Space Reactor Power System Research Articles

A cascade control strategy for a space nuclear reactor system

This work presents a linear feedback control for the space nuclear reactor power system TOPAZ II. The point-kinetics approximation with six-delayed-neutron-group is used to represent the neutron field dynamics. A favorable choice of input control variables is demostrated, which leads to a cascade control configuration with two classical either PI or P controllers. The strategy is based on linearizing-like feedback control endowed with a modeling error estimator via a reduced order-observer. The effectiveness of the control law to the tracking of a given thermal power profile in the start-up regime and the tracking of a given electric power profile in the operation regime are illustrated via numerical simulations.

Moving Towards the Next Milestone of Submarine Design

ABSTRACT The principal drivers in U.S. submarine design over the past 30 years are the size and weight requirements of the propulsion system. Almost half the submarine's volume and dimensions are fixed by the propulsion plant design, limiting what can be done with the rest of the platform. NASA has developed a Space Reactor Power System (SRPS) design using new technologies for applications requiring lightweight, high power systems. A concept evaluation comparing a pressurized water reactor design to a propulsion system based on a current SRPS design demonstrates tremendous potential savings in the size and displacement of the submarine, and thus the cost, without losing any mission capabilities. Adapting SRPS technology to submarine use would provide tremendous design flexibility, potentially leading to the next milestone in submarine design.

“Romashka” reactor-converter

On August 14, 1964, the “Romashka” reactor-converter—the world's first setup with direct (thermoelectric) conversion of heat from235U fission into electricity—was started up at the I. V. Kurchatov Institute of Atomic Energy and service-life nuclear tests were begun. In 1999, 35 years have passed since the “Romashka” reactor-converter was first started up and trials began. “Romashka” successfully operated for about 15000 hours and generated ∼6100 kW·h of electricity. The startup and successful tests of the “Romashka” reactor-converter recieved in its time high marks from the world scientific community and they demonstrated that the world's first operating nuclear reactor-converter, capable of generating electricity without the participation of any moving working bodies or mechanisms, was developed in the short time of about 3 years in the Soviet Union, and it was shown experimentally that the system was capable of prolonged operation. The technology created in the process of developing the “Romashka” reactor-converter and, specifically, the thermoelectric silicon-germanium transducers have found application in operating space nuclear (reactor and isotopic) power systems. 3 figures.

Sliding mode control of the space nuclear reactor system

The automatic control system (ACS) of the space nuclear reactor power system TOPAZ II that generates electricity from nuclear heat using in-core thermionic converters is considered. Sliding mode control technique is applied to the reactor system controller design in order to improve robustness and accuracy of tracking of a thermal power reference profile in a start-up regime and a payload current reference profile in an operation regime. Extensive simulations of the TOPAZ II reactor system with the designed sliding mode controller showed an improvement of the reactor system performance.

Space nuclear power - An overview

Nuclear power sources have enabled or enhanced some of the most challenging and exciting space missions yet conducted, including missions such as the Pioneer flights to Jupiter and Saturn; the Voyager flights to Jupiter, Saturn, Uranus, and Neptune; the Apollo lunar surface experiments; the Viking Lander studies of Mars; the Ulysses mission to study the polar regions of the sun; and the Galileo mission to orbit Jupiter. This article surveys the early missions and continues to the present Galileo and Ulysses missions and provides a summary of the power technology that was used in each mission. Current activities aimed at improving the specific power and efficiency of space nuclear power sources are summarized. In addition to radioisotope power sources, this article surveys the U.S. space nuclear reactor program focusing on the flight of the SNAP-lOA reactor and the technology developed in the SP-100 space nuclear reactor power system program. The general attributes of space nuclear power sources are described and possible future applications are identified.

Status report on the U.S. space nuclear program

During the 1980s and 1990s the U.S. sponsored a number of space nuclear power and propulsion programs and studies covering many different mission plans. These space nuclear activities spanned the range from the 300-watt radioisotope thermoelectric generators currently in use on the Galileo mission to Jupiter and the Ulysses mission to explore the polar regions of the Sun to multi-megawatt space nuclear reactor concepts that could be used to provide power for neutral particle beams, free electron lasers, electromagnetic launchers, and orbital transfer vehicles. Studies were undertaken on both nuclear electric propulsion (NEP) and nuclear thermal propulsion (NTP) largely in support the proposed Space Exploration Initiative (SEI). Upgrades to radioisotope power sources involving dynamic (turbine-alternator and linear oscillator) and improved static (thermophotovoltaic and alkali-metal thermal-to-electric conversion) conversion systems were investigated. A major undertaking in the 1980s and early 1990s was the SP-100 space nuclear reactor power system which was designed to span the power range from 10 kWe to 1000 kWe to encompass most high-power missions then being studied. In addition, various efforts to explore the uses of thermionic reactors were undertaken, including an initiative with Russia to test the ENISY (TOPAZ II) thermionic reactor. This paper summarizes these activities and highlights future trends in an era of smaller spacecraft that will be built and launched in shorter periods of time under more tightly constrained budgets.

