Complex sentence: Physicist Raja Ramanna played an essential role in nuclear weapons technology research; he expanded and supervised scientific research on nuclear weapons and was the first directing officer of the small team of scientists that supervised and carried out the test.
Split into simpler sentences: Physicist Raja Ramanna played an essential role in nuclear weapons technology research. He expanded and supervised scientific research on nuclear weapons and was the first directing officer of the small team of scientists that supervised and carried out the test.