Methane Rockets: Opening the Solar System for Exploration

Most rocket engines that fly in space either are liquid fueled, using liquid oxygen and either hydrogen or, as in the case of the F-1 engines that powered the Saturn V to the Moon, kerosene, or else solid fuels, as are currently used on the space shuttle. Now a new type of rocket engine, using methane and liquid oxygen as a fuel, is being tested for deep space vehicles.

A company called XCOR Aerospace is conducting test firings of an engine that uses a methane/liquid oxygen mix that generates 7,500 pounds of thrust. The engine is a prototype for a planned larger methane/liquid oxygen engine that could propel deep space vehicles. The engine was developed under a NASA contract in a joint venture with Alliant Tech Systems (ATK). NASA envisions the larger engine for possible use on the lunar and Mars version of the Orion space craft now under development.

A rocket engine using methane/liquid oxygen has a number of advantages over conventional rocket engines.

Methane is much easier and safer to handle than other rocket fuels, such as hydrogen, which has a tendency to burn or explode if not handled properly. Methane is easier to collect and store. Methane can be handled without the use of HAZMAT suits and is classified as a "green" propellant.

Unlike hydrogen, methane need not be supercooled to -253 degree Celsius, twenty degrees above absolute zero. Liquid methane can be stored at a more manageable temperature of -162 degrees Celsius. Methane is denser than hydrogen, thus making better use of space in fuel tanks.

The biggest advantage that methane has as a rocket fuel is that it is readily available throughout the solar system. On Mars, for instance, methane can be produced through the Sabatier process, combining carbon dioxide and hydrogen to create methane and water. Mars has an abundance of carbon dioxide in its atmosphere, so a space vehicle landing on Mars would just need to bring a small amount of hydrogen to create the reaction.