y to make an efficient SPR is to pack as much solid propellant into a chamber volume as possible. Theoretically, it would be ideal to burn the propellant like a cigar, from one end to the other. For this reason, scientists created an end-burning grain, which has proved extremely successful. Electric Rockets There are three types of electric propulsion systems (EPS); the three include electromagnetic, electrothermal and electrostatic. They are, in some ways more a rocket of the future then one of the present, somewhat like the NERVA project (see next section). In the electrothermal system the propellant is heated or vaporized electric heaters. The hot gas is then expanded through a nozzle the way it is in a chemical rocket. In an electrostatic system, interacting electrostatic fields and small charged particles such as colloidal particles achieve acceleration. In an electromagnetic rocket, acceleration is achieved by placing propellant plasma (a high temperature, electrically natural gas that contains electrons, ions and neutral molecular species) in an electromagnetic field thus causing a reaction that releases thrust. Nuclear Rockets Unlike the aforementioned rockets, nuclear rockets do not generate its power through chemical combustion. The way its power is formed, is through nuclear fission. It heats a propellant like hydrogen in a fission reactor and the explosion expels the propellant at amazing speeds, which exceed twice what any other rocket can produce. Its efficiency rating is around 850, as compared to the 450 of the next best type, the cryogenic rocket. Unfortunately due to the extreme dangers of nuclear fission inside a shuttle, the main project for researching the nuclear rockets, NERVA, was scrubbed. Most likely, in the future, scientists will devise a plan to minimize the risks, whereupon research will begin again. SECTION 3 A History INTRODUCTI...
