In the late 1980s and early 1990s, an engineer by the name of Robert Zubrin came up with a radical new plan to get humans to the surface of Mars and return them safely to Earth. The plan was called Mars Direct, and its architecture included a key feature known as In-Situ Resource Utilization, ISRU. This meant that when we send human to Mars, it will be essential to use Martian resources to manufacture our own propellant for the return journey, so that the launch vehicle from Earth will not be excessive in both size and cost. The Martian atmosphere is 96% CO2, so there will be an abundance of both carbon and oxygen at our disposal. Since about 93% of the mass of the liquid oxygen/liquid methane propellant combination is carbon and oxygen, we can split the CO2 molecules into carbon and oxygen, combine the carbon with an on-board feedstock of hydrogen to produce methane, and use the oxygen for both propellant and breathable air for the crew.
Methane is also higher in energy density than liquid kerosene and easier to store than liquid hydrogen. This means it is also considerably cheaper than other fuels, making it the perfect choice for the Leon I.
Liquid Oxygen (LO2)/Liquid Methane (LCH4)
1,040 psi (7.2 MPa)
2,000 lbf (8.9 kN)
GPI Prototype & Manufacturing
LEON-1 Hydro Test
The Mars Underground Movie