AFRL to Give Bunker-Busting a Boost

Declaring that hard and deeply buried targets -- command bunkers and other facilities -- are becoming more numerous and difficult to defeat, the U.S. Air Force Research Laboratory is seeking ideas for technologies to be incorporated into a high-velocity penetrating weapon -- a 2,000lb munition that would fit inside an F-35 but have the bunker-busting capability of a 5,000lb weapon.

According to a newly released broad agency announcement (BAA), the goal of AFRL's High Velocity Penetrating Weapon (HVPW) Flagship Capability Concept (FCC) is to "reduce technical risk for the eventual demonstration of air-delivered weapons with increased kinetic energy derived from boosting the velocity of the warhead before impact to better penetrate into the target."

Graphics: AFRL

Rocket boosting may seem a logical way to give a 2,000lb weapon, small enough to be carried internally by an F-35, the penetrating capability of the 5,000lb GBU-28 gravity-dropped bomb (below), but it poses some technical problems, including guiding the weapon to a precisely angled impact and ensuring its warhead and fuze survive the high-velocity penetration to explode inside the bunker.

Photo: US Air Force

According to an AFRL presentation on the HVPW, boosting with a rocket introduces issues in controlling a weapon that must strike its target, which could be slanted, at a precise angle to ensure it penetrates and doesn't bounce off. These include motor misalignment, control authority and the adverse effects of acceleration and vibration.

The BAA says: "The guidance associated with the penetrators must be robust enough to overcome GPS degraded environments and orient warhead impact to stringent angle-of-attack and angle-of-obliquity requirements." Obliquity is how far off perpendicular the weapon impacts the target and is coupled to its angle of attack, which in turn affects its controllability.

Research is planned into anti-jam GPS, angle-of-attack sensing, guidance laws and RF seekers. "Of particular interest with the use of an RF seeker are the use of multilateration and offset tracking guidance concepts. The engagement of featureless fixed targets must provide information for guidance alignment of the weapon before and during boost, provide off-boresight tracking of features and derive guidance estimates for closed-loop offset guidance," the BAA says.

The BAA makes clear the "HVPW FCC will not integrate all sub-components into a 'full-up round' ... The objective is to develop subsystem and component technologies to a maturity level sufficient to transition to a potential technology demonstration program beginning in FY14." Development of an integrated flight-test vehicle is not part of the FCC, but a survivable ordnance package (casing, warhead and fuze) is to be sled-tested.

Tags: ar99, AFRL, F-35, afa11