...with the help of advanced, light-weight composite materials for the construction of its body & lighter warhead designs.
This was one of the findings of an analysis carried out of the Agni-1 Ballistic Missile, that has been deployed under the operational command of the country's SFC, using open-source data. One 'vivek_ahuja', a well-regarded members of the Bharat Rakshak Forum, has authored this paper. A look up on the Internet for his name threw some information about his credentials. Credible.
For the completion of its mission, the missile has been calculated to be carrying 8510 Kg of Solid Rocket Fuel - HTPB. It is stored in what is described as a 'star grain' configuration [Photograph on left]. It basically refers to the manner in which the solid fuel is arranged or shaped inside the missile. One significant advantage of using liquid rocket fuels is that the characteristic nature of combustion, at any given time, can be dynamically varied, if required, by controlling the flow of fuel and oxidisers into the combustion chamber with the help of control valves. Solid rocket fuel combustion can not be similarly controlled. Once ignited, the solid fuel will continue to burn till all of it has been consumed. A method that enables a degree of control over its combustion characteristics is the fuel stacking arrangement, or grain of the propellant. This '6-pointed Star Grain' configuration, he concludes, can provide the Agni-I with an effective combustion [and corresponding thrust] characteristics, both inside the atmosphere [low velocity, therefore less drag losses], as well as when almost out of it [higher acceleration]. The diagram to the right gives an idea of how solid rocket fuel gets consumed in flight. The missile has been estimated to take 9 minutes to reach its target, with the powered flight [stage where fuel burns] lasting for around 40 seconds & the missile warhead attaining velocity of Mach 7 prior to its impact on target.
Being the outcome of a development programme initiated earlier, the missile has an all-metal body construction, built using Maraging Steel. Since that time, with the Agni-IV project, DRDO has demonstrated successfully its ability to utilise high strength but light weight composites to build casings. Therefore, it would be logical to assume that this manufacturing technology would also find application in the building of future Agni-1s. Use of composites would enable its users to lob the missile, with its existing warhead, even farther, up to a distance of 1250 Km, claims the author.
The range of Agni 1 missile has been estimated assuming a warhead mass of 1000 Kg. It corresponds to BARC's untested 200 Kt boosted fission warhead design, with the Agni-1's Re-Entry Vehicle [RV] designed accordingly. Carrying a warhead weighing lesser would, therefore, enable it to reach targets further down-range. Calculations suggest a distance of 1500 km can, theoretically, be reached if the missile were to be made of composites & carrying a lesser [unspecified] mass of payload. However, it seems unlikely that, in the current scenario there would be any major re-design on that front. That is because, following Operation Shakti, India declared a self-imposed moratorium on further tests. Thus, any new design will, therefore, also remain untested, unless it decides to take a break from the moratorium. An unlikely proposition. A 1000 Kg mass would provide you with the leeway to over-engineer the design, thus making up for not testing it. It is also being debated whether the data generated from just 5+1 tests are enough to create models for simulations that can help design newer warheads without physically testing them with sufficient reliability+. Therefore, a conservative conclusion would state that there will be no major changes in the Agni-1's warhead design, and will continue to weigh in the range of 1000 kg. Thus, going by this assumption, one can conclude that the missile's range can be practically extended to 1250 km. There have been speculations, that one of the clauses during the signing of the upwards of $12 billion USD contract with France for the acquisition of around 126 MMRCA includes access to its Inertial Confinement Fusion facility near Bordeaux. There, however, has been no further "leaks" elaborating this proposal.
You may read the entire paper below.
1st image source: www.wired.com
+ = Anecdotal reports state that Dr R. Chidambaram, then Chairman of the AEC & DAE, asked for the remaining device, scheduled for testing, to be taken out of the ground, as the tests already conducted had generated sufficient data.