WP - illuminating or not?

#1
dingerr and I have been having a bit of a discussion regarding the luminary abilities of WP and it's time to start it's own thread to get a wider viewpoint.

I've come across a few posts (mostly US blogs) that suggest that some US illuminating ammunition provides light from a WP composition.

dingerr insists that WP is solely used to produce smoke, stating:
Burning WP does cause flame but not light intense enough to produce the luminosity required on the battlefield. Also this flame is quickly shrouded by the dense smoke that is the primary product of WP on contact with the air.

Difficulties would also be encountered deploying WP as a flare. Illuminating munitions invaribly have to be deployed at height to gain the best effects. WP only burns (or rather decomposes of we are getting technical) on contact with air. It would be practically imposible to deploy WP in an aerial capacity where its burning could be controlled and its smoke effects reduced in such a manner as to be effective on the battlefield.
While I would not disagree vehemently with the gist of dingerr's comments, I can see some holes in his arguments. These are:

The British use of WP as a smoke generator requires the missile to burst apart on striking the ground, spreading the WP over a large area. In this scenario, the brightness of the flame is obscured by the smoke that spreads around it. Indeed, it is the brightness of the flame reflecting off the smoke particles that aids obscuration.

Were the WP to be deployed in the base of a parachute-retarded munition, the ejected smoke would rise above the munition due to both thermal convection and also the descent of the munition. The smoke would therefore not obscure the light but would reflect the light towards the ground. To some extent this would provide less harsh illumination of the battlefield than is the case using British illuminating rounds.

Because the WP is not burst from the projectile, I'd presume that the smoke would be less dense and a longer duration of illumination would result.


So, has anybody any experience of a WP illuminating round? And are there any ATOs who can throw in some technical comment?
 
#2
WP smoke rounds, both mortar and Artillery don't actually strike the ground and break apart, they eject WP canisters whilst still in the air, it gives a better distribution of smoke...but that was just a technical point.

Phosphourus when it burns (on contact with air) does give off light, but it is pretty pathetic. It can be refined in such a way to give off less smoke and more light.

The main problems with WP is the fact that is reacts very quickly to air and so is quite unstable to move around in anything but a nice solid container (so there goes your light weight hand carried light) it also gives of Phosphene gas which is toxic and also is quite expensive to manufacture.

Magnesium and suchlike is generally cheaper, gives better light and isn't going to kill you or randomly explode if carried round in a lightweight container.

generally WP is not nice, which is why it is being replaced by Red Phos...which is similar but less nasty.

J_T_4T
 
#3
After 20 odd years working with ammo I can quite honestly say I have never come across WP used in anything but the smoke and incendiary role.

I'm not saying it isn't possible, just highly unlikely.

WP isn't that good an illuminating composition. It moderately bright enough initially (found out after prodding SIP grenades with a really long stick). Then is either obscured by smoke or the cake/residue that builds up on the surface in contact with air. It's this residue that means WP tends to be primarily used in bursting munitions where the phosphorus is blown apart into small pieces. This gives each piece a greater surface area in contact with the air which in turn produces a more rapid cloud of obscurating smoke/larger area of burning. If you were to have a solid lump then it would self extinguish as the outer layers are covered with the residue, denying oxygen to the fresh phosphorus beneath.

Probably not too helpful but then I'll do some digging at work tomorrow...

edited to add:

http://en.wikipedia.org/wiki/White_phosphorus_(weapon)

a bit of light reading.
 
#4
Jones_the_4Tonner said:
WP smoke rounds, both mortar and Artillery don't actually strike the ground and break apart, they eject WP canisters whilst still in the air, it gives a better distribution of smoke...but that was just a technical point.
It's going back 25 years since I last looked at a cutaway drawing, but I seem to recall that the 81mm mortar WP smoke bomb comprised a hollow casing filled with the WP composition and was fitted with a L35 fuze. This fuze initiated by striking the ground, detonating a small amount of explosive that broke the casing and caused the WP composition to spread over a wide area. It certainly had no means of dispensing canisters while still in flight.
 
#5
Cheers, apfsdsdu, but part of your argument is where I'm coming from. A parachute-retarded munition isn't going to be affected by the smoke as this either goes upwards by convection or stays at the same altitude (approximately) while the projectile continues its downward motion. While it would be useless for projecting light upwards, I can see that casting light downwards could be a possibility. The deciding factor is whether the WP burns bright enough to be of use.

