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Comment by alphadog_78 | Hacker News Reader

Congratulations ISRO.. Good step in right direction.

If we compare this to current SpaceX Falcon 9 (not Falcon Heavy ) http://www.spacex.com/falcon9

Falcon 9 can deliver 8300 Kg to GTO and 22,800kg to LEO.

GSLV MK III delivers 4000 Kg to GTO and 8000KG to LEO ( http://www.isro.gov.in/launchers/gslv-mk-iii )

Mr. Musk will be delivering hell lot of stuff to space with his reusable rockets. SO, he will be very cost competitive to ISRO w.r.t launch price.

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Falcon 9 FT beats Mk III hands down.

But ISRO reached 2 Tons for GSLV just last year, This is rated at 4 Tons, and future improvements to 8 to 10 tons is on cards within 1-2 years. Even a proposal for 15 Tons by 2020.

http://www.thehindu.com/news/national/Mega-launchers-for-ISR... (https://en.wikipedia.org/wiki/SCE-200)

The ISRO is pegging the price at Rs 400 Cr which is almost identical to a Falcon 9 at $62M at current exchange rates. Falcon 9 appears to win on price/payload, but ISRO is in the ballpark, impressive.

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.

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.

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.

thanks for the writeup!

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.

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.

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.

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.

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.

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

> http://www.spacex.com/falcon9

According to the technical overview, Falcon 9 can also deliver 4020 kg to Mars :)

To put that into perspective, India's last Mars satellite https://en.wikipedia.org/wiki/Mars_Orbiter_Mission weighed 1.3 metric tons, and was launched on PSLV-XL.

Thanks for the wiki. ISRO has been consistently performing well. They can be a role model for other government agencies in India.

Hmm this is weird. The description says "about 10 tons to Low Earth Orbit (LEO)" but the technical specification says "8000KG".

10 [US] tons = ~9000 kg

I am pretty sure ton in India means metric ton, not [US] ton.

8 tons to GTO is the expendable weight limit. With reuse it is around 5.5 tons.

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