What are some lesser known things about Dr.APJ Abdul Kalam?

While APJ Abdul Kalam was interacting with school kids. One kid stood up and asked him, Sir you have done so many successful researches. Out of them, which success gave your heart more happiness.

This was APJ's reply to the kid,

You are very intelligent little one, you ask good questions. (After a laugh) 
I made rockets with the help of my friends and teachers, that rocket put a satellite in space. That was a happy news.

Then I made missiles called Agni and Prithvi along with my colleagues. That went into production and it was a happy moment.

Then, people talk about something called nuclear..nuclear.. nuclear weapons. In that too, I worked along with other departments and did something and it became a success and made me happy. 

But are there bigger happiness than these?

When I was working on missiles I invented a composite material made from fiber glass and epoxy and it was 7 times lighter than metal. This material was used for making missiles.

Then one day, Prof. Prasad of Nizam institute of medical science came to our lab in Hyderabad. Then he said to me, missiles injures and causes pain and you should try something to remove pain. Then he took me to a orthopedic hospital. There I saw kids below 15 years suffering from polio and they were struggling to walk with their 3 kg callipers.  Dr. Prasad said, You have very light material for making missiles, can you help these kids in any way.  

Then after 1 week, I made FRO(Floor reaction orthosis) of 300gm for 3 girls and 2 boys. These callipers were 10 times lighter than their previous callipers. Then I saw them playing very happily and some were also driving cycle. 

You see, those three things I said before, gave me happiness but this gave me joy and I saw joy.