Despite being a very potent greenhouse gas, methane as a new rocket fuel also seems to be quite eco friendly because of its burning efficiency. “If you produce a good propulsion unit, the efficiency of that unit can be as high as 99.5%,” said Maggi.
New possibilities will comeup using methane fuel.
Comparison of methane fuel to other fuels
Methane vs kerosine
As exclusive plan of in-situ fuel production, Methane can be prepared on Mars by Sabatier process, which will be very helpful to refuel the rocket.
Methane fuel have more specific impact (370s) than Kerosene (360s) in a vacuum at the same chamber pressure (reference value of 7MPa). But this is counter balanced by RP-1’s lower bulk density which is the density of fuel plus oxygen. Although the density of Methane is 430kg/m3, which needs 3.5 parts of oxygen as compared to only 2.1 parts for RP-1. Hence, conclusively the Methane engine will carry less fuel but more oxygen by weight
Coke formation temperature for Methane is estimate double as high in the rocket chamber that support the re-usability of vehicles. While RP-1 produce chain of carbon and minute particles that degrades the re-usability of the rocket.
Methane fuel vs Liquid Hydrogen
Liquid hydrogen is most popular first stage rocket fuel with specific impulse of approx. (350s – 540s). This have been also used as second and further next stage propellant if RP-1 was used as first stage fuel.
Liquid hydrogen technology was once considered a very important achievement of NASA because of the challenge of its cryogenic characteristics that means it requires extreme care to handle its liquid form at -423°F. But now, production of Methane doubles every decade and deformity.
External energy is not required for methane fuel so Methane does not need active cooling during passive cooling will work.
While testing hydrogen propellant, many important failures in components have occurred due to the process called Hydrogen embrittlement.
Numerous contact between gaseous hydrogen molecule and metal components at the temperature range (-260°C to more than 2000°C) creates an uncertainties in brittle character of the used component.
Various metal like hydrides are also produced causing critical issues. In case of methane fuel this Expansive and laborious wall treatment of components can be avoided.
Hydrogen turbo pump are more complex than Methane turbo pump, which reduces complication in plumbing of fuel.
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Money make us choose methane as fuel in starship
All the private space companies function on the profit basis. The price of Methane fuel is reduced a lot more than other fuels due to technological advancement. Kerosene (RP-1) are produced in small batches on the other hand Methane use industrial grade LNG (Liquid Natural Gas) in a broad industrial.
Why methane fuel is not used earlier as Starship Rocket???
The answer to this why methane-fueled rockets have not flown before is total matter of chemistry and engineering complexity. But in the new designs we prioritize reusability as well as in-site resource utilization (ISRU) for missions to Mars, the combination of methane and oxygen exclusively become the standard for next-generation launch vehicles.
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Why SpaceX use liquid fuels??
SpaceX uses liquid engines which use liquid propellant to generate thrust in its Merlin engines, which are powered by the kerosene. The rocket fuel is mixed with an oxidiser in the combustion chamber, where they chemically react together and make new molecules, including a gas which burns and produces heat.
Methalox race likely to be won in 2022, but winner is not clear yet
Right now, several methane-fueled rockets are in a race to the orbit. With Starship from SpaceX, Vulcan from United Launch Alliance (ULA), and Neutron from Rocket Lab, all of the most active US launch providers are committed to use this new methalox-methane and oxygen.
Upcoming launchers such as New Glenn from Blue Origin and the Terran family from Relativity Space are also on the way towards use this fuel for flight.
Using Methane as a fuel provides a great environmental benefit, producing more heat and more light energy by mass comparison to other hydrocarbon, or fossil fuel, including coal and gasoline refined from oil, while producing significantly less carbon dioxide and other pollutants that contribute to smog and unhealthy air.
The fundamental advantage of using methane as spacex fuel is that it has higher performance than others, allowing the rocket to be smaller. It lower the cost that also means that the overall cost of launching can be reduced.
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