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Tactical High Energy Laser

THEL/ACTD

The Tactical High-Energy Laser, or THEL, is a laser developed for military use, also known as the Nautilus laser system. The mobile version is the Mobile Tactical High-Energy Laser, or MTHEL.

Demonstrator
Countermeasures
See also

Lasers
Laser weapons

External links

Demonstrator

The cooperative Tactical High Energy Laser (THEL) Demonstrator ACTD was initiated by a memorandum of agreement between the United States and the Government of Israel on July 18, 1996. The THEL is a high-energy laser weapon system that uses proven laser beam generation technologies, proven beam-pointing technologies, and existing sensors and communication networks to provide a new active defense capability in counter air missions. The goal of THEL is to provide a different solution than other systems or technologies for the acquisition and close-in engagement problems associated with short- to medium-range threats, thereby significantly enhancing coverage of combat forces and theater-level assets. The THEL's low cost-per-kill (about $3,000 per kill, as opposed to the $444,000 cost of a Rolling Airframe Missile) could also provide a cost-effective defense against low-cost air threats. It features up to 60 shots without reloading and, if it meets design goals, a probability of kill of nearly 100% at a range of 5 km.

An Israeli designed, U.S funded program has been initiated to develop a THEL demonstrator using deuterium fluoride laser (chemical laser) technologies. Israeli THEL team members have completed a Concept Design Review in Israel for the demonstrator. Approximately 21 months will be required to design and build the system, followed by 12 to 18 months of field testing at the High Energy Laser Systems Test Facility in Israel. This program will deliver a THEL Demonstrator by March 1998 with a limited operational capability to defend against short-range rockets. The THEL weapon system concept definition studies using advanced technologies were awarded to four contractors on September 30, 1996. The prime contractor for THEL is Northrop Grumman (formerly TRW.)

THEL conducted test firing in FY1998, and Initial Operating Capability (IOC) was planned in FY1999. However this has been significantly delayed due to reorienting the project as a mobile, not fixed design, called Mobile Tactical High Energy Laser (MTHEL). The original fixed location design eliminates most weight, size and power restrictions, but is not compatible with the fluid, mobile nature of modern combat. The initial MTHEL goal was a mobile version the size of three large semi trailers. Ideally it would be further downsized to a single semi trailer size. However doing this while maintaining the original performance characteristics is difficult. Furthermore the Israeli government which had been providing significant funding decreased their financial support in 2004, stretching out the IOC date to at least 2010.

In 2000 and 2001 THEL shot down 28 Katyusha artillery rockets and 5 artillery shells. On November 4, 2002, THEL shot down an incoming artillery shell. A mobile version has completed successful testing. During a test conducted on August 24, 2004 the system successfully shot down multiple mortar rounds. The test represented actual mortar threat scenarios. Targets were intercepted by the THEL testbed and destroyed; both single mortar rounds and salvo were tested.

Even though military experts such as the former head of the Administration for the Development of Weapons and the Technological Industry, Aluf Yitzhak Ben Yisrael, were calling for the implementation of the THEL, the project was discontinued. During the 2006 Israel-Lebanon conflict, Ben Yisrael, currently the chairman of the Israeli Space Agency, renewed his calls to implement the THEL against high-trajectory fire.

Countermeasures

In theory certain countermeasures could reduce the effectiveness of THEL. These could include heat hardening and reflective coating of the projectiles, which would increase the necessary laser exposure time. However THEL has primarily been developed to intercept relatively primitive threats such as homemade Qassam rockets and World War II-era Katyusha rockets, which thus far have not incorporated sophisticated countermeasures.

Classifications of Possible THEL countermeasure techniques:

A review of the types of technologically feasible countermeasures would include (though not be limited to) the following :

1) Reflective coatings which attempt to reflect a large proportion of the incident radiation which is incident upon the aimed projectiles. This would not necessarily reduce the absorbed incident radiation to such an extent that the projectile is not destroyed - but in combination with other types of countermeasure, reflective coatings would feasibly ensure that target kill is achieved despite the use of THEL.

2) Modification of projectile geometries to take into account the possibility that laser light radiation might be used to neutralize the projectiles. Such geometries might also be concomitant with the purpose of improving the aerodynamic properties of the projectile - thus ensuring that it can travel faster (and, conceivably, would thus be able to rely upon the increased convective dissipation which is associated with heat transfer between the air and the projectile). NOTE : This includes the possibility of using projectile shapes which are NOT cylindrical: A missile form that helps to ensure that a minimum cross-section surface area is exposed to laser light.

