"Propellant accounts for 80 to 85% weight of Rocket"
Source> "Gatha Isrochi",
a marathi book written by Dr. Vasant Govarikar
, EX ISRO Scientist
this above fact is crucial.
Agni 3 weights 48 tons
without its 1.5 Ton payload it weighs 46.5 Tons.
From above fact mentioned it can be assumed that Propellant accounts for 80% weight of Nuclear Missile.
Hence weight of Propellant in Agni 3
is 46.5x80%=37.2 Tons
Hence weight of Agni 3 without payload and propellant will be just 9.3 Tons
now we know that both stages of Agni 3 are made of Maraging Steel.
so if DRDO uses Composites and reduces weight by 15%, empty weight of new Agni 3( lets call it Agni 3 M) will be 7.44 Tons (without payload and Propellant)
now we all know ," less payload=more range".
in case we reduce payload by 10%, range increases by 10%.
so if Agni 3 M has its both stages made of composite it will weigh 44.64 Tons (46.5-15% of 46.5) and 46.14 Tons with 1.5 Ton Payload.
reducing weight of missile is like reducing payload
less payload=more range
so this new Agni 3 M with 46.14 Tons weight (1.86 Tons less than Current Agni 3) and having ability to be canister ed can easily have minimum range of 5,000 KM while Retaining Payload of 1.5 Tons
and if we reduce payload it's range will be 6,000 KM
the 3rd stage may be a post boost vehicle
so in my opinion, DRDO has used the above technique to turn Agni 3 into Agni 5
i would appreciate your opinion friends
Note> Special Thanks To Book "Gatha Isrochi", written by Dr. Vasant Govarikar, EX ISRO Scientist