was searching for information sources that I could use to write the Wikipedia article on the GSLV. My last bit of work on that article was on improving the history of the GSLV. I am happy to notice that the recent success of the GSLV has also cleaned up that article visually. Now, I was looking at the cryogenic stage to improve that section of the article.
I noticed that a link had been added to the indigenous cryogenic engine called the CE-7.5. I think that was the name given to the Russian cryogenic engine, KVD-1 supllied to India and not the indigenous one. I could be wrong. However, the Indian cryogenic engine has been called CUS-12 here. I could not find similar places where the indigenous engine has been called the CE-7.5. I left a note on the talk page of the article to see if anyone else could find any reference.
Another thing to notice is that Indian engines are usually named after the propellant loading. This is true for the S-139, L-110 and also the CUS-12, which is loaded with 12.8 tonnes of propellant. CE-7.5 just rings odd to me.
This brought me back to the Russian engine. These are the KVD-1s. These are modified versions of the RD-56 engines that the Russians developed for their N-1 moon rocket. The KVD-1 were never actually test-flown before they were sold to power the third stage of the GSLV. GSLV hence acted as a test bed for these. As per this, it also seems that the Russians used this to validate their design and to prove to themselves, that the designs actually flew. Hence, they too were quite happy with the success of the first three flights (one was a partial success though ISRO claims it as a success) of the GSLV.
An interesting paper [PDF] published in the AIAA in 2006 provided better information and details. These are a better source of information since these are by the people from the institution that actually designed this engine. The paper is in itself worth a blog post and I will perhaps read it in its entirety before writing here again. For the purposes of this post, the paper clarified that the KVD-1 was a modified version of and not a rename of the RD-56. The two are quite different. The KVD-1 was developed specifically to power the upper stage of launch vehicles, hence suited to the need of the GSLV. It may also be worth your while to read up on gas generator cycles – especially the staged combustion cycle.