Defence, Science & Technology

POF Wah’s International Seminar 2001

Columnist Col (Retd) EAS BOKHARI visualises the annual POF Seminar.

Pakistan Ordnance Factory (POF) Wah is holding a seminar on Defence S&T sometime in the middle of November this year. It used to be a regular affair till about December 1993, when it was discontinued.

The specific area this year is the production of ammunition of all types including gun ammunition and propellants. POF Wah produces large quantities of variegated types of ammunition both for domestic consumption and export.

One interesting sub-topic of the seminar is the artillery ammunition and its production with special reference to range extension, lethality and accuracy within the framework of the existing types produced. Knowing that our capability is largely derived, this topic is not totally self-defeating but it is somewhat difficult.

Artillery is a dynamic arm and has always kept up well ahead of the developments of its supported arm i.e., infantry and armour. But sometimes the technology produces such quantum leaps that the Third World countries may not be able to keep pace, as all new technologies involve huge financial resources for R&D.

I have tried to muster some of the more relevant points in this regard, in the accompanying presentation. Range is a function of the length of barrel, gas pressure/rate of propellant burning which produces the initial projection velocity and the angle of projection et al. But when the velocities are large, the projectile shape and drag plays havoc with projectile flight. This problem has been tackled by such titans as Galileo and the German Carl Cranz most admirably — but in the present day fluidity of war has rendered their solution of the projectile motion somewhat obsolete. With the projectile being the primary artillery weapon, many innovative projectiles are being tried these days and some of the more novel ones are the ‘smart’ and guided ones. Their characteristics are just touched upon in the presentation.

Accuracy is important for being cost effective. In equipments which are manually operated the human factor also contributes in this regard besides the basic potential of an equipment — ammunition relationship. All the same a ‘guided’ ammunition is definitely superior to the

so-called ‘fused’ ammunition.

Survey i.e., the accuracy with which the target and guns are surveyed is another very important consideration and the speed with which this can be done is equally important. The current satellite survey has made the gunner problem much easier and accurate.

Lethality is more a matter of rate of feed at the target end and the amount of ‘treatment’ cum saturation that the target receives. It is here that the multi-barrel launchers have an edge over the age old single barreled workhorse, their partial inaccuracy notwithstanding.

Of course, purely from the support point of view it would be ideal to have as much SP (Self- Propelled) Artillery, that a country can afford to keep pace with the fluidity of operations especially in support of the armour.

Having given a deep thought to the problems that entail my feeling is that, in our environment we may be able to play about with the operational parameters but as I have said somewhere, the present single barreled gun has reached its optimum  efficiency as a support cum neutralization weapon. Further playing about with the existing parameters may not be fruitful, and a new way must be found out along with the existing workhorse.

Future Trends in Enhancing Range, Accuracy and Lethality Of Exhausting Artillery Ammunitions

There is an interesting ballad — somewhat sardonic and which has been quoted even by the great historian of Artillery Col Hime. It runs:

“Gonners to schew their art

Into the town in many a parte

Schot many a fulle great stone

Thanked be God and Mary mild,

They hurt neyther man, woman, nor child;

To the houses, though, they did harm.”

This is quite realistic. The older artillery was employed more for battering and for instilling fear of God in the enemy’s heart than anything else. Over a period of time the artillery has become one of the most lethal arm and has produced the maximum number of casualties in the battlefield. During the Second World War, almost 60 percent of all battle casualties were caused by artillery fire. Any combat veteran will tell you how fearsome artillery is as an arm.

There is no doubt, that the gun which is somewhat figuratively termed as a single cylindered ‘IC’ (Internal Combustion) engine by the great historian of armament and military science Gen JFC Fuller, the real artillery weapon is the ‘projectile’ and gun is just a means to project the projectile. It is the projectile which instills the fear of God in the enemy. This does not mean that we can ignore refinements in the equipment side and other force multipliers like the ballistics and survey. All these help the projectile to be more cost effective and lethal.

From the good old grape shot, shrapnel and other such projectiles, the present day projectile is of generally carrier type and much more sophisticated both chemically, ballistically and from the point of view of the results, at the target end. There is a definite trend in the modern projectile — though perhaps such shells have not been mass produced for smart or Guided projectiles, which hardly miss the target and their accuracy is optimum.

The examples of these shells are the US SADARM (Search and Destroy Armour). These munitions sometimes are referred to as PGMs (Precision Guided Munitions).

