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Breakthrough Research

Enabling research such as that described in this plan is an essential element in maintaining the continuous evolutionary advances needed to achieve a transportation system that can meet the needs of the 21st century. However, recent decades have made clear that success in the future will also require more than evolution---it will also rest on periodic injection of breakthroughs from the world of basic research that significantly alter and expand the technological options available to the transportation enterprise.

It is the nature of basic research that its practical implications are not immediately clear. Often, many years go by before the major impacts are felt. However, the technological acceleration in the latter part of the 20th century has generally shortened the period between scientific findings and invention and realization of real-world innovation. Potential users as well as the scientific community are becoming more and more sensitized to the potential value of research products, so that the interval between discovery of new knowledge and practical application has become relatively brief.

Further, the pressure of the challenges we face, and the rewards for successful exploitation of scientific and technical advances, often combine to encourage research in areas where the outputs are particularly likely to have special value. This is as true for transportation as for any other human endeavor. For that reason, this section of the National Strategic Transportation Research Plan identifies three of the numerous areas of important basic research now being pursued which have especially clear and substantial potential benefits for the designers, builders, operators and users of future elements of the national and global transportation system. These areas are:

• Nanotechnology
• Biofuels
• Complex Systems and High-Confidence Software

All three areas are addressed in the specific enabling research discussion in Section 4 of this plan, but their importance warrants the more focused discussion that follows.

Nanotechnology

"Nanotechnology" is the building of devices and materials at the level of atoms and molecules and the exploitation of the novel properties at this scale. It gets its name from "nanometer," the unit of measurement representing one-billionth of a meter, or about ten times the size of an individual atom. (In comparison, microtechnology is at the level of microns---a millionth of a meter---gargantuan by the standards of nanotechnology.) "Nanotechnology" generally refers to work done at the scale between 0.1 and 100 nanometers. The novel properties are due to the different behavior of things at this scale as compared with either isolated molecules or larger structures.

Nanotechnology implies the direct control of atoms and molecules. Broadly, it comprises (1) the design of atomically engineered "building blocks"; (2) the assembly of these building blocks into new, "nanostructured" materials with specific characteristics; and (3) the assembly of these materials into useful devices.

There are two overall approaches to building things at the nanoscale. The first is to etch, chisel, or sculpt such features into an existing, larger structure, using techniques such as scanning tunneling or atomic-force microscopy or various forms of lithography (the process now used to make computer chips). Nano-size gears and smaller integrated circuits are just some of the objects being fabricated using this approach, which is sometimes referred to as "top-down." The second method---and the most revolutionary---is the "bottom-up" approach: building things up from the atoms and molecules themselves. One recent breakthrough resulting from bottom-up assembly is the single-electron transistor.

Yet, although researchers can now make single molecular structures in the laboratory, they have yet to find a cheap and commercially feasible way of mass-producing them. One answer may lie in a process called "self-assembly." This relies on chemistry to position atoms and molecules, taking advantage of certain molecules' abilities to arrange themselves in complex structures.

Impact on Transportation

In the last few years, nanotechnology has yielded products with sales totaling billions of dollars, including giant magneto-resistance multilayers (for computer memory); nanostructured coatings (for data storage and the photographic industry); nanoparticles (drug-delivery devices in pharmaceuticals and colorants in printing); and nanostructured materials (nanocomposites and nanophase metals). It is revolutionizing virtually every area of technology and will have a direct and dramatic impact on transportation.

Nanotechnology's potential benefits for transportation are broad and pervasive: lighter, more efficient cars using nanostructured materials; corrosion-free bridges and no-maintenance roads; tiny "traps" that remove pollutants from vehicle emissions; and robotic spacecraft that can explore the solar system and yet weigh only a few pounds. Among the potential transportation breakthroughs are the following:

Information Technology. With molecular electronics, a single computer chip could hold billions of miniscule transistors, making computers orders of magnitude more powerful than they are today. Specific applications for transportation include: (1) uninhabited vehicles for civilian and defense use; (2) advanced communications that maximize the benefits of intelligent transportation systems and obviate the need for some travel altogether; and (3) advanced sensors that continuously monitor the condition and performance of infrastructure, vehicles, and operators.

