Today, we will explore the engineering aspects of SpaceX Starship Rocket, just like we promised in our previous video. This is the first video in the Starship Engineering series. So, don't forget to subscribe to the channel for future videos in the series. This video focuses on the Raptor engine, the next generation liquid rocket engine, developed by SpaceX to power the company's Starship Rocket. Starship Rocket is expected to be used in various applications, including Earth-Orbit satellite delivery, sustainable human exploration of the moon, and the exploration and colonization of Mars. Before dealing with the Raptor, let's make a quick look into the basics of a rocket engine. If you are familiar with the basics of a rocket engine and combustion cycles, you can skip this part and move forward. The Raptor engine is a liquid-fueled rocket engine, which, just like any other rocket engines, operates on the principle of Newton's Third Law. A liquid fuel engine consists of a combustion chamber that burns a mixture of fuel and oxidizer. The hot exhaust is then allowed to pass through a converging diverging nozzle, which expands the gas and provides the thrust required to propel the rocket forward. The SpaceX Raptor operates under a full-flow staged combustion cycle. In a full-flow staged combustion cycle, propellant flows through multiple combustion chambers, and is thus combustion in stages. A staged combustion cycle engine is known for its higher fuel efficiency, but is much difficult to manufacture, compared to other rocket engines. The propellant flows through two types of combustion chambers. The first is called the pre-burner, and the second is called the main combustion chamber. Pre-burners are of two types, fuel rich and oxidizer rich. The fuel rich pre-burner powers the fuel turbo pump, and the oxygen rich pre-burner powers the oxidizer turbo pump. These turbo pumps supply, propellant from fuel and oxidizer tanks, into the combustion chamber. The fuel coming out of the fuel tank first circulates around the nozzle, thus removing the heat of combustion, through a process called regenerative cooling. The fuel then reaches the fuel control valve, which supplies fuel to both pre-burners. On the other hand, the oxidizer control valve redirects the oxidizer into both pre-burners. The partially-combusted fuel and oxidizer, coming out from the pre-burners, is then fed into the main combustion chamber. By the time both propellants reach the engine injector, they are completely in their gaseous phase. The fuel and oxidizer then get mixed inside the main combustion chamber, and are ignited by a spark igniter. The combustion products then expand along the nozzle, and provides the thrust required to propel the rocket forward. Now, let's move on to the Raptor engine. The Raptor engine is powered by cryogenic liquid methane as fuel, and liquid oxygen as oxidizer. The earliest concepts for Raptor considered liquid hydrogen as fuel, rather than methane. But methane, which can be easily produced on Mars with Martian resources, for the return journey to Earth, became the right choice as the fuel. Compared to RP1, methane engines have a major advantage of providing more cleaner combustion. Thus, eliminating concerns with sitting on the engines, especially when looking at regular reuse, without significant refurbishment between flights. SpaceX arrived at the choice of a methane engine, after ruling out RP1 and hydrogen, by considering five crucial factors. While vehicle size favored caracene, and reusability favored hydrogen as fuel. Vehicle size, cost, reusability and Mars propel and production favored methane as the fuel. The Raptor chamber pressure is about 300 bars, and it provides 2,200 kilonewtons of thrust. Specific impulse, which is the total change in momentum per unit of propellant consumed, is 330 seconds at sea level, and 380 seconds at vacuum for Raptor. Specific impulse measures how effectively a rocket uses its propellant. For comparison, the Saturn V rocket, which took Neil Armstrong to the moon, had a specific impulse of 263 seconds at sea level, and 421 seconds at vacuum. Both sea level and vacuum version of Raptor has restart and throttling capabilities. Both Starship and Super Heavy uses Raptor engines for propulsion. While Super Heavy has 31 Raptors on it, Starship has 6, 3 of which are vacuum optimized. According to Musk, the combined mass of Starship and Super Heavy propellant is about 4,800 tons, with 78% oxygen and 22% methane. He estimates the fuel price will be $100 per tonne in volume. On February 2014, Tom Mueller, the head of rocket engine development at SpaceX, revealed in a speech that nine Raptor engines together can put over 100 tons of cargo to Mars. He also mentioned that they target a 6,900 kilonewtons of sea level thrust, and 8,200 kilonewtons of vacuum thrust from Raptor. But on January 2015, Mr Musk stated that the thrust they were currently targeting was around 2,300 kilonewtons, much lower than the previous target. SpaceX developed INKINAL SUPER ALLOWS, for the construction of Raptor. The Turbo Pump and many of the critical parts of the injectors were 3D printed by SpaceX. 3D printing engine components improves the speed at which design changes can be implemented on the engine, because traditional manufacturing methods requires spending weeks and months in recasting the components, based on the updated design. The Raptor engine uses coaxial swirl injectors to admit propellants to the combustion chamber, rather than the pintel injectors, used on SpaceX's Merlin rocket engines. Raptor also uses a dual redundant torch igniter to ignite the fuel and oxidizer mix inside the combustion chamber. The 3.1 meters long and 1,500 kilograms Raptor engine uses propellants that are cooled near to their freezing points. The subcooled propellants, with increased density, allows more propellant to be stored in their tanks. The engine performance is also improved with subcooled propellants. Musk confirmed that each engine currently costs more than $2 million. He also claimed that, in future, the figure would reduce 10 fold, which could mean an engine costs just $200,000. The engine development, from 2009 to 2015, was funded exclusively through private investment by SpaceX. In January 2016, the USA Air Force awarded a $33.6 million development contract as SpaceX to develop its Raptor engine. With the goals set for their new Raptor engine, SpaceX began tests and subsequent design changes unwrapped it. Discussing the entire developmental history of Raptor, from 2009 to 20, requires making a separate video on that topic. So, don't forget to subscribe to the channel for part 2 of this video series. We will be also covering more SpaceX-related stuffs in the future. So, stay tuned. And as always, thanks for watching.