Your comment about the formation of residue is an interesting one. If the WP is enclosed within a casing and therefore has only one aperture to escape from, wouldn't this cake be continuously broken off as the WP burns, exposing more fresh WP? Alternatively, if the WP is mixed with beads of a material that expands on burning, the residue could be encouraged to break off more readily. Small iron, copper or aluminium pellets could achieve this (just a guess - it's what I'd try as a solution).
 
#6
To answer the question: Does WP burn sufficiently brightly to be of significant utility as a battlefield illuminant?

Answer: No.

As far more learned persons (above) have already stated, WP burns in air and produces shedloads of very hot smoke, which plumes rapidly, creating distinctive white columns. It is white due to the hygroscopic nature of the smoke, drawing in water vapour from atmosphere - hence it's white.

The actual 'burn' is entirely confined to the surface of the WP in contact with free air - not very much - and contains nothing in the way of an accelerant or booster to improve light quality. For that, we tend to use aluminium powder and certain metal salts.

Quick one on red phosphorus - it is just as effective but does not burn on contact with air. This means that mortar bombs are going to get a lot more complicated, as they will require a new SAFU system.

Edited to add: It's also non-toxic, unlike WP and BE Smk...

I'll get me coat.....
 
#7
Firstly i am an Ammo Tech (ATO if you must) and have been for a number of years.

Secondly i have tried to avoid being too technical because i just know my fellow brethren will pile on me for being so anoraky, but hey ho here goes arms wide open. SO lets begin.

Jones - WP munitions do not burst break out in WP canisters, they burst spreading the WP over a wide area thus exposing more of the surface area to air and producing a rapid, dense cloud of smoke.
I presume you mean phosgene gas? WP does not produce phosgene gas when it burns this would make all WP natures chemical and that is very naughty and us Brits are good little soldiers. Also during their AT/ATO course students walk through a cloud of WP smoke and it is used as a smoke screen and therfore troops are exposed to it. Not heard of anyone suffering from pulmonary endema in either case. WP does not necessarily need a thick cased munition to be use/stored (i.e Grenade Hand Smoke No80 White Phosphorus (obsolete)). WP is surprising cheap to manufacture, more so than other chemical compositions, its expense is increase slightly due to the deleivery system required for WP munitions and also the fact that they have to be filled under liquid. Munitions do not randomly explode. WP cannot be refined in any way to alter its chemical state, it does not bind with other additives that may for instance produce different coloured smoke or reduce the smoke produced. Red Phosphorus burns to WP, but requires an external ignition source to initiate the chemical reaction.

Is there anything if failed to correct you on?

Puttees - I appreciate that a lot of the info you have collected is from US blogs, however these people appear to be the end user and not the chemists, munition designers or technicans, they do appear to be the normal blustering pontificating yanks. The trouble with thrying to contain the burning rate of WP to reach a desired effect is the fact that WP burns so hot that it easily burns through metal so it is difficult to contain it in an object and control the burn.
 
#9
Yes i know

Now zipping anorak right up, deploying smoke and legging it.
 
#10
Oh Jeez. I've started one here.

Having done some web searching, there seems to be a lot of contradiction about WP. Even the Wiki links don't agree with each other.

Examples:

http://en.wikipedia.org/wiki/White_phosphorus_(weapon)#Military_regulations
On November 30, 2005, General Peter Pace justified use of WP, declaring that WP munitions were a "legitimate tool of the military", used to illuminate targets and create smokescreens
Perhaps the spams use the term "illuminate" where we would say "identify?"


http://www.nsc.org/ehc/chemical/phsphor.htm
White phosphorus is a poison which can be absorbed through skin contact, ingestion, or breathing. If its combustion occurs in a confined space, white phosphorus will remove the oxygen from the air and render the air unfit to support life. Long-term absorption, particularly through the lungs and the gastrointestinal tract, can cause chronic poisoning, which leads to weakness, anemia, loss of appetite, gastrointestinal weakness, and pallor.

Eating or drinking less than one teaspoon of white phosphorus can cause vomiting; stomach cramps; liver, heart or kidney damage; drowsiness; and even death. Being burned with white phosphorus can cause heart, liver, and kidney damage. Breathing white phosphorus may damage lungs and throat.

White phosphorus can cause changes in the long bones; seriously affected bones may become brittle, leading to spontaneous fractures. White phosphorus is especially hazardous to the eyes and can severely damage them.