Materials. Nanotechnology will yield transportation materials that are lighter, stronger, and, ultimately, programmable---reducing costs through longer service life and lower failure rates. Among the key applications are: (1) nanocoating of metallic surfaces to achieve super-hardening, low friction, and enhanced corrosion protection; (2) "tailored" materials for infrastructure and vehicles; and (3) "smart" materials that monitor and assess their own status and health and repair any defects---including self-healing, fire-resistant materials in vehicles and aircraft.

Aeronautics and Space. New materials developed through nanotechnology will meet the strength, weight, and thermal stability requirements of space planes, rockets, space stations, and high-speed aircraft. Moreover, nanotechnology will permit the ultra-miniaturization of space systems and equipment, including the development of smart, compact sensors; miniscule probes; and microspacecraft. Applications include: (1) economical supersonic aircraft; (2) low-power, radiation-hard computing systems for autonomous space vehicles; and (3) advanced aircraft avionics.

Environment and Energy. Nanotechnology has the potential to reduce transportation energy use and its impacts on the environment. For example, nanosensors could be used to monitor vehicle emissions and to trap any pollutants. Other applications include: (1) nanoparticle-reinforced materials that replace metallic components in cars---those now being developed could reduce CO2 emissions by more than five billion kilograms a year; (2) replacement of carbon black in tires with nanoparticles of inorganic clays and polymers, leading to tires that are environmentally friendly and wear-resistant; and (3) carbon-based nanostructures that serve as "hydrogen supersponges" in vehicle fuel cells.

Biofuels

The transportation sector is currently heavily reliant on petroleum-based fuels such as gasoline and diesel fuel. Petroleum is not renewable on the time scale during which it is used, and is becoming increasingly obtained from politically unstable regions. This creates the potential for both long-term price increases and short-term supply disruptions. Petroleum also consists mainly of carbon that is oxidized to form carbon dioxide-the dominant human-induced greenhouse gas-during the combustion process.

Many other possible fuel feedstocks have the potential to increase energy security and/or reduce net greenhouse gas emissions. Examples include coal, tar sands, shale, and natural gas Another alternative is electricity, which can be used to either recharge electric vehicles or produce hydrogen for use in internal combustion engines or fuel cell vehicles. Electricity can be generated using a wide range of energy sources, including renewable sources like wind and solar power. Another increasingly attractive potential option is based on the use of biomass. Biomass offers the unique promise of addressing both energy and climate concerns in a manner that could be reasonably compatible with the existing infrastructure for distribution and delivery of liquid transportation fuels.

Biomass, which is defined as plant matter of recent origin, represents a massive renewable resource. In the US, from 10 to 40 billion gallons of gasoline could be displaced with biomass ethanol through the use of wastewood, agricultural waste, cropland, and rangeland/grassland.

Carbon dioxide from the atmosphere and water from the earth are combined in the photosynthetic process to produce carbohydrates (sugars) that form the building blocks of biomass. The solar energy that drives photosynthesis is stored in the chemical bonds of the structural components of biomass. When biomass is burned efficiently, oxygen from the atmosphere combines with the carbon in plants to produce carbon dioxide and water. The process is cyclic because the carbon dioxide is then available to produce new biomass.

The chemical composition of biomass varies among species, but biomass typically consists of about 25 percent lignin and 75 percent carbohydrates or sugars. The carbohydrate fraction consists of many sugar molecules linked together in long chains or polymers. Two larger carbohydrate categories that have significant value are cellulose and hemi-cellulose. The lignin fraction consists of non-sugar type molecules linked together in large two-dimensional sheet-like structures that look like "chicken wire."

In part because of process inefficiencies, fuels from biomass are not economically competitive at this time. Breakthrough in biological and thermal conversion techniques could make it possible to transform biomass into fuels much more efficiently. Although serious ethical questions and potential risks to ecosystems must be considered, genetic engineering could be the basis for a breakthrough in biological processing of biomass. Separately, new thermal conversion techniques coupled with chemical catalysis could make it possible to exploit the previously discarded lignin fraction by converting it into valuable chemicals that are currently derived from non-renewable fossil sources.

