Newbie Corner & Military Miscellaneous

[koti]

What will be range advantage, presumably if we use ICL-20 as propellants in Nag (especially air launched Helina version) and Akash missiles. TIA.

That would be suicide.

Propellants are always slow burning compared to explosives and high explosives. Low Explosives burn up fully in a very short time. High explosives burn up in an even shorter time. Propellants need to burn relatively slowly and evenly to produce combustion products (gas) at a predictable and controlled rate. ICL 20 is high explosive. Diwali crackers are low explosive.

Using high explosive as propellant would cause the missile or gun barrel to explode. With explosive power metal is bent and twisted. With high explosives, metal is sheared and shredded.

I disagree sir.
Also, NASA has several hypersonic trans-space vehicle concepts that employ precisely this mechanism to achieve long ranges and very high speeds.

[shiv]

Shivji as per following CL-20's use as propellant is being researched .

http://www.drdo.gov.in/drdo/English/dpi ... _HEMRL.pdf

CL-20 a molecule that can be incorporated into both propellants and explosives

http://nopr.niscair.res.in/bitstream/12 ... 87-192.pdf

Blow me down!!

Now I know why the ancients used to put alcohol in cough mixture. Who'da thunk it?

[shiv]

What will be range advantage, presumably if we use ICL-20 as propellants in Nag (especially air launched Helina version) and Akash missiles. TIA.

That would be suicide.

Propellants are always slow burning compared to explosives and high explosives. Low Explosives burn up fully in a very short time. High explosives burn up in an even shorter time. Propellants need to burn relatively slowly and evenly to produce combustion products (gas) at a predictable and controlled rate. ICL 20 is high explosive. Diwali crackers are low explosive.

Using high explosive as propellant would cause the missile or gun barrel to explode. With explosive power metal is bent and twisted. With high explosives, metal is sheared and shredded.

Well as others have said it appears that CL 20 can actually be used as propellant. I am guessing it is mixed with some inert stuff so it does not blow up. When I was looking at some links a few days ago the description of CL-20 and similar high explosives was that if you made a 1 mile long cord of the stuff and lit one end - the other end would blow up in one second.

[ashokpachori]

I have a newbie question.

Why is the radar antennae shaped like a plate. In modern day AESA, why not shape it like the inside of the nose cone. It will give a lot more area to put more modules or make the nose thinner.

I can see a problem with the fact that very few of the modules will be directed in the direction of the nose of the aircraft. However we can go for a hemispherical design or a flattened hemispherical design. This would help us get more are for the modules or help us make the nose thinner with the same number of modules.

Why is such geometry not adopted for the antenna?

Antenna tutorial

[bapatnikhil]

Hi everyone, my first post and a newbie question:

In Orbat section here, we have structure of infantry battalion. Each section has 7 assult troops (I am assuming they all carry INSAS) and support group of 3 soldiers. Do they carry insas LMG? If yes then 3 LMGs? Like one per soldier? But then the total number of soldiers in support groups in the battalion is 108 soldiers in supporting fire role. But the whole battalion of about 900 soldiers are authorised only 40 LMGs? Or is there somthing I am missing from the table of authorised equipment?

Second question, who then carries the MGL? Is it standard issue to all? And where the MGL person fit into assult-support sections of a section?

[Indranil]

Antenna tutorial

Thank you. If I find my answer there, I will provide the crux here.

[PratikDas]

I have a newbie question.

Why is the radar antennae shaped like a plate. In modern day AESA, why not shape it like the inside of the nose cone. It will give a lot more area to put more modules or make the nose thinner.

I can see a problem with the fact that very few of the modules will be directed in the direction of the nose of the aircraft. However we can go for a hemispherical design or a flattened hemispherical design. This would help us get more are for the modules or help us make the nose thinner with the same number of modules.

Why is such geometry not adopted for the antenna?

Sirji, what you're suggesting is entirely possible. In fact, why stop at a continuously varying radar surface, as opposed to planar surface, confined within the nose of the aircraft? Why not utilise much more of the aircraft's surface for active radar and communications? While there are many challenges including mathematical complexity of signal processing, power requirement, cabling weight and volume, ease of maintenance, etc., the idea is not without precedence.

