Hart (born October 27, 1946) is an American mechanical and electrical engineer, a retired United States Air Force lieutenant colonel and pilot, and former NASA astronaut.

In August 1979, he completed a one-year training and evaluation period, making him eligible for flight assignment on future Space Shuttle crews.

The crew included Robert Crippen (spacecraft commander), Dick Scobee (pilot), and fellow mission specialists, George D. Nelson and James van Hoften.

During this mission, the crew successfully deployed the Long Duration Exposure Facility (LDEF); retrieved the ailing Solar Maximum Satellite, repaired it on board Challenger, and replaced it in orbit using the robot arm called the Remote Manipulator System (RMS).

The mission also included flight testing of Manned Maneuvering Units (MMUs) in two extravehicular activities (EVAs); operation of the Cinema 360 and IMAX camera systems, as well as a bee hive honeycomb structures student experiment.

His principal duties included electrical and mechanical design responsibilities for a variety of electronic power equipment used in the Bell System.