symontk wrote:Going by what ISRO always does, the C-15 can be expanded to C-25. ISRO always uses the 60% - 70% capacity ones for first few launches and then only use them with full capacity
Going b the link that Singha posted..Cryogenic Upper Stage
, it seems that the work is underway to increase the thrust to 90KN against the current 75KN.
The current version of the Indigenous Cryogenic Engine develops a thrust of 73 kilo Newtons (kN) in vacuum with a specific impulse of 454 seconds and provides a payload capability of 2200 Kg to Geosynchronous Transfer Orbit (GTO) for GSLV.
Work is underway to increase the thrust to 90 kN.
Eventually, all GSLVs will use the Indian Cryogenic Upper Stage (CUS) that develops 90 kN ton of thrust, against 75 kN of the Russian CUS; and they will carry 15 ton of propellant against 12.5 ton of the Russian engine.
If it is going to develop 90KN /9tons thrust and carry 15ton of propellant, the burn time will be like I said around 150s longer, that leaves only fixing the inefficiencies in the lower stage.
Maybe they are waiting for the Semi Cryo stage to come about to do a clean replacement of the L40+Core+Stage 2 and go for a 2 stage GSLV (Semi Cryo first stage and a CUS with 9T thrust and 15 ton propellant) which will put a 2 to 4 ton class satellite to GTO. That will be one heckuva vehicle and will be very competitive with anything out there in the near future.
Time to get rid of the solid stages and the UDMH/N204 engines with their low Isp . High Isp with cheap rockets coming from dhoti clad engineering is what is needed.
I have misgivings about the 1st stage of the MKIII with the enhanced Vikas twin cluster (Clustered Twin Weak Ass Engines)
. Ideally you need a Semi Cryo (Hydrocarbon + LOX... I know ISRO is going Kerosene way, but ideally would have loved LCH4 with it's higher Isp,even if it results in a more voluminous stage) and the Weak Ass engines are retired.
Ah well, maybe when the Semi Cryo stage comes to fruition, we will have the GSLV MK2 and the MK3 morphing into a newer class called EGSLV (Evolved GSLV) or Rajiv/Indira Gandhi / JL Nehru Rocket or whatever names the Politicos & Baboons manage to come up with.