A Nandy wrote:Ok, I am no expert, but the strap-ons are lifting dead weight after that time. Maybe the first stage firing time can be increased to coincide with the end of the the strap-ons firing.
Not necessary. Even after the thrust from solid core is shut-off, until the acceleration followed by velocity imparted comes back to zero, one can hug the solid core.
The solid core is a fast burn motor, that is it gives a very large initial thrust sustained by the "boosters". The beauty of the design is the core is the "booster" and the surrounding strap-ons are "sustainers".
This was done specifically to ensure that the solid core is not ignited pre-maturely when the liquid sustainers cannot perform (or may underperform.
In so far of some 9 GSLV Launch programmes - the failures attributed due to the liquid straps are
two. In first launch program, the liquid strap-on did not perform nominally (underperformed) and was caught and launch sequence aborted. In another failure (GSLV-F02), one of the liquid strap-on failed causing the rocket to be destroyed. That is like @25% failure (2 in @eight).
The caution thus of igniting solid "booster" followed by reliable "sustainer" is thus warranted.
What ISRO has done with the launch of GSLV is
* Master the cryogenic (given)
* Master "clustered" liquid propulsion (simultaneous ignition of 4 liquid-strapons)
* Scaling of liquid propulsion (the first stage of GSLV-MkIII is clustered large liquid engine)
* Validation of RLG INS - the precision on perigee is ~40 meter than expected and on apogee is some
~50 KM (this is
@0.025% deviation at apogee!! or twisting it differently if ISRO were to target something at 36000 KM, it will be within 50 KM of the target - at 200 KM, ISRO will be 40M of target!! - others should dhoti-shiver here only).
At this stage, ISRO's path towards GSLV Mk III is clear.
PS: One more thing, ISRO should have a bullock cart to transport something to GSLV/PSLV and make a song and dance around it complete with photos and videos.
Edit: Fixed the precisions - mentioned in this video http://www.youtube.com/watch?v=Y7HIvfhoFHM
in post launch speeches.