International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / In support of the X-33 single-stage-to-orbit program, NASA Dryden Flight Research Center was selected to provide continuous range communications of the X-33 vehicle from launch at Edwards Air Force Base, California, through landing at Malmstrom Air Force Base, Montana, or at Michael Army Air Field, Utah. An extensive real-time range simulation capability is being developed to ensure successful communications with the autonomous X-33 vehicle. This paper provides an overview of the various levels of simulation, integration, and test being developed to support the X-33 extended range subsystems. These subsystems include the flight termination system, L-band command uplink subsystem, and S-band telemetry downlink subsystem.