bipropellant

In 1976, Professor Robert Ash, now of Old Dominion University, and some JPL collaborators published a paper laying out some extremely simple, robust, and well established (Gaslight Era, to be precise) chemical engineering processes that would produce a methane/oxygen bipropellant on Mars, provided a source of water (H2O) could be found.

The Case for Mars Robert Zubrin 1996

For example, I estimate that a 1-tonne pressurized ground rover would require about 0.5 kilograms of methane/oxygen bipropellant to travel one kilometer.

The Case for Mars Robert Zubrin 1996

Methane/oxygen bipropellant costs about $0.20/kilogram, so $14 of propellant costs will be incurred for every kilogram lifted to orbit.

The Case for Mars Robert Zubrin 1996

Since the hydrogen component of the bipropellant mixture represents only about 5 percent of the total propellant weight, it can be imported from Earth.

The Case for Mars Robert Zubrin 1996

While in principle any bipropellant combination could be used, transportation logistics dictate that at least most of the propellant used be manufactured on Mars out of indigenous materials.

The Case for Mars Robert Zubrin 1996

Though its two propulsion stages will consume some 96 tonnes of methane/oxygen bipropellant on the return flight, the ERV arrives at Mars with its fuel tanks essentially empty, carrying just 6 tonnes of liquid hydrogen propellant production feedstock.

The Case for Mars Robert Zubrin 1996

If all the hydrogen is expended cycling the propellant production process through reactions (1) and (2), then each kilogram of hydrogen brought to Mars will have been transformed into 12 kilograms of methane/oxygen bipropellant, with an oxygen-to-methane mixture ratio of 2:1.

The Case for Mars Robert Zubrin 1996

In addition, the carbon monoxide/oxygen bipropellant it produced was a poor quality rocket propellant with a specific impulse of only about 270 seconds.

The Case for Mars Robert Zubrin 1996

Burning the bipropellant at such a ratio would provide a specific impulse of about 340 seconds.

The Case for Mars Robert Zubrin 1996

As in the standard Mars Direct plan, it would now deploy its reactor and start its propellant plant to turn its 20 tonnes of hydrogen cargo into 332 tonnes of methane/oxygen bipropellant 320 tonnes for the trip back, 12 tonnes for the surface rovers plus 9 tonnes of water.

The Case for Mars Robert Zubrin 1996