Here are a few pics of one of NASA's WB-57 aircraft.
The WB-57 is a mid-wing, long-range aircraft, developed in the 1960s, originally used by the USAF. The WB-57 can fly for ~6.5 hours, at altitudes exceeding 60,000 feet, has a range of ~2500 miles, and can carry up to 8,800 lbs of payload.
NASA's 3 WB-57s are based at Ellington Field, near Johnson Space Center (JSC) in Houston, as part of their High Altitude Research Program.