AVIATION AND THE ENVIRONMENT: CHALLENGES AND OPPORTUNITIES

The adverse environmental by -products of aviation - primari ly noise and emissions - are major constrains on the growth of aviation. Public concerns over the environmental impact of aircraft and airport operations, as well as increasingly stricter requirements embodied in laws and regulations, can severely constra in the ability of the aviation system to meet the world's need for mobility, increased trade/market access, and sustained economic growth. What are the prospects of offsetting aviation environmental impacts during the next century of flight? Hundred -year forecasts tend to be wrong, and often times miss the transformational impact of "disruptive" events (think of the societal and economic impacts of the internet - a capability unimaginable at the turn of the twentieth century!). And yet, a bold vision of the future is key to ensuring a safe, environmentally responsible expansion of the aerospace infrastructure. This paper starts by outlining key assumptions and drivers - and key amongst these assumptions is that, despite the negative impact of terrorism in the early 21 st century, air traffic will continue to grow - and that the public will demand inexpensive air travel AND protecting the environment. As we push the edges of technology to meet public expectations, aerospace systems will become more comple x, and interdependencies between noise and aviation emissions, amongst aviation emissions, and economics will drive the science agenda. To achieve mitigation along with efficiencies, we must understand and exploit these interdependencies. From assumption s and drivers, the paper moves to challenges. To deal with these challenges, discussion focuses on goals and scenarios for future operations and technologies. In the "near" (~20 years) future, the most likely scenario is reliance on evolutionary noise an d emissions reductions predicated on engine and airframe architecture improvements. However, environmental demands will continue to outpace technology, and leveraging science to enhance operations and better manage land use becomes critical. In the mid -term (20 -50 years), kerosene will likely remain the aviation fuel of choice. Yet, hybrid fuels systems and fuel cells can make inroads if we focus research programs in these technologies on the volume and weight reduction needs of aviation. We can also e xpect that additives could enable "designer" fuels that reduce emissions - allowing the designer to focus airframe/engine optimization efforts on noise. And what of the far term? The paper does not attempt to foreshadow the future - but rather closes wit h perspectives on a possible future dominated by alternative energy and multi -modal choices. Potential "disruptors" enabled by bio, info, and nano technologies breakthroughs could open new frontiers. A push toward higher speeds could expand the debate on aviation's impact on climate change and renew sonic boom concerns. To tackle these issues we will need to rely on an increasingly "planet -centric" worldview. And ultimately, to ensure continued economic growth and prosperity, we will need to consider en vironmental impact from an overall transportation sector perspective - and set goals according to the best overall payoff for suites of technologies and regulations using an "environmental design space" approach.