September 2006: DARPA asks Raytheon to develop football-field-size radar for future surveillance airship

The low-power-density radar is to derive its sensitivity from an extremely large aperture that occupies much of the surface of the blimp-like airship. SAS is also charged with devising a means to bond the radar to the hull or other structure of the airship to save weight.

Although it would contain “millions of electronic components,” the thickness of the antenna as envisioned by Raytheon would no thicker than half an inch. Only when bonded to the hull of the airship would the array be stiff enough to behave properly as an antenna.

March 2010: DARPA's Solar Powered Radar Blimp to Hover 12 Miles over Future Battlefields

As its name implies, ISIS features a highly creative design that takes the performance-to-mass ratio to a new level. In comparison with a conventional airship, in which the payload is two or three percent of the system mass, the ISIS payload will approach 30 percent.

[Indranil]

Thank you for the information ... please drop the sir

[Pratyush]

Guys,

Can a ground based radar be adapted for airborn application without too many modifications.

[Gaur]

Guys,

Can a ground based radar be adapted for airborn application without too many modifications.

No, especially if you want look down mode. For fighters, space and power also become a major issue. Not to mention that ground based radars may not use X-band that we need for fighters.

[Pratyush]

I was thinking in terms of the Ground based 3d radars to be mounted on Aerostates to provide cheap AEW type solution.

[K_Rohit]

http://www.bharat-rakshak.com/IAF/Galle ... _Mem01.jpg

What is the "S-22" in the list of aircraft and people lost in this photograph?

EDIT: Looks like S-22 is the SU-7. Why is it called S-22? SU-22 was the SU-17 fitter, right?

[Jagan]

"S-22" is short for "Type S-22" aka Sukhoi-7 BMK. Just as the MiG-21s had Type designations (T-77, T-96 etc), Sukhoi-7 had the Type-S22 designation (I think based on the Soviet Design Bureau's classifications)

[Jagan]

Hi everyone, my first post and a newbie question:

In Orbat section here, we have structure of infantry battalion. Each section has 7 assult troops (I am assuming they all carry INSAS) and support group of 3 soldiers. Do they carry insas LMG? If yes then 3 LMGs? Like one per soldier? But then the total number of soldiers in support groups in the battalion is 108 soldiers in supporting fire role. But the whole battalion of about 900 soldiers are authorised only 40 LMGs? Or is there somthing I am missing from the table of authorised equipment?

Second question, who then carries the MGL? Is it standard issue to all? And where the MGL person fit into assult-support sections of a section?

The Support Group of 3 Troops whould carry only 1 LMG per the three person team. One is a leader - the other is the LMG Loader). This was the old Bren/LMG system. Things may have changed with the Insas LMG induction. I remember vaguely that the section leader or the loader carries a Carbine as well. (not the Rifle). will dig up the notes and let you know.

[manish.rastogi]

okay can anyone direct to some article or whatever or tell me about the various band radars and their pros and cons....??

[Gurneesh]

What tank is this ?

[Pratyush]

CV 90-120

[Pratyush]

Guys,

Building a ship using conventional methods has the following basic steps.

1.Laid down
2.Launch
3.Fitting out
4.Trials
5.Commissioning

This is a time consuming process. It is not unusual for a s ship to take 5 to 7 years to be commissioned using this method.

Now the question I have is when a ship is built using modular construction. Do the modules before being fitted on the ship are fitted out with what ever they are supposed to contain. E.g the module which will go on to become the engine room will have the engine and transmission gear fitted into it before taking its place in the ship. So on and so forth.

[Anil_L]

link spammer

[jamwal]

I've been reading about Air Force ordering more Akash systems after getting convinced about it's performance from the systems it purchased earlier. I was wondering what exactly they did with the systems ? Testing ?

[Jeff Wickline]

Is there a BRF thread which discusses strategic rare earth?
I understand that most rare earths are mined and purified in China and many such rare earths are strategically important for high power magnets (EM Guns, EM actuators, Gyros), compact batteries, catalysts for synthetic compounds and additives.
Thanks in advance.

