Rockets |
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Hot gas is expelled at very high speed and the rocket is pushed forward. The total momentum of fuel plus rocket remains constant (zero). A small plastic bottle of gas at high pressure works better as a rocket if it is ~one third full of water. The math is a little complicated because the mass ... (rocket + remaining fuel) ... decreases with time and the acceleration increases. Rockets are of two types; solid fuel - nitroglycerine (dynamite), and liquid fuel - (2H2 +O2). Liquid hydrogen and oxygen are very difficult to handle and must be stored at very low temperatures. They are used because burning just the right 2:1 mixture of H2 and O2 produces more energy (heat) per kilogram (~1200 MJ) than any other chemical reaction, (3x that of petrol). |
| The hydrogen/oxygen reaction has been studied in detail for a long time. In the early 19th century a paper was presented to the Cambridge Philosophical Society entitled, "On the Application of Hydrogen gas to produce Moving Power in Machinery". This paper described a hydrogen powered engine, using a mixture of hydrogen and oxygen. Why do we not yet have hydrogen engines in common use? |