Results for “Nuclear propulsion” — Page 25

NASA NTRS1991

Electric thruster models for multimegawatt nuclear electric propulsion mission design

Three types of electric thrusters currently under development at JPL have potential to support future missions which utilize multimegawatt nuclear electric propulsion. These electric thrusters are the electron bombardment ion thruster, the magnetoplasmadynamic (MPD) thruster, and the electron-cyclotron-resonance (ECR) thruster. The electron bombardment ion thruster is a relatively mature technology which has been developed for operation at kilowatt power levels but will require new development for application in the multimegawatt regime. The MPD engine represents a technology which may be very well suited to steady-state multimegawatt applications but which has been limited to sub-scale (100's of kW) and pulsed (MW) testing thus far. The ECR plasma engine represents a class of very promising new concepts which are still in the basic research phase of development, but which may possess important fundamental advantages over other electric thruster technologies. Models of these thrusters are described and used to make projections of thrusters specific mass, efficiency, and power handling capacity for operation in the multimegawatt regime.

Leifer, Stephanie D.↗

DOE OSTI2025

Uncertainty quantification and sensitivity analysis of a nuclear thermal propulsion reactor startup sequence

The research presented in this article describes progress in applying stochastic methods, uncertainty quantification, parametric studies, and variance-based sensitivity analysis (also known as Sobol sensitivity analysis) to a full-core model of a nuclear thermal propulsion (NTP) system simulated via the radiation transport code Griffin to simulate neutronics. Our goal is to develop a reduced-order (surrogate) model that can be rapidly sampled with perturbations to multiple input parameters. In this NTP system, reactivity and power feedback affect the rotation of control drums (CDs), which is itself controlled by a hybrid proportional-integral-derivative (PID) controller actuated by the power demand and reactivity feedback from the numerical model. This model uses reactor kinetic feedback (mean generation time [Λ] and effective delayed neutron fraction [ β eff ] from a transient Griffin simulation executed via Griffin’s improved quasi-static solver to provide the kinetic parameters) as inputs to functions that control the CD rotation angle. By investigating numerous stochastic approaches, we developed a dual-purpose surrogate model of the NTP system, using polynomial regression in the Multiphysics Object-Oriented Simulation Environment (MOOSE) Stochastic Tools Module (STM). The trained model can be rapidly sampled while simultaneously perturbing various input parameters, such as coefficients on the PID control or temperature (directly affecting the neutron cross section). The surrogate model delivers accurate (within 5%) results at speeds orders of magnitude faster (minutes, not days of computational time) than the base model. Once the surrogate model has been trained, distributions of the uncertain parameters can be changed at will to investigate the effects of perturbing multiple inputs as well as the effects of these inputs on the model output. For example, coefficients used in the PID control system may vary due to some type of physical interference, or uncertainty may exist in the temperature of the neutron cross sections in various regions of the reactor. A distribution can be placed on these parameters, and operational boundaries can be determined. The goal of this work is to support development of an advanced control system for operating CDs in a functioning NTP system. This work is a scoping study of the MOOSE STM.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗

NASA NTRSDate not supplied

Concept of Operations of Cryogenic Fluid Management for Nuclear Thermal Propulsion

Cryogenic Fluid Management (CFM) is a critical capability for a hydrogen NTP vehicle for a crewed mission to Mars. AMA has investigated the concept of operations for zero boiloff CFM systems and provided feasibility assessment for a zero-boiloff CFM system based on gravity-independent technologies. This includes identification of CFM-critical mission stages, modelling of CFM operational modes in steady state and transient conditions, thermal analysis of the NTP vehicle and CFM systems, hydrogen leakage analysis, and system margins and fault tolerance. This work illustrates the feasibility of a zero boiloff mission with a set of technology performance assumptions.

cryogenic fluid management↗

NASA NTRS1971

Thermionic reactor power conditioner design for nuclear electric propulsion.

Consideration of the effects of various thermionic reactor parameters and requirements upon spacecraft power conditioning design. A basic spacecraft is defined using nuclear electric propulsion, requiring approximately 120 kWe. The interrelationships of reactor operating characteristics and power conditioning requirements are discussed and evaluated, and the effects on power conditioner design and performance are presented.

