In miles-per-gallon, spaceflight doesn't really match up. We're talking gallons per mile - thousands of gallons per mile. But there are benefits to getting things out beyond the atmosphere that make it worth pushing against this crazy gravity well.
NASA scientists have just conducted a test of a new rocket engine using methane, instead of hydrogen.
Liquid hydrogen fuel used by the space shuttle must be stored at a temperature of -252.9Â°C â€”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 -161.6Â°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."
Methane is also a fuel that appears to be readily found throughout the solar system. And even planets like Mars (the likeliest first step outside our own orbital band) which don't have ready supplies of frozen methane on the surface can provide the raw materials to produce methane from CO2 and hydrogen. Long range human flight programs may be preceded to their destinations by robot factories that will collect and process local methane in order to refuel the spacecraft for the return trip home.
via: Beyond the Beyond
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