sam_kamath wrote:So are the Brahmos missiles solid fuled? I am assuming here that you are referring to the problem of Liquid sloshing. Physical properties of liquids staying same, sloshing should happen in both these missiles, not to mention a Brahmos carrier carries 3 missiles.
From what I have read (so i can be mistaken here) canisterising of a missile involves fuel stabilization too, read (gasoline to napalm)
No, I am not pointing to sloshing issue but structural stresses when the lady is pregnant with loaded fuel.
Again comparison with jet engine powered missile like Brahmos with rocket powered Prithvi is inappropriate, the former has significantly higher ISP and is not a flying fuel tank, OTOH ISP of rocket engine Prithvi is much lower thus carriers a large fuel weight, and is more of a flying fuel tank going up and an empty light weight fuel tank coming down (when its light skin can afford some aerodynamic maneuver).
ramdas wrote:Arunji,
Did'nt you assume for the A-3 range-payload graph that the first stage has composite motor casing ? Shri. Avinash Chander clearly says that as of now, both A-3 casings are metallic. As for A-5 , 2 stages will be metallic though by around 2015 they are moving to all stages composite.
So, is'nt that likely to mean A-3 range is less than what your range payload graph says, maybe 4500-5000 km @1500kg rather than 5500km @ 1500kg ?
However, reports of testing large composite motor casings have been circulating for a while- the PS-3 PSLV 3rd stage has such a casing. So I do not know why they stuck to maraging steel. Is it that right now they do not have manufacturing scale with composites as of now ? Or is it this great "separating strategic from civilian" business that has landed us up in this ?
As for the life time of liquid fuelled missiles. Many Soviet SLBMs were liquid fuelled. they were fuelled in the manufacturing plant itself . Special care was taken to see to it that no leaks occurred. The main engines were largely submerged in the fuel tanks. The fuel used was NTO/UDMH. Still, they had lifetimes of at least 15 years. Maybe even more than 20 years.
Suggest to read the Agni news report again:
http://www.thehindubusinessline.com/200 ... 721200.htm
The first half of the article quoted below generally talks about DRDO missiles and Agni (and not Agni-3) meaning older versions of Agni (A1, A2, A2AT).
M. Somasekhar
Hyderabad, Sept. 24 With an intention to make the country’s missiles lighter, cost-effective and possess greater hit power, the Defence Research & Development Organisation (DRDO) is augmenting its composite materials facilities and capabilities.
An independent centre for composite testing and evaluation is being set up at the Hyderabad-based Advanced Systems Laboratory (ASL), the premier lab guiding the long range missile — Agni programme and providing key technology inputs to other missiles.
ASL already has composites production centre (Comproc), which fabricates the lightweight material for Agni and other missiles. “In 6-7 years, we want to make all the stages of the Agni missile composite structured,” said Mr Avinash Chander, Director of the Laboratory under DRDO.
“At present, the payload and a small portion (nose tip) of Agni is made of composites, while the rest is metallic. Progressively, we will make the airframe, the upper stages and payload completely composite,” {Arun: He is alluding to the Agni-2AT that is now headed by Ms Thomas. A2AT second stage will be composite while the booster will stay metallic albeit much stronger and lighter maraging steel. The composite nose tip again refers to A1,A2 RV, because A3 RV is all carbon composite body with no metal backing}he told Business Line. There is lot of interest from the private sector in the composites arena and no dearth of raw materials, he added. Composite material, which can withstand very high temperatures and are robust, finds application in aerospace, the light combat aircraft and satellites.
The ASL provides composites and solid propulsion systems to most missiles such as Prithvi, Akash, Nag and Astra, Mr Chander said. Another initiative taken up by ASL is in the area of non-destructive evaluation of materials. This would help in assessing the health of the missile systems and components.
The second half of the article then transitions to Agni-3 discussion, quoted below:
Cost-effective
Since we cannot bring these back from the field, the testing done through NDE tools and methods on site would make it cost-effective, he added.
These techniques are useful in detecting degradation of materials, cracks or other minor defects, which can reduce the life of the missile or make it ineffective.
Typically, ultrasound and nuclear magnetic resonance techniques are used. Asked about Agni-3, the long-range, surface to surface missile, Mr Chander said it has been cleared for induction into the Defence forces.
“We will do user trials when required, but it is ready for manufacture and induction,” he said. The missile was tested thrice between July 2006 to May 2008, with the first being a failure.
On Agni-V, he said the development is progressing.
“We can test it in two to two and half years. Two out of three stages will be composite, which will reduce its weight and increase range,” he added.
ramdas wrote:"At present, the payload and a small portion (nose tip) of Agni is made of composites, while the rest is metallic. Progressively, we will make the airframe, the upper stages and payload completely composite,”
So , A-3 is right now, maraging steel casing...
Wrong context. See above response.
The 3 A3s that were tested all had Composite booster motor and second stage casing was maraging steel. 3'rd or 4'th A3 test was expected to use composite case for second and/or 3rd stage motoralso (it is still intriguing why the choice was made, to fly the initial missions with upper stage made of maraging case).
JMT.