In 2012, the US intelligence community estimated over 10,000 potential underground facilities exist worldwide, with the majority of them unidentified and the expectation that their numbers will continue to increase dramatically over the next decade.
Countries across the world increasingly recognize the benefit underground facilities provide in protecting and securing strategic assets. These facilities are becoming “ubiquitous,” able to conceal resources, capabilities, and intent. High on the list of nations making significant investments in underground facilities is China, whose underground tunnel network reportedly stretches 5,000 km.China’s underground facilities are emblematic of the US HBDT (Hard and Deeply Buried Target) defeat problem, highlighting gaps in intelligence (represented by the operational capability elements of detect, characterize, plan and assess) and weapons capability ( represented by the operational capability element of defeat).
As countries continue to expand the use of tunneling for underground facilities, testing against facilities protected by rock revealed the ineffectiveness of 2,000 lb penetrating bombs, including use of skip bombing tactics into tunnel entrances. To defeat these facilities, weapons developers determined that several thousand pounds of high explosives “coupled to the tunnel” (i.e., a 20,000-30,000 lb munition) would be required in order to destroy blast doors and send the required overpressure through the complex.
Such an optimized penetrator weapon may penetrate 5-8 times farther than current 2,000 lb weapons. In addition, by employing the optimum dual delivery tactic, “ where a second penetrator follows immediately behind the first, and boosting the penetrator velocity with a rocket motor, a depth of up to 40 meters can be achieved in moderately hard rock.
Leveraging Nanotechnology to Enhance Kinetic Weapon Effectiveness
In order to develop an effective family of systems designed to functionally defeat HDBTs, the benefits of nanotechnology cannot be ignored. Recent breakthroughs in nanotechnology have occurred in a range of relevant specialties from materials to sensors to energetics. The implications of these breakthroughs are that improved ISR capabilities may become available to enhance location and characterization of HDBTs. Moreover, enhanced energetics and improved material properties may improve penetration and thermobaric effects especially against WMD-related materials contained in HDBTs.
Los Alamos National Laboratory (LANL) has made substantial progress in the development of nanotechnology materials designed to enhance weapon penetration/payload survivability and lethality. Scientists have made significant progress in creating core structural properties of materials through the use of nano-sized particles.
Through the development of diamond-SiC nanocomposites, LANL has developed the technology to enhance fracture toughness while maintaining superhardness
Scientists anticipate that weapons utilizing nano-energetic materials will be comprised of up to two orders of magnitude less overall mass as conventional weapons.
In addition, energetic materials can be designed for a specific application by controlling density and sensitivity to initiation.
The Defense Threat Reduction Agency has accomplished extensive work on advanced energetics as well. Near-term efforts include enhanced thermobarics and shock-dispersed fuels. Mid-term efforts emphasize advanced multi-functional energetics and all/high nitrogen species. Far-term efforts include metastable molecular clusters (5 to 50 times greater energy than conventional high explosives (HE)), nuclear spin and shaped isomers (104 times greater than HE), small-scale fusion (108 times greater than HE), and anti-matter annihilation (over 1000 times greater than HE).
Standard hard concrete versus publicly known US bunker busters
The GBU-57A/B Massive Ordnance Penetrator (MOP) is a U.S. Air Force, precision-guided, 30,000-pound (14,000 kg) “bunker buster” bomb. This is substantially larger than the deepest penetrating bunker busters previously available, the 5,000-pound (2,300 kg) GBU-28 and GBU-37.
In 2012, the Pentagon requested $82 million to develop greater penetration power for the existing weapon. A 2013 report stated that the development had been a success, and B-2 integration testing began that year.
The bomb can penetrate 200 feet of 5000 psi hardened concrete and is accurate enough for multiple hits on the same location to penetrate deeper targets or targets with even stronger concrete. One GBUJ-57A/B can only penetrate 8 meters of 10,000 psi rock or concrete. This could drop to 2 meters of 30,000 psi material.
Rock of over 10,000 psi is considered hard. The strongest granite is about 30,000 psi. In 2007, the University of Tehran made several concrete cubes between 50,000 to 60,000 psi, and possible stronger. The aggregate to be made from quartz, and had some steel fibers in the mix.
High-strength concrete has a compressive strength greater than 40 MPa (5800 psi).
Ultra-high-performance concrete is a new type of concrete that is being developed by agencies concerned with infrastructure protection. UHPC is characterized by being a steel fibre-reinforced cement composite material with compressive strengths in excess of 150 MPa (21750 psi), up to and possibly exceeding 250 MPa (36250 psi). UHPC is also characterized by its constituent material make-up: typically fine-grained sand, silica fume, small steel fibers, and special blends of high-strength Portland cement. Note that there is no large aggregate. The current types in production (Ductal, Taktl, etc.) differ from normal concrete in compression by their strain hardening, followed by sudden brittle failure. Ongoing research into UHPC failure via tensile and shear failure is being conducted by multiple government agencies and universities around the world.
Micro-reinforced ultra-high-performance concrete is the next generation of UHPC. In addition to high compressive strength, durability and abrasion resistance of UHPC, micro-reinforced UHPC is characterized by extreme ductility, energy absorption and resistance to chemicals, water and temperature. The continuous, multi-layered, three dimensional micro-steel mesh exceeds UHPC in durability, ductility and strength. The performance of the discontinuous and scattered fibers in UHPC is relatively unpredictable. Micro-reinforced UHPC is used in blast, ballistic and earthquake resistant construction, structural and architectural overlays, and complex facades.
Ducon was the early developer of micro-reinforced UHPC, which has been used in the construction of new World Trade Center in New York
DUCON® Micro-Reinforced Concrete Systems is an innovative, high-performance strengthening and force protection system designed for extreme load resistance and energy absorption. DUCON® combines an infuseable ultra high-performance grout with a densely layered MicroMat® steel reinforcement system. The highly-engineered and test-proven system can be custom-designed to a project’s specific performance requirements.
Like concrete in placement versatility, DUCON® can be applied to new and existing structural members, or prefabricated off-site to create a wide range of precast shapes and sizes.
Like steel with its ductility and energy dissipating qualities, the DUCON® system allows for the highest level of performance for the most challenging applications.
One World Trade Center in New York rests on a 20 story, bombproof foundation that reaches 60 meters underground. Overall, at points within the building where safety is especially critical, several thousand square meters of safety concrete have been used to shore up the construction.
One World trade center cost $3.9 billion.
Reinforcing any bunker in Iran with a lot of micro reinforced UHPC would cost billions. They would have to excavate the already hard rock that is there and replace it with any new superconcrete.
On 25 June 2010, USAF Lt. Gen. Philip M. Breedlove said that the Next-generation Penetrator Munition should be about a third the size of the Massive Ordnance Penetrator so it could be carried by affordable aircraft. In December 2010, the USAF had a Broad Agency Announcement (BAA) for the Next Generation Penetrator (NGP).
Global Strike Command has indicated that one of the objectives for the Next-Generation Bomber is for it to carry a weapon with the effects of the Massive Ordnance Penetrator. This would either be with the same weapon or a smaller weapon that uses rocket power to reach sufficient speed to match the penetrating power of the larger weapon.