Laser Countermeasures in the Littoral
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LASER COUNTERMEASURES IN THE LITTORAL
CONSIDERATIONS ON THE USE OF AN AUTOMATIC
LITTORAL MODE RESPONSE
By: Gerald S. Blyth CD
President, EWTS Ltd.
gsblyth@ewts.ca
Introduction
A paper was recently produced by Rheinmettal Waffe Munition (RWM) to address issues
related to the ‘hardwired’ Littoral Mode Response between a Laser ESM (LESM) system
and their MASS (Multi Ammunition Softkill System) on the UAE Navy’s Baynunah Class
corvettes. In this implementation, both the LESM and the MASS have the ability to
communicate directly via an Ethernet connection, and it was considered as prudent to
explore the advantages of using this to provide a rapid countermeasure response to laser
threats. This rapid response would entail the immediate (reflex-like) launch of a predetermined pattern of Omni-TRAP ECM rounds on the bearing of the illuminating (threat)
laser.
Background
Any warship operating in the littoral, (ostensibly, within several km of any non-friendly or
un-controlled shoreline) is in a distinctly exposed and potentially vulnerable position. The
Baynunah, however, has been designed to operate in this very environment, and is
appropriately fitted with a highly-capable suite of sensors, weapons and countermeasures
specifically intended to allow it to defend itself.
Two of the ship’s sensors are capable of automatically activating or initiating defensive
countermeasures from the MASS System.
• The Ship-board ESM and Location (SEAL) System can be programmed to initiate
an immediate launch of the MASS Omni-TRAP ECM rounds.
• The NLWS 310/500, Naval Laser Warning System, if desired, can also be enabled
to initiate an immediate launch of the MASS Omni-TRAP ECM rounds. The
implementation of this option is, in fact, the very substance of Rheinmettal’s White
Paper.
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Laser Countermeasures in the Littoral
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The SEAL System is presently configured to provide this automated, quick-reaction
response – the logic being that, with the hi-speeds of modern anti-ship missiles (ASMs),
and the close range at which they activate their homing radars and ‘lock on’, there is not
sufficient time for an operator, or even the Combat Management System (CMS), to identify
the threat and initiate an appropriate response. The CMS requires up to 3 seconds to
process the input from the LESM and initiate a response from the MASS. The SEAL
System is configured to command a response action directly from the MASS, thus bypassing the operator as well as the CMS.
It has been proposed by the MASS supplier, Rheinmettal, that this capability be further
extended to include the NLWS-310/500 Laser ESM system, viz. upon detection of laser
illumination of the NLWS sensor head a command would be sent directly to the MASS to
deploy the Omni-TRAP munitions in the direction of the illuminating laser. Since the
Omni-TRAP munitions disperse a highly-effective red phosphorus smoke cloud it is
theorized that any laser beam such as from a laser beam-rider missile (LBR) or laser
designator (LD) would be either absorbed or reflected by this smoke and would no longer
reach or reflect off its intended target. Thus any inbound weapon homing on the reflected
laser energy would either fly up and over the ship, or down into the sea once it actually
enters the cloud and completely loses any target designation.1
According to RWM, recent testing by the German Navy has apparently validated this
theory, however, evidence of the test results has not been made available to EWTS. Even
if we were privy to the results it would be incumbent upon us to consider them within the
context of an operational scenario. Simply verifying the effectiveness of the smoke would
not be sufficient to suggest that it could be used operationally without first considering all
tactical implications. Red phosphorus smoke has been proven to be highly effective as a
military obscurant in the IR and Visible spectrum2, but this doesn’t dictate its relevance in
any specific littoral (or other) scenario.
The application of any countermeasure - particularly one that would be mutually exclusive
to all others forms of active or passive defence - must certainly be based on the
Commanding Officer’s discretion, and not on the rote response of a software program.
This Review deals specifically with the use of the Littoral Mode, or automatic ‘Reflex
Action’ by the MASS System to any detected laser threat. More importantly, I think, it
questions the logic for any fully-automatic use of the MASS off-board countermeasures in
response to any sensor being stimulated by any threat – whether RF, IR or laser!
1
As explained by RWM at a meeting during IDEX 2007.
Phosphorous aero-dispersions generated from smoke grenades containing these pyrotechnic compositions
under field conditions could screen infrared radiation (0.82 µm, 3-5 µm, 10.6 µm wavelengths) with high
efficiency. Article, The Use and Application of Red-Phosphorous Pyrotechnic Composition for
camouflage in the infrared region of radiation, Ladislav Klusáek, P. Navrátil , Military Technical Institute
of Protection, 602 00 Brno (Czech Republic).
