[tankenmate]

Except ISRO's margin can't be as good on the materials (although it's probably better on the staff costs). Th F9 FT has a take off mass of 549 metric tons and can put just under 23 metric tons into LEO, the GSLV-III has a mass of 640 metric tons and can put 10 metric tons into LEO. The combined propellent mass for the F9FT is approx 508 metric tons, the GSLV-III is 554 metric tons. So the non propellent mass for the F9FT is 41 metric tons, and the GSLV-III is 86 metric tons. What's more I'm fairly certain that the solid booster propellent costs more per ton, they are much much simpler to manufacture than liquid fuelled engines. F9 however is reusable and is almost completely assembled if not manufactured in house.

So I strongly suspect that SpaceX's margins are much better than ISRO's and that the development costs have been viewed as sunk cost by the Indian government.

Still it is a huge (100% plus) leap for ISRO; I'm sure as they launch more as well as more often their costs and mass fractions will improve.

[baq]

good analysis, but i think you're missing the fact that the upper stage has a hydrolox engine, which destroys the falcon 9 stage 2 in terms of Isp (wikipedia gives 443 s). i wouldn't be surprised if it can carry more to geo-1500 than the f9.

edit: well the same wikipedia cites 4000kg to GTO so my guess is wrong.

[InclinedPlane]

Isp is only one factor. The GSLV Mk. 3's upper stage is LOX/LH2 but it's also fairly small. The Falcon 9's upper stage is 4 tonnes empty 107.5 tonnes fueled, with an Isp of 348s. The GSLV Mk. 3's upper stage has an Isp of 443s (good) a dry mass of 5 tonnes (not as good) and a wet mass of 33 tonnes. The mass fraction on the F9 upper stage utterly dominates the GSLV's upper stage Isp.

Let's look at GTO payloads and upper stage delta V.

GSLV Mk. 3: 4 tonnes, which translates to a stage delta V of ln((4+33)/(4+5)) x 4.34km/s = 6.135 km/s

F9 FT: 8.3 tonnes -> ln((8+107.5)/(8+4)) x 3.41 = 7.72 km/s

So the Falcon 9's upper stage is able to push twice as heavy a payload through about 1.6 km/s more delta V despite having nearly a full km/s lower exhaust velocity, all because it has a better mass ratio.

[baq]

thanks for the writeup!

[alphadog_78]

I would be esctatic if ISRO just breaks even..It's not about margins. Just Imagine the fact NASA or ISRO does not need to depend on Govt and they generating their own money and continuing their research without interruptions.

No Tax payer money going to them and don't need to depend on Congress/Senate/President/ Prime minister mood to fund them.

Where as Musk, he is a private entrepreneur. He is upping the space game like anything.