The allowed flight in regimes and conditions not obtainable with available operational airplanes. The aircraft was used to provide spaceflight training at a fraction of the cost of fully rocket-powered research aircraft.
The 2700 kgf thrust rocket engine was built into the tail of the aircraft and allowed it to reach altitudes of over 36.5 km, where the atmospheric pressure was only one percent of that at the earth's surface. Control at these altitudes was accomplished through the use of hydrogen peroxide thrusters which were used to orient the NF-104, just as was the case for the X-15 and manned space capsules.
Other modifications to the aircraft included the extension of the wing tips by 61 cm to house the reaction control jets; the substitution of a larger vertical tail; and the forward extension of the engine air inlet cone for better pressure recovery and thrust. The nose cone also contained reaction control jets for pitch and yaw control at high altitudes.
The trainer enabled pilots to experience zero gravity flight, orientation of the aircraft in an airless environment for re-entry, and recovery and re-light of the jet engine at lower altitude.
Gross mass: 10,000 kg (22,000 lb).