Jacobsen, A. S.↗

NASA NTRS1991

Numerical analysis of a nuclear fuel element for nuclear thermal propulsion

A computational fluid dynamics model with porosity and permeability formulations in the transport equations has been developed to study the concept of nuclear thermal propulsion through the analysis of a pulsed irradiation of a particle bed element (PIPE). The numerical model is a time-accurate pressure-based formulation. An adaptive upwind scheme is employed for spatial discretization. The upwind scheme is based on second- and fourth-order central differencing with adaptive artificial dissipation. Multiblocked porosity regions have been formulated to model the cold frit, particle bed, and hot frit. Multiblocked permeability regions have been formulated to describe the flow shaping effect from the thickness-varying cold frit. Computational results for several zero-power density PIPEs and an elevated-particle-temperature PIPE are presented. The implications of the computational results are discussed.

Wang, Ten-See↗

NASA NTRS2004

Nuclear Electric Propulsion Application: RASC Mission Robotic Exploration of Venus

The following paper documents the mission and systems analysis portion of a study in which Nuclear Electric Propulsion (NEP) is used as the in-space transportation system to send a series of robotic rovers and atmospheric science airplanes to Venus in the 2020 to 2030 timeframe. As part of the NASA RASC (Revolutionary Aerospace Systems Concepts) program, this mission analysis is meant to identify future technologies and their application to far reaching NASA missions. The NEP systems and mission analysis is based largely on current technology state of the art assumptions. This study looks specifically at the performance of the NEP transfer stage when sending a series of different payload package point design options to Venus orbit.

McGuire, Melissa L.↗

NASA NTRS2019

Thermal, Avionics, and Power Considerations for Designing a Nuclear Thermal Propulsion Flight Demonstrator

As part of the Appropriations Bill passed by the US Congress in February 2019, NASA was instructed to develop a nuclear thermal propulsion (NTP) flight demonstrator by 2024. [4] In response to this directive, the Advanced Concepts Office (ACO) at Marshall Space Flight Center (MSFC) was tasked with beginning concept studies for the flight demonstration (FD) mission. During the NTP study formulation, two philoso- phies emerged with regards to FD concept design. The first, Flight Demo 1 (FD1), strictly observes the 2024 schedule requirement at the expense of lower engine performance than expected of theoretical NTP engines. The second concept, Flight Demo 2 (FD2), relaxes the schedule requirement to allow for higher engine performance and more traceability to future operational systems. Both the FD1 and FD2 concepts present considerable challenges for subsystem design, specifically in the areas of thermal control, avionics, and power. To guard against undesired graveyard orbits, a requirement to keep the NTP engine and the reaction control system (RCS) separate was put in place. As a result of this requirement, the avionics subsystem must provide separate command and data handling (CDH) and instrumentation for each propulsion system. In-space instrumentation and monitoring of a NTP system has never been done before, necessitating the development of novel strategies and unique hardware. The heating rates produced by the NTP engine are extremely high, leading to difficulties with thermal control. The FD1 concept utilizes high-pressure gaseous hydrogen (GH2), which is largely insensitive to temperature fluctuations. The FD2 concept, however, utilizes cryogenic liquid hydrogen (LH2) which must be kept stable near 20 Kelvin. A high-performance thermal control system (TCS) will be required to ensure all components and subsystems are maintained within their operational temperature ranges. This paper will highlight the thermal, avionics, and power solutions required for the full scope of challenges for a NTP flight demonstrator.

Johnson, W. E.↗

NASA NTRS1993

Nuclear electric propulsion operational reliability and crew safety study: NEP systems/modeling report

The objective of this study was to establish the initial quantitative reliability bounds for nuclear electric propulsion systems in a manned Mars mission required to ensure crew safety and mission success. Finding the reliability bounds involves balancing top-down (mission driven) requirements and bottom-up (technology driven) capabilities. In seeking this balance we hope to accomplish the following: (1) provide design insights into the achievability of the baseline design in terms of reliability requirements, given the existing technology base; (2) suggest alternative design approaches which might enhance reliability and crew safety; and (3) indicate what technology areas require significant research and development to achieve the reliability objectives.