[ashokpachori]

Is there a BRF thread which discusses strategic rarer earth?
I understand that most rare earths are mined and purified in China and many such rare earths are strategically important for high power magnets (EM Guns, EM actuators, Gyros), compact batteries, catalysts for synthetic compounds and additives.
Thanks in advance.

The prices of rare earth elements (REE) are northbound, cause only one country (China) with 97% has the monopoly in the world.

Each missile uses samarium-cobalt permanent magnet motors to direct the moving flight control surfaces (fins) (Hedrick and Templeton, 1991).

From Abrams tanks to sophisticated radars, just about every advanced weapons system used by the Pentagon contains some form of rare-earth elements. Indeed, there is no single military system in use by the Pentagon that does not contain rare earths — a category that spans 17 elements, from lanthanum to lutetium, scandium and yttrium. Increasingly, though, US and European defence equipment manufacturers are at the mercy of Chinese rare-earth suppliers

You may start the thread yourself should you so wish.

Very interesting subject indeed.

[Jeff Wickline]

Is there a BRF thread which discusses strategic rarer earth?
I understand that most rare earths are mined and purified in China and many such rare earths are strategically important for high power magnets (EM Guns, EM actuators, Gyros), compact batteries, catalysts for synthetic compounds and additives.
Thanks in advance.

The prices of rare earth elements (REE) are northbound, cause only one country (China) with 97% has the monopoly in the world.

Each missile uses samarium-cobalt permanent magnet motors to direct the moving flight control surfaces (fins) (Hedrick and Templeton, 1991).

From Abrams tanks to sophisticated radars, just about every advanced weapons system used by the Pentagon contains some form of rare-earth elements. Indeed, there is no single military system in use by the Pentagon that does not contain rare earths — a category that spans 17 elements, from lanthanum to lutetium, scandium and yttrium. Increasingly, though, US and European defence equipment manufacturers are at the mercy of Chinese rare-earth suppliers

You may start the thread yourself should you so wish.
Very interesting subject indeed.

Thanks, but I would rather wait for the Mods or Seniors to take the lead. I am unsure whether this should fit "Strategic Issues & International Relations Forum" or "Technology & Economic Forum"

[neerajb]

How is the water stopped from entering a sub through the propeller shaft opening in the hull?



Cheers....

[ashokpachori]

How is the water stopped from entering a sub through the propeller shaft opening in the hull?



Cheers....

Aha....

Its a big (custom made) bearing!

[Indranil]

How is the water stopped from entering a sub through the propeller shaft opening in the hull?



Cheers....

Just like in any other ship. You will find a lot on this on the web.

[Jeff Wickline]

How is the water stopped from entering a sub through the propeller shaft opening in the hull?

Cheers....

The problem of water ingress through propeller shaft is not unique to submarines. The same is (qualitatively) true for ships as well as in household water pumps. The major difference in submarine is quantitative, because the external water pressure may be many times more.
For ship's propeller shaft the bearing is generally called "stern tube" with usual glands and stuffing box. I guess in submarines, such stern tubes would also use hydrostatic pressures from inside (through gear pumps) to partially balance the external pressure. But I may be wrong.

[rahuls]

A newbie question, so please spare the stick.

Is there a difference in the way the Army people are taught to salute from the way Air force and Navy people are taught ? To be specific, in the pic below, the Navy and Air force chiefs and their subordinates have their palms facing the ground where as the Army chief and his subordinates have their palms facing to the front.

I observed this on Navy day too when some other general stood in place of Army chief at the Amar Jawan jyoti.

[atreya]

Rahuls, you are right. I have no clue about Air Force, but it is the Navy people who salute differently from Army guys. It all started with the Britishers during the Age of Sail. Sailors regularly worked with tarred ropes and stuff and consequently had greasy and dirty hands. It was considered disrespectful to show your dirty hands to your superiors, so they developed a palm down salute. Another story I heard is that once, some Queen was on a visit to the deck and was quite unimpressed. A sailor, busy with his work, saw her and popped a palm down salute since his hands were dirty. The Queen then made that a rule for all Navy personnel to use that salute. I guess the tradition has continued ever since then. Why the Air Force salute like that, I have no idea.