SADARM or the M483 AI 155mm Cargo shell is primarily designed for attack against armour.

And then, there is the Bofor fabrication I55 + BONUS OBG - the smart artillery ammunition. OBG stands for Obus — Bofor Giat, and as Indicated, this projectile is a result of the French-Swedish collaboration. It is sensor fused anti-armour artillery projectile. As will be seen that these projectiles are totally different from the conventional projectile in their configuration, but then there are such projectiles like the HEER (HE-Extended Range) which provides additional range — but I suppose the extra range is traded at the cost of abnormal gunwear and only a limited number is available in the first line ammunition.

I may be somewhat pessimistic, but I have come to think that the present day single barreled gun —which has been our workhorse for centuries may have come to the end of the tether, the various ballistic and other refinements in ammunition notwithstanding.

We know it for certain that the Multiple Rocket Launchers in the 1991 Gulf War were terribly effective and saturated the target area quickly and gave no respite to the enemy, whereas the gun units were somewhat slower in this despite the employment of UAVs and satellite fixations (which no doubt improved accuracy).

Some details of the US  Howitzer SP ‘The Crusader’ — which replaces, the Paladin are impressive. But then its cost is also prohibitive. The new SP Howitzer can move at the rate of 47 Km/h and has a rate of fire of I0 RPM and has a range of upto 40 Km. It cost $23 millions per set of basic equipment and the resupply vehicle.

Finally if we examine the basic (motion in vacuum) configuration of the projectile motion equation i.e.

Y + x. Tan ø -       g.x2

                                    2vo  .  Cos2 ø

To this, we add the biggest bugbear i.e., the projectile drag. Hence, we can definitely come to a range extension arrangement but at what cost? I suppose it exists only theoretically.

Finally, I do not reject the options of additional range, lethality and accuracy with added articulation in all the parameters discussed above — but for the task of saturating the target area more effectively (and where even the armour is not quite safe), the Multiple Rocket Launchers are awesome as has been proved in the 1991 Gulf War. These weapons may be ballistically somewhat inaccurate.

However, for countries which cannot afford a large proportion of SP artillery and multiple rocket launchers — a zealous effort in ballistic research (in a wind tunnel) for a more efficient ballistic shape, a more powerful and regular burning propellant (probably liquid), such force multipliers as the UAVs, satellite fixation of both the guns and the target will be a recommended line of action.

The Quest for Range

The human fist can be considered the first missile. But it had a very limited range. It could be used for a close quarter battle only. The stone thrown through crude engineering devices went further, and the sleek arrow went still further and engaged the enemy at far away distances. Then came the Age of Gun Powder — which in fact democratised fighting in a big way and fighting was no more the domain of rich knights and lords at arms. Anyone could fight.

Incidentally, the discovery of gun powder and the use of gun powder in firearms, especially guns cannot be related in terms of time and these two events apparently were independent of each other. The word gun appears in an extinct Arabic source and the invention of gun powder has been claimed by a number of countries — and perhaps the most creditable are the Chinese.

In a modern battle it is always advantageous to engage the enemy at a distance, thus deploy him and gain time — for that matter by successive deployments impose attrition on him. All commanders would wish to do this. The craze for range has fascinated all commanders as well as the manufacturers of guns. This incidentally is one of the topics for the S&T Seminar at POFs Wah during their Golden Jubilee Celebration in middle November 2001.

Sometime back, I had two, rather distinguished looking visitors here in my ramshackle and rag tag office. This was quite unusual and unexpected and I think it were the columns in ‘Nation’, which had brought these rather urbane people to my rural habitat. My place in any case was perhaps the most improbable place for the type work, as none of the facilities needed to do this type of work existing here. There is not even a small library in Lalamusa.

These two gentlemen were interested to discuss “HEER” (not of the Ranjha connection but implying High Explosive Extended Range). One of them, the more polished, inquisitive and aggressive looking had done Ph.D in Chemistry and seemed to have studied explosives — both High and Low ones in detail. I came to know later that, he was running a glass factory in Jhelum. He was also a researcher of considerable repute and often took assignments abroad. The other gentleman was interested in rocket propulsion. We had a fruitful discussion. Some of the points that cropped up in this unusual meeting are presented in the paragraphs that follow. It had somehow fallen to me to be the main participant in the discussions.

