Consider the following: Liquid hydrogen fuel used by the space shuttle must be stored at a temperature of -252.9°C—only about 20 degrees above absolute zero! Liquid methane, on the other hand, can be stored at the much warmer and more convenient temperature of -161.6°C. That means methane fuel tanks wouldn't need as much insulation, making them lighter and thus cheaper to launch. The tanks could also be smaller, because liquid methane is denser than liquid hydrogen, again saving money and weight.
Methane also gets high marks for human safety. While some rocket fuels are potentially toxic, "methane is what we call a green propellant," Tramel says. "You don't have to put on a HAZMAT suit to handle it like fuels used on many space vehicles."
But the key attraction for methane is that it exists or can be made on many worlds that NASA might want to visit someday, including Mars.
Wednesday, May 09, 2007
An article on NASA.gov talks about a May 4 test of an Alliant Techsystems/XCOR Aerospace methane-powered rocket, and discusses the many advantages of this fuel, not the least of which is it's availablity throughout the solar system. As the article mentions, it's amazing that nobody has built a methane rocket until now.