That's the XB-70 Valkyrie, with it's wingtips cranked down for a high-speed run. A MACH THREE bomber - we sure used to turn big dreams into big reality with just a slide rule. The emergence of ICBMs as the nuke delivery system of choice made the Valkyrie obsolete before the flight testing was complete (and one of the prototypes was destroyed in a particularly spectacular mid-air collision).
btw, I was not aware that the first Black Birds carried a small drone aircraft on the back of the airplane. From the rear of the plane (at the Museum), it looks like two humongous engines and a curious peewee engine in the middle.
Only two of the SR-71 type aircraft (designated M-21s) were fitted to carry the drone (it was more often carried by a B-52H). Interesting story behind that drone:
The United States signed a treaty to end flights of manned vehicles over the Soviet Union, which meant an end to SR-71 (manned) overflights of that country. To prevent undermining the treaty, the D-21 unmanned vehicle was built to continue the same sort of overflights that had previously been handled by the SR-71. I believe one of the M-21s collided with a drone while launching it, causing the Air Force to use the B-52 as the drone launch platform.
According to the gubmint, none of the D-21 drones was *ever* used for an overflight of the USSR. Uhhh... okay, if they say so. Wink-wink, nudge-nudge.
A page from the history books. Is there an XB 70 still around ?