The story of the modified ‘Scuds’ by the Iraqis during the Gulf War 1991 is well known as the Iraqis had literally changed the entire ballistics of the Soviet supplied Scud -B and by putting two motors in one Scud, they sacrificed the original ballistics for additional range to reach out to Tel Aviv and Riyadh. They managed to do it but at what cost? It is known that these modified Scuds broke into two while in the re-entry phase of their own, and not to any external influence.

It is somewhat erroneously reasoned that this break up was due to the employment of “Patriots’ and this claim of Ratheon has been debunked by a Congressional inquest. The point I am making is that stop gap and ad hoc arrangements can never succeed and the problems in ballistics must be tackled in their entirety and all the relevant parameters must be taken into consideration.

The trajectory issue notwithstanding, the range problems of both guns and rockets are nearly the same, involving knowledge of a number of modern disciplines such as physics and chemistry et al. Range in fact is a function of a cluster of variables. Some of these can be determined mathematically (especially with the help of computers), but some others have chosen not to yield even to the rigours of pure mathematics and ballistics. One such bug bear is the projectile drag.

The major variables — just to name a few are the gun itself, its calibre length, the angle of projection at which it is fired, the powder charge used to impart initial velocity, the barrel grooving system, its driving band and drift pattern etc. The propellants play a very important part as these provide the initial pressure at the base of the projectile in the initial stages of projectile movement through the bore.

From the point of view of the propellants, their rate of burning i.e. uniformity of burning and their calorific values are most important.

Their type i.e. solid, liquid or single base, double base or treble base is also of consideration.

And then, there are such parameters as the earth’s gravitational pull, air resistance (as already mentioned and the cost of some repetition) the base drag in the wake of flying shell which is a spinning body and not a point, all these are a brake on the range and sure parasites. Another set of parasites are the atmospheric conditions such as the wind speed, direction or perhaps the sudden change of direction. All these variables affect the projectile range and these EFFECTS must be worked out.

The artillerist is not a chicken hearted fellow and he has now developed a highly sophisticated system of internal and external ballistics (and so has the rocket engineers) to tackle the projectile flight problem. Before a weapon goes for field/prototype trials, the best possible weapon ammunition shape/weight configuration is worked out to give the best possible performance. Generally it is unfair to break the rules as the Iraqis did to their utter dismay. Sometimes a lot of  ‘Wind Tunnel’ work is essential for determination of a new projectile and its performance in a particular tube.

Of course there is never an end in research and some of the latest trends are:

• There are the Generation II propellants under development which employ a new formulation that provides a 13 per cent increase in the energy per gramme compared with its predecessor. It also provides 50 per cent increase in loading density — and layers of the propellant have a different burn rate.

• Work is also in hand to provide a recoil management that will permit high energy launch from a lighter gun.

• The use of active boat tailing by altering the shape of the rear of the projectile during the flight, in order to weaken the recompression shock. Thinner control surfaces are also being tried out to lower supersonic drag and allow for maximum altitude.

• Increased range in the subsonic glide portion of the flight.

• Changes in the shape of the projectile body and control surfaces (by active cambering), eliminating the hinge pivot in order to decrease trim drag, and exploiting unsteady aero-elasticity.

• Greater stability, achieved through body shape changes.

• Increased band width for actuation system, exploiting faster actuators and other methods.

• And interestingly, unsteady aerodynamics (which are widely employed by birds and insects) exploit the fact that a plunging airfoil generates thrust.

Of course there are a variety of projectiles with extended range in service worldwide — and some of these and their characteristics will be discussed in the concluding presentation.

So, we continue with HEER (High Explosive Extended Range) projectile and some of its variations. At the very outset, it should be appreciated that any gun calibre has a variety of projectiles — these could be HE, smoke (and other carriers) and even anti-tank projectile to make the gun versatile. To this, the Extended Range ammunition could be added.

One of the more acceptable technology for range extension is the use of a rocket booster at the base of the projectile (Base Bleed), which works in the opposite direction of the direction of movement of projectile, thus giving it extra boost/range. In certain cases even additional 30 percentage of the range may be achieved. There are some experts who opine that even better fragmentation may also result with base bleed. Of course some loss in the total weight of the projectile has to be accepted due to the insertion of the base bleed rocket.

