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| Fig. 1: Concept design for the Lunar Orbital Module working in tandem with its constituent components. (Courtesy of NASA. Source: Wikimedia Commons) |
With increasing advancements in efficient and innovative technologies, mankind continues looking at methods to expand its frontier into deep space to establish better scientific understanding of the universe and some of the fundamental properties that govern it. Thus, being a leading pioneer in extraterrestrial discoveries, NASA looks towards their next research breakthrough with the establishment of their proposed Lunar Orbital Platform-Gateway (LOP-G) visually rendered as a whole mechanism in Fig. 1.
Already planned for several individual module launches by 2020, the system will exist in high lunar orbit above the poles of the Moon in support of crew visits, scientific experiments, and eventually exploration into the depths of space as far as Mars.
Given the incredibly imperative and complex conditions that must be met, the LOP-G is compromised of several subsystems each with its own specialized purpose to help achieve the overall goal of both reliable and efficient space exploration. The system is essentially divided into two major components: an outpost station, the Gateway itself, which will exist as a passive celestial vehicle comparable to the ISS, working in tandem with the agency's Space Launch System (SLS) and Orion deep-space capsule, an inbound station for two way visits and deployment. The outpost station thus looks to be a versatile rendezvous point for any type of aspiring research across various nations, institutions, etc; offering such lofty capabilities, the Gateway is proposed with components such as robotic arm, a crew habitat module and airlock, and many other features with the consequential success of each new launch. [1] However, quite possibly the most notable aspect to the outpost station is the Power Propulsion Element (PPE) which acts as the module to actively transport between the SSL-Orion Capsule and the Gateway itself. Given the inherent expensive nature of deploying astronauts to this deep lunar orbit, the propulsion system demands a higher order of efficiency and sustainability than the average propulsion units.
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| Fig. 2: Concept design as proposed by NASA for the PPE system. (Courtesy of NASA. Source: Wikimedia Commons) |
While looking to innovate the way in which human beings can explore space, the necessary units and hardware to achieve that process have already been implemented into heritage parts. The costly and ineffective means of typical combustion engines in combination with their resultant toxic pollutants have steadily begun to lose traction as a viable means of energy over the years with a heavy emphasis shift on electric propulsion for vehicles. Rendered visually in Fig. 2, the PPE looks to be the first of the launched components to the system by the mid 2020's to "mark the first use of ion propulsion to meet the primary propulsion requirements of a solar system exploration mission and will usher in a new era in the application of advanced propulsion for deep-space missions." [2] Given the fact the PPE sits at the core of the Gateway's success, this latter main technology integrated into the spacecraft is based off of heritage solar electric propulsion (SEP) units being developed by the NSTAR, a NASA SEP program, based off of NASAs 30-cm diameter xenon ion engine. With a 15-year lifespan, this unit can ensure input power of each NSTAR power processor unit (PPU) varying from a maximum of 2.5 kW to a minimum of 0.6 kW during thruster operation with each thruster initially carrying 83 kg of xenon. [2] With a sustainable power source to readily propel man to the moon, lofty ventures for colonization of planets like Mars and understanding the affects of space environment become increasingly easier.
Solar electric propulsion takes advantage of magnetism and electricity to push a ship through space. The PPE, utilizing monopropellant hydrazine, generates electricity from the solar power accumulated from the solar panels producing a positive ionized electric charge of atoms inside of the chamber. With SEP technology, energy is fed to the thrusters with advanced magnetic shielding that pull this ionized propellant back through the engine to be provided as thrust that exits as an exhaust plume of plasma propelling the spacecraft forward. With this new wave technology, the goals of deep space exploration are much closer for man than ever imagined.
© William Mangram. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Gateway Memorandum for the Record," U.S. National Aeronautics and Space Administration, 2 May 18.
[2] J. R. Brophy and M. Noca, "Electric Propulsion for Solar System Exploration," J. Propul. Power 14, 700 (1998).
