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Z-Pinch Magneto-Inertial Fusion Propulsion Engine Design Concept
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Author and Affiliation:
Miernik, Janie H.(Engineering Research and Consulting, Inc., Jacobs Engineering Science and Technology Services Group, Huntsville, AL, United States);
Statham, Geoffrey(Jacobs Technologies Engineering Science Contract Group, Huntsville, AL, United States);
Adams, Robert B.(NASA Marshall Space Flight Center, Huntsville, AL, United States);
Polsgrove, Tara(NASA Marshall Space Flight Center, Huntsville, AL, United States);
Fincher, Sharon(NASA Marshall Space Flight Center, Huntsville, AL, United States);
Fabisinski, Leo(International Space Systems, Inc., Jacobs Engineering Science and Technology Services Group, Huntsville, AL, United States);
Maples, C. Dauphne(Qualis Corp., Jacobs Engineering Science and Technology Services Group, Huntsville, AL, United States);
Percy, Thomas K.(Science Applications International Corp., Huntsville, AL, United States);
Cortez, Ross J.(Alabama Univ., Propulsion Research Ctr., Huntsville, AL, United States);
Cassibry, Jason(Alabama Univ., Propulsion Research Ctr., Huntsville, AL, United States)
Abstract: Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human spaceflight missions. Magneto-Inertial Fusion (MIF) is an approach which has been shown to potentially lead to a low cost, small fusion reactor/engine assembly (1). The Z-Pinch dense plasma focus method is an MIF concept in which a column of gas is compressed to thermonuclear conditions by an estimated axial current of approximately 100 MA. Recent advancements in experiments and the theoretical understanding of this concept suggest favorable scaling of fusion power output yield as I(sup 4) (2). The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this is repeated over short timescales (10(exp -6) sec). This plasma formation is widely used in the field of Nuclear Weapons Effects (NWE) testing in the defense industry, as well as in fusion energy research. There is a wealth of literature characterizing Z-Pinch physics and existing models (3-5). In order to be useful in engineering analysis, a simplified Z-Pinch fusion thermodynamic model was developed to determine the quantity of plasma, plasma temperature, rate of expansion, energy production, etc. to calculate the parameters that characterize a propulsion system. The amount of nuclear fuel per pulse, mixture ratio of the D-T and nozzle liner propellant, and assumptions about the efficiency of the engine, enabled the sizing of the propulsion system and resulted in an estimate of the thrust and Isp of a Z-Pinch fusion propulsion system for the concept vehicle. MIF requires a magnetic nozzle to contain and direct the nuclear pulses, as well as a robust structure and radiation shielding. The structure, configuration, and materials of the nozzle must meet many severe requirements. The configuration would focus, in a conical manner, the Deuterium-Tritium (D-T) fuel and Lithium-6/7 liner fluid to meet at a specific point that acts as a cathode so the Li-6 can serve as a current return path to complete the circuit. In addition to serving as a current return path, the Li liner also serves as a radiation shield. The advantage to this configuration is the reaction between neutrons and Li-6 results in the production of additional Tritium, thus adding further fuel to the fusion reaction and boosting the energy output. To understand the applicability of Z-Pinch propulsion to interplanetary travel, it is necessary to design a concept vehicle that uses it. The propulsion system significantly impacts the design of the electrical, thermal control, avionics, radiation shielding, and structural subsystems of a vehicle. The design reference mission is the transport of crew and cargo to Mars and back, with the intention that the vehicle be reused for other missions. Several aspects of this vehicle are based on a previous crewed fusion vehicle study called Human Outer Planet Exploration (HOPE), which employed a Magnetized Target Fusion (MTF) propulsion concept. Analysis of this propulsion system concludes that a 40-fold increase of Isp over chemical propulsion is predicted. This along with a greater than 30% predicted payload mass fraction certainly warrants further development of enabling technologies. The vehicle is designed for multiple interplanetary missions and conceivably may be suited for an automated one-way interstellar voyage.
Publication Date: Jul 01, 2011
Document ID:
20120016553
(Acquired Dec 05, 2012)
Subject Category: SPACECRAFT PROPULSION AND POWER
Report/Patent Number: M11-0190, M11-0436
Document Type: Conference Paper
Meeting Information: 7th Symposium on Realistic Advanced Scientific Missions INternational Academy of Astronautics Dept. of Mechanics of the Politechnico of Turin; 11-14 Jul. 2011; Aosta; Italy
Contract/Grant/Task Num: NNM05AB50C
Financial Sponsor: NASA Marshall Space Flight Center; Huntsville, AL, United States
Organization Source: NASA Marshall Space Flight Center; Huntsville, AL, United States
Description: 8p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: ZETA PINCH; NUCLEAR PROPULSION; MAGNETOHYDRODYNAMIC FLOW; INERTIAL CONFINEMENT FUSION; ENGINE DESIGN; MAGNETIC NOZZLES; MAGNETIC FIELDS; SPECIFIC IMPULSE; INTERPLANETARY FLIGHT
Miscellaneous Notes: PDF includes Conference abstract and paper.
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