Karns, James↗

NASA NTRS2018

Design Options for a Versatile Nuclear Thermal Propulsion (NTP) Stage

A study was initiated to investigate propulsion stage and mission architecture options potentially enabled by fission energy. One initial concept is a versatile Nuclear Thermal Propulsion (NTP) system with a maximum specific impulse of 900 s and a maximum thrust (per engine) of 15 klbf. The system assumes a monopropellant stage (hydrogen), and is designed to also provide 300 lbf of thrust (potentially split between multiple thrusters) at an Isp > 500 s. Boost pumps are used to assist with engine decay heat removal and low thrust engine burns, and to compensate for partial tank depressurization during full thrust engine burns. Potential stage assembly orbits that take full advantage of launch vehicle payload mass and volume capabilities are being assessed. The potential for using NTP engines to also generate a small to moderate amount of electrical power is also being evaluated.

Fission Power Propulsion↗

NASA NTRS2019

Versatile Nuclear Thermal Propulsion (NTP)

A study was initiated to investigate propulsion stage and mission architecture options potentially enabled by fission energy. One initial concept is a versatile Nuclear Thermal Propulsion (NTP) system with a maximum specific impulse of 900 s and a maximum thrust (per engine) of 15 klbf. The system assumes a monopropellant stage (hydrogen), and is designed to also provide 300 lbf of thrust (potentially split between multiple thrusters) at an Isp > 500 s for orbital maneuvering and station keeping. Boost pumps are used to assist with engine decay heat removal and low thrust engine burns, and to compensate for partial tank depressurization during full thrust engine burns. Potential stage assembly orbits that take full advantage of launch vehicle payload mass and volume capabilities are being assessed. The potential for using NTP engines to also generate a small to moderate amount of electrical power is also being evaluated. A first generation versatile NTP stage could enable 8 of 9 upcoming opportunities for short (less than 24 month) round trip human missions to Mars. A second generation versatile NTP is under consideration that could potentially provide a maximum specific impulse of 1800 s at 15 klbf, and enable ambitious missions throughout the solar system. The second generation NTP system under consideration would also allow a choice of volatiles to be used as propellant. This would potentially allow in-situ resources such as water, ammonia, methane, or other compounds to be used directly as propellant by the second generation engine.

Houts, Michael G.↗

NASA NTRS2019

Versatile Nuclear Thermal Propulsion (NTP)

A study was initiated to investigate propulsion stage and mission architecture options potentially enabled by fission energy. One initial concept is a versatile Nuclear Thermal Propulsion (NTP) system with a maximum specific impulse of 900 s and a maximum thrust (per engine) of 15 klbf. The system assumes a monopropellant stage (hydrogen), and is designed to also provide 300 lbf of thrust (potentially split between multiple thrusters) at an Isp > 500 s for orbital maneuvering and station keeping. Boost pumps are used to assist with engine decay heat removal and low thrust engine burns, and to compensate for partial tank depressurization during full thrust engine burns. Potential stage assembly orbits that take full advantage of launch vehicle payload mass and volume capabilities are being assessed. The potential for using NTP engines to also generate a small to moderate amount of electrical power is also being evaluated. A first generation versatile NTP stage could enable 8 of 9 upcoming opportunities for short (less than 24 month) round trip human missions to Mars. A second generation versatile NTP is under consideration that could potentially provide a maximum specific impulse of 1800 s at 15 klbf, and enable ambitious missions throughout the solar system. The second generation NTP system under consideration would also allow a choice of volatiles to be used as propellant. This would potentially allow in-situ resources such as water, ammonia, methane, or other compounds to be used directly as propellant by the second generation engine.

Houts, Mike↗

NASA NTRSDate not supplied

Point Design for a Nuclear Electric Propulsion Mission to Uranus

Explore the source record for details and available documents.

NEP↗

NASA NTRS2020

Simulation of Hydrogen Flow in a Nuclear-Thermal Propulsion Reactor Subsystem: Conjugate Heat Transfer in Surrogate Fuel Elements and Flow Through the Dome Inlet to the Fuel Elements

