A system includes a nuclear reactor having a plurality of fuel rods of radioactive decay material distributed within and embedded within a heat exchange matrix. A plurality of coolant tubes is distributed within and embedded within the heat exchange matrix, interspersed with the plurality of fuel rods. The heat exchange matrix is configured to conduct heat from the fuel rods to the coolant tubes.

A nuclear engine system includes: a pump configured to pump a propellant; a fuel element including a set of nuclear fuel particles; a moderator configured to surround the fuel element and defining a set of moderator coolant channels configured to cool the moderator; a reflector including a neutron-reflecting material and a reflector coolant channel arranged within the reflector to cool the reflector, the reflector configured to at a first time, operate in a closed configuration to reflect neutrons to the fuel element to increase an energy flux, and at a second time, operate in an open configured to leak neutrons out of the engine system to decrease the energy flux; and a thrust nozzle configured to outlet propellant from the fuel element to produce thrust including a nozzle coolant channel arranged within a wall of the thrust nozzle configured to cool the nozzle.

A controlled reactor comprises a reactor core thermally coupled to one or more heat pipes and an active cooling loop. A fluid may be circulated through the active cooling loop. A heat exchanger is thermally coupled to the active cooling loop and extracts heat from the fluid as the fluid is circulated through the active cooling loop. A heating system may be provided to deliver the heat extracted by the heat exchanger to a community. A thermoelectric generator may be provided to convert heat extracted by the heat pipes to electricity for delivery to the community.

Methods, systems, and devices for satellite operations are described. A system for satellite communications may include a payload, a power system, and a thermal management component. The payload may be configured to provide a service with varying levels of capacity based on a demand profile. The payload may consume electrical energy at a peak rate when a level of demand indicated by the demand profile is above a threshold and at a lower, off-peak rate when a level of demand indicated by the demand profile is below a threshold. The peak rate may exceed a rate at which electrical energy is generated by the power system. The thermal management component may process excess thermal energy generated by the payload when the payload operates at the peak rate. Processing the excess thermal energy may include storing thermal energy while the payload operates at the peak rate.

A nuclear reactor system includes a nuclear reactor core disposed in a pressure vessel. Nuclear reactor system further includes control drums disposed longitudinally within the pressure vessel and laterally surrounding fuel elements and at least one moderator element of the nuclear reactor core to control reactivity. Each of the control drums includes a reflector material and an absorber material. Nuclear reactor system further includes a control drum controller with a counterweight to impart a reverse torque on the control drum. Control drum controller includes a driven pulley coupled to the counterweight, a tension member coupled to the driven pulley to rotatably control the driven pulley and apply torque to the driven pulley, and an actuator to apply a tension force to the tension member. The actuator counteracts the reverse torque with the applied tension force, and the tension member applies the torque in response to the tension force.

A thermal power reactor (100) includes a reactor core (102) that generates thermal energy and a solid state thermal conductor (106) extending into and thermally integrated with the reactor core (102). The solid state thermal conductor (106) transfers thermal energy generated by the reactor core (102) away from the reactor core (102).