Hip Hop Dance and Rap Music

The origin of hip-hop can be traced back as far as the ancient tribes in Africa. Rap has been compared with the chants, drumbeats and foot-stomping African tribes performed before wars, the births of babies, and the deaths of kings and elders. Historians have reached further back than the accepted origins of hip-hop. It was born as we know it today in the Bronx, cradled and nurtured by the youth in the low-income areas of New York City.

Hip-hop dance refers to social or choreographed dance styles primarily danced to hip-hop music or that have evolved as part of hip-hop culture. This includes a wide range of styles notably breaking, locking, and popping which were developed in the 1970s by Black and Latino Americans. What separates hip-hop dance from other forms of dance is that it is often freestyle (improvisational) in nature and hip-hop dancers frequently engage in battles—formal or informal freestyle dance competitions.

Cryogenic Engine

A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer are gasses liquefied and stored at very low temperatures.Notably, these engines were one of the main factors of the ultimate success in reaching the Moon by Saturn V rocket.

During World War II, when the powerful rocket engines were first considered by the German, American and Soviet engineers independently, all discovered that rocket engines need high mass flow rate of both oxidizer and fuel to generate a sufficient thrust. At that time oxygen and low molecular weight hydrocarbons were used as oxidizer and fuel pair. At room temperature and pressure, both are in gaseous state. Hypothetically, if propellants had been stored as pressurized gases, the size and mass of fuel tanks themselves would severely decrease rocket efficiency. Therefore, to get the required mass flow rate, the only option was to cool the propellants down to cryogenic temperatures (below −150 °C, −238 °F), converting them to liquid form. Hence, all cryogenic rocket engines are also, by definition, either liquid-propellant rocket engines or hybrid rocket engines.