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Laser Countermeasures in the Littoral
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The Issues
There are several issues which must be taken into account prior to committing the ship’s
defence to a single countermeasure such as smoke derived from the MASS Omni-TRAP.
These include:
a. Is this Omni-TRAP red phosphorus smoke, by itself, 100% effective against lasers?
Figure – 1 Mass Extinction Coefficient of Red-Phosphorus Smoke
[Graph courtesy of RWM]
Rheinmettal’s Paper indicates in the opening graph (see also Figure 1) that the Mass
Extinction3 (ME) factor is directly related to the ambient relative humidity as well
as wavelength. The ME decreases quite rapidly as the wavelength increases. One
must also keep in mind that maximum effectiveness is only established while the
smoke is at maximum density – and its density drops off over a relatively short
period of time.
Mass Extinction (α): An essential factor for the effect of the aerosol formed with respect to
electromagnetic radiation in the IR range [or other] is a parameter defined as mass extinction coefficient.
This parameter expresses the capacity of the aerosol to attenuate the electromagnetic radiation. The mass
extinction coefficient is defined as α = ln T:x…..c, where ln T is the natural logarithm of the transmission,
x is the thickness of the aerosol screen in m and c is the aerosol concentration in g per m3. Only if the α
values are ≥1 gram per m3, can an effect be expected in the IR range. Screening smokes: A review of
recent literature, N. Davies, RMCS Cranfield University Report DEOS/ASET/ND/468/99 (1999).
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Laser Countermeasures in the Littoral
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b. Is it effective against all incoming weapon types such as MANPADS or the
(double-digit) Russian anti-tank missiles, etc.?
The frequency response of the smoke is non-linear, thus, its effectiveness against
various laser emitters depends greatly on the wavelength of the laser. It is proven
to be quite effective against Infra Red (IR) heat seekers so one would expect it to
be a very efficient counter to heat-seeking MANPADS missiles. Significantly, as
the smoke cooled it was found to be equally effective against lasers – being highly
reflective and dispersive at wavelengths even shorter than the IR. 4
c. Is its effectiveness significantly affected by environmental conditions or ship’s
maneuvers?
As illustrated in Figure 1 there is a distinct correlation between relative humidity
and the ME of red phosphorus smoke. Wind will no doubt have a distinct effect
and would probably disperse the smoke quite rapidly if wind velocity is high. The
ship can only be protected by the smoke as long as it remains behind it. Naturally,
this severely restricts the options of the ship’s captain to maneuver the ship to clear
his firing arcs, escape the area, or even to address additional threats.
d. Does it prevent other sensors from operating effectively?
The Omni-TRAP countermeasures rounds are omni-spectral – they produce not
only the red phosphorus smoke cloud but an IR source as well as a large volume of
broadband chaff. None of the ship’s sensors is capable of operating effectively with
smoke, chaff and IR flares between it and any target it is trying to detect. These
sensors are effectively blinded until the Omni-TRAP products have dissipated
sufficiently for their use – and depending on the sensor to be used this could require
several minutes.
Ironically, the sensor that initiated this countermeasure – the laser warner – is now
also blinded, and it’s entirely a matter of conjecture whether the laser designator
(the threat) or the laser warner will be the first to acquire the necessary visibility to
accomplish its objective as the cloud dissipates.
4
The following description of the effectiveness of red phosphorus compounds was provided within a US
patent application No. 639685, “On detonation of the resulting device at a position between an infra-red
source and an infra-red radiation detector, a dense cloud of smoke was produced dispersed upwardly and
outwardly of the device, the cloud itself initially producing infra-red radiation which completely masked
the radiation from the source, preventing its detection by the detector. As the cloud cooled, it served to
block the passage of radiation from the source to the detector. The total time for which the cloud was
effective in blocking detection of radiation from the source was in excess of 30 seconds. It was also
observed that the cloud was impenetrable by laser beams. The cloud would therefore provide effective
blocking of the operation of laser-guided projectiles and missiles, and laser range-finding devices.”
Pyrotechnic composition for producing radiation-blocking screen. US Patent Issued on March 1, 1988 by
Geoffrey M. Simpson; Assignee Haley & Weller Limited; Application No. 639685 filed on 1984-04-04.
