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Role of Smokes in Warfare

Role of Smokes in Warfare

Defence Science Journal, Vol 44, No 2, April 1994, pp 173-179 @ 1994, DESlDOC

REVIEW PAPER

Role of in Warfare

p .K. Mishra

Institute of Armament , Pune-411 025

ABSTRACT

The role of smokes in warfare is reviewed with particular reference to the world wars, and various types of smokes are discussed. The smokes that can defeat modem opto-electronics including (IR)/millimetre wave (MMW) guidance and thermal imager are de!>cribed. Environment-friendly non-toxic smokes are dealt with briefly. The future of smokes in these circumstances is mentioned .

I. INTRODUCTION The introduction of military aircraft, especially bombers which could attack important reariarea targets, Use of in warfare is probably as old as warfare created a definitive need for large-area smoke screens itself. The details are certainly lost to antiquity , yet for protection. Consequently much of the efforts, occasional references do Q/.;cur in ancient texts. In between the two world wars was directed towards addition to screening, smokes could flush out the hidden enemy from the cover of thick foliage, natural tunnels, development techniques for producing large-area smoke screens. The principal screening material used caves, etc. For such pu~ses, smoke was generated by included SO3 -OSO3H mixture, a corrosive liquid for burning natural substances like grass, straw, resins, use in projectiles and airplane spray , gums, and asphalt. The American Red Indians were known to be great users of smoke in a very intelligent -Zn, a buming-type filling in and smoke pots, and white pJtosphorus for filling in manner. They could send a smoke signal asking for grenades, bombs and projectiles. These materials were reinforcement, convey enemy strength/weaknesses and superior to those used in , yet were not even relay the messageby repetition. completely satisfactory .The efficiency of German air Although smoke from the use of gunpowder in the operatiL -against British cities during 1940-44 was battlefield was considered a nuisance, deliberate considerably reduced through the use of large-area artificial generation of smoke for military purposes did smoke screens which prevented accurate aiming. The not occur to anybody for quite some time. The credit British protected important industrial centres with for artificially generating smoke for screening goes to smoke pots. They later developed truck-mounted the German Navy which successfully used this mobile smoke generators which produced grey-brown knowledge at the battle of Jutland in 1916. Hence, both smoke by burning and vapounsing crude oil. Allies and Germans developed pyrotechnic screening smokes for use on both land and sea during World War After the World War II, there was hardly any improvement in this field. The Korean and Vietnam I. The tactical significance of the planned use of smoke, which was not fully realised until the close of World wars did not ~ntribute anything. The Falkland war showed that fear of fire and smoke could claim the lives War I, was strongly considered early in World War II. of many sailors. Consequently, extensive research and development programm~s were established early during World War 1.1 Revival or Interest in Smokes II to obtain the information necessary to develop the Since the end of World War II till the advent of tactically required smoke-producing items. Arab-Israeli conflict in October 1973, smoke was a

Received 2 February 1993

"'3 DEF SCI J, VOL 44, NO 2, APRIL 1994

neglected field. The importance of smoke and its (b) Reactive chlorides of TilSi, Chiorosulphonic

capacity to give an edge at the face of sure defeat was acid2-4,6. , realised by the Israelis during the heat of battle after TiC14 + 4H2°-+ Ti ( OH)4 + 4HCl losing 130 tanks in 120 minutes when they discovered SiC14 + 2H2O-+ SiO2 + 4HCl smoke could blind the gunners of A T -3 Sagger missiles of Egyptian Infantryl. The Americans and Russians C1SO3H + H2O-+ H2SO4 + HCl then gave smokes a very important role in warfare. (c) Pelleted in en substances like talc, , SiO2, After the Falkland war it has become a standard practice TiO2, metal flakes, metal fibres, glass fibres, in many a navy to expose sailors to smoke (training carbon fibresS-12. exposure on board ships) .With the introduction into battlefield of sophisticated opto-electronics like laser 2.3. pyrotechnic Means designators, rangt: finder with fire control systems, (a) Generating smoke from hygroscopic chlorides laser/IR guidance, detection in the dark with sensitive (HC smokes)2.3.5.12ZnCI FeCI SiCJ Ti C1 and 2' 3' 4' 4' thermal imager, TOW-tube launched optically guided AJCJ3 formed by pyrotechnic reactions, react with weapons, surveillance satellites, and Strategic Defence the atmospheric moisture to generate smoke. Initiative (SDI), smoke appears to be the only countermeasure that can convincingly defeat all the (b) Generating coloured smokes by volatilizing above hi-tech. dyes3-5.&-14. (c) Generating carbon particles from carbon-rich substances3.5.14-19 1.2 pyrotechnics

