The X-15 (56-6670), seen here on the lakebed at Edwards Air Force Base, Edwards, CA.
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The X-15 (56-6670), seen here on the lakebed at Edwards Air Force Base, Edwards, CA, was still equipped with two XLR-11 engines pending installation of the XLR-99 engine, which first flew on November 15, 1960, in X-15 #2.1960NASA Photo / NASA photo› X-15 Project Description