Examples of solid fuels include filter paper, wood, and coal. Liquid fuels include gasoline and kerosene. Propane and hydrogen are examples of gaseous fuels. Air, which contains oxygen, is a particularly common oxidizer. An electrical spark is an example of an ignition stimulus.
Combustion is a key element in many of modern society's critical technologies.
Electric power production, home heating, ground transportation, spacecraft and aircraft propulsion, and materials processing are all examples in which combustion is used to convert chemical energy to thermal energy. Although combustion, which accounts for approximately 85 percent of the world's energy usage, is vital to our current way of life, it poses great challenges to maintaining a healthy environment. Improved understanding of combustion will help us deal better with the problems of pollutants, atmospheric change and global warming, unwanted fires and explosions, and the incineration of hazardous wastes. Despite vigorous scientific examination for over a century, researchers still lack full understanding of many fundamental combustion processes. Some objectives of microgravity combustion science research are to enhance our understanding of the fundamental combustion phenomena that are affected by gravity, to use research results to advance combustion science and technology on Earth, and to address issues of fire safety in space.