[ashokpachori]

A newbie question, so please spare the stick.

Is there a difference in the way the Army people are taught to salute from the way Air force and Navy people are taught ? To be specific, in the pic below, the Navy and Air force chiefs and their subordinates have their palms facing the ground where as the Army chief and his subordinates have their palms facing to the front.

I observed this on Navy day too when some other general stood in place of Army chief at the Amar Jawan jyoti.

It is also probable that the Army and Air Force salute with the palm facing outward to indicate that it is empty. However, the naval salute has the palm facing inwards. The accepted explanation for this is that since a sailor's hands are invariably dirty and calloused from work, keeping the palm hidden is more appropriate. Salutes are always rendered using the right hand, but in case of physical disability, the left hand may be used.

[abhinavjo]

The Airforce earlier saluted like the Army guys. they changed it recently. Theirs is now something like a compromise between Both navy and the Army. So in laymen terms you can say that the Army salutes by keeping the palm at 90 degrees, Navy by 0 Degrees and Airforce at 45 Dergrees

[K_Rohit]

^^^^^^^^^
Its not just the palms. Army goes "longest way up and longest way down". Navy goes "shortest way up and shortest way down", IIRC ...or was it "longest way up, shortest way down". Well, either ways, there is a difference in how the salute is rendered.
Man, I can't believe I forgot these things.

[Jeff Wickline]

Is there a BRF thread which discusses strategic rarer earth? -----snip ------------------

-----snip -----------------You may start the thread yourself should you so wish.
Very interesting subject indeed.

Thanks, but I would rather wait for the Mods or Seniors to take the lead. I am unsure whether this should fit "Strategic Issues & International Relations Forum" or "Technology & Economic Forum"

Just discovered. There IS a thread, called "Mining & Processing", in the "Technology & Economic Forum", which contains discussions on rare earth minerals. Thank god, didn't make the blunder of starting a new one.
There goes the saying: "whichever is not in (Maha) bharat (Rakshak forum) is not in Bharat!"

[manish.rastogi]

one quite noobish question....what exactly is the role of light jet fighters in wartime??

[Jeff Wickline]

one quite noobish question....what exactly is the role of light jet fighters in wartime??

The same questions from me too. Could not get satisfactory answers from Wiki or Google. Most links point to Tejas only. But we would like to know what a "light" fighter/combat aircraft is expected to do and what it is not.
Gurus please help. Thanks in advance.

[Gaur]

Well, there are two reasons for light fighters:

1> Maintainability: Light fighters are single engined fighters and are thus "supposed" to be more maintainable with shorter turnaround time. If the turnaround time is short enough, it is a huge advantage. This is because every mission does not need exceptional payload. This also gives much respite to ground crew. Considering that the maintainance performed during Wartime is at a very hectic pace, easier maintainability will result in relatively lower losses due to maintainance. This is also very important as nearly half the accidents occur due to technical issues even during peacetime.

Eg: A light fighter like Gripen may be able to carry out 2-3 CAS missions in the same time as a heavy fighter will perform 1. Please note that this is just for the sake of explaining. I am not claiming that Gripen can do that..although SAAB claims much more than that.

2> Cost: This is somewhat linked to point 1. Ideally, any AF would like to have exclusively heavy fighters in large nos. But that is not economically feasible.

It is like any Military would like to have thousands of Ballistic, Cruise missiles & SAMs instead of a few hundred fighters. That would be much more effective than aircrafts but it would not be economically feasible.

In short, you've got a limited amount of money. So, one has to strike the right balance between quality vs quantity.

