Simplify the following text for a Grade 6 native English-speaking person.
Original: Space Shuttle Discovery ( Orbiter Vehicle Designation : OV-103 ) was one of the Orbiters in the Space Shuttle fleet of NASA , the space agency of the United States , and was operational from her maiden flight , STS-41-D on 30 August 1984 until her final landing , STS-133 on 9 March 2011 .
Simplified: Space Shuttle Discovery ( OV-103 ) is the third space shuttle run by NASA .