**4.3 Shipping vessels**

Shipping vessels range from recreational boats to the largest oil tankers and cruise ships. The vast majority of these are run by liquid fossil fuel (diesel etc.), the exception being nuclear powered defense ships and submarines. Compressed gas and its accompanying gas cylinders, while largely feasible for marine power, would present engineering and safety issues for vessels and ships.

#### **4.4 Airplanes**

As liquid (aviation) fuel continues its path to depletion, and rises in cost, we look to sources besides fossil fuel for the powered flight of airplanes. A gas powered airplane, would have the engineering problem of having a large number of gas cylinders to store the equivalent of the large quantities of aviation fuel formerly stored in the wings. The inherent risks of having gas cylinders all over the body and wings would be a major engineering problem, and a prohibitive risk for airplanes in the air.

A coal powered plane would require the likes of a coal-powered plant right inside an airplane. This would be prohibitive in various ways, such as in weight of the plant, electric motors, propeller-driven, and not jet-powered flight.

Solar panels on a plane may produce only about the order of a hundredth of the energy needed for flight, and would be propellor-driven, and have electric motors, clearly too heavy for flight. Also, night time flight would require batteries, which is another prohibitive addition to weight. For demonstration purposes, a solar-powered planes has circumnavigated the globe. (solarimpulse.com). This plane had the wingspan of an Airbus A340, the weight of a family car, and the power of a scooter.

A nuclear powered airplane is almost an impossibility, considering the great weight and space needed for a nuclear reactor. For powered flight, the only real alternative to liquid fossil fuel is biodiesel (Table 2).
