Can Be Produced in Space
Even Yields Water as a Byproduct
As the paradigm of space launch vehicles shifts, rocket fuel is also transitioning to methane.
Kerosene, which has a higher energy density than liquid hydrogen or methane and can be stored at high temperatures and pressures, is a type of kerosene widely used as the 'standard fuel' for launch vehicle systems. It is a highly refined form of aviation fuel (RP-1), which is more purified than Jet A-1, a jet engine fuel made by adding additives to kerosene.
Rockets contain two tanks. Since they must operate in the vacuum of space, oxygen is liquefied and stored in a separate tank. While kerosene is highly efficient at high temperatures, liquid oxygen must be kept at cryogenic temperatures, making separate storage unavoidable. In contrast, methane can be stored at cryogenic temperatures and remains efficient even at lower temperatures, allowing for the use of a common bulkhead that simply divides a single tank, thereby utilizing space more efficiently.
Kerosene, as a fossil fuel, produces residues such as soot during combustion, which can adhere to engine nozzles or turbine components and cause blockages. For repeated use, thorough cleaning is necessary, and the longer it is used, the faster its durability declines. As a result, maintenance costs and inspection times increase, making it difficult to achieve economic viability through reuse.
Methane, on the other hand, has different combustion characteristics from kerosene, requiring a newly designed engine, which is a drawback. Even when used, there is a lack of long-term reliability data for methane-based engines, resulting in higher insurance premiums. At present, it is a fuel system that incurs significant costs.
The reason SpaceX's Starship in the United States has accumulated data through four failures since its first test launch in April 2023 is another important aspect of methane. Methane can also be produced in space. Synthesizing carbon dioxide and hydrogen yields methane and water. It can be produced from the atmosphere of Mars, and its byproduct is water, giving this fuel tremendous strategic value.
In the United States, companies developing methane engines include SpaceX's Starship, Relativity Space's Terran R, Stoke Space's Nova, Blue Origin's New Glenn, and ULA's Vulcan Centaur.
Other launch vehicles planning to use methane as propellant include China's iSpace Hyperbola-3, LandSpace Zhuque-3, China Academy of Launch Vehicle Technology (CALT) Changzheng-9, Russia's Progress Rocket Space Center Amur (Soyuz-7), European Space Agency (ESA) Ariane Next, Avio's Vega Next, France's MaiaSpace Maia, and the Indian Space Research Organisation (ISRO) Surya.
An official from the Korea Aerospace Administration stated, "It is a matter of choice between launching frequently at a low cost now or changing the system with the future in mind," adding, "By the 2030s, all launch vehicles will use methane, which is highly efficient for reuse."
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