It works by forcing fuel directly into the combustion chamber of each cylinder to mix air and gas simultaneously at the point of combustion, rather than mixing air and gas in a separate chamber like more conventional engines.

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For instance, when you do combustion studies, flames on Earth burn in a teardrop fashion because the air comes in from underneath it and feeds the flame, but we can't do that here since the air doesn't know where up is, there's no convection.

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These devices, which work by combining hydrogen with oxygen from the air to produce electricity, are popular candidates to replace internal-combustion engines in road vehicles.

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