45 metres, convey these signals from the equipment bay and the wires terminate in the three stages of the vehicle. Since these wires are so long, they are connected by devices called connectors, which are akin to plugs and sockets. It is these connectors that hold these wires in place.
An authoritative ISRO rocket technologist said four such connectors came loose or were prised open because of “some disturbance” in the flight and so the wires, which convey the signal for controlling the rocket, lost their continuity. “If some connectors open up, the wires will not have continuity. It is a very, very trivial issue. So the command for controlling the rocket from the equipment bay did not reach the first stage. An uncontrolled rocket will fail. That is what happened. We are in the investigation mode,” he said."
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#195
by
input~2
on 27 Dec, 2010 09:48
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#196
by
ugordan
on 27 Dec, 2010 10:54
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#197
by
racshot65
on 27 Dec, 2010 13:14
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Is it pretty standard to use 'connectors' on such critical wires rather than solder them ?
Seems like it would be better to solder them so you dont have to worry about a connector failing ?
Or am I missing something ?
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#198
by
jimvela
on 27 Dec, 2010 13:29
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Is it pretty standard to use 'connectors' on such critical wires rather than solder them ?
Seems like it would be better to solder them so you dont have to worry about a connector failing ?
Or am I missing something ?
In cryo environments it is different, but for most other environments modern crimped contacts are actually MORE reliable than soldered connections.
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#199
by
Jim
on 27 Dec, 2010 15:00
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Is it pretty standard to use 'connectors' on such critical wires rather than solder them ?
Seems like it would be better to solder them so you dont have to worry about a connector failing ?
Or am I missing something ?
Connectors are used across interfaces whether at the component, subsystem, or stage level. It provides a point to do testing and a method for the ease of assembly.
The wires are soldered or crimped in the connectors.
