KrishG wrote:When designing GSLV, ISRO wanted to make it as an extension of the PSLV. That's why, they took almost the same solid core of the PSLV and put in on the GSLV. Instead of the solid boosters of the PSLV, liquid boosters were added. Even the second stage of the PSLV and GSLV were decided to remain same. The 3rd and 4th stages of PSLV were replaced with the cryogenic stage. This is how ISRO arrived at the GSLV.
So, GSLV is very much based on the PSLV. And rightly so. At that point ISRO really did the best with what technology they had. It's a commom misconception that GSLV was based on the Ariane 4. No, GSLV was based on the PSLV. If ISRO wanted, they could have gone to Ariane 4 route and decided to cluster the Vikas engines for core stage of GSLV. But, Liquid engine tech was still not mature at that time.
Indeed. If you look at the basic take off thrust of the PSLV and the GSLV Mk1/2, they are remarkably the same. The PSLV S139 + 4 * 50KN + 2* 50KN boosters (air lit), i.e S139 + 300 KN, is very similar to GSLV Mk1/2 with S139+ 4*70 KN (i.e. S139 + 280 KN) . So basically what saves the day for GSLV is the higher Isp due to the Cryo stage and longer duration use of higher Isp than solid Vikas engines.
Symontk wrote:A lighter GSLV would also do good, like a TSTO option of a single S-140 and CS15(CE7.5) would be lobbing a 1.5 - 2 tonne satellite to GTO. It would be in the same lines of PSLV-3S which ISRO was planning, replace the two upper stages with cryo and you would get this
A S200 and CS25(CE20) would also do good
Yes of course. That as a stop gap would be the way to go. Those kind of combos would be more efficient than the GSLV Mk1/2 and PSLV. The PSLV I think, frankly due for retirement and the GSLV Mk1/2 is too inefficient to see any large scale service. However, I do hope that these come about with a LOX/Hydrocarbon core.
KrishG wrote: Once LVM3 is fully operational, it and the PSLV will be the ones that will be logging in the maximum number of flights. If we assume a total of 6 launches every year, it will something similar to 3 PSLV, 2 LVM3 and 1 GSLV.
I do think your split up in numbers will be correct with the current inward focused ISRO model. However, there is a whole wide world of commercial launches waiting for a competitive entry and for you to conquer . ISRO should not get into the export pessimism promoted by the sclerotic Govt/ISI/Planning Commission/DSE/ISI ding dong cabal. At least the planning commission is now history, and with SHAR now in CB Naidu's Seemandhra, I do hope that some of his pirate like instincts and no prisoners taken attitude/ approach in business rubs off on ISRO.
For that you need highly efficient (both capital and operational cost wise) proven launchers . We have the cryo stages needed for that in place and the missing link in that is a good LOX/Hydrocarbon stage . Have that last link in place and we are globally competitive and can give the global launch and satellite market hell.
For eg.. The base GSLV MKIII for a 4 ton to 5 ton GTO has a lift off mass of 660 tons (a mass fraction of 0.7% or so), and it is a 3 stage vehicle to boot. A base Atlas V with a similar 4 to 5 ton GTO has a lift off mass of around half of that at just 330 tons (a mass fraction of 1.5% or so, double that of GSLV MKIII) and the Atlas V is a 2 stage vehicle ! The Atlas burns kerosene (dirt cheap, okay special grades albeit) from refineries, while the GSLV burns up gargantuan amount of solid propellants and carcinogenic UDMH and N2O4 which needs special plants to produce it and require special hazmat handling.
ISRO desperately needs the LOX/Hydrocarbon stage ASAP. All efforts and funds should go into that. This manned space flight thingy is just a whole load of baloney and a distraction. Hand it to NASA and the Chinese and focus on what you need to get.
Like I said earlier, if the science "fundamentalists" like Bade Mian whine, do a moon shot or mars shot or something once a while to quite them. But otherwise, follow the money, and rake it in. You can never go much wrong with that.