OTHER ARTICLES IN THE WTC SERIES
Why Did the World Trade Center Collapse? Science, Engineering, and Speculation by Thomas Eagar and Christopher Musso
Better Materials Can Reduce the Threat from Terrorism by Toni G. Maréchaux
An Initial Microstructural Analysis of A36 Steel from WTC Building 7 by J.R. Barnett, R.R. Biederman, and R.D. Sisson, Jr.
. . . you will never have a perfect defense, not against the bullet, not against the tank and not against nuclear weapons. What you can do is vastly complicate an attackers calculations, blunt his force and save millions of lives. --Wall Street Journal, April 8, 1983
Materials scientists and the materials-processing
community have been asked throughout the ages to respond to societys demands.
From the Stone Age to the industrial revolution, materials have been integral
to progress. Starting in the 1960s, materials responded to the call to develop
technology for the space race, and in the 1970s, to address the demands of the
energy crisis. In the1980s, societys need for improved information technology
reaped the benefits of advances in materials and processing.
Today, the cry for help is coming from the need for antiterrorism and terrorism consequence management technologies. Countering the threat from terrorists use of chemical, biological, radiological, and nuclear materials, or high-yield explosive devices (CBRNE), will require a wide range of materials technologies. Both the transfer of existing technologies from defense and industrial applications as well as the development of entirely new materials and processing science will be needed to meet this challenge.
New sensors to monitor, detect, and characterize CBRNE are needed with improved systems aspects. Todays sensor systems for biological or chemical weapons are difficult to transport and have little flexibility. Sensors are needed with detect-to-warn capability, which means they need to resemble smoke detectors or handheld devices and not the trailer-sized chemical laboratories available today. Innovative sensor technologies for a constantly changing set of biological and chemical weapons are also needed, with increased standoff distances to protect personnel who investigate packages or cargo containers with suspicious pedigrees. Sensors are also needed to routinely screen airline baggage or a ship full of cargo quickly and reliably. Better characterization and understanding of potential weapons, such as advanced energetic materials, and of the packaging and transportation for such weapons, is needed. Ways to deploy early warning devices that are hidden and rugged are also needed for use in monitoring electromagnetic and personnel traffic in sensitive areas.
Imaging technology is needed for more reliable screening of carry-on bags and checked bags for aviation security. Different schemes are needed for imaging the contents of cargo containers on aircraft that carry mail or fresh food. More than 90 percent of imports come in to the United States via ship and are then transported on trucks or trains. These are unloaded very quickly, and must be screened quickly. Through-structure imaging inside buildings or under rubble is another difficult application. Locating difficult targets is yet another challenge, such as underground structures and those beneath either natural or artificial camouflage. More thorough imaging technology with fewer health effects is also needed for personnel screening.
Hardened structures are needed that are harder to breach, harder to damage, and less susceptible to fire. Materials and design strategies will be needed to toughen such structures as buildings, aircraft, and cargo containers. Structures that are harder to breach might have integral sensors in entry portals, which might include both passenger and galley doors on aircraft. Structures that are harder to damage might have blast-resistant windows or walls of self-healing materials that could mend a bullet hole.
Throughout the history of aviation, aircraft engineers have had to balance three overarching design factors: cost, safety, and efficiency. Over recent years, the push toward a lighter-weight, more efficient craft has in some ways gained precedence in design. In practice, cost and safety factors are kept constant while designers continually strive for improvements in weight and efficiency. This emphasis may be attributed to rising fuel costs, the dynamics of competition among airframe manufacturers, and the previously low rate of catastrophic failure due to aircraft design.
This emphasis has resulted in an overall lack of a systems approach to aircraft function and security. Recent developments in smart materials and integrated sensors could considerably improve aircraft functionality. There has also been limited development and implementation of improved fuels. Such technologies as lower volatility fuels, inerting fuel tanks, gelling agents, and anti-misting fuel additives can reduce impact. Combinations of these approaches may yield the best results.
Specifically on passenger planes, recent design strategies have resulted in a thin door between the pilots and the cabin. A better-designed, yet lightweight door, bullet- and bomb-proofed, would be far less easily breached. There is also no screening technology on either passenger or galley doors. Adding an additional level of screening for weapons or explosives on board can dramatically decrease risk. There is also very limited use of hardened unit load devices for cargo containment. Though developed, these units are currently heavy and expensive.
