RPG Defeat Mechanism. Important characteristics that limit the
penetration of an RPG jet are primarily material density, strength, and the
tendency of certain materials to rebound on the jet. In addition,
predetonation of the RPG at a standoff distance from the material or creating
an oblique line of attack can limit RPG effects.
Material Density. In general, the amount of penetration achieved
by a continuous jet is approximately inversely proportional to the square
root of the density of the material. Consequently, materials with greater
density have a greater stopping capability.
Material Strength. Material strength becomes increasingly
important as the jet slows down and/or becomes particulated, i.e., when the
pressure exerted by the jet is no longer large compared to the strength of
the target. An approximate indicator of strength is the Brinell Hardness
Number (BHN) of the material. In general, materials with higher BHN have
better stopping ability.
Rebound Defeat Mechanisms. Rebound or hole "closure" is a
phenomena where target material moves back into the cavity caused by a jet
and interferes with subsequent portions of the jet, reducing its effective
length and penetrating capability. Only certain materials like steel,
ceramics, aluminum, and glass-reinforced plastics exhibit rebound. In
general, this phenomenon effects jets that have particulated. Rebound occurs
when the material flows back toward the cavity axis and closes the hole
behind each particle. Thus, the next particle must penetrate the closed
cavity before impacting the cavity bottom.
Oblique Attack Effects. Barrier surfaces that are at some angle to
the line of attack of the jet create a thicker material cross section for the
jet to penetrate.
RPG Defeat By Predetonation and Standoff. Screens can be used to
predetonate an RPG at a standoff distance away from the barrier. At large
standoffs the jet particulates and slows down before hitting the target and
consequently is easier to stop.
Hardening Design Options. This section provides guidelines for
hardening both new construction (par. 7.4.1), as well as the retrofit of
existing construction (par. 7.4.2) against an RPG attack.
New Construction. In designing a new building against an RPG
attack, one or more of the following should be considered: (1) proper site
layout to minimize attack line-of-sight; (2) the use of building sacrificial
areas; and (3) appropriately designed barriers with or without predetonation
Site Layout. Since the RPG is a line-of-sight (LOS) weapon, the
facility should be sited to limit, or preferably block, RPG attack sightlines