"Seizing the initiative: tanks take active protection system advances on board" (by RM Ogorkiewicz, Janes International Defence Review, August 2008), discusses option for protecting military vehicles from attack. It mentions "collateral damage" where the protection system injures people, but none of the systems mentioned seem to place enough emphasis on this for urban warfare. Also they seem to be single use systems only suited to mounting on large and expensive tanks. Perhaps a cleverer, lower cost, and less than lethal system is needed for peacekeepers.
Active protection system (APS) are mounted on a vehicle to protect it typically from rocket propelled grenades (RPGs). The APS could use jamming or decoys to defeat smart missiles, but an unguided RPG needs a hard kill system exploding next to it or hitting it. The problem is to hit the RPG but not harm those around it.
Systems typically use small missiles which explode near the target, such as TROPHY and Drozd. All such systems have the problem of collateral damage, some try to limit this by attacking from above and others by using very precise and focused explosives or showers of particles.
Another problem with such weapons is that they can only be used on large armoured vehicles. The vehicle needs to be large enough to carry the APS and needed to be armoured protection from the effects of the APS. This precludes use in small light vehicles.
Less Lethal Ammunition
The APS currently about to be fielded all use either high explosive or projectiles to intercept an RPG. It would be feasible to use a less than lethal warhead, such as a flexible baton round or high strength net to intercept the RPG. This would cause less injury to bystanders. Currently produced less than lethal rounds might be able to be used, fired from standard weapons, removing the need for new development, testing and manufacture. This would provide a dual use device which could be used as an APS and for riot control.
Lightweight fast RWS for APS
Another problem with such weapons is that they are single use. The 1980s UK Marconi TAMS system was to use 7.62 mm machine guns, much as naval Close-in weapon systems (CIWS) do, but this was not further developed. With the availability of low cost sensors, computer control and need for urban combat, relatively lightweight remote weapon stations (RWS) are now widely used. These might be adapted for an APS. This would provide a dual use system which could be for offence and well as defence.
A machine gun or automatic mortar on a lightweight RWS could be automatically targeted on RPGs. Special ammunition could be used which would be effective over a limited range, to reduce collateral damage and increase the probability of interception. A smaller calibre weapon could be used, reducing the weight and increasing the rate at which it could be aimed. RWS commonly allow for dual feed weapons so the weapon could be switched automatically from offensive to defensive ammunition.
The RWS' electronic sight would be supplemented by an additional 360 degree optical and/or radar surveillance system. When an incoming RPG was detected, the RWS would be slewed in the correct direction and then its own sights would automatically track the target and fire.
Such a system could be made small and light enough to be mounted on a Land Rover sized vehicle. As well as being used for defence the sensors and weapons could be used for surveillance and attack. A version having only less than lethal ammunition could be used by peacekeepers.
All the APS in development appear to be single vehicle systems. A more effective and safer system would network several vehicles. The sensors of all vehicles in a vicinity could share the surveillance and the most appropriate weapon used. This could greatly reduce the risk of collateral damage and increase the effectiveness of the system. The system could also track people, assuming them to be either friendly forces or non-combatants and so minimise causalities.