Who invented the Vikas engine?

Vikas engine was invented by the scientists of ISRO. One of the scientists who played a vital role is Nambi Narayanan. You can read about the GSLV Mk III – A Comprehensive Overview of Heavy Lift Launch Vehicle in the given link.

Further readings:

1. Mars Orbiter Mission (MOM) – A Complete Overview of Mangalyaan Mission
2. Reusable Launch Vehicle – Technology Demonstrator (RLV – TD)