SAPI is a revolutionary lightweight body armor system that can stop rounds from automatic rifles. While so called “bulletproof” vests have existed for quite a while, these vests don’t stand up to the high muzzle velocities encountered on modern battlefields. Flak jackets, while effective at stopping shrapnel, are also found lacking in terms of bullet-stopping power. SAPI bridges the gap between flak protection and automatic rifle round protection, providing soldiers with reliable lightweight protection.
Transitioning from the Flak Jacket
The first flak jackets consisted of manganese steel plates and weighed 22 lbs. It was unwieldy armor plating that provided moderate protection against shrapnel from artillery and frag grenades. By the time of the Korean and Vietnam wars, the manganese steel was replaced by lighter materials. These jackets weighed between 6 and 10 lbs and were composed of ballistic nylon and Doron, a fiberglass weave. Still, this type of body armor lacked the ability to actively protect the user from rounds fired from automatic weapons.
During the Persian Gulf War, DARPA and the US Army began work on a lightweight body armor that could protect soldiers from both shrapnel and rifle rounds. The result was the Personnel Armor System for Ground Troops, or PASGT. It was met with derision from some military personnel, however, who compared it to the traditional flak jacket. While this jacket was lighter than previous versions of US soldier body armor, it still could not stop a round at close range. During the early to mid ’90s, when US soldiers increasingly found themselves in urban settings, the need for a new type of body armor became greater than ever. The solution came in the form of SAPI, or the Small Arms Protective Insert.
SAPI, with its small inserts, marked a significant change in body armor design. The plates consist of a sophisticated ceramic on the front side and a Kevlar-like material—known as Spectra—on the back side. SAPI works by absorbing and dissipating the kinetic energy of an incoming bullet and then catching the bullet fragments so that they don’t reach the wearer’s skin. This action doesn’t prevent injury, of course. Wearers can still suffer broken ribs and bruises, but it does significantly reduce the risk of fatal injury from a bullet. Used in both the Improved Outer Tactical Vest and the Modular Tactical Vest, SAPI has been thoroughly field-tested and has been declared a resounding success.
The plates provide protection against rounds fired at a muzzle velocity of up to 2,750 ft/s. ESAPI, an even more durable version of the technology, can stop a .30 cal M2 armor-piercing round, but it costs 50% more than standard SAPI plates at around $600 per plate. The US Army is currently developing a new generation of SAPI technology that could stop even faster rounds and weigh even less.
Usage in the Field
SAPI-like plates first saw use in the streets of Somalia in the ’90s, and the concept’s potential was immediately obvious. The numbers of soldiers killed in action fell drastically. One of the system’s life-saving features that may not be readily apparent is its low weight. Currently, the extra-small SAPI plate weighs in at 2.8 lbs, while the extra-large comes in at 5.3 lbs. The low weight allows soldiers to get through a hostile area faster, and it gives them an edge against enemies wearing older, bulkier vests. The key to SAPI’s life-saving prowess is its Spectra back side, however. Spectra is 40% stronger than Kevlar.
SAPI is a lightweight, portable body armor system that will be improved as lighter, stronger materials become available. The system itself is an improvement over all previous forms of body armor, and both DARPA and the US military consider it the way forward.