The art of producing smokes comes under the 2.4 Tbennal Means science of pyrotechnics, derived from the Greek 'Yord Dropping oiUorganic liquid on a hot surface 'pyr' meaning fire and 'techne' meaning art, i.e. art of generates /oil smokes2.4.5.20. (The hot exhaust of making fireworks2.3. internal combustion engines is a freely available heat source and is used or can be used for producing such 1.3 Smokes smoke. ) Smokes are defined as fine particles suspended in air as the medium3.4 and come under with the 3. TYPES OF SMOKES particle size extending up to 10 Jim. Depending on end use, we can categorise smokes into the following: 2. GENERATION OF SMO~

Smokes can be generated by the following means 3.1 Training Smokes

Such smokes are characterised by their inertness and 2.1 Reacting Metal Phosphid~.4 with Water lack of toxicities20.24, and are extensively used for outdoor training/familiarisation and fire fighting CaJP2 + 6H2O-+ 3Ca( OH)2 + 2PHJ training. Sailors who have familiarised themselves with MgJP2 + 6H2O-+ 3Mg( OH)2 + 2PHJ smoke will not panic under real-rife conditions of battle AlP + 3H2O -+ AI( OH)J + PHJ and will take appropriate steps to save themselves. Many a British sailors were drowned because of panic 2.2 Dispersal by Detonation in the last Falkland war. KCPO.21, NH4Cf, and fog oil smokes are ideal for training outdoors/indoors. (a) Pyrophoric substances like white phosphorus3-5, plasticized white phosphorus3, trialkyl 3.2 Phosphide Smokes based formulations 7; Metal phosphides of Ca, Al and Mg react with water vigorously, releasing copious amounts of phosphine, 4P + 502 -+ 2P2Os which on spontaneous ignition gives flame and the 2AJ(C1H5>3 +2102-+AJ2O3 + 12C02 + 15H2O smoke formed gives night time visibility as well3.

174 MISHRA : ROLE OF SMOKES IN WARFARE

3.3 Screening Smokes (Bursting Type) VEES (vehicle engine exhaust smoke systems) generate smoke by irrjecting fuel (diesel) into the hot exhaust20. White /plasticized white phosphorus smokes are generated by dispersing the material by a Such smokes give visual obscuration and can cover some vital installations/troop/tank formations, etc. in a very burster charge. The smokes are perfectly white but last only a short while. Similarly TiCI4, SiCI4, and short time. chlorosulphonic acid when dispersed by a burster give smoke suitable for screening. Here again, the duration 3.7 Alkali Halide Smokes of smoke is short. Smokes containing inert NaCl/KCl particles can be formed very easily from pyrotechnic formulations 3.4 Screening Smoke (Burning Type) containing KC1O4/NaOO4, Mg and a binder. The screening efficiency of such smokes at 50 per cent RH 3.4.1 HC Smokes is rather low. At 65 per cent RH the smoke has a very Hygroscopic chloride (HC) smokes find extensive good screening power. Hence these smokes are ideal use the world over for screening. Here a -rich for naval use20or for training outdoors. substances like hexachloroethane (HCE) or hexachlorobenzene (HCB) or chlorinated paraffins 3.8 Coloured Smokes react with ZnO, TiO2, Zn, Ti, Si, Silumin, etc. to (a) Coloured smokes are generated by volatilizing generate metal chlorides which spontaneously react with coloured dyes or a mixture of dyes from a the moisture in the atmosphere to form hydrated heat-generating pyrotechnic formulation. Here the chloride/hydroxychloride/hydroxides to give smok~ fuel and oxidizer, usually sugar and KC/03, with good screening properties. TiO2 containing generate the heat and vaporises the dye without formulations give an yellowish white smoke. Fe203 degradation and appears as coloured smoke. containing composition gives orange-coloured smoke. (b) Short-duration coloured smoke clouds can be Longer durations are possible with buming-type generated by detonating dye-explosive mixtures. compositions only. 3.9 Opto-Electronic Defeating Smokes 3.4.2 Red Phosphorus Smokes Modern-day hi-tech has changed completely the Red phosphorus-based smoke formulations give a concept of battle. Sophisticated weapon systems have perfect white smoke but the powerful flame limits its been developed with unparalleled accuracy, range and use by land services. However, it finds extensive use as naval markers with both day and night visibility. killing power using the various regions of Recently, rubber binder based, encapsulated red electromagnetic spectrum for target acquisition, automatic/semiautomatic guidance. Such advances have phosphorus formulations have found use in rapid made the ever elusive dream of first-round hit a distinct deployment smoke formulations for defeating laser possibility. With the development of fibreoptic guidance range finders. The L.gA1/L.gA3 red phosphorus-rubber system in NLOS (non-line of sight) weapon system, the based formulation is used by all NA TO forces fo- such target need not be on the line of sight of the weapon. purposes'. The so-called inaccurate weapons, like mo~ars and 3.5 Day/Night Visible Smokes rockets, of yester years have become accurate by virtue of the added on guidance-'dumb ammunition' have/can The only smoke that has both day and night visibility become 'smart'. The guns can launch CLGP (cannon is chemiluminescent smoke generated by dispersal by launched guided projectiles) or SADARAM (sense and burster of an aluminium trialkyl based formulation 7. destroy armour) to take advantage of high muzzle velocity and can tackle moving targets. Even SADARM 3.6 Oil Smokes can distinguish an armoured vehicle from a truck. Special vehicle-mounted smoke generators are Obscurant materials in the battlefield environment can available which generate copious amounts of have a deleterious effect on the performance of grey-brown smoke by burning/vaporising crude oils. electro-optical sensors. The battlefield-induced

