Nuclear Rocket Engine Controls in an Orbital Transfer Role

It is assumed that the mission for a nuclear rocket upper-stage vehicle is the transfer from a 300-mile earth orbit to a corotational earth orbit. An engine of the solid fuel, heat exchanger type is assumed and briefly described. The engine duty cycle requirements are deduced from the incremental velocity requirements of the mission. Controls attention is fixed on the thrust programmer without discussion of the equally important sequence control aspects. A constant specific impulse, variable thrust controls approach is taken. Basic principles underlying this approach are discussed. Fineness of control and restart capability are pointed out as inherent features of the engine. These augment the well-known performance advantages due to the high specific impulse of nuclear rocket engines.