Avul Pakir Jainulabdeen Abdul Kalam was not the best engineer India has ever produced. Nor was he the most erudite of its 13 presidents. But he was undoubtedly the most-loved person to have ever occupied Rashtrapati Bhavan and his would probably be the first name mentioned (in error) if the man on the street was asked to list pre-eminent Indian scientists.
Kalam possessed an amazing knack for inspiring people and motivating them. Dissected for content, his public speeches weren't glowing examples of oratory. He said obvious things. But perhaps, the obvious needs to be said sometime.
He was transparently honest and sincere when he spoke onstage, to the point where he came through as almost naive in outlook. He preferred talking to young folks, once famously remarking that he wanted to meet 100,000 kids every year. Maybe, the message was kept deliberately simple and geared for their consumption, rather than being designed to impress cynical oldies.
"He said obvious things. But perhaps, the obvious needs to be said sometime."
Despite the simplicity of speech and the apparent naiveté, Kalam was a master of bureaucratic judo. He is remembered for leading successful teams in ISRO (Indian Space Research Organisation), and then DRDO (Defence Research and Development Organization). He convinced a multitude of bright young men and women to park themselves in unglamorous sarkari jobs rather than seek their fortunes abroad. He was brilliant at getting resources out of the government, and also for sidestepping the poisonous politics of the babu-neta nexus.
The technological record is spotty, however. ISRO boosted Rohini into space during his tenure and they got the initial PSLV design right when he was Project Director. Those were big successes. But ISRO has since struggled to ramp up to the larger, more powerful GSLV (Geosynchronous Satellite Launch Vehicle). That programme was conceived during Kalam's tenure, and that inability to get GSLV going has been a stumbling block to India's space ambitions.
India is still not comfortable with cryogenic engines and associated technology and so, the GSLV is not yet completely stable. The first successful launch with an Indian cryogenic engine (as opposed to Russian engines) was as recent as December 2014 - some seven or eight years behind schedule. The PSLV had to power the Mars mission. It required a complicated slingshot manoeuvre to use Earth's gravity because the PSLV isn't powerful enough to plot a more straightforward path to Mars.
Kalam's record with the DRDO is also nowhere near perfect. The development of the missile deterrent has indeed been impressive. Prithvi, Agni, Akash and Nag have all become operational components of India's nuclear deterrent.
But many other key defence projects have languished. The Main Battle Tank, the Light Combat Aircraft, Gun-radars etc., even rifles, are decades behind schedule. Obviously, the fault for those delays should not be shouldered purely by Kalam. But he was the man in charge of DRDO for a long while and he didn't manage to get these projects moving or deliver to the satisfaction of the defence forces. If he gets the credit for the missiles, he must also share some of the blame for the stuff that hasn't come through.
Pokhran II was also reckoned a "semi-success" in scientific terms. India successfully demonstrated its mastery of small "suitcase" nukes. But it did not apparently manage to get a thermo-nuclear device (aka a hydrogen bomb) to work.
"He lacked the essentials of a Phd and the scientific heft that comes from churning out multiple peer-reviewed papers."
The failure in itself is no big deal - no nation has ever managed to get a H-bomb to work first shot. This involves setting off a "shaped" fission explosion (an atom bomb) by banging radioactive material together. This first explosion creates the high temperature and pressures required to start a fusion reaction, which leads to the second, larger explosion. Thermonuclear devices show up with a characteristic double-explosion signature and the energy yield jumps.
The consensus of opinion, given seismic data and energy yields, is that the H-bomb demonstration did not work. Several DRDO scientists involved with Pokhran II and Pokhran I have said so. However, Kalam insisted the test was successful. That difference of opinion created a controversy that continued till 2009-2010 at the very least. Even now, this is the one subject where you will hear bitter words directed at the late President.
More important than the internal dynamics between scientists, Agni's long-range delivery systems (and India's nuclear submarine options) should be backed by credible capability to build thermonuclear warheads. The important thing is the credibility. Most nations don't believe India has thermo-nuclear capability. (Even if India does have it, it is unlikely to ever be used).
Pokhran II apart, people involved with the official Indian scientific-engineering establishment generally tend to have somewhat similar views on Kalam. Most people liked, and even loved him, personally. They admired his leadership qualities and his ability to cut through bureaucratic hurdles.
But he wasn't regarded as an aeronautical engineer of more than average competence. The IIS, Bangalore, and IIT Madras both politely declined to have him teaching. He lacked the essentials of a Phd and the scientific heft that comes from churning out multiple peer-reviewed papers.
However, quite apart from the missile programme, Kalam did make at least two useful contributions to healthcare. One was the Kalam-Raju stent and the other, the light callipers for supporting the legs of polio victims.
In the wider world of politics and public perception, he was revered, and rightly so, as an honest, apolitical technocrat who devoted his life to the nation. Honesty and patriotism are qualities more often extolled by scoundrels, than actually displayed by people in public life. On that basis alone, he was a truly extraordinary man.