High concentrations of the vapors evolved by burning white phosphorus are irritating to the nose, throat, lungs, skin, eyes, and mucus membranes.

Breathing white phosphorus can cause coughing and the development of a condition known as phossy jaw -- poor wound healing in the mouth and a breakdown of the jaw bone. The most common symptom of exposure to white phosphorus is necrosis of the jaw.

Exposure to white phosphorus can also cause nausea, jaundice, anemia, cachexia, dental pain, and excess saliva.
http://en.wikipedia.org/wiki/White_phosphorus_(weapon)#External_links
Burning WP produces a hot, dense white smoke. Most forms of smoke are not hazardous in the kinds of concentrations produced by a battlefield smoke shell. However, exposure to heavy smoke concentrations of any kind for an extended period (particularly if near the source of emission) does have the potential to cause illness or even death.

WP smoke irritates the eyes and nose in moderate concentrations. With intense exposures, a very explosive cough may occur. However, no recorded casualties from the effects of WP smoke alone have occurred in combat operations and to date there are no confirmed deaths resulting from exposure to phosphorus smokes
I could go on, but I think this illustrates some of the contadiction.
 
#11
Why do you think we use WP mixed with HE on objectives?

To mark the objective for subsequent attack from the air - they look really really bright through FLIR, and to identify the objective clearly for ground based sensors...and because chunks of WP whizzing about your ears isn't nice.

Oh sorry - I mean we clearly don't do that. Ahem.
 
#12
Its not really contradiction. Its all about concentration levels. The first quote you posted appears to be worst case scenario. The second appears to be 'real life' what we would expect to be exposed to. I've been exposed to WP smoke quite a bit in the past so have many of my collegues to no apparent ill effect.
 
#13
Darth_Doctrinus said:
Why do you think we use WP mixed with HE on objectives?

To mark the objective for subsequent attack from the air - they look really really bright through FLIR, and to identify the objective clearly for ground based sensors...and because chunks of WP whizzing about your ears isn't nice.

Oh sorry - I mean we clearly don't do that. Ahem.
Of course not. Dolly mix on Helicopter LZs to degrade the performance of the helicopters and confuse the pilot as to where the ground is, but switch to HE once they've landed. Shame about time of flight.
 
#14
dingerr said:
Its not really contradiction. Its all about concentration levels. The first quote you posted appears to be worst case scenario. The second appears to be 'real life' what we would expect to be exposed to. I've been exposed to WP smoke quite a bit in the past so have many of my collegues to no apparent ill effect.
Yes, I recall a mortar concentration where the wind changed direction during a mass WP shoot. Cough, cough, weep, weep, vomit - RUN!
 
#15
I nearly got brained by the base of an artillery smoke round in BATUS; I was told by a gunner that the round "functions" while in flight.
 
#16
Thats not like the Arty to drop short :twisted:
 
#18
Back to first principles etc etc

Even if WP did produce enough long lasting light (which it doesn't)... Why bother making a WP ILLUM rd when you can get get a better performing, safer, easier to store rd from other compounds? Doesn't make sense.

Also.... Red Phos smoke may not be 'toxic' in the medical sense, but..... in the right concentrations, it'll still kill ya :)


.
 
#19
Given the direction of the advice so far, I think I'm starting to play the role of Devil's Advocate. Still, I'll carry on with it.

The 81mm Illum round emits a very bright light and very effectively lights up the battlefield. A fault with this is that, being a point source, the shadows that are cast are very sharp. Visually, everything in view appears two-dimensional. This effect is lessened, and consequently the view of the battlefield is improved, when there is a fairly low cloud cover (though above the altitude of the flare pot) as this reflects diffused light over the area. Lower cloud has a similar result as the flare passes through it, though this also reduces the overall illumination.

A WP Illum flare, as it would produce more smoke than the 81mm Illum, would essentially produce its own "cloud" above it, resulting in a more diffused area illumination.

The effect would be similar to comparing a 100W bulb in a room with a black ceiling against a 40W strip light in a room with a white ceiling - one is brighter, but the other is more user-friendly.

A further advantage of a dimmer flare is that night vision would be less impaired when the flare finally burns out. Obviously, the flare would have to be bright enough, this being the point of the question.
 
#20
Edited and removed because I got a tap on the knuckles from work, due to mentioning things about work products on a public site without permission even though it is mainly all available over the internet anyway, but those are the rules and I have been told so...

Anyway...interesting conversation, will watch from the sidelines on this one.

J_T_4T
 

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