Hi,
Yes you can get internship in DRDO etc, by contacting the HR through your department. Request them to send letter of recommendation stating that so and so gas rhis educational background and having knowledge of particular subjects and send them through post. By the way the rarely accept second year students but, ypu have high chance to get in third year. Refer to link for further information
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.drdo.gov.in/drdo/English/index.jsp%3Fpg%3Djob_student.jsp&ved=2ahUKEwjh98Pf_q7iAhUNXisKHU5NAeMQFjAAegQIARAB&usg=AOvVaw1pcEeCv-GTswJYejyZNFU7