The X-15A #2 (56-6671) launches away from the B-52 mothership with its rocket engine ignited.
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The X-15A #2 (56-6671) launches away from the B-52 mothership with its rocket engine ignited. The white patches near the middle of the ship are frost from the liquid oxygen used in the propulsion system, although very cold liquid nitrogen was also used to cool the payload bay, cockpit, windshields, and nose.Early 1960sNASA Photo / NASA photo› X-15 Project Description