175 DEF SI VOl 44. N, APRIL 99,

contammants such as dust, smoke and foreign gasescan in the extended spectral regions. The dual capability is degrade the atmospheric medium between a target and possible9-11.15.17.19.20.27.These smokes have visual cum senso~ .Devices for target acquisition, ranging and IR cum microwave/ defeating9.10. identification require line of sight contact with the target and in principle can be defeated by tactical obscurants20.

Countermeasures for tanks beating smart These smokes; in addition to the conventional visual munitions26 give type of sensors and the role smokes smoke component, release particles and can play. The visible range of electromagnetic spectrum metaUglass fibre for attenuation in the IR and is 0.4-0.72 .um. TV , LLL TV , and visual guidance fall microwave/radar Tange. Visual and IR attenuation in this range. If the target is no longer visible, none of capability is also attainable8,15-11.31.The US Army the above system5 can be made operational/effective. M 76 has29.41this capability. Weighing 4 Ib, a As long as the target is invisible, it is safe by all means. plastic-bodied, electrically-initiated, propellant- Some types of smoke are capable of providing visual launched, the grenade explosively disseminates a obscuration by virtue of complete scattering of the screening smoke cloud 30 m forward of Abrams tank incident radiationJ. The screening smoke particles cover capable of defeating threat weapon sensors operating a range of 0.05-0.5 .um and may go up to 1 .um. The from visual to far-IR. Formulations capable of this feat screening range extends up to 1.2 .um in the are available9-11.21. electromagnetic spectrum20.Hence common obscurant smokes are transparent to infrared (IR) radiations 3.10 Environmentally Acceptable Smokes beyond 1.2 .um. The operating range of Nd- Yag laser With the increased awareness about the based range finder or designators is 1.06 .um. Hence environment, the danger from smoke these can be easily attenuated by any screening smoke. formulations/ingrecfJents and smokes to the Although IR covers a very wide range, only two narrow environment has been realised lately. Some of the inputs windows covering 3-5 .um and 8-13 .um are useful. As like HCE, HCB, naphthalene, anthracene and end none of the common obscurants is capable of performing products like ZnC12 are outright carcinogenic/toxic, or in this range20,extensive work has been carried out to both. Some of the dyes used in the colour smoke find obscurants. IR radiations of up to 13 .um are easily formulations are carcinogenic. Both the USA and the obscured by fibrous carbon particles of 1:14 JnnI5-20 UK have carried out extensive studies in this .um lengthsls-l9 generated from carbon-rich substances regardI2,13,24-26.Tolerance levels of some of the like naphthalene lanthracenes, styrene-butadinne ingredients have been revised and lowered from time rubbers, chlorine-rich substances like HCFJHCB with to time. Substitutes for HCE/HCB have been found. Mg. Carcinogenic dyes can be replaced by safer ones2(),31-33. Ka, and NaCl aerosols are completely safe and The attenuation is a combined effect of scattering, environment-friendly. Training smokes were generated absorption and reflection of the incident radiation26. earlier from a burning-type composition containing The devices that can be defeated by these smokes are tar/pitch, KNO3, borax and S. The smoke was night-vision devices including FLIR (forward looking suffocating and troops had to pass through it without IR), laser range finders, laser antipersonnel weapons, using face masks. NH4a smoke, perfectly white, and IR sensors based guidance systems of missiles. generated from a composition containing Kao3, sugar , These devices can also be defeated by particulate cloud rosin and NH.cP3, will be the ideal substitute. Fog oil made up of metal flakes and fibres7-11,2S,27.pyrotechnic smokes are also ideal for training purposes2S.In the smokes containing CsN°J are reported28to be effective UK, cinnamic acid smokes have been found suitable in attenuating in the IR region. Many a guidance system for training pUrposeS24.Work carried out in the USA of missiles use more than one mode to sense targets shows that chlorinated waxes, terephthalic acid, glycols more efficiently and resist countermeasures. Thus and red phosphorus are safer raw materials for screening multi-spectral sensors, combination of visuaVlR or smoke generation 13,2J-2S,29,30,34.Further, TiO/silica , IR/MMW (millimetre wave), are used. So a single zinconia can be dispersed by explosives to provide safe, obscurant smoke should have the capacity to attenuate non-toxic screening smokeI2.13.21.27.

