Track 2: Mission Concepts and Logistics
Paper and Podium Presentation
Paper and Podium Presentation
A PROPOSED SOLUTION TO ADDRESS NUCLEAR THERMAL PROPULSION FUEL EMBRITTLEMENT AND CRYOGENIC HYDROGEN REQUIREMENTS
This paper introduces the concept of a minimally intrusive power generation system that may be applied to a nuclear thermal propulsion (NTP) engine. Most bimodal or dual-mode NTP designs are optimized for maximum electrical power generation but require significant changes to the reactors configuration. This greatly diminishes their usefulness to modern NTP programs that focus on affordability and expediency. Nevertheless, the benefits of successfully generating additional power from the reactor, especially while it is not in use, include reducing the total system mass by several metric tons, avoiding fuel embrittlement concerns, and assisting with cryogenic hydrogen propellant storage. Thus, a system designed for fewest reactor modifications rather than greatest power generation could provide the right compromise between theoretical and practical design efficiency. This paper outlines the relevant design requirements for such a system before listing several candidate solutions.Download Paper
AN ARCHITECTURE FOR A NUCLEAR POWERED CRYOBOT TO ACCESS THE OCEANS OF ICY WORLDS
The icy moon oceans beckon with ingredients that potentially may harbor extant life. Beginning with the Galileo and Cassini missions, measurements have revealed the presence of global oceans under the icy crust of several moons of Jupiter and Saturn. Among those moons, Europa and Enceladus have their ocean in contact with the rocky core, providing an environment similar to the conditions existing on the terrestrial sea-floor where life has developed at hydrothermal vents. A detailed trade space study was conducted to develop a technology architecture defining a system that would access an icy moons ocean. This paper outlines the architecture with specific consideration to the power source necessary to drive the system.Download Paper
AN EXPLORATION OF MISSION CONCEPTS THAT COULD UTILIZE SMALL RPS
The NASA Radioisotope Power Systems (RPS) Program Mission Analysis Team at the Jet Propulsion Laboratory (JPL) requested a JPL Innovation Foundry Architecture Team (A-Team) study to assess mission pull for small RPS (1 mWe - 40 We) in order to inform the RPS Program Office on what future power system developments should be focused on. The A-Team is JPLs concurrent engineering design team for science definition and early mission concept development, targeting concept maturation levels of 1 through 3. The requested small RPS study was tasked to identify the architecture space of potential small RPS missions, and suggest power levels that could enable or enhance potential future small spacecraft missions.
This paper describes the collaborative engineering processes that the A-Team and Mission Analysis Team used to reach results quickly and the findings to inform the RPS Program about mission concept power requirements on RPS for small missions.Download Paper
HISTORY AND CHALLENGES OF SPACE NUCLEAR REACTOR POWER SYSTEMS
Nuclear reactors are anticipated to power manned mission to Mars and other prospective deep space endeavors in the future and lots of attempts have been made in the U.S. and Russia since 1950s. This paper aims to present a retrospective review of the history of space nuclear reactor power systems from technology and non-technology perspectives and to put forward reflections on opportunities for future developments.Download Paper
LEU NTP ENGINE SYSTEM TRADES AND MISSION OPTIONS
The future of human exploration missions to Mars are dependent on solutions to the technology challenges being worked by NASA and industry. One of the key architecture technologies involves propulsion that can transport the human crew from Earth orbit to other planets and back to Earth with the lowest risk to crew and the mission. Nuclear Thermal Propulsion (NTP) is a proven technology that provides the performance required to enable benefits in greater payload mass, shorter transit time, wider launch windows, and rapid mission aborts due to its high specific impulse (Isp).
Aerojet Rocketdyne (AR) has stayed engaged for several decades in working NTP engine systems and has worked with NASA recently to perform an extensive study on using Low Enriched Uranium (LEU) NTP engine systems for a Mars campaign involving crewed missions from the 2030s through the 2050s.
The impacts of the NTP engine system on the Mars transfer vehicle (MTV) configuration have been assessed via several trade studies since 2016, including thrust size, number of engine systems, liquid hydrogen stage size, reaction control system sizing, propellant losses, NASA Space Launch System (SLS) payload fairing (PLF) size impact, and aggregation orbit.