Certainly, some safety and security advances have been and continue to be made. Preventing and mitigating fire has been a major consideration in all aspects of aviation design. Current designers of commercial and military aircraft incorporate a broad array of fire safety features, such as firewalls, shrouded and break-away fuel lines, flame arrestors, fuel-line isolation, explosion-proof electromechanical equipment, detectors and extinguishing systems, and fire-resistant materials, into their designs. None of these, however, can mitigate the effect of explosive combustion of tonnes of jet fuel due to impact.
It is suggested that advances in materials and sensor technologies, advances in fuel composition and fuel system design, and the transfer of new technologies from other fields to aviation have the potential to dramatically improve safety and security without compromising efficiency and performance. Our goal is to determine how, and to what extent, integration of new technologies can reduce the impact due to kinetic force, explosive combustion, or toxic release from the downing of military or commercial aircraft. An additional goal is to use technologies to mitigate such threats as terrorist attacks, individual suicides, human error, or mechanical failures through the use of smart and hardened systems.
Self-healing materials that could mend a bullet hole, for example, or materials with energy-absorbing substructures could be used. Improved heat-resistant materials and longer-lived insulations are needed as well.
New active materials are needed to neutralize explosions, passive ones to contain large vehicle bombs, and still others to mitigate bombs in buildings. Technologies are needed to safely destroy weapons of known design and also to disarm improvised devices. Non-destructive techniques to render harmless manufacturing facilities for explosives and their products are also needed to minimize collateral damage. Most explosives are disarmed today through detonation of the entire device or facility. Though this method is effective, it also tends to destroy most of the evidence needed to trace the origin of the weapon. New technology is needed to precisely disassemble terrorist devices at a safe distance. Such non-destructive methods will also serve to protect law enforcement officials.
Technologists from many disciplines are being called on today to protect the U.S.mail.The absorbency, transparency, and reactivity of paper are all important properties when considering biological or chemical contamination. Scanning technologies to detect such contamination with x-rays, neutrons, or light are all possible ways to deal with potential threats. Cleansing technologies that employ radiological or chemical means must also be evaluated in terms of their effects on shipping materials and their contents.
New technologies are needed for forensics against weapons of mass destruction, as are methods to quickly identify terrorists who have released biological, chemical, or nuclear weapons. Easy-to-obtain evidence is needed to determine intermittent, yet less-than-lethal, exposure to chemical warfare nerve, blister, blood, and choking agents, or radiation from nuclear weapons, radiological dispersion devices, or biological warfare agents. New equipment and methods are needed for field assays and for definitive laboratory procedures to analyze residues and traces, including hair, skin, blood, bodily wastes, teeth, and bone, as well as personal effects, cars, and buildings.
For materials scientists to make their maximum contribution to this new endeavor of homeland security, they will need to learn some new languages. Just as metallurgists learned what properties were desirable for a turbine blade or ceramists learned how to utilize electron microscopes, we will need to learn other priorities and new ways for materials to contribute to societys needs.
In addition to the short-term needs that are now in demand by our homeland defense forces, we also need to look at protecting our manufacturing base from terrorist acts. How can we make processing more agile and redundant? How can we make facilities more resistant to explosions or chemical attack?
Finally, societys needs for the long term include decreasing the cost of materials and manufacturing to improve access to technologies by local law-enforcement and public-health departments. Lower-cost night-vision goggles or passive-restraint systems can put these technologies where they are needed most. Certainly, more flexible ways to manufacture pharmaceuticals would allow new vaccines to be produced with timely response to demand. An even more overarching need is to create a national strategy for a strong U.S. manufacturing base and materials supply to support future wartime efforts. Materials science must continue to be on call to meet societys needsboth old and new.
Toni Grobstein Maréchaux is director of the National Materials Advisory Board in Washington, D.C.
For more information, contact Toni Maréchaux at National Research Council, 2101 ConstitutionAve. NW, National Materials Advisory Board, Washington, D.C., 20418; e-mail email@example.com.; www.nationalacademies.org/nmab.
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