Silver is found embedded in several different minerals, namely copper, zinc and lead, and the refining process varies depending on the source. Silver derived from copper and its derivatives, including copper sulfide, requires different handling and refining techniques than silver minerals taken from zinc deposits and lead sources. These metals have different physical properties, which accounts for the different methods needed for proper extraction.
Regardless of size, rockets work in the same manner, which is by burning fuel to produce heat and energy. Most rockets transform fuels into hot gas or vapor, which is then funneled out of the engine by exhaust pipes or fans. The gases produced help to propel rockets forward, and unused portions are eliminated through the engines' back ends.
Rocket engines come in two basic varieties: those that use liquid fuels and those that use solid fuels. Engines that use liquid fuels are primarily found in space shuttles. Liquid-fueled engines are generally larger than those that operate on solid fuels, which are found in fireworks, model rockets, and cars.
Rocket engines are similar in appearance to jet engines. Unlike jet engines, however, rocket engines do not require air to operate. This allows them to function in space and in higher levels of the atmosphere. Rockets serve many purposes in daily life but are not novel creations. The first rockets emerged in China in the 1200s and were used for firework displays. As technologies improved, their uses extended to wars and machinery as well.