3) As is the case in "hyper-planing torpedoes", which envelope the torpedo in a gaseous envelope so that they may travel at supersonic speeds underwater, it is also found that the use of similar (supersonic) gaseous envelopes around a missile would ensure that a sufficiently cool gas will carry away proportion of the incident radiation energy which is incident upon the missile by both convective and diffusive effects (ie: partial reflection, partial expansion upon being heated by the laser radiation and partial convection due to the temperature increase, though the latter two could arguably be considered as being of similar affect). This would thus also have the effect of a countermeasure to the THEL system. The enveloping gas/substance can be modified so as to consist of fine droplets which carry away a significant proportion of incident radiation and heat on the projectile as they are vaporised (provided, of course, they are chosen so as to absorb the heat radiation corresponding to the frequency of the incident radiation). Note, the larger the gaseous diameter around a cylindrical projectile (measured in terms of its cross section), the disproportionately larger the amount of incident radiation required by the THEL laser to destroy the projectile (consider the volume of the envelope and the highest level of heat dissipation which this corresponds to).

4) An oscillating or chaotic trajectory (one which is difficult to predict, but which will still ensure that the target is killed) will increase the difficulties in the use of the THEL system due to guidance. If guided into windy or turbulent environments, such a chaotic trajectory would also ensure that there more of a turbulent gaseous flow around the missile (though this would be due to the nature movement of air due to the fast moving missile rather than any specifically designed affect as in the case of (3)).

5) Similar in vein to the above, a rotating missile will halve the effective area over which the radiation is incident, yet another countermeasure technique or method. This occurs as it is assumed that there would only be one direction from which the THEL radiation would be incident ? but this technique has a countermeasure affect even when there are multiple THEL laser radiation sources pointed at the same projectile (assuming that there is some outer boundary area of the missile upon which no laser radiation is incident).

6) HEAT RESISTANT COATING LAYERS (HRCLs). These are similar to the use of a reflective coating in the sense that coating layers attempt to avoid too much heat causing guidance system malfunction or propellant autoignition within the THEL countermeasure projectile. However, in the case of HRCLs, internal capillaries/coolant mechanisms can be built quite simply into a projective design (consider wrapping the exterior of the projectile in a series of hollow air-pipes which allow air to flow parallel to the fast-moving projectile, but in a manner which does not impede air flow around the projectile - perhaps even aided via the use of a simple internal refrigeration system). Of course the notion of using an internal refrigeration mechanism within a small projectile system is, a priori, not something which seems sensible (though it might very well be economically feasible in the realms of missile design). However, the use of a 'disposable' interior to a THEL type system would ensure that excessively large amounts of heat which are generated due to incident radiation on the missile could be dissipated via the use of 'fall away' layers ? such as occurs with the NASA space shuttle as it re-enters the earth's atmosphere (within this type of a design, what occurs is that ceramic heat blocks at the base of the shuttle become red to white hot and are designed to fall off the shuttle, carrying away excess heat with them as they fall ? this is clearly a heat dissipation strategy which could be applied as a countermeasure to the THEL type system, and, due to the way in which the heat blocks dissipate large quantities of heat (when they are white hot, say), this method could be applied to artillery as only a thin heat dissipation based ceramic layer would be required for the purposes of carrying away incident heat energy.

Advanced warheads can be protected against almost any atmospheric laser system; but such measures prove increasingly difficult to integrate. As stated above, the intended targets of this missile system will be small, low cost, and low tech devices like shells and improvised rockets.

As a final note, it is seen that knowledge of the use of radiation intensive THEL like lasers within a combat situation at the design stage of a missile ensures that it is possible to make simple (and, perhaps, more ubiquitous) design modifications to missile systems which ensures that it will take orders of magnitude more in the way of incident laser directed missile radiation (in Watts) in order to destroy a missile than would otherwise be the case. Re-designing propellant exteriors within a projectile, as well as the type of propellant used within a projectile can also increase the amount of energy required to eliminate a projectile using the THEL type system.

7) No mention is made of the fate of multi-stage projectile systems within this countermeasure system ? though it might be imagined that designing a warhead which ?dummies? a THEL kill, and then re-ignites to carry on its previous trajectory after a certain fall time period would be worth consideration for certain types of multi-stage projectile system.