The nuclear rocket program - Its status and plans.

Abstract

The second SPAROAIR III flight-test vechicle was launched on May 26, 1966. Aircraft separation, first-stage operation, coast, and second-stage ignition appeared normal. However, approximately 6 sec after second-stage ignition all telemetry signal was lost, and all radar operators reported explosion of the vehicle. Examination and reduction of the telemetry data indicated that during the entire period of second-stage operation the chamber pressure was ~75% above predicted values, although the curve was of the predicted form. Examinations of the trace for the solar-aspect cell showed that the mechanical arming-and-firing mechanism functioned as anticipated by arming and firing 0.25 and 2.0 sec, respectively, after first-stage ignition. Additional analysis of this trace shows that there was essentially no roll until shortly after first-stage burnout. The abrupt increase in roll rate after burnout was probably due to the loss of the roll damping provided by the first-stage fins, and indicates that the stages drag-separated as planned. Calculations indicated that the increase in the propellant's burning surface necessary to provide the high chamber pressures would have to result from severe grain cracking, most probably in the star points. The fact that the motor withstood 105 kg/cm at ignition, but burst 6 seconds later at 56 kg/cm, indicates that a propellant burnthrough occurred. Examination of the history of this second-stage motor shows that it was 2 years old when launched, beyond the normal shelf life for this propellant, and the environmental conditions and handling history at NAVMISCEN during storage could not be established. Therefore age, rather than any basic defect, is believed to have been the failure cause. Further flight-test verification and vehicle utilization are under consideration. Although the performance capabilities shown in Fig. 7 have not been totally confirmed by flight test, the flight-test program has provided sufficient confirmation of the basic assumptions (weights, launch conditions, and drag coefficients) that were used in these calculations to show them to be realistic values.