Head over to the James S. McDonnell Space Hangar, where more than 152 space artifacts are on display, including a model of the Mars Sojourner rover. (The real rover landed on Mars on July 4, 1997, and transmitted images of and data about the planet’s surface until September 27 of that year.)
Before you leave, ride the elevator to the top of the Donald D. Engen observation tower, where you’ll have a 360-degree view of airplanes landing at and taking off from nearby Washington Dulles International Airport. Also inside the tower are exhibits on the U.S. air traffic control system, and the basic features of an airport.
On second thought, to take in everything the Museum has to offer, perhaps you should allow three days.