Lyman J. Petrosky

Nuclear thermal propulsion engine system design analysis code development

A Nuclear Thermal Propulsion (NTP) Engine System Design Analyis Code has recently been developed to characterize key NTP engine system design features. Such a versatile, standalone NTP system performance and engine design code is required to support ongoing and future engine system and vehicle design efforts associated with proposed Space Exploration Initiative (SEI) missions of interest. Key areas of interest in the engine system modeling effort were the reactor, shielding, and inclusion of an engine multi‐redundant propellant pump feed system design option. A solid‐core nuclear thermal reactor and internal shielding code model was developed to estimate the reactor’s thermal‐hydraulic and physical parameters based on a prescribed thermal output which was integrated into a state‐of‐the‐art engine system design model. The reactor code module has the capability to model graphite, composite, or carbide fuels. Key output from the model consists of reactor parameters such as thermal power, pressure drop, therm...

Nuclear engine system simulation (NESS) program update

The second phase of development of a Nuclear Thermal Propulsion (NTP) engine system design analysis code has been completed. The standalone, versatile Nuclear Engine System Simulation (NESS) code provides an accurate, detailed assessment of engine system operating performance, weight, and sizes. The critical information is required to support ongoing and future engine system and stage design study efforts. This recent development effort included incorporation of an updated solid‐core nuclear thermal reactor model that yields a reduced core weight and higher fuel power density when compared to a NERVA type reactor. NESS can now analyze expander, gas generator, and bleed cycles, along with multi‐redundant propellant pump feed systems. Performance and weight of efficient multi‐stage axial turbopump can now be determined, in addition to the traditional centrifugal pump.Key code outputs include reactor operating charactertistics and weights and well as engine system parameters such as performance, weights, dimensions, pressures, temperatures, mass flows and turbopump operating characteristics for both design and off‐design operating conditions. Representative NTP engine system designs are also shown. An overview of NESS methodology and capabilities is presented in this paper, with special emphasis being placed on recent code developments.The second phase of development of a Nuclear Thermal Propulsion (NTP) engine system design analysis code has been completed. The standalone, versatile Nuclear Engine System Simulation (NESS) code provides an accurate, detailed assessment of engine system operating performance, weight, and sizes. The critical information is required to support ongoing and future engine system and stage design study efforts. This recent development effort included incorporation of an updated solid‐core nuclear thermal reactor model that yields a reduced core weight and higher fuel power density when compared to a NERVA type reactor. NESS can now analyze expander, gas generator, and bleed cycles, along with multi‐redundant propellant pump feed systems. Performance and weight of efficient multi‐stage axial turbopump can now be determined, in addition to the traditional centrifugal pump.Key code outputs include reactor operating charactertistics and weights and well as engine system parameters such as performance, weights, dim...

IMPULSE—an advanced, high performance nuclear thermal propulsion system

IMPULSE is an advanced nuclear propulsion engine for future space missions based on a novel conical fuel. Fuel assemblies are formed by stacking a series of truncated (U, Zr)C cones with non‐fueled lips. Hydrogen flows radially inward between the cones to a central plenum connected to a high performance bell nozzle. The reference IMPULSE engine rated at 75,000 lb thrust and 1800 MWt weighs 1360 kg and is 3.65 meters in height and 81 cm in diameter. Specific impulse is estimated to be 1000 for a 15 minute life at full power. If longer life times are required, the operating temperature can be reduced with a concomitant decrease in specific impulse. Advantages of this concept include: well defined coolant paths without outlet flow restrictions; redundant orificing; very low thermal gradients and hence, thermal stresses, across the fuel elements; and reduced thermal stresses because of the truncated conical shape of the fuel elements.

An Evaluation of the Impulse NTP System Core Configurations

The results of a neutronic study of an Impulse reactor using cermets and carbide based fuels are presented in this paper. Earlier studies have shown that a fast reactor for an NTP system using tungsten cermet fuel eliminates the water submersion criticality problem due to the poisoning effect of the tungsten when the spectrum is thermalized by the incursion of water into the core. A thermal reactor is required to have an active shutdown system to protect against inadvertent reentry of an NTP system into Earth after having reached criticality in space. When immersed in water, the neutron flux is moderated and the tungsten becomes a strong absorber. Also, cermet fuel may have better fission products retention than the graphite based fuel elements used for a thermal reactor at the same or higher temperature. The results of the analysis demonstrated that a fast reactor version of the Impulse is feasible; however, it lends itself better to larger thrust engines than 334kN (75000 lbf). A significant increase in...

ENABLER‐II: a high performance prismatic fuel nuclear rocket engine

The Rover/NERVA program demonstrated graphite/carbide based prismatic fuel nuclear thermal rockets (NTR). The fuel performance increased steadily throughout the program, but data received late in the program did not have an opportunity to be incorporated into the engine designs. This article investigates NTR engines derived from the Rover/NERVA program database, utilizing all the available data developed in the program. This work does not assume any material advancements; the engine designs are based on demonstrated fuel performance levels and utilize established design margins. The Rover/NERVA database guarantees a minimum achievable performance, but has considerable growth potential which has yet to be realized. This article discusses the design issues and presents the performance figures for the ENABLER‐I and ENABLER‐II engines designs, which represent a low‐risk first stage embodiment of this growth potential.