slow. Inclusion of such armor in older vehicles as a part of a re-design is possible, as in the numerous types derived from the T-72. Slat armor is lighter and as such can be added to many vehicles after construction but still adds both bulk and weight. Particularly for vehicles that are designed to be transported by cargo aircraft, slat armor has to be fitted in the field after deployment. Either approach can never offer complete coverage over the vehicle, leaving tracks or wheels particularly vulnerable to attack. Jamming Jamming is potentially an effective countermeasure to specific missiles that are radar guided, however, as a general purpose defense, it is of no use against unguided anti-tank weapons, and as such it is almost never the only defense. If jamming is used continually, it can be extremely difficult for a missile to acquire the target, locking on to the much larger return from the jammer, with the operator unlikely noticing the difference without a radar screen to see the return. However, any missile that has a backup tracking system can defeat jamming. Active Active protection systems show a great deal of promise, both in counteracting ATGMs and unguided weapons. Compared to armor systems, they are very lightweight, can be fitted to almost any vehicle with the internal space for the control system and could, in the future, be a near-perfect defense against any missiles. The weaknesses of the systems include potential developments in missile design such as radar or IR decoys, which would drastically reduce their chance to intercept a missile, as well as technical challenges such as dealing with multiple missiles at once and designing a system that can cover a vehicle from any angle of attack. While these may be answered and allow for lightweight, highly maneuverable vehicles that are strongly defended against missiles and rockets that are extremely well suited for urban and guerrilla warfare. However, such a system is unlikely to be as effective against kinetic energy projectiles, making it a poor choice for fighting against tanks. As kinetic energy projectiles move faster than guided missiles. This often means that the sensors attached to an active protection system can't keep up. Testing in 2007 showed that explosive reactive armor, fitted to a T-72 had no impact on a missile fitted with a kinetic energy projectiles. Other Traditionally, before "fire-and-forget" ATGMs were used, the most effective countermeasure was