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Laser Countermeasures in the Littoral
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e. Does it prevent the weapons systems from defending the ship?
The ships weapons cannot be used to defend the ship against any inbound threats,
or even against the platform that is targeting it. Not only is the ship concealed by
the smoke, chaff and flares, but the incoming threat is even more concealed from
the ship’s weapons, and thus, is itself protected by them. As well, all of the weapons
on the ship require some sort of aiming cue, and whether this is visual, radar or
electro optic – they will all be blinded by the Omni-TRAP countermeasures. This
would imply that no weapons can be brought to bear or fired in self defence until
the intervening chaff, IR flares and Red Phosphorus cloud disperses5.
f. Should a countermeasure be implemented without any form of tactical input or
operational, human consideration.
There are numerous good reasons that the use of any countermeasure should only
be considered exclusively within the context of the tactical situation. In addition,
other factors such as defence doctrine, appropriate operational considerations,
ZIPPO procedures, vessels in company, environmental conditions including the
relative wind, and, as we now know, the relative humidity must be considered. The
Littoral Mode, if engaged, obviously can’t consider any of these factors – when
engaged, it is merely responsive.
g. Is it more effective than the other ship’s weapons systems, i.e., does it offer a greater
probability for successfully defending the ship (against threats in the littoral
environment) than the ESSM or RAM, or even the 27 mm guns? Would an active
laser countermeasures system (i.e., laser jammer) be more effective?
The answers to these questions are not entirely clear. Would an active defence be
more appropriate in the circumstances? Would the ship’s weapons, or perhaps a
specific weapon system such as RAM, have a higher probability of success. Should
the RAM be fired followed by a MASS deployment? These questions could only
be answered by focused research, weapons tests and operational trials, and are
certainly the kinds of questions that need to be answered before any reflex action
should be considered.
5
No alternate smoke composition has been found that can match the performance of red phosphorus based
smoke obscurants for military applications in the visible and infrared regions. THE USE OF RED
PHOSPHORUS IN PYROTECHNICS – RESULTS OF AN INTERNATIONAL INVESTIGATION
Peter J. D. Collins, Research Programme Leader, Research Acquisition Organization, Ministry of Defence,
Schrivenham, Wiltshire, UK.
K. J. Smit, Defence Science and Technology Organisation, Edinburgh, SA, Australia
Bill R. Hubble, Pyrotechnics Development Division, Naval Surface Warfare Center, Crane Division,
Crane, Indiana, USA
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Laser Countermeasures in the Littoral
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Summary
The implementation of any reflex action, such as the Littoral Mode, is definitely a question
requiring input from the naval operational and tactical community. Should the ship’s
defence be entrusted to a passive off-board countermeasures when absolutely no evidence
is available to suggest this is prudent – let alone effective.
The tests performed by the German navy may have been quite successful against lasers.
But were they performed in isolation – indicating merely that the smoke cloud blocks or
absorbs lasers of certain wavelengths. Proving the smoke to be highly effective at
concealing a ship is one thing. Proving that using this smoke in an operational scenario, in
the littoral, is an entirely different question.
Such an important decision should never be made without factoring in current tactical,
environmental and doctrinal variables – all of which a ship’s captain must do.
Rheinmettal has no doubt invested considerable time, effort and money developing their
highly effective and proven MASS System. They have, however, only provided anecdotal
reference to testing that proved their proprietary Red Phosphorus smoke compound is an
effective obscurant and absorber to military laser designators and beam-rider system
illuminators. A more effective and convincing proof of effectiveness, and one that would
remain unclassified and thus available to potential users, would be from an obscurant
modeling and simulation tool such as the Chorale developed by the French DGA6.
Conclusion
Rheinmettal has demonstrated that implementing the Littoral Mode is, in fact, relatively
easy to do. From a technical perspective it is exceptionally simple to implement. The
Navy, however, may wish to consider the operational and tactical implications.
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Obscurant representation for realistic IR simulation Patrick Gozard, Alain Le Goff, Jean Latger, Thierry
Cathala. DGA/DCE/ETBS, BP 712, 18015 Bourges, France. DGA/DCE/CELAR, BP 7419, 35174 Bruz
cedex, France. OKTAL Synthetic Environment, 2 rue de Boudeville, 31100 Toulouse, France
www.oktal-se.fr
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Ottawa, Ontario, Canada K0A 3M0. +1 613 796 4653