AR study activity in 2018 included examining NTP stages derived from Mars crew mission elements to deliver extremely large cargo via multiple launches or directly off the NASA Space Launch System (SLS). This paper provides an update on the results of the on-going engine system and mission trade studies.Download Paper
NUCLEAR THERMAL PROPULSION DYNAMIC MODELING WITH MODELICA
Oak Ridge National Laboratory (ORNL) is participating in the nuclear thermal propulsion (NTP) research and development effort supported by the National Aeronautics and Space Administration (NASA). This effort involves collaboration between multiple research groups that represent various government agencies and industry partners. ORNL has developed a Modelica-based modeling package for dynamic system modeling of nuclear reactors called the Transient Simulation Framework of Reconfigurable Models (TRANSFORM). While this software has been successfully demonstrated in simulations of traditional pressurized-water reactors, boiling-water reactors, liquid-metal reactors, and molten-salt reactors, it has also been adapted for nontraditional use in modeling hybrid energy systems and in tritium transport. This versatility is being applied to the current NTP project, where specific modules within TRANSFORM are being developed for and applied to transient modeling of the NASA NTP design. This paper presents the current state of the ORNL-NTP model, the utility of TRANSFORM methodologies in NTP transient simulations, the ability to develop NTP-specific modules, and proposed future work for the model.Download Paper
PASSIVE AND ACTIVE COOLING ANALYSIS FOR DECAY HEAT OF NUCLEAR THERMAL PROPULSION SYSTEMS
Methods for decay heat removal are analyzed with the goal of reducing propellant consumption using TRansient Investigation COde for Reactor DEvelopments and Research (TRICORDER) tool developed by Ultra Safe Nuclear Corporation. TRICORDER is used to perform two-dimensional steady state conduction analysis to determine system radiative capabilities. 2-D results show significant reductions in cooldown time over legacy estimates. TRICORDER is also used to simulate three-dimensional transient active cooling through fuel and tie tube channels in order to evaluate hydrogen flow profiles. Legacy flow profiles are tested and deemed to be wasteful of hydrogen. Methods for reducing hydrogen consumption through more efficient flow profiles are discussed, and an example improved profile is simulated and commented upon.Download Paper
SPACE FISSION POWER: NASAS BEST BET TO CONTINUE TO EXPLORE THE OUTER SOLAR SYSTEM
Implementation of balanced, cost-efficient programs to develop power technologies would enable future Voyager- and Cassini-class missions at the outermost planets; open up subsurface missions at Europa, Enceladus, and Titan; and facilitate orbiter and lander missions at Neptune and Triton. A rebalancing of the NASA power technology portfolio could establish the option of using fission power in space. The timing is right for the development of a small nuclear reactor design (such as KRUSTY) that can provide power for multi-year robotic missions and serve as a pathfinder and risk reduction strategy for the larger needs of future human exploration space power systems. *Download Paper
THERMAL MODEL OF A ZERO BOIL OFF SYSTEM FOR THE NUCLEAR THERMAL PROPULSION SYSTEM
NASA is currently developing an updated concept for a nuclear thermal propulsion (NTP) system. To enable this concept, efficient thermal insulation and cryocooler heat exchanger systems are required to eliminate boil-off of propellant. This paper presents the results of a thermal model used to assess the feasibility of using active cooling with a tube-on-tank heat exchanger configuration for the inline tank of the NTP system. Results show that: (1) cryocooler working fluid temperature and mass flow rate can be adjusted to achieve zero boil off (ZBO) with broad area cooling, (2) over-sizing the cryocooler lift directly translates into a reduction in tank pressure, and (3) broad area cooling may still maintain ZBO despite the reduced heat transfer between tank wall and propellant that is expected in reduced gravity.Download Paper
TRADES ON DENSIFIED PROPELLANT FOR NUCLEAR THERMAL PROPULSION
Nuclear Thermal Propulsion is an enabling technology for expanding both manned and unmanned spaceflight capability. For most efficient use of propellant by mass it must use cryogenic hydrogen, but its mass density is low compared to other propellant options. This results in large propellant tanks which can be heavy and absorb more heat from the space environment than smaller propellant tanks. Hydrogens density can be increased by storing it at lower temperatures, but such densification is usually discussed in the context of launch vehicles or other Earth applications. This paper explores trades on in space liquid hydrogen propellant storage that result from densified liquid hydrogen. It was found that during spacecraft coast storing close to the freezing point results in a small reduction of required active cooling power compared to storing near the boiling point. During burns when the Nuclear Thermal Propulsion emits neutrons and gamma rays increased liquid hydrogen density increases the amount of heat absorbed from the radiation per unit area and depth of hydrogen, but the higher density allows for more favorable tank geometries that reduce net heating.Download Paper
NTP LUNAR DESIGN REFERENCE MISSIONS
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