The explosion of Blue Origin’s New Glenn rocket on May 28 highlighted how methane in the fuel tank ignited somehow, leading to a massive explosion visible from tens of kilometers away from the launch pad. To date, the company has not disclosed the cause of the incident, but public opinion continues to question why rockets using methane can explode.
Currently, both SpaceX and Blue Origin’s gigantic rockets utilize methane (CH₄) as fuel, a hydrocarbon compound consisting of one carbon atom and four hydrogen atoms. According to Ryan C. Fortenberry, an associate professor of chemistry at the University of Mississippi, methane has its own advantages and disadvantages when used as rocket fuel.
In the Apollo program (1961-1972) in the United States, early crewed space rockets and even the main engines of the space shuttle primarily used hydrogen gas as the main propellant due to its lightweight and extremely efficient reaction with oxygen, producing a significant amount of energy. Due to its small size, hydrogen molecules can seep through the walls of most fuel tanks. To address this issue, hydrogen must be liquefied after being cooled to -250 degrees Celsius. Filling the rocket’s fuel tank with liquid hydrogen also takes a considerable amount of time because it needs to be done slowly to avoid clogging the fuel lines.
To overcome these challenges, both aerospace companies, SpaceX and Blue Origin, chose methane instead of liquid hydrogen as the fuel for their Starship and New Glenn rockets. According to Conversation, although methane still needs to be cryogenically cooled and liquefied, the cooling process to -162 degrees Celsius is much less costly compared to the -250 degrees Celsius required for hydrogen. Additionally, methane molecules are significantly larger than hydrogen molecules, which prevents leaks through containers and fuel lines, making it easier to transport and fill the tanks more quickly. As a result, the entire rocket can be reused, making the launch process cheaper.
The Starship SN10 rocket prototype exploded during its launch on March 3, 2021. Photo: Spadre.com/YouTube
According to ACS Omega, in essence, methane is still a type of hydrocarbon that reacts vigorously with oxygen if not properly controlled. In rocket engines, this reaction is directed through the nozzle to generate thrust. If the fuel ignites uncontrollably, that energy can turn into a destructive explosion. Such accidents are not uncommon in the aerospace industry, and SpaceX has also experienced several similar explosions during the development of the Starship rocket. Zhuque-2, the world’s first orbital rocket using methane developed by China, also failed to reach its target orbit during its first flight on December 14, 2022, and exploded after leaving the launch pad.
Using methane as rocket propellant can lead to serious incidents due to several physical and operational challenges. Methane has extremely high flammability, igniting with very little energy and having a wide combustion range. Just a small spark in an oxygen-rich environment is enough to create an explosive mixture. Maintaining cryogenic temperatures requires strict pressure control. If valves, seals, or tanks leak, methane can explode, resulting in a large fireball. Advanced methane engines operate at extremely high pressures and temperatures to maximize performance, which can cause instability during combustion, potentially destroying the engine from the inside.
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