Abstract: A heat exchanger includes a block having a first group of passages arranged in a generally circular pattern, a second group of passages spaced radially outward from the first group of passages and multiple groups of channels extending generally normal to and fluidly coupling the first and second groups of passages for radial flow therebetween. Selected pairs of passages, each including one passage from each passage group, are adapted for coupling to a first circulation line. The other ones of the passages are adapted for coupling to a second circulation line so that fluid heat from one of the circulation lines can be transferred to fluid from the other one of the lines in the heat exchanger. With this dense flow configuration, a compact heat exchanger can be constructed which, for example, is especially advantageous when used in conjunction with nuclear thermal rocket engines where space is at a premium. The dense fluid flow pattern also reduces material requirements and, thus, advantageously reduces weight.

Abstract: A nuclear rocket engine comprising a primary feed system (4) for pumping rocket propellant from a propellant source (10) to a nuclear reactor (6) and an auxiliary feed system (60) coupled to the primary feed system. The auxiliary feed system includes a space radiator (84) for discharging excess reactor heat into space and a motorgenerator (74) for creating electricity from the excess reactor heat. A recuperator (20) operates to heat liquid propellant before it enters the reactor and to retain heat within the system. The auxiliary power system can be configured into a high thrust mode (see FIG. 1) for withdrawing heat from the engine when the reactor is operating at full power, a low thrust mode (see FIG. 2) for throttling propellant flow and radiating heat from the engine during reactor shutdown and a zero thrust mode (see FIG. 3) for cooling the nuclear reactor and generating electricity for the rocket's auxiliary power requirements for the remainder of the mission.

Abstract: A nuclear thermal rocket engine is provided with an integrated and compact construction that facilitates vehicle size and weight reduction. The engine includes a nuclear reactor core having multiple fuel assemblies and moderator rods disposed therebetween. A reactor vessel surrounds a reflector assembly which surrounds the core and includes multiple passages formed therein for circulating coolant therethrough. The reactor vessel is surrounded by a nozzle assembly which includes a nozzle block having a plenum fluidly coupled to the outlets of the fuel assemblies and a nozzle throat region. Multiple struts extend from the reactor vessel and through the nozzle throat region to divide that region into multiple nozzle throats. Each strut includes multiple channels for circulating coolant (e.g.

Abstract: A heat exchanger for use in nuclear reactors includes a heat exchange tube bundle formed from similar modules each having a hexagonal shroud containing a large number of thermally conductive tubes which are connected with inlet and outlet headers at opposite ends of each module, the respective headers being adapted for interconnection with suitable inlet and outlet manifold means. In order to adapt the heat exchanger for operation in a high temperature and high pressure environment and to provide access to all tube ports at opposite ends of the tube bundle, a spherical tube sheet is arranged in sealed relation across the chamber with an elongated duct extending outwardly therefrom to provide manifold means for interconnection with the opposite end of the tube bundle.