WikipediaTechnologyThe concept of stacked projectiles (multiple projectiles loaded nose to tail in a single gun barrel with propellant packed between them) predates Metal Storm (for example Scott in 1902 and Broyles in 1974). Mike O'Dwyer demonstrated a method whereby projectiles placed in series along the length of a barrel could be fired sequentially and selectively without the danger associated with unintended propellant ignition.
In the original Metal Storm patents the propellant immediately behind the projectile closest to the muzzle of the gun barrel was ignited by an electronically fired primer. The explosion propelled the projectile in the direction of the muzzle. At the same time a reactive force acted on the remaining stacked projectiles in the barrel, pushing them backwards. By design, the remaining projectiles would distort under this load, expanding and jamming against the gun barrel wall. This created a seal which prevented hot propellant gases from prematurely igniting the remaining propellant charges in the barrel (blow-back). As each propellant charge was selectively ignited, the force 'unjammed' the projectile in front and propelled it down the gun barrel.
The stacked projectile and electronic ignition technology eliminated the need for cartridges, and for many moving parts associated with traditional guns. Multiple barrels containing stacked rounds could be grouped together in arrays allowing unprecedented (albeit very brief) rates of fire of up to 1,000,000 rounds per minute. As testing of the technology progressed, it was thought that in addition to very high rates of fire, very high barrel pressures and hence high muzzle velocities could be achieved as a number of charges (and projectiles) could be fired before the first projectile had travelled as far as the gun muzzle. To date Metalstorm has not been able to succesfully test this theory as they have yet to develop a viable high velocity solution.
Subsequent patents taken out by Metal Storm eliminate the 'jamming' concept by containing all of the propellant charges within skirts at the base of each projectile. Each skirt rests on the front of the following projectile forming a seal. The backwards force created as propellant charges are fired 'ahead' in the barrel compresses this seal, preventing hot gases from prematurely igniting the following charges. Because this technology does not rely on creating a seal between the projectiles and the barrel wall it can be employed in rifled gun barrels, and could theoretically lead to a reduction in barrel wear. Demonstrations of the Metal Storm prototype low velocity 40mm guns and ammunition in Singapore and New Jersey in February and March 2006 apparently employed this technology.
FeaturesSeveral proposed designs, and prototypes have clustered together a number of metal storm gun tubes in box-like arrays. In this configuration each gun tube is loaded with stacked projectiles, and the firing of each of these projectiles is under separate electronic control. Metal Storm has demonstrated integrated electronic fire control systems in conjunction with prototype arrays. The arrays are effectively multi-barrel weapons, similar to volley guns, but with individually selectable fire control, and with the capacity of 3 to 6 (or more depending on how many projectiles are in the stack in each tube) shots per tube. These designs have been proposed for use as close in defence for fixed assets, vehicles and ship defense, and as an offensive weapon when mounted on aircraft or unmanned vehicles (ground or air based).Designs for the arrays have included options where the gun tubes at the edges of the array are angled outwards from the main axis so that a gun tube array mounted on a tracking platform would have the potential to engage a target before the bulk of the centrally located gun tubes reached the optimal aiming position. This feature, combined with the 'always loaded' nature of the technology, and the potential to produce a very high density (low distance of separation) of projectiles 'in the air' is put forward by the company as an advantage for this technology in close-in weapons support roles. Other gun tube array designs have incorporated variable calibre gun tubes with mixed payloads; such as a variety of non-lethal and lethal munitions allowing a selectable and/or escalating response. This design is intended to particularly meet the requirements of urban insurgent warfare where forces normally equipped with lethal force weapons may be dealing with civilian crowds. The U.S. Department of Defense is currently examining the use of other non-lethal crowd control technologies such as microwaves (to produce subcutaneous heating), aural projection (to cause discomfort or disorientation), and 'dazzling' (using lasers to produce temporary blindness). Potential applicationsMetal Storm technology is not currently deployed. Consequently applications of the technology can only be described as potential at this time. Potential applications include area denial (replacing fixed minefields), minefield destruction, close-in weapons support for ground vehicles, airships and ships, anti-torpedo defence; combined gun/grenade launcher for infantry - the Advanced Individual Combat Weapon (AICW); unmanned ground vehicle offensive capability; unmanned aircraft (fixed and rotary wing) offensive capability.
LimitationsWidespread public awareness of Metal Storm technology was due to media coverage in relation to the theoretical 1 million rounds/minute rate of fire. In the United Kingdom it was featured along with its inventor on the popular BBC show Tomorrow's World.
Limitations with the technology became apparent during the late 1990's as development continued. Some of the limitations are materials dependent, while others relate to the nature of the technology. Much of the detail of the technology remains classified but it is understood that:
Barrel wear may have been a significant issue with the original shell/barrel jamming design. The high pressure generated in the barrel was apparently a concern with 50mm+ calibres. Metal Storm patented a method of 'barrel pressure relief' but have not been able to overcome the high pressure limitations of the system. While the simplified mechanics and relative light weight of a metal storm gun barrels suggested that they might have advantages when deployed on light unmanned aerial vehicles, recoil management becomes a significant issue relative to the light weight of the vehicle and consequently to flight stability. Metal Storm have suggested that this may require a partly avionics (flight control) solution. Some issues arise from the fundamental aspects of the technology:
Manual, automatic and semi-automatic reloading concepts exist, incorporating breech and muzzle loading into permanent barrels, throw-away barrels (and barrel arrays), a belt-fed stacked-cartridge gun patent, and a patented breechless continuous feed gun with injected propellant. With the exception of the belt-fed and the breechless gun patents, all of Metal Storm's gun concepts are limited to bursts of no more the number of bullets or shells pre-loaded into the barrel(s). A barrel array might contain more shells in fact than a traditional 'clip' or 'belt', but would not be able to compete with ship or aircraft mounted guns or dedicated belt fed machine guns with very long ammunition belts (unless the barrel array was duplicated to allow alternate reloading). Single-barrel designs appear to currently be limited to 3 or 5 stacked rounds before reloading. That limitation in the case of 9mm bullets may appear restrictive, while in 40mm and above calibres it is competitive with current capacities in traditional technology guns. In cases where sustained rates of fire are required, or where manual reloading would be hazardous, automatic reloading technology will need to be incorporated with Metal Storm technology, reducing the advantage of 'mechanical simplicity' inherent in the original Metal Storm concept.
Metal Storm has stated that the different barrel lengths travelled by each of the stacked shells would have no significant effect on accuracy. It is not clear what the size of the actual effect is, or whether using variable propellant charges has been used to mitigate this effect. It is understood that the effect is 'less' in the case of the low pressure relatively short range 40mm weapons currently being developed. Metal Storm has indicated that single-use throw-away barrels could be manufactured to 'lower' tolerances than multiple-use barrels and hence an array of barrels (or spare throw-away barrels) would be lighter than an equivalent number of traditional technology barrels. It is not clear whether Metal Storm have been able to quantify the tolerances or indicate an acceptable method of deployment of such barrels that did not involve undue risk to the operators. (H) × 12.5 mm (W) × 1.2 mm (D) (i.e., ~1/4 the size of Duo)