NASA is performing research related to a Nuclear-Thermal Propulsion (NTP) engine as a step toward future manned missions to Mars. BWX Technologies (BWXT), in conjunction with NASA, is developing the reactor subsystem for that NTP engine design. As a subset of the reactor subsystem, the fuel elements have continued to evolve in design, as well. A set of experiments within the Nuclear Thermal Reactor Element Environmental Simulator at NASA Marshall has been developed to compliment that design process, including a series of surrogate fuel elements. Before the experiments of each surrogate can be completed, they must be deemed safe using structural analysis, which itself requires thermal and conjugate heat transfer analyses of the articles. Therefore, conjugate heat transfer simulations of the hydrogen flow through the test article fuel element surrogates were developed to provide estimates of heating, as well as to provide assessments of the fluid flow through the elements. The set of simulations involved not only the separate test conditions, but also a sensitivity study to estimate the effect of physical parameter uncertainty on the selected quantities of interest. Additionally, the fluid flow through the fore section inner plenum dome to the entrances of the fuel elements, another section of the reactor subsystem still under active development, was simulated and analyzed. The simulations show the extent of non-uniformity in the mass flow distribution across the dome outlets. Furthermore, additional analyses estimate the effects of required flow blockages on the potential development of flow dynamics. These analyses were used in the design cycle to make improvements to the reactor subsystem design.

Kalen E. Braman↗

NASA NTRS1972

Nuclear electric propulsion mission engineering study development program and costs estimates, Phase 2 review

The results are presented of the second six-month performance period of the Nuclear Electric Propulsion Mission Engineering Study. A brief overview of the program, identifying the study objectives and approach, and a discussion of the program status and schedule are presented. The program results are reviewed and key conclusions to date are summarized. Planned effort for the remainder of the program is reviewed.

Source record↗

NASA NTRS1982

Nuclear electric propulsion /NEP/ spacecraft for the outer planet orbiter mission

The design, operating features, and a possible Neptune orbit for the spacecraft powered by the SP-100 nuclear electric propulsion (NEP) system under study by NASA and the DOE are described. The system features a reactor and a payload situated on opposite ends of a 0.5 m diam, 11 m long astromast. Mercury-ion thrusters are located beneath the reactor for side thrusting, and no contamination of the payload or obstruction of the viewing angles for scientific objectives occurs with the system, which would not degrade in performance even under high insolation during near-sun maneuvers. Results of a theoretical study of earth escapes are presented to show that an NEP powered spiral trajectory out of a 700 km Shuttle orbit and using a Triton gravity assist would be superior to departing from a 300 km orbit with a Centaur boost. The mission profile includes a 1249 kg Galileo payload. The SP-100 has a 1.4 MWth reactor with UO2 fuel tiles and weighs 19,904 kg.

Garrison, P. W.↗

NASA NTRS1976

A nuclear electric propulsion vehicle for planetary exploration

A study is currently underway at JPL to design a nuclear electric-propulsion vehicle capable of performing detailed exploration of the outer planets. Evaluation of the design indicates that it is also applicable to orbit raising. Primary emphasis is on the power subsystem. Work on the design of the power system, the mission rationale, and preliminary spacecraft design are summarized. A propulsion system at a 400-kWe power level with a specific weight goal of no more than 25-kg/kW was selected for this study. The results indicate that this goal can be realized along with compatibility with the shuttle launch-vehicle constraints.

Pawlik, E. V.↗

NASA NTRS1991

Nuclear electric propulsion mission performance for fast piloted Mars missions

A mission study aimed at minimizing the time humans would spend in the space environment is presented. The use of nuclear electric propulsion (NEP), when combined with a suitable mission profile, can reduce the trip time to durations competitive with other propulsion systems. Specifically, a split mission profile utilizing an earth crew capture vehicle accounts for a significant portion of the trip time reduction compared to previous studies. NEP is shown to be capable of performing fast piloted missions to Mars at low power levels using near-term technology and is considered to be a viable candidate for these missions.

Hack, K. J.↗

NASA NTRS1972

Application of MORSE to radiation analysis of nuclear flight propulsion modules

Several modifications and additions were made to the multigroup Monte Carlo code (MORSE) to implement its use in a computational procedure for performing radiation analyses of NERVA nuclear flight propulsion modules. These changes include the incorporation of a new general geometry module; the inclusion of an expectation tracklength estimator; and the option to obtain source information from two-dimensional discrete ordinates calculations. Computations comparing MORSE and a point cross section Monte Carlo code, COHORT, were made in which a coupled discrete ordinates/Monte Carlo procedure was used to calculate the gamma dose rate at tank top locations of a typical propulsion module. The dose rates obtained from the MORSE computation agreed with the dose rates obtained from the COHORT computation to within the limits of the statistical accuracy of the calculations.

Woolson, W. A.↗