The first complete ground based simulator built by the Flight Simulator Laboratory (FSL) was for the X-15 program. As with the GEDA, the FSL's X-15 simulator was very large. The electronics were encased in cabinets that nearly reached the ceiling. Several engineers were required to operate, adjust, and maintain the system. The X-15 simulator also lacked the ability to provide landing training, due both to its design and lack of a visual display.

		With the computer revolution of the 1980s and 1990s, digital computers became smaller and more powerful, making later simulators, such as for the HARV and X-31, more realistic. For the X-15, a computer was programmed with the flight characteristics of the aircraft. Before actually flying a mission, a research pilot could discover many potential problems with the aircraft or the mission while still on the ground by "flying" the simulator. This did much to improve safety. The X-15 simulator was very limited compared to those available in the 21st century. The video display was simple, while the computer was analog rather than digital (although it became hybrid in 1964 with the addition of a digital computer for the X-15A-2).
Chief Research Pilot Walker is sitting in its simulator here.

Before each 10-12-minute research mission, X-15 pilots train as long as 10 hours in the electronic simulator at Edwards AF Base. The simulator duplicates the X-15's cockpit, instruments, and control system, including hydraulics and dummy control surfaces, and is nearly as long as the aircraft itself.

The X-15 research aircraft, which first flew in 1959, also marked an important milestone in the development of flight simulators. The X-15 was the first aircraft where a simulator was used to practice flight maneuvers before they were tried in the aircraft, whereas previous simulators had been developed only after the plane's flying characteristics were already known. There were two simulators developed for the X-15. The first was used to prove its reaction control system, which used jets to change the attitude of the aircraft. The second simulator was more sophisticated (stylish) and enabled a pilot to gain a sense of how the aircraft would respond as it was made to do things that had not been accomplished before.

The X-15 was a rocket-powered aircraft. The original three aircraft were about 50 ft long with a wingspan of 22 ft. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as testbeds to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis.

Other Simulators:

1960 UDOFT (Universal Digital Operational Flight Trainer)
A special machine therefore, was designed at the University for their UDOF computer simulator, which was named UDOFT (Universal Digital Operational Flight Trainer). This computer was manufactured by the Sylvania Corporation and completed in 1960. The UDOFT project had demonstrated the feasibility of digital simulation and was mainly concerned with the solution of the aircraft dynamic equations.

1960s Link Mark I computer for real-time simulation
In the early 1960's Link developed a special purpose digital computer, the Link Mark I, designed Link Mark I computer for real-time simulation. This machine had three parallel processors for arithmetic, function generation, and radio station selection. In the late 1960's general purpose digital computers designed for process control applications were found to be suitable for simulation, with its large input/output requirement, and the use of special purpose machines declined. Today special purpose digital computers are only used in applications demanding very high speed processing, such as computer generated imagery.