Although land availability limits the potential of biomass to supply all of the energy required for transportation, breakthroughs in the areas mentioned above could make it possible to meet a significant fraction of that demand in a manner that also significantly reduces greenhouse gas emissions.

Impact on Transportation

Concern over the impact of carbon dioxide and other greenhouse gases on the global climate have been increasingly steadily in recent years. The transportation sector is a key player in this complex issue, producing approximately 1/3 of total human-produced carbon dioxide emissions. (For example, combustion of a single gallon of gasoline generates about 20 pounds of CO2.) Should the US and other national governments at some point find it necessary not only to prevent further growth in emission of greenhouse gases, but also move to achieve significant reductions, the impact on transportation-and the associated consequences for economies the world over-would be very substantial. There would not only be a reduction in the level of transport of goods and people, but it would inevitably become much more costly. Allocation of the pain of any such transition would be a highly contentious matter, and the choices made could generate serious strains on the social fabric.

Under those circumstances, availability of fuel feedstocks that play a far more benign role in CO2 production would be enormously valuable to the whole world, and particularly to the US, which accounts for the largest petroleum consumption of any nation. This consideration alone warrants continued aggressive research to find practical ways to exploit biomass-based fuels.

Complex Systems and High-confidence Software

The rapid development and interrelationship of computer, sensing, communication and navigation technologies is having a powerful impact across the spectrum of transportation operations in all modes. Originally nurtured by space- and defense-related R&D, and now driven largely by global business and consumer markets, this revolution is proceeding rapidly in the private sector. Public sector applications, particularly in transportation, are for the most part only in early stages of implementation, but are seen as having great near- and long-term promise. One important and highly visible area currently being actively addressed is applications to traffic management on ground, air and sea, where congestion often exacts a high societal cost in terms of time, accidents, air pollution and quality of life for all those affected by it. More generally, the efficiency of transportation system operations, regardless of the mode, is also critical to the productivity and overall health of the entire economy.

Progress is already rapid in development of systems in which information technologies and ready access to many types of data are integrated into virtually all system elements and functions to enable greater efficiency and improved performance. The rapid infusion into the marketplace of "smart" products, which combine sensing and computation to make a wide range of decisions for their users, is just the first wave of ubiquitous automation. However, as their power and economic attractiveness stimulates large-scale application of the next generations of intelligent transportation systems, severe challenges can be expected. In particular, as safety-critical systems (e.g., motor vehicle crash avoidance, aircraft flight management technology) and very widely distributed systems (e.g., highway traffic control across an urban area, or global air traffic management) proliferate, the reliability and failure modes of the technology will become ever-more critical. At the same time, system complexity and sophistication will similarly be increasing, to the degree that a truly comprehensive analysis of reliability and failures under all circumstances becomes extremely difficult.

Thus, the steadily increasing complexity of intelligent or otherwise highly-automated systems, accompanied by ever-greater dependence on them, will require new extremes of reliability, robustness, and non-catastrophic failure modes ("graceful degradation") in the face of subsystem failures or severe and unexpected circumstances. The challenge thus posed is daunting: not only must the design process generate systems meeting these standards, but means must also be developed to confirm that the resulting systems meet the goals. As system size and complexity grow, and the systems themselves involve large populations of distributed and often autonomous users, new conceptual approaches and development tools will be required. Transportation, in which safety considerations must always be paramount, is a key user of technological advances in this area, but the necessary enabling research is most naturally done in the information technology community, both public and private. The Departments of Defense and Commerce have generally had the lead in this discipline.

Impact on Transportation

If the challenge of developing super-reliable and highly forgiving or self-correcting software-based systems is successfully met, the safety and performance of the transportation system will benefit greatly. Advances that enhance operator situational awareness and capabilities, and correctly identify and respond to hazardous circumstances, could provide the key ingredient needed to bring about a significant decline in transportation accident and fatality rates, which have been relatively flat in recent years.

Systems operating at or near full capacity can provide very high efficiency, but this is coupled with severe consequences from any disruption, such as weather constraints affecting busy air routes and accidents or breakdowns on crowded highways. The fullest use of automation for traffic management in all modes will only be possible when very high capacity automated systems achieve sufficiently high reliability and robustness to avoid the risk of new extremes of gridlock and system collapse should any element fail or the operating environment alter.

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