A long time ago, human beings would look up at the starry sky. The development of science and technology allowed human beings to rush out of the blue planet of life and start to explore the vast universe. To go further, rocket fuel is of course important.
US start-up Green Hydrogen International (GHI) recently announced a 60GW renewable hydrogen project in Texas, powered by wind and solar power, stored in salt caverns.
The “Hydrogen City” in Duval, South Texas, will be the world’s largest green hydrogen production and storage center. After completion, it can produce more than 2.5 million tons of green hydrogen (hydrogen obtained from renewable energy sources such as photovoltaic power generation, wind power and solar energy) per year, which is approximately equal to today’s global grayscale. Hydrogen (fossil fuel combustion produces hydrogen) production 3.5%. Centered on the hydrogen storage facility at Piedras Pintas Salt Dome in Duval, green hydrogen will be piped to Corpus Christi and Brownsville for conversion into green ammonia, sustainable aviation fuel and other products, or across the state Hydrogen power plants and other users.
One of Green Hydrogen International’s planned green hydrogen uses is sustainable rocket fuel, and it is considering combining hydrogen with carbon dioxide at Brownsville to create green methane rocket fuel for South Texas launch operations. Brownsville is also home to the SpaceX South Texas launch site, which SpaceX announced in 2018 would be a dedicated launch site for the SpaceX Starship.
SpaceX is developing a new rocket engine, the SpaceX Raptor, for use with the developing Starship. The Raptor engine will be fueled by cryogenic liquid methane and liquid oxygen, rather than kerosene-based fuel. When SpaceX was established, Musk said that the destination for space exploration is Mars. To land on Mars, how to go and how to get back are important issues. To rush out of the earth to reach Mars, the engine must generate enough specific impulse, and the upper limit of the specific impulse is determined by the fuel. If the return fuel is carried at the start, it is not realistic to increase the rocket load, and it is necessary to replenish the fuel in the universe to return to the earth.
At present, the ideal fuels should be liquid hydrogen and liquid oxygen, but liquid hydrogen is difficult to manufacture and store. The melting point of methane (-182°C) is comparable to the boiling point of liquid oxygen (-182.96°C). The temperature difference between kerosene, liquid hydrogen and liquid oxygen has lower requirements on the fuel storage tank, which can also reduce the structural weight.
The specific impulse of the methane liquid oxygen engine is between the liquid hydrogen oxygen engine and the liquid oxygen kerosene engine, and it can sail to Mars. What’s more, the Martian environment has carbon dioxide and ice that can be made into methane and oxygen, meaning SpaceX Raptor rockets can be refueled on Mars.
Renewable energy is undoubtedly the future development direction. The hydrogen obtained by Green Hydrogen International using renewable energy has various uses. With the help of GHI hydrogen, I hope that the day when the SpaceX rocket will land on Mars will come soon.