Environmentally responsible air and ground transportation

Among all modes of transportation, travel by airplanes and automobiles continues to experience the fastest growth. Currently, there are approximately 500,000 air vehicles (335,000 Active General Aviation Aircraft, 18,000 Passenger Aircraft, 90,000 Military Aircraft, 27,000 Civil Helicopters, and 30,000 Military Helicopters), and 750 million ground vehicles in service worldwide. They are responsible for 50% of petroleum (oil) consumption and 60% of all greenhouse gas (GHG) emissions worldwide. These numbers are forecasted to double by 2050. Therefore the environmental issues such as noise, emissions and fuel burn (consumption), for both airplane and ground vehicles, have become important for energy and environmental sustainability. This paper provides an overview of specific energy and environmental issues related to both air and ground transportation. For air transportation, topics dealing with noise and emissions mitigation by technological solutions including new aircraft and engine designs/technologies, alternative fuels, and materials as well as examination of aircraft operations logistics including Air-Traffic Management (ATM), Air-to-Air Refueling (AAR), Close Formation Flying (CFF), and tailored arrivals to minimize fuel burn are discussed. The ground infrastructure for sustainable aviation, including the concept of 'Sustainable Green Airport Design' is also covered. For ground vehicles, the technologies related to reduction in energy requirements such as reducing the vehicle mass by using the high strength low weight materials and reducing the viscous drag by active flow control and smoothing the operational profile, and reducing the contact friction by special tire materials are discussed along with the portable energy sources for reducing the GHG emissions such as low carbon fuels (biofuels), lithium-ion batteries with high energy density and stability, and fuel cells.