As an example — which probably would need an update — the Belgian Company PRQ - SA Brussels has produced a HEER projectile which can improve the range of 130 mm gun (held both by Pakistan and India), considerably to 40 Km with special PRB charge (and may be even more if the charge is preheated). The following table shows the comparative performance and is self-explanatory:

Operating temperature in both cases — 400 C to + 600 C

A little detailed description of the base bleed technology may be found in the paragraph that follows:

“Gas injection at the rear end of the shell moving at transonic or supersonic speeds, have a favourable effect on the shell base drag (If gases are injected at a low rate). This concept is attractive since the base drag is about 40 to 50 per cent of total drag for common projectiles ... The base bleed ammunition comes from an adaption of the projectile by fitting burning pyrotechnic materials inside the base of the projectile... The burning gases, thus injected into the depressional flow area tend to balance the base pressure and the ambient pressure during the first part of the projectile flight.... This technology has been perfected by the French firm SNPE, France, who are famous the world over for their explosives ....” I am sure they will have representation at Wah.

One of the SNPE’s main activities is the development and production of different base bleed grains with adapted and optimised propellants. The first step in the preliminary design of a base bleed grain is to get a propellant grain configuration from shell performance. Before experimental investigations, calculations of reactive injecting flow are computed with a base drag reduction  model. Propellant specialists determine the burning gas’s theoretical composition and the temperature using classic thermodynamically calculations.

HEER ammunition is currently available for several equipment but I am not sure if it can be used as a matter of course as it is likely to wear out a gun barrel whose life is determined/measured in terms of EFCs (Equivalent Full Charges) and HEER employs proportionally higher charges. All the same, it is a definite force multiplier.

The other day I was just scanning through the Janes IDR of July 2001 and came across some interesting material on this issue. The magazine has shown the photograph of a South African (Naschem) product — Assegal M2000 base bleed rounds. These rounds were fired in Germany (Meppen) at 600 C with a muzzle velocity of 994m/s and at a pressure of 4I0 MPS using Krauss- Maffei Wegmann PzH 2000 I55 mm SP Howitzer.

The projectile was compatible with the provisions of the Joint Ballistic Memorandum of Understanding (JB MoU) for 52 Calibre I55 mm artillery system and was successfully fired from a German Army PzH2000 in conjunction with the Rheinmetall- produced DM-72 MTLS charge module.

Some 20 rounds were fired, including one in which the charge has been preheated to 350 C giving a maximum range of 41.8 Km. The others fired at the standard temperature (210 C  at sea level) achieved distances slightly in excess of the predicted 40.23 Km.

The driving bands remained intact and there was no side wall engraving either. These problems seems to have existed in the original German ammunition.

The British Army is still to choose the HE ammunition for 52 Calibre Ordnance Braveheart. The procurement will be under TACAS (Tubed Artillery Conventional Ammunition System). The British may conduct firing in US with the Crusade SPH.

“Naschem is expected to enter the TACAS contest not only with the M-2000, but also with the ballistically matched M-2002 screening smoke and M-2003 illuminating projectiles which form part of the Assegai family... The company is, meanwhile, continuing with design and development of its JBMOU compliant hybrid rocket assisted  / base bleed M-2005 velocity enhanced long range artillery projectile (V-LAP), which has a computed range of 52 Km at Zone 6 (54 Km at 1000 m altitude).

It is interesting to see that the quest for range is not only confined to guns / howitzers but efforts are afoot to enhance the range of current mortars especially the 120 mm Mortar, which is almost the standard mortar calibre.

A local public sector outfit in Pakistan has successfully increased the range of the standard 120 mm  Mortar ammunition, which is being manufactured at POF Wah. The project designated as “Glider Project” was undertaken and the range of the mortar was increased to about 10,000 meters plus with rocket assistance.

The outfit had meticulously studied the design features of continental rocket assisted projectiles (RAP) notably the French ones and then taken on hand the range extension of the POF’s unassisted projectile. The modification was carried out by modifying the current unassisted mortar bomb with the incorporation of a rocket motor (at the base) and by re-designing the tail / stabilizing configuration to obtain dispersion pattern of the continental assisted mortar ammunition.

After extensive lab tests and static firings, the ammunition was range tested at Nowshera (Artillery School) and Sonmiani ranges. The ‘Glider System’ was gradually improved and presently the mortar can achieve a range, which exceeds the  French version i.e. PEPA-LP by about 14 per cent with no additional dispersion.

Worldwide, 120 mm Mortar RAP is in the service of many armies particularly Gt. Britain, Germany, France, Israel, India et al. The Pakistani version, it is claimed, has 40 per cent greater range than the unassisted one — and the mortar can engage targets on the reverse slopes (particularly in mountainous terrain) effectively and with impunity.

The technical credentials of the ‘Glider Ammo’ are as below: