Small Arms Protective Insert

The Small Arms Protective Insert (SAPI) is a ceramic plate first used in the Interceptor body armor, a bulletproof vest. It is now also used in the Improved Outer Tactical Vest as well as the Modular Tactical Vest, in addition to commercially available "plate carriers". The kevlar Interceptor vest itself is designed to stop projectiles up to and including 9mm submachine gun rounds, in addition to fragmentation. To protect against higher velocity rifle rounds, SAPI plates are needed.

ESAPI

In May 2005, the US Military began replacing the standard Small Arms Protective Insert plates with the Enhanced Small Arms Protective Insert (ESAPI). [http://www.globalsecurity.org/military/systems/ground/interceptor.htm Interceptor Body Armor ] ] [http://www.defenseindustrydaily.com/up-to-160m-for-enhanced-interceptor-vest-protection-updated-0986 Up to $160M for Enhanced Interceptor Vest Protection (Updated) - Defense Industry Daily ] ] ESAPI provides protection from armor piercing bullets but cost about 50% more than SAPI plates, at about $600 per plate. They are produced by Ceradyne, Armor Holdings, and ArmorWorks Enterprises. [http://www.defenseindustrydaily.com/plate-inserts-for-us-body-armor-04416/ Plate Inserts for US Body Armor - Defense Industry Daily ] ]

XSAPI

A call for a next generation plate, to stop even greater velocity threats that the ESAPI plate has been issued by the US Army. They have specifically allowed scalar or flexible systems, and are also calling for greater coverage, with less than a pound of additional weight. [ [http://www.defensetech.org/archives/003567.html Defense Tech: Army Seeks Body Armor for New Threat ] ] [https://acquisition.army.mil/asfi/upload/W91CRB07R0041/Atch02-REVXSAPI-PD_A_.pdf]

Material and capabilities

The standard plate for the Interceptor body armor is made of boron carbide or silicon carbide ceramic. [ [http://www.globalsecurity.org/military/systems/ground/interceptor.htm Interceptor Body Armor] ] New ESAPI plates are also made of boron carbide. [http://www.co.washington.wi.us/washington/Pubs/VET_BodyArmorFacts.pdf] A SAPI is able to stop up to three rifle bullets of a caliber up to 7.62×51mm ball and of a muzzle velocity up to 2,750 feet per second (838 m/s). The ceramic plate is backed with Spectra shield, a material up to 40% stronger than Kevlar.

The standard plates are rated as NIJ III when used alone and NIJ IV when backed by the soft armor of the OTV.

Sizes & Weights

SAPI plates meant for body armor come in front and back plates which are identical, and smaller side plates. The front and back plates come in five sizes, extra-small thru extra-large. Their dimensions are the following:http://adg.armorholdings.com/pdfs/Hard%20Body%20Armor.pdf]

Front and back SAPI plates:
*Extra Small - 1.27kg (2.8lb) | .184 x .292 m (7.25 x 11.5 in)
*Small - 1.59kg (3.5lb) | .222 x .298 m (8.75 x 11.75 in)
*Medium - 1.82kg (4.0lb) | .241 x .318 m (9.5 x 12.5 in)
*Large - 2.09kg (4.6lb) | .260 x .337 m (10.12 x 13.25 in)
*Extra Large 2.40kg (5.3lb) | .280 x .356 m (11 x 14 in)

ESAPI plates are the same size but slightly greater in weight.
*Extra Small - 1.70 kg (3.75 lb)
*Small - 2.08 kg (4.60 lb)
*Medium - 2.50 kg (5.50 lb)
*Large - 2.85 kg (6.30 lb)
*Extra Large - 3.25 kg (7.20 lb)

Torso side plates are as follows:
* 1 kg (2.3 lb) | .15 x .2 m (6 x 8 in)

Physics

The mechanism of effect lies in absorbing and dissipating the projectile's kinetic energy in local shattering of the ceramic plate and blunting the bullet material on the hard ceramic. The Spectra backing then spreads the energy of the impact to larger area and stops the fragments, preventing injury to the wearer.

The same principle is used for the ceramic tiles used for the armored cockpits of some military airplanes, and the spall liners used in modern armored personnel carriers.

References

See also

* Ceramic plate
* Tactical Vest Antenna System