Methane race to orbit

 Methane seems to becoming the fuel of the future with SpaceXs huge starship using it as well as ULA’s Vulcan and Relativity’s Terran series of Launch vehicles. We have seen successful flight of an methane fueled vehicle before with SpaceX’s sub-orbital prototypes but we have never seen a full orbital vehicle take flight. But why all of a sudden so much interest in this new molecule for a rocket fuel.

Why methane

For the last 70 years of rocket propulsion there has been two main fuels used with liquid oxygen (Lox) and those are kerosene and its derivatives and liquid hydrogen. Kerosene is a long chain hydrocarbon and therefore is a liquid at room temperature. This has its benefits in ground handling and transportation as it doesn’t have to be supercooled to be in its liquid state. However SpaceX started using super chilled Kerosene in their full thrust falcon 9 upgrade, which increase the density of this fuel. The density of kerosene provides many benefits as you can make your tanks smaller to hold the same mass of fuel, and it also has higher thrust as more mass can be expelled out of a rocket nozzle. However it has its down sides as the long chain hydrocarbons have a greater mass so can’t be accelerated as fast in the rocket engine which lead to lower specific impulse which is the measures of efficiency in a rocket engine. These long chains also form sort which coats the insides of rocket engines preventing fuel rich gases being pumped back into the combustion chamber of a rocket engine for extra performance as seen in closed cycle rocket engines. This soot also covers everything is touches and is not conducive to re-use, but it can be done as demonstrated to the falcon 9.

Liquid hydrogen is the opposite in most senses, it requires very cold cryogenic temperatures to be a in liquid state. And the small size of its molecules makes it extremely difficult to store and transport as it can sometimes phase through solid materials if the gaps between the molecules are large enough. These leaks are so common NASA just accepts it will happen. It’s small side also means it has a low density therefore tanks holding the same mass must be a lot larger. The main benefit of hydrogen is its efficiency as the small molecules don’t require much energy to be blasted out of the rocket engine at high speeds. It alisado burns far cleaner allowing fuel rich gasses to be pumped back into the combustion chamber 

The contenders 

Currently two rockets powered by methane seem to be weeks away from completing their first test flight, Relativities Terran 1 and LandSpace’s Zhuque-2. Relativities Terran is powered by 9 Aeon-1 engines on its first stage and 1 Aeon-1 vacuum optimized engine on its second stage. It has a feature too which sets it apart from any other rocket that has ever flown, it is mostly 3D printed. It major tank structure is printed on the largest metal 3D printer in the world called star gate. This is supposed to decrease part counts and make the rocket more simple. It also has the far future benefit of being able to produce rockets on other planets with out bringing an entire manufacturing facility to the moon or mars.

LandSpace is one of the new breed of private Chinese rocket companies competing in the launch vehicle market. It is powered by 4 TQ-12 engines on its first stage and one vacuum optimized engine on its first stage as well a TQ-11 engine which will control the rockets pitch yaw and roll.