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Dankanich J.W.,Gray Research Inc. | Patterson M.J.,NASA
47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2011 | Year: 2011

Electric propulsion thrusters with specific impulses from 1000s to 4000s are of interest for various mission applications. Mass constrained missions desire higher specific impulses, while time constrained GEO missions will optimize towards lower specific impulse and a higher thrust-to-power ratio. In the range of 1000 - 4000s specific impulse, thrusters are typically Hall thrusters for the higher thrust-to-power and gridded-ion engines for higher specific impulse. Mission flexibility can be increased by a thruster with a range of operability while maintaining high efficiency. A Dual-Mode Hybrid engine can provide mission flexibility with a single device providing either shorter transfer times or higher delivered mass without system complexities of multiple thruster systems. Dual-Mode Hybrid engine mission performance capabilities are presented herein. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. Source


Smitherman D.,NASA | Griffin B.N.,Gray Research Inc. | Griffin B.N.,Jacobs Engineering
AIAA SPACE 2014 Conference and Exposition | Year: 2014

Future missions under consideration requiring human habitation beyond the International Space Station (ISS) include deep space habitats in the lunar vicinity to support asteroid retrieval missions, human and robotic lunar missions, satellite servicing, and Mars vehicle servicing missions. Habitat designs are also under consideration for missions beyond the Earth-Moon system, including transfers to near-Earth asteroids and Mars orbital destinations. A variety of habitat layouts have been considered, including those derived from the existing ISS designs and those that could be fabricated from the Space Launch System (SLS) propellant tanks. This paper presents a comparison showing several options for asteroid, lunar, and Mars mission habitats using ISS derived and SLS derived modules and identifies some of the advantages and disadvantages inherent in each. Key findings indicate that the larger SLS diameter modules offer built-in compatibility with the launch vehicle, single launch capability without on-orbit assembly, improved radiation protection, lighter structures per unit volume, and sufficient volume to accommodate consumables for long duration missions without resupply. The information provided with the findings includes mass and volume comparison data that should be helpful to future exploration mission planning efforts. Source


Dux I.J.,NASA | Huwaldt J.A.,SAIC | McKamey R.S.,SAIC | Dankanich J.W.,Gray Research Inc.
IEEE Aerospace Conference Proceedings | Year: 2011

The Mars ascent vehicle is a critical element of the robotic Mars sample return mission jointly planned by NASA and ESA. The Mars ascent vehicle must be developed to survive a variety of conditions including the trans-Mars journey, descent through the Martian atmosphere and the harsh Martian surface environments while maintaining the ability to deliver its payload to a low Mars orbit. The primary technology challenge of developing the Mars ascent vehicle system is designing for expected conditions while ensuring the mass limitations of the entry descent and landing system are not exceeded. The NASA In-Space Propulsion technology project has initiated the development of Mars ascent vehicle technologies with propulsion system performance and launch environments yet to be defined. To support the project's evaluation and development of various technology options the sensitivity of the Mars ascent vehicle gross liftoff mass to engine performance, inert mass, target orbits and launch conditions has been completed with the results presented herein. © 2011 IEEE. Source


Dankanich J.W.,Gray Research Inc. | Dankanich J.W.,NASA
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit | Year: 2010

The use of electric propulsion for near-Earth application has become routine and its capabilities continues to grow. However, there is limited experience with electric propulsion for planetary science missions. Low-thrust trajectory analysis is considered an art more than science with independent analyses producing inconsistent results. Planetary missions often have characteristics counterintuitive to standard ballistic trajectory design. A standard application of subsystem margins with the use of electric propulsion may not be appropriate due to margin associated interdependencies. An introduction to primary electric prolusion thrusters, mission design characteristics associated with low-thrust implementation and application are presented. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source


Dankanich J.W.,Gray Research Inc. | Dankanich J.W.,NASA
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit | Year: 2010

The planetary science of small bodies includes missions for fly-by, rendezvous, and return samples from a diverse set of targets. Asteroids, comets, and deep space objects are found throughout the solar system over a wide range of heliocentric distances, inclinations, and eccentricities. The great diversity of targets and negligible gravity wells limits the use of chemical propulsion to the vast majority of targets. Electric propulsion enables the scientific exploration of several small body targets. The results of studies of small body missions enabled by electric propulsion are presented. Missions are evaluated for feasibility, performance, and propulsion and power system requirements. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

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