Why was APJ Abdul Kalam known as the Missile Man?

India lost its most popular President on July 27, 2015 in Shillong. APJ Abdul Kalam was known as the 'People's President' and served as the 11th head of state, between 2002 and 2007.
Born on October 15, 1931 and raised in Rameswaram in Tamil Nadu, Dr. Kalam studied aerospace engineering at the Madras Institute of Technology after which he joined the Defence Research and Development Organisation (DRDO). His outstanding work earned him the title of the "Missle Man of India".
Find out about his scientific career and why was APJ Kalam called the "Missile Man of India":
Education
During his school years, he was deeply interested in mathematics. He graduated in Physics from Joseph's College, Tiruchirappalli, after which he studied aerospace engineering in Madras Institute of Technology where he was threatened that his scholarship would be cancelled.
Dr. Kalam had dreamt of becoming a fighter pilot but he ranked 9th in the qualifiers whereas only 8 positions were available in the IAF.
His years at the DRDO
His time at DRDO was utilised in focusing on research in defense and space arena as a scientist. In the beginning, he designed a small hovercraft and started working on an expandable rocket project independently. In 1969 he was shifted to the Indian Space Research Organisation (ISRO) where he was the project head of India's first Satellite Launch Vehicle (SLV-III). It was during this time he got the government's approval to expand the program.
The Missile Developer
Within 20 years, Dr. Kalam was successful to develop the Satellite Launch Vehicle (PSLV) and SLV-III projects. In the 1970s he also directed two projects which developed the ballistic missiles from the technology of the SLV programme, for this he was given secret funds from then PM Indira Gandhi through her discretionary powers as the Union Cabinet was against these projects.
Kalam was appointed as the Chief Executive by then Defence Minister R. Venkataraman of a project which worked on development of a quiver of missiles. A fund of 388 crores was allocated for this mission named Integrated Guided Missile Development Programme (IGMDP). He developed many missiles under this mission including Agni and Prithvi.
Role in Pokhran-II
ABJ Kalam served as the Chief Scientific Adviser to the Prime Minister and he served as the Chief Project Coordinator of the Pokhran-II nuclear tests. The massive media coverage this project got made Kalam a well known nuclear scientist.

APJ Abdul Kalam has received Bharat Ratna and played a major role in the testing of nuclear weapons in 1998 during the Vajpayee government.