United Launch Alliance's Vulcan Centaur rocket, powered by two methane engines and the longest single-segment solid rocket booster ever built, is set to make its inaugural flight today, carrying the Peregrine 1 moon lander. The Vulcan also includes Northrop Grumman's 63-in (160-cm) diameter, extended length Graphite Epoxy Motor (GEM 63XL) solid rocket booster, making its first-ever flight.