The engine that powers the multiplanetary dream.
The Humankind has dreamed with Mars since the discovery of this red dot in the infinite sky. Scientists, philosophers, seekers of expanding human consciousness, and even people who do not work in these fields know the importance of becoming a multiplanetary species, not only because it is an opportunity to expand humankind but also the primitive feeling of exploring the stars. Mars is capable of transmitting an almost glorious illusion of dreaming about a second home, but first, we need to power that illusion, and that's when there is one name that captures this sentiment: Raptor.
A Raptor engine being installed prior to his first ever firing (Credit: Elon Musk)
The birth of a legend.
If you like the amazing world of rocketry, there is one rocket that probably sounds familiar to you, not just because it has the record of the most powerful rocket ever made, but also because it is the rocket that promises to take us to Mars, our desired second home.
But how could Starship achieve this goal?
Starship lift off from Starbase, Texas (Credit SpaceX
The unknown.
The gas generator cycle, that powered the Merlin engine wasn't enough, and SpaceX knew this. They did need a new cycle, capable of delivering high thrust and reliability at a low cost, and that's where the full-flow staged combustion cycle comes into play.
The Full Flow Staged Combustion is a power cycle of a bipropellant rocket engine. Unlike gas generators, where the fuel used to turn the turbo pumps is discarded, on the FFSC cycle, the propellant is sent to a pre-burner, which converts the liquid cryogenic fuel into a mixture of super-hot gases that, in addition to moving the turbines, is redirected to the combustion chamber, this implies an increase in thrust capacity since the combustion chamber igniters finds it easier to mix and completely burn a gas-gas mix of fuel, the main advantage relative to other rocket engine power cycles is the high fuel efficiency, while the main disadvantage is the engineering complexity.
These efforts ended in the most complex engine ever made: Raptor.
The first.
Raptor, developed and manufactured by SpaceX, was designed with the Full Flow Staged Combustion cycle (FFSC) in mind; it holds the honor of being the first engine to power a vehicle in flight, but what are the characteristics of the first version of this legend?
The Raptor being prepared for the first ever fire test (Credit: SpaceX)
This engine drinks liquid oxygen and liquid methane as the fuel, a mix commonly known as Methalox, on a mixture ratio of 3.6 (78% O₂, 22% CH₄) and a mass flow of ~650 kg/s or 1,400 lb/s split into ~510 kg/s or 1,100 lb/s for the liquid oxygen and ~140 kg/s or 310 lb/s for the liquid methane. Part of this fuel is used to cool down the nozzle by sending it to a jacket that dissipates the heat.
And we know that he likes to go to the gym because it weighs approximately 2080 kilograms with a pressure inside the combustion chamber of 250 bar; all of this results in 185 tons of thrust with a specific impulse of 350 seconds and a thrust-to-weight ratio of 89.
Raptor 1 was used on many vehicles, including Starhopper and Block zero ships, during the suborbital high-altitude tests era.
But this engine was able to improve. SpaceX knew this, and they started working on the next generation.
Raptor 2 was born.
Bodywork and paint.
You may ask how SpaceX was able to refine the Raptor 1. The answer is quite complex, but I am here to explain it. Let's get started.
Raptor 2 is a complete redesign of the previous generation and, in my opinion, is like a new engine, but that is a theme for later.
The turbomachinery, chamber, nozzle, and electronics were all redesigned. Many flanges were converted to welds, while other parts were deleted. Simplifications continued after production began following the iterative design.
Raptor 2 (sea level variant) (Credit:SpaceX)
The characteristics and performance were greatly improved, starting with an additional thrust of 45 tons, or 507,000 pounds, at sea level. Raptor 2 was the first variant to add a new capability, operating in the vacuum of space thanks to an optimized nozzle for this task. This variant was able to provide up to 258 tons of thrust, or 569,000 pounds.
The elimination of some parts along with refined parts was able to reduce the weight of the Raptor 2 down to 1630 kilograms, the pressure inside the combustion chamber was greatly increased up to 300 bar, and the specific impulse was reduced down to 347 seconds but it is a minor detail that we shouldn't take seriously. All of this ended by increasing the thrust-to-weight ratio up to 141.
But of course, SpaceX wants more, and they knew that the Raptor 2 was able to improve a lot.
Raptor 3 was born.
Pushing the boundaries of engineering to the limits.
What I can say about the Raptor 3, in my opinion, a sublime masterpiece, it looks clean, powerful, and minimalist. Remember when i said that the Raptor 2 is like a new engine? You are going to be speechless with Raptor 3, but the question is, how can they still improve it?
Producing up to 280 tons of thrust, an increase of 50 tons more than Raptor 2, weighing 1525 kilograms reducing the mass by 105 kilograms, but that's not all, they achieve an increase of the specific impulse by 3 seconds and also increase the pressure of the combustion chamber, reaching an incredible 350 bars of pressure, increasing by 50 bars the pressure that the Raptor 2 could withstand. All of this ends with a thrust-to-weight ratio of 184, a TWR that the new generation of starship needs to, in the near future, take us to Mars to have the honor of calling Mars home.
The first production unit of the Raptor 3 (Credit:SpaceX)
Personal opinion.
The people that enjoy and follow this program, knows that errors can happen, try after try and that fix or upgrade may work or not but, after all, we have the priceless opportunity to witness with astonishing quality and freedom how humanity makes history every day, maybe not archieving a milestone but knowing that the workers inside SpaceX, personel at McGregor, Starbase or working on Hawthorne or even remotely are working very hard and with a passion inside their hearths wanting that humanity prospers on the Moon, Mars or even beyond should be a huge reminder that errors can be fixed, upgrades can work and most importanly, we will reach Mars, so prepared to shout "Starship has landed on Mars".
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