[shiv]

The concept of "light" and "heavy" came in the years after world war 2. It is well worth remembering that the only ountries that could design and build aircraft after WW2 were the USA, Britain, France, Germany, Italy and Russia (USSR), and Sweden. (India, China, Spain, Argentina, Brazil, Romania, Czechoslovakia, Poland, Indonesia etc joined the club much later. Most countries in the world do not make aircraft)

Of all these countries - the only countries left with any resources for innovation after WW2 were the US and the USSR. Germany and Japan were banned from developing military aircraft by treaties. Britain and France had the engineers but not the money. Since nuclear weapons had just come into the hands of the US and USSR it was imagined that all air warfare in the future would be by "heavy bomber". The "heavy" part was needed to carry a nuclear bomb weighing a ton and a lot of fuel to fly from US to USSR or the opposite direction. These planes would fly very high and it was thought that nobody would be able to intercept them and that wars would start and end with nuclear weapons. But something was needed to counter these high flying bombers. "Light" aircraft were designed to be nothing more than engines with wings - carrying 2 or 4 missiles to shoot down those high flying bombers.

But for India the real meaning of "light" came with the purchase and manufacture of the Folland Gnat. The Gnat was a small and relatively low tech fighter designed to take on high flying Soviet bombers. But what was unknown even by the manufacturers was that it was stealthy because it was small - so it could often not be spotted until it was too late.

Another "light" fighter that the IAF got was the MiG 21 - again an aircraft designed primarily to shoot down high flying American bombers. But it was little more than an engine with wings and two missiles - and turned out to be very agile. I think every child can understand that being light and being agile can go go hand in hand simply because of inertia, or lack of it (in the absence of thrust vectoring). In order to counter the MiG 21 the US came up with the F-16. In order to counter the F-16 India bought the Mirage 2000 and the MiG 29.

A "light fighter" is light on fuel and light on armament as well. It is possibly cheaper to build in large numbers. Since India has (unfortunately in my view) never been a belligerent nation sending our armies and air forces to invade other countries - we have always been on the lookout for "defensive" weapons. In the case of aircraft a "light fighter" makes a good defensive weapons platform. If an aircraft needs to do CAP (Combat Air Patrol) close to its own base - great range is not required. Both the Gnat and the MiG 21 served this role. I am certain that these were the thoughts that prompted the development of a "light fighter" in India.

But if you are looking at attack into another country then you are looking at heavy or "medium". Heavy means long range and plenty of weapons - but it is costly and is a huge target to get shot down. Medium is a compromise between light and heavy. "Multirole" generally means "medium" - although even the MiG 21 has now become a multirole aircraft.

[manish.rastogi]

thanks for that.....so basically light aircrafts are for CAP!??!

[Rahul M]

manish, it's not possible to demarcate that clearly. there is always a fuzzy area. in modern warfare light aircraft get used in the same roles as medium/heavy ones, only at a lesser range and/or with lower payload. the F-16, US' idea of light fighter was used in everything from CAP to long range strike.

the primary motive behind the continued development of light fighters is cost, cost of acquisition and cost of operation. for most air forces, 90% of the missions can be carried out with light fighters. the heavy fighters are retained by the larger air forces for that rainy day when the light ones won't do.

caveat : the definition of light and heavy changes with the era, the mosquito at 8.5 tonnes was a heavy fighter in WW2 when the spitfires tipped the scales at 3 tonnes. the LCA at 13.5 tonnes MTOW is considered the lightest fighter in the world !
many of today's fighters are heavier than yesterday's bombers !

[shiv]

thanks for that.....so basically light aircrafts are for CAP!??!

This would have been true in the days before air to air refuelling and fuel efficient engines, lighter, stronger materials (like titanium and composites) as well as PGMs.

In the days of plain dumb bombs you might have needed to drop 16x500 kg bombs to disable one bridge, radar installation or an airfield. That may have required four aircraft in the past. One aircraft can do that now. A light, small fighter full of composites is fundamentally stealthy - a fact that can be utilized in many ways.

You need to remember that some expressions used are Indian in origin. "Hot and high" is an Indian definition and Indian requirement. So is "light multirole fighter". If you try and look for equivalents in foreign (non India) countries you will not find an exact match because each country designs stuff for itself - and stuff that can be exported to many countries. "Light" and "hot and high" are not necessarily suitable for many countries of the world.