An Integrated Model of the TOPAZ-II Electromagnetic Pump

A detailed model of the electromagnetic pump of the TOPAZ-II space nuclear reactor power system is developed and compared with experimental data. The magnetic field strength in the pump depends not only on the current supplied by the pump thermionic fuel elements in the reactor core but also on the temperature of the coolant, the magnetic coil, and the pump structure. All electric and thermal properties of the coolant, wall material of the pump ducts, and electric leads are taken to be temperature dependent. The model predictions are in good agreement with experimental data.

Spacecraft and mission design for the SP-100 flight experiment

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the SP-100 Space Reactor Power System (SRPS) Flight Experiment, are outlined. The vehicle design is based on a 93 kW(e) ammonia arcjet system operating at an experimentally measured specific impulse of 1031 s and an efficiency of 42.3 percent. The arcjet/gimbal assemblies, power conditioning subsystem, propellant feed system, propulsion system thermal control, spacecraft diagnostic instrumentation, and the telemetry requirements are described. A 100 kW(e) SRPS is assumed. The spacecraft mass is baselined at 5675 kg excluding the propellant and propellant feed system. Four mission scenarios are described which are capable of demonstrating the full capability of the SRPS. The missions considered include spacecraft deployment to possible surveillance platform orbits, a spacecraft storage mission, and an orbit raising round trip corresponding to possible orbit transfer vehicle (OTV) missions.

Civilian uses of nuclear reactors in space

The potential for civilian mission applications of space nuclear reactor power systems is addressed in this paper. A wide range of possible civilian missions, including human and unmanned solar system exploration, are identified, along with earth-orbit applications. These missions would require versatile, high-capacity space power systems whose attributes can best be provided by nuclear technology. The long mission durations, the high power levels required to fulfill many of the challenging mission objectives, and in some instances the lack of solar energy render the use of nuclear power sources as either mission-enabling or very advantageous.

Arcjet propulsion system for an SP-100 flight experiment

The design and performance of a arcjet nuclear electric propulsion spacecraft, suitable for use in a space reactor power system (SRPS) flight experiment, are outlined. The vehicle design is based on a 92-kW ammonia arcjet system operating at a specific impulse of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power processing unit, and propellant feed system are described. A 100-kW SRPS is assumed and the spacecraft mass is baselined at 5250 kg, excluding the propellant and propellant feed system. A radiation/arcjet efflux diagnostics package is included in the performance analysis. This spacecraft, assuming a Shuttle launch from Kennedy Space Center, can perform a 35-deg inclination change and reach a final orbit of 35,860 km with a 120-day trip time, thus providing a four-month active load for the SRPS. Alternatively, a Titan IV launch could provide a mass margin of 120 kg to a 1000km, 58-deg final orbit in 74 days.

Nuclear-electric reusable orbital transfer vehicle

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined that utilize electric propulsion supported by the nuclear reactor's power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the orbital transfer vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925-km altitude, 28.5-deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an orbital maneuvering vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO for transfer by OMV to the Shuttle. OTV propellant is resupplied, and the ion thrusters are replaced, by the OMV before each sortie to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg, with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo or by changing to mercury propellant.

SNAPSHOT Launch Operations

SNAP 10A, the first space nuclear reactor power system, was launched and brought to full power on April 3, 1965. The unit consists of a compact reactor, cooled by a liquid metal and coupled to a thermoelectric conversion system. The reactor uses a fully enriched uranium-zirconium hydride material as the combined fuelmoderator and beryllium as the reflector. The demonstration of one primary SNAPSHOT objective - verifying the safe and routine, transport, test and launch of a nuclear system, culminated in the launch at Vandenberg Air Force Base. Launch preparations began with the establishment of generalized procedures for the factory-to-flight sequence. A safety analysis followed, resulting in development of safety devices, administrative controls and emergency procedures. Training of the crew and the validation of the support equipment was accomplished by handling and testing usage in the operations at Atomics International. Further training, procedure verification and equipment validation was obtained by a trial shipment and by sending a test system through the operations sequence. SNAP 10A arrived at VAFB on February 16. After a brief reassembly and checkout period, it was transported to the launch pad. A double pad cycle was instigated to ensure safe and complete checkout. In the first cycle, the system mated to the Agena was subjected to a SNAP 10A-Agenalaunch complex compatibility test. A simulated flight test followed, wherein a complete launch through orbital startup sequence using the backup systems was checked. A second simulated flight test exercised the primary systems.