Lockheed F-104 Starfighter NF-104A

The NF-104A grew out of the transformation of the US Air Force test pilot school at Edwards. With the advent of human spaceflight in the early 1960s, the Experimental Flight Test Pilot's School was renamed the Aerospace Research Pilots School (ARPS), and its training moved away from the traditional test pilot course towards a spaceflight-oriented curriculum. The school needed an aircraft able to take its students to the edge of space at a fraction of the cost of the experimental rocket planes, and the answer was a mixed-power Starfighter, both jet and rocket, conceived as a low-cost aerospace trainer for the North American X-15 and the projected Boeing X-20 Dyna-Soar programs.

Before any aircraft was modified, the ARPS had already used standard production F-104s, including two-seat F-104Ds, to simulate the low-lift, high-drag glide approaches of the X-15 and the future X-20. The manoeuvre began at about 3,700 metres with the engine throttled back to 80 percent power and flaps, speedbrakes and landing gear extended; the aircraft was set up in a 30-degree dive and the pull-out for the landing flare started about 500 metres above the ground, leaving very little room for error. Another problem remained: in the thin air of the upper stratosphere, conventional control surfaces have little or no effect, so a reaction control system was needed. After initial trials with a modified Bell X-1, which was grounded by technical problems, NASA modified an F-104A (55-2961) in 1959 with thrusters in the wingtips and nose; designated JF-104, it reached about 25,300 metres, and Neil Armstrong was among the pilots who gained experience with it. Pilots complained that its instruments were hard to read and not accurate enough for the critical zoom climbs.

In 1962 the Air Force contracted Lockheed to convert three F-104As into dedicated aerospace trainers. The airframes were taken out of storage at AMARG and moved to the factory. Everything superfluous was removed: the fibreglass radome gave way to an aluminium nose housing the pitch and yaw thrusters; the M61 Vulcan cannon, the radar and unnecessary avionics were deleted; oxidiser tanks were added, together with a nitrogen tank to pressurise the cockpit, since there would be no engine bleed air after the jet was shut down during the climb. The wings received tip extensions to house the roll thrusters, which also reduced wing loading, and the fin and rudder were replaced by the larger units of the two-seaters, strengthened to carry the rocket. The intakes kept the fixed geometry designed by Ben Rich, but with extended inlet cones for better operation at high Mach numbers.

A Rocketdyne AR2-3 rocket engine of about 27 kN was fitted at the base of the fin. It burned JP-4 and 90 percent hydrogen peroxide, carried enough oxidiser for roughly 100 seconds of operation and had its own throttle lever on the left of the cockpit to select maximum or about half thrust. The reaction control system comprised eight pitch and yaw thrusters of about 500 N and four roll thrusters of about 190 N, fed from a dedicated 70 kg peroxide tank and controlled through a handle on the instrument panel.

The typical profile combined a zoom climb with the rocket: level acceleration at about 10,700 metres to Mach 1.9, rocket ignition and, at Mach 2.1, a pull-up to a 50 to 70 degree climb at 3.5 g. At around 21,300 metres the afterburner was throttled back, and near 25,900 metres the J79 was shut down by hand to keep rising temperatures from damaging the turbine; after the top of the ballistic arc the aircraft fell back into denser air, where the jet was restarted by windmilling for the recovery and landing.

The first NF-104A (56-0756) was accepted on 1 October 1963, quickly set an unofficial altitude record of 36,230 metres and on 6 December 1963 bettered it with 36,800 metres. An in-flight rocket motor explosion in June 1971 retired it and ended the programme; it is now displayed at Grass Valley, California. The second (56-0760), accepted on 26 October 1963, was mounted on a pole outside the Edwards test pilot school; its wingtip extensions, reaction controls and nose were loaned to Darryl Greenamyer for his record attempts and were lost with his aircraft. The third (56-0762) was delivered on 1 November 1963 and crashed on 10 December 1963 with Chuck Yeager at the controls, an accident told in his autobiography and in the book and 1983 film The Right Stuff. The three aircraft served with the ARPS from 1963 to 1971.