Indian Missile News And Discussion

[Arun_S]

Good article by TSS.





Some observations:



[quote name='osman' date='04 May 2012 - 02:14 AM' timestamp='1336077386' post='114792']

[url="http://www.frontline.in/stories/20120518290912400.htm"]http://www.frontline...18290912400.htm[/url]



Frontline on Agni V. A lot of details. Did not post the entire article. Just technical details.



At 8-07 a.m., as the Agni-V shot out smoothly from its launch pad, roared into the sky and built up a powerful thrust, there was no doubt about the mission's success. The three stages ignited on time and their separation was clean and precise. The missile climbed to a height of about 600 km before starting to descend. The powered flight, with the three stages igniting and separating, lasted about 220 seconds. As each stage fired and decoupled, the MCC and the adjacent hall reverberated with applause. There was a long gap between the third stage separation and the re-entry vehicle knifing into the atmosphere at an altitude of 100 km.After the third stage separated and the re-entry vehicle was ejected at a velocity of about six km a second, the mood in the MCC was relaxed. [/quote]



The "velocity of about six km a second" does not mean the reentry velocity was 6 km/sec. The re-entry velocity was still 7 Km/sec (Mach 24). Just that when the third stage bunt off teh velocity was between 6 and 7 km/sec. In fact ROCKSIM shows the velocity at apogee was about 6.1 km/sec, on the way down gravity imparts another 1 km/sec velocity to make it 6.85 km/sec Mach 25, speed of sound at that altitude is 270m/sec

Thirdly, the composite motors of the size used in Agni-V has given the DRDO the confidence to go for missiles with larger motors and manoeuvring warheads because the motor casings, made out of composites, will be light in weight but provide a higher performance.

It was indeed manuvering warhead.

Although the DRDO's missile complex in Hyderabad comprising the DRDL, the ASL and the Research Centre, Imarat (RCI) played important roles in developing the components, systems and subsystems for Agni-V, the ASL's contribution stood out. The ASL, which Sekaran heads, designed and developed the Agni-V, built the powerful propulsion systems for its three stages, developed the light-weight rocket-motor casings made of composites and the heat shield too. Chander praised Sekaran's role in designing and developing the heat shield.

PTI/DRDO is on record durign initial Agni-III flights that the booster was composite. They reported those days that second stage was margaing steel (which has similar performance liek composite case in terms of mass fraction {read lighter and stronger}) that did not make sense then as well as today. IMHO the second stage was always compsoite (in A3 as well as now A5). All that was added now was the upper stage motor was composite carbon (compared to earlier reported compsoite that did not mention carmon, ostensibly meaning composite based on fiber that was other than carbon fiber. E.g. kevlar etc).



It all fits with in teh A3 mass of 48 tonne and now A5 mass of 50 tonne. the 2 tonne difference is mainly for added 3'rd stage.

Although the ASL had made heat shields for previous Agni missions including that of Agni-III, the shape, size, diameter and angle of the heat shield for Agni-V was different. The heat shield's diameter in Agni-V was 1.5 metres, while it was 1.2 metres for Agni-III.

This is good data.

Another strength of the ASL lay in designing and developing motors propelled by solid fuel for Agni missions. For the Agni-V test flight also, the ASL designed and developed solid motors for its three stages. Besides, it developed the all-important light-weight composite for the second- and third-stage motors, which led to a reduction in their weight but far better performance. A crucial step towards developing Agni-V was taken when the ASL developed in 2007 a large rocket motor casing made entirely of carbon-filament wound composite. This casing, developed indigenously, formed the third upper stage of Agni-V. The casing went through full qualification trials in 2007.

See my earlier comment.

Systems engineering is also one of the strengths of the ASL because it specialises in building up from what it already has. With the addition of a third upper stage and with minor modifications, the two-stage Agni-III metamorphosed into an awesome Agni-V. Yet the weight remained the same for both vehicles despite the addition of a third upper stage to Agni-V because the second- and third-stage motor casings were made out of light-weight composites. A lighter missile can be easily transported by rail or on road. Besides, it can carry a payload over a longer range.

Could mean that A3 second stage was composite, now it is even lighter carbon composite.

The RCI developed the navigation system for Agni-V, and its architect was the young G. Satheesh Reddy, Associate Director, RCI. “Our navigation for Agni-V was different from the one used for Agni-IV. It was a redundant, reliable system with high-performance and accuracy,” he said. Agni-V had two navigation systems: ring-laser gyro-based system and a micro-navigation system with good accuracy. Fault-tolerant features were incorporated into the navigation system and on-board computers. “Our on-board computers have been developed in such a way that they can recover transient failures. Besides, the entire data computation in avionics is highly reliable and robust,” he said.

Reminds me of someone couple of decades ago who had proposed /developed a distributed reduendent avionics framework (including INS) for high mission robustness albiet without panelty of dual redundency, where a backup system takes over albiet at reduced precision, for rocketery application. Quite gratifying.