176 MISHRA : ROLE OF SMOKES IN WARFARE

4. FUTURE OF SMOKES for tanks-can be defeated if smoke can defeat the Diverse varieties of smoke fonnulations are sensorsl.25.35.36.41.A modern, sophisticated, hi-tech available, there being a specific smoke for a specific system of today can be counteracted by a more than purpose. Be it safer, non-toxic training smoke or half a century old low-tech system. And again, when millimetre wave attenuating smoke, a number of choices new are ushered in, older established ones are available to the potential user. Visual smokes can bow out unceremoniously. Here, for a change, both defeat line of sight guidancel.2o and laser-guided new and old technologies are able to coexist on merits missiles. In the line sight guidance systems, the target alone. The importance of smokes in warfare has finally should be visible to the gunner. When the target is not been realised and the prominence given to smokes visible because of the obscurant smoke cloud, the appears to be well justified and remains secure not only gunner can no longer guide the projectile to its for this decade but probably well into the next century destination. In laser-guided missiles, the missile nose as well. has the sensor, detecting the reflected laser energy off the target. When smoke comes in between the sensor ACKNOWLEDGEMENTS and the target on the path of the laser energy, the smoke I have heavily borrowed from Engineering and cloud scatters the laser radiation. As a result, the sensor Design handbook4 for the introductory text and can no longer sense it; hence the missile cannot lock IiberaIIy from the chapter 'Investigation of onto the target. materials that obscure in the middle to far IR' by Smoke fonnulations/weapons/manufacturing facili- Richard A Kenley (ref 32, p. 66) and 'Obscurants as a ties are easy to plan/fonnulate, cheap to countermeasure to modern weapon system' by John P manufacture/fabricate, simple to use safe to store; have Bulger (ref 32, p.891) for the text of 'Opto-electronic long shelf life, and are completely reliable as well as defeating smokes'. I hereby express my gratitude to foolproof. It cannot be subjected to jamming or both the authors. countermeasures. I thank Dr SP Panda, Chairman, Facult)' of The American war gaming and other similar Explosives and Applied Chemistry and Rear Admiral exercises indicate that use of smoke gives an advantage Dr Ajay Sharma, Director & Dean, IA T , Pune for their by a factor of 4 in both offensive and defensive encouragement and permission to publish this work. deployments34.36.Similarly, Russians depend heavily on Appendix A gives some smoke formulations. the use of smoke in reducing losses in tank warfare and in countering long-range NA TO anti-tank weapons37. REFERENCES Laser range finder, laser target designator, laser anti-material, antipersonnel weapons (BLW-battlefield Hoist, G .C. Tactical smoke increases survivability. laser weapons) are being deployed38-4I. Nd- Yag laser Armour, 1984,20-25. could probably be replaced by CO21aser in due course26. 2 Shidlovskiy, A.A. Foundations of pyrotechnics. Even the SDI programme visualises the use of this Foreign Technology Division, USAF, 1964. energy system40. A smoke scatters coherent energy and AD-602,687. p. 4. hence can degrade the effectiveness of such systems20.39. 3 Ellern, H. Military and civilran pyrotechnics. High-tech opto-electronics means high cost. For Chemical Publishing. New York, 1968. p 3. example. a copperhead missile deployed to destroy a tank costs $ 45,000 .This missile guided by Nd- Yag 4, Engineering design handbook, Part I: Military laser designator can be very ea~ily defeated if the smoke pyrotechnics-theory and applications. US Army is generated either between the laser designator and Material Command Report 705-13, April 1967. p 5-7. the target or missile head sensors and the target. Thus a $ 45.000 system can be defeated by smoke at less than 5 Ellern H. Modem pyrotechnics. Chemical a hundredth of the cost. Terminally guided bomb Publishing, New York, 1961. p. 26. (TGMB) or multi-launch rocket system with terminal 6 Karl, B.O. Handbook of Pyrotechnics. Chemical guidance with SADARM .-potential threat weapons Publishing, New York, 1974. p. 20.

