First flown in June 1947, the XB-48 was Martin’s initial venture into the jet field (discounting the partially jet powered P4M) and was a competitor of Boeing’s B-47, North Americans’ B-45, and the Convair B-46. Like most of the competing designs, the XB-48 had straight wings; probably the design’s most radical feature was the bicycle landing gear. Six GE J35s were installed in large wing pods, giving the XB-48 a top speed of 522 mph. The two prototypes were unarmed, but production aircraft would have had a pair of .50-caliber machine guns in a tail turret, aimed with the aid of an AN/APG-27 radar.
“Martin Proving Six-Jet XB-48” Aviation Week June 1947 p.60
Irving Stone “New Expediting Techniques Proved in XB-48 Production” Aviation Week September 8, 1947 includes structural photos
Artist’s depiction of a T40-powered turboprop XB-48 derivative Aviation Week April 18, 1949 p.17