Browsing by Author "Bhaskaran, Amal"

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    Baseload Fission Reactor for Lunar Operations
    (IAF, 2020) Schubert, Peter J.; Doshi, Jeel; Munyala Kindomba, Eli; Bhaskaran, Amal; Conaway, Adam; Electrical and Computer Engineering, School of Engineering and Technology
    Breakout performance for human operations will be realized once there are MW-class continuousoperation fission reactors on the Moon. This is likely to be realized only when there is a means for producing fissile fuel from ISRU resources, such as lunar thorium, because of the concerns associated with earth-launch of radioactive materials. Space is pervaded by gamma rays which produce neutrons upon interaction with beryllium. When moderated by graphite said neutrons can be captured by the thorium nucleus, which transmutes into protactinium, which further decays into the U-233 isotope of uranium. U233 is an excellent source because the radioactive byproducts of spent fuel are short-lived, becoming safe after about 80 years. Thorium dioxide (ThO2 or thoria) is much more dense than the regolith average, and is found in concentrations exceeding those on earth in certain craters of the north Near Side, possibly because of the excavation of rich subsurface deposits due to meteorite impacts. Using jaw crushers and trommels made of durable lightweight metals a lunar mining operation can extract hundreds of kilograms of thoria by using a polymeric adaptation of a Wilfley sorting table laid along the sloped wall of a crater. An acid leach process can be used to remove intermediate protactinium from further neutron irradiation, which will decay to U-233. After processing the transmutated urania (UO2) is packed into fuel rods for a first-generation lunar fission reactor. The same gamma rays and beryllium will initiate a controlled chain reaction to provide baseload power. A Brayton cycle generator can produce power in a manner similar to the small modular reactor concept in development for terrestrial loads. With power outputs in the range of 10 to 60 MW, a single reactor can provide heat and power for a sizeable human base plus mining operations, as well as electromagnetic launchers to deliver payloads into orbit. Water harvested from polar craters can be shipped to any orbit. Greenhouses on the Moon can become the breadbasket to the Solar System. Electric power can be delivered over transmission lines, or via wireless power transfer to a variety of loads such as rovers, orbiting spacecraft, and even multiple habitats. With no nuclear materials needing to be launched from the earth’s surface, and with relatively short-lived hot waste, this is a pathway to the long duration settlement of the Moon.
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    Nuclear Thermal Rocket with Fissile and Reaction Fuel from Lunar ISRU
    (International Astronautical Federation, 2020) Schubert, Peter J.; Daniel, Ebin; Conaway, Adam; Bhaskaran, Amal; Electrical and Computer Engineering, School of Engineering and Technology
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    Ultra-safe nuclear thermal rockets using lunar-derived fuel
    (Elsevier, 2021-09-01) Schubert, Peter J.; Marrs, Ian; Daniel, Ebin; Conaway, Adam; Bhaskaran, Amal; Electrical and Computer Engineering, School of Engineering and Technology
    Rocket launch failure rate is slightly higher than five percent. Concerned citizens are likely to protest against private-sector launches involving fission reactors. Yet, fission reactors can power long-duration lunar operations for science, observation, and in situ resource utilization. Furthermore, fission reactors are needed for rapid transport around the solar system, especially considering natural radiation doses for crews visiting Mars or an asteroid. A novel approach is to create nuclear fuel on the Moon. In this way, a rocket launched from the earth with no radioactive material can be fueled in outer space, avoiding the risks of spreading uranium across Earth's biosphere. A solution is to harvest fertile thorium on the lunar surface, then transmute it into fissile uranium using the gamma ray fog which pervades the deep sky. It is only at lunar orbit, at the very edge of cislunar space, that the Earth-launched machine becomes a nuclear thermal rocket (NTR). Thorium is not abundant, but can be concentrated by mechanical methods because of its very high specific density relative to the bulk of lunar regolith. Thorium dioxide (ThO2) has an extremely high melting point, such that skull crucible heating can be used to separate it from supernatant magma. When filled into a graphite-lined beryllium container (brought from Earth) and set out on the lunar surface, high-energy gamma rays will liberate neutrons from the Be. After moderation by the graphite, these thermal neutrons are captured by the thorium nucleus, which is transmuted into protactinium (Pa91). This element can be extracted using the THOREX process, and will then decay naturally into U-233 within two or three lunar days. The uranium is oxidized and packed into fuel pellets, ready to be inserted into a non-radioactive machine, which now becomes an NTR. Additionally, hydrogen can be extracted from deposits in permanently-shadowed regions on the Moon, providing reaction mass for the NTR. A novel method of solid-state hydrogen storage, which can be entirely fabricated using in situ resources, can deliver said hydrogen to the fission reactor to provide high and efficient propulsive thrust. These combined operations lead to an ultra-safe (for the Earth) means for private sector, commercial transport and power generation throughout the Solar System. With the hydrogen storage material used as radiation shielding for crewed spacecraft, and greatly-reduced transit times relative to chemical rocketry, this innovative approach could fundamentally transform how humans work, play, and explore in outer space.