77 DEF SCI J. VOL 44, NO 2, APRIL 1994

Urbo, L.A. Ethyl Corporation. Chemiluminiscent 22 Turetsky, Abe. Pyrotechnic aerosolization from smokes. US patents 3,551,341; 1970. p. 3; novel imbibed liquid matrices. US Army Chemical 3,576,753; 3,576,754; 1971. p. 3. Research and Development and Engine Centre 8. Howard, M.J. Pyrotechnics. Franklin Institute Aberdeen proving ground. Proceedings of the 13th Press, Philadelphia, 1980. Symposium on Explosives and Pyrotechnics, 9 Bern, G. Messerrchmitt-Boelkow-Blohn GmbH. South Carolina, 2-4 December 1986. p. IV-43. Screening smoke with broad absorption band. 23 Uwe, Krone. Nico pyrotechnik: A non-toxic German patent DE 3,147,850. 1983. p. 6. screening smoke for training purposes. 10 W~ber, M. Smoke projectile. .German patent DE Proceedings of 15th International pyrotechnic 3,238,445. 1984. p. 17. Seminar, Colorado, 9-13 July 1990. p. 581. Milsted, Leon R. et aJ. Method of assembly of 24 Gilmore, A.P. & Strudley J .J .Procurement of low compacted particulates and explosive charges for toxicity smoke systems by UK. Proceedings of visual and IR screening. US patent 4,704,967. 10 Smoke/Obscurant Symposium-X111, Maryland, November 1987. 7 p. 1989. p. 713. 12 Rouse, William G. etaJ. Method of forming a safe 25 Turetsky, A. L. et aJ. Advances in pyrotechnically visual . US Dept of Army, Statutory based visual smoke system s.Proceedings of 13th Inventory Register US 769. 03 April 1990. 3 p. International pyrotechnic Seminar Colorado, Ratzel, A.C. & Constantineau, E.J. Aerosol cloud 11-15 July 1988. pp. 805-10. generation experiments. Proceedings of 15th 26 Ogorkiewicz, R.M. Counter measures to tanks International Pyrotechnic Seminar, Colorado, beating smart munitions. Int. Del. Rev., 1989, 9-13 July 1990. p. 779. (1),53-57. 14 Conkling, John A. Chemistry of pyroteclu1ics. 27. Sellman, L. R. et al. AAI Corporation, Marcel Dekker, New York, 1985. p. 174. USA. Method of forming IR smoke screen. US 15 Buck Chemish Technische Werke. Pyrotechnical patent 4,704,966. 10 November 1987. 7 p.; smoke charge German patent DE 2,953,469. 11 Takashashi, Shigeru. Hosoya Fire Works Co Ltd. November 1982. 3 p. Japan patent 60,155,591. 15 August 1985. 4 p. 16. Etat, Francis. Smoke developing pyrotechnical 28 Loilland, R.H. IR defeating munition M 76. Army composition opaque to IR. NL patent 8,302,651. R&D A, 1985, September-October 25. 1 August 1985. 15 p. 29 Labrecque, B & Couture. G. Development of a 7 Simpson, G. M. for castable white based on producing radiation blocking screen. Great Britian chlorinated paraffins. Proceedings of 13th patent 2,188,921. 14 October 1987.3 p. International Pyrotechnic Seminar Colorado, 18 Simpson G.M. Radiation absorbing screen. Great 11-15 July 1988. p. 526. Britain patent 2,188,920. 14 October 1987. 9 p. 30 Karton, Yishai, et aJ. Composition for production 19 Simpson G.M. Pyrotechnic composition for of coloured smoke. Israeli patent 79,737. 9 generating IR blocking screen. Their manufacture February 1990. 11 p. and means for their distribution. German patent 31 Chin, A et aJ. Insensitive pyrotechnics -improved DE 3,443,778. 19 May 1988. 6 p. binders for coloured smoke. Proceedings of 15th 20 Elkins, Rush E. & Kohl, R.H.G (Eds). International Pyrotechnic Seminar, Colorado, Proceedings of the Smoke/Obscurant 9-13 July 1990. p. 129. Symposium- V held at Maryland, 28-30 April 1981, 32 Reed, A. & Brady, Vicki L. A new class of VollI.NTIS,Springfield. AD-A 104761. p. 773. coloured smoke. Proceedings of 15th International

