[swatkat]

GSLV Mk III is a brand new launch vehicle. Usually, ISRO starts with conservative payload numbers for all their launch vehicles, and keep improving them iteratively. We have seen this happening with PSLV and GSLV Mk II as well. We can expect ISRO to bump up GSLV Mk III payload capacity in subsequent launches.

[alphadog_78]

I'm not doubting whether ISRO will reach the weight range or not. It is how quickly they can reach in par with falcon 9.

As the payload doubles from 4000KG to 8000KG (to be in par with Falcon 9 ), You need to add more fuel and which increases the cost and total weightage of the rocket.

This additional weightage on the rocket will hamper the margins.

I'm not saying anything negative here and they have lot of work cut out for them because of re-usability of Falcon 9.

Overall, this is very good for us as competition drives the cost down and more and more services at lower cost.

Good positive start.

[tankenmate]

Actually having a higher percentage of mass for your propellant (fuel and oxidiser) compared to your total mass (minus payload which can vary flight to flight) is a good thing; it means you can deliver more mass to orbit. [0] Conversely the more mass you use to build your rocket the less mass you can deliver to orbit. For the F9FT the propellant mass fraction is 92.43% (507.5/549), and for the GSLV-III it is 86.56% (544/640). [1][2] If the GSLV-III had the same PMF as the F9FT its dry weight would drop from 86 tons to 45.5 tons. Then it would probably be able to deliver 25 to 26 tons to LEO, an increase of 2.5 times.

I'm sure the ISRO will improve the mass fraction over time. It should be noted however that the F9 with all its single core iterations have been within 1% of each other propellant mass fraction wise.

[0] https://en.wikipedia.org/wiki/Propellant_mass_fraction

[1] https://www.reddit.com/r/spacex/comments/3lsm0q/f9ft_vs_f9v1...

[2] https://en.wikipedia.org/wiki/Geosynchronous_Satellite_Launc...

[EDIT] minor grammar fix

[rst]

For comparison, expendable payload of Falcon 9 more than doubled between the first launch and the current version. (Reusable payload of the current version is less, but still exceeds the expendable payload of the original Falcon 9 1.0.) That Falcon 9 increase includes the significant engine upgrade to Merlin-1D, but ISRO is already planning to replace the core stage of its GPSV with a larger stage taking different fuels, which should boost capability significantly.

[tankenmate]

Yes, and I think the ISRO has great vision for the future; its second stage engine is its first truly home grown engine and it performed admirably. Once it gets its own home designed and built engine to replace the Vikas (which is based on the French Viking 4A engine from the 70s) it will greatly boost the GSLV's lift capability.