21 Uwe, Krone. Pyrotechnic composition for Pyrotechnic Seminar, Colorado, 9-13 July 1990. generating smoke screens and ignition p.1033. composition ther~ for. German patent DE 3,728, 33 Hoel(stein, Karel Christiaan. Smoke producing 380. 24 November 1988.4 p. agent. NL patent 8,400,700. 1 October 1984.4 p.

178 MISHRA : ROLE OF SMOKES IN WARFARE

34. Hoffman, Klaus & Roth, Paul. Use of c c

polyethylene glycol in preparing smoke screens. HCE54.7 HCE59

German patent DE 3,411,533. 10 Octo.ber 1985. Zn43.3 Mg18

7 p. Anthracene 23

35 Reardon, Mark J. Countering Soviet smoke. D III Colour Smoke Armour, 1986, May-June, 36-39. HCE76.2 A 36. Donnelly, C.N. Soviet tactis for overcoming Mg23.2 KCIO320-35 NATO anti-tank defences. Int. Dei. Rev., 1979, Sugar 23-35 July, 1099-106. E Dye 30-54 37. Anderberg, Bengt et al. Blindin~ lasers: the HCE81.4 nastiest weapon? Military Technology, 1990, (3), NaHCOJO-15 58. A118.6 F B 38. Turbe, Gerard. Laser weapons at sea. Int. Dei. Rev., 1990, (8), 853. Dye 30-50 Carbohydrate 20-35 39. Madsen, Ellis M. Defending against battle field CC1440 lasers. Military Review, 1987, May, 28-33. Zn30 KClO322-33 NaCIO314 NaHCO33-10 40. Hecht, Jeff. Beam weapons: the next arms race. Paraffin oi12-4 Plennm Press, New York, 1984. p. 5. NH4C19 Infusorial earth 3 Infusiorial earth 0-4 41 Daskol, Steven. A hot issue: IR sensors and IR Red iron oxide 0-3 countermeasures. Military Technology, 1990, (9), 97-105. IV Alkali Halide Smok~

APPENDEX A KC/0465% NaCIO454% NaOO479% VARIOUS SMOKE FORMULATIONS NaO10% KC/0425% Mg5% Mg5% Mg5% LiC122% I Screening Smoke Formulation II Block Smoke Li2CO]2% LiCI2% Binder 140;0 A A Binder 18 % Binder 14 %

HCE45 KCIO355

ZnO45 Anthracene 45 v Smokeand Illuminating Fonnulation CaSi2 10 Mg8

B B RedP51

HCE44.5 HCEfi) MnO235

ZnO46.5 Mg19 Zn°J

A19 Napthalene 20 Linseedoil3

17Q

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