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  • 1
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    Bidirectional Brush Seals: Post-Test Analysis (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A post-test analysis of a set of inside-diameter/outside-diameter (ID/OD) bidirectional brush seals used in three-port wave rotor tests was undertaken to determine brush bristle and configuration wear, pullout, and rotor coating wear. The results suggest that sharp changes in the pressure profiles were not well reflected in bristle tip configuration patterns or wear. Also, positive-to-negative changes in axial pressure gradients appeared to have little effect on the backing plates. Although the brushes had similar porosities, they had very different unpacked arrays. This difference could explain the departure of experimental data from computational fluid dynamics flow predictions for well-packed arrays at higher pressure drops. The rotor wear led to "car-track" scars (upper and lower wear bands) with a whipped surface between the bands. Those bands may have resulted from bristle stiffening at the fence and gap plates during alternate portions of the rotor cycle. Within the bristle response range the wear surface reflected the pressure distribution effect on bristle motion. No sacrificial metallurgical data were taken. The bristles did wear, with correspondingly more wear on the ID brush configurations than on the OD configurations; the complexity in constructing the ID brush was a factor.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA-TM-107501 , E-10803 , NAS 1.15:107501 , International Symposium on Transport Phenomena and Dynamics of Rotating Machinery; Feb 22, 1998 - Feb 26, 1998; Honolulu, HI; United States
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  • 2
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    FFRE Powered Spacecraft (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Describes concept of the Fission Fragment Rocket Engine (FFRE).
    Keywords: Spacecraft Propulsion and Power
    Type: M12-2281 , 2012 Advanced Propulsion Workshop; Nov 27, 2012 - Nov 29, 2012; Huntsville, AL; United States
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  • 3
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    A Nuclear Cryogenic Propulsion Stage for Near-Term Space Missions (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The potential capability of NTP is game changing for space exploration. A first generation NCPS could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Near-term NCPS systems would provide a foundation for the development of significantly more advanced, higher performance systems. John F. Kennedy made his historic special address to Congress on the importance of space on May 25, 1961, "First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth..." This was accomplished. John F. Kennedy also made a second request, "Secondly... accelerate development of the Rover nuclear rocket. This gives promise of some day providing a means for even more exciting and ambitious exploration of space, perhaps beyond the Moon, perhaps to the very end of the solar system itself." The investment in the Rover nuclear rocket program provided the foundation of technology that gives us assurance for greater performing rockets that are capable of taking us further into space. Combined with current technologies, the vision to go beyond the Moon and to the very end of the solar system can be realized with space nuclear propulsion and power.
    Keywords: Spacecraft Propulsion and Power
    Type: Paper 6716 , M13-2393 , Nuclear and Emerging Technologies for Space 2013; Feb 25, 2013 - Feb 28, 2013; Albuquerque, NM; United States
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  • 4
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    Feasibility of Large High-Powered Solar Electric Propulsion Vehicles: Issues and Solutions (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Human exploration beyond low Earth orbit will require the use of enabling technologies that are efficient, affordable, and reliable. Solar electric propulsion (SEP) has been proposed by NASA s Human Exploration Framework Team as an option to achieve human exploration missions to near Earth objects (NEOs) because of its favorable mass efficiency as compared to traditional chemical systems. This paper describes the unique challenges and technology hurdles associated with developing a large high-power SEP vehicle. A subsystem level breakdown of factors contributing to the feasibility of SEP as a platform for future exploration missions to NEOs is presented including overall mission feasibility, trip time variables, propellant management issues, solar array power generation, array structure issues, and other areas that warrant investment in additional technology or engineering development.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA/TM-2012-217275 , AIAA Paper-2011-7251 , E-18030 , Space 2011 Conference and Exposition; Sep 27, 2011 - Sep 29, 2011; Long Beach, CA; United States
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  • 5
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    Metallographic Analysis of Brush Bristle and Integrity Testing of Brush Seal in Shroud Ring of T-700 Engine (1995)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform 'smeared' bristle interface between the first and last axial rows of bristles. Several bristles were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristles near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle with no apparent change within 1 to 2 micron of the interface except for possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA-TM-106361 , ARL-MR-119 , E-8155 , NAS 1.15:106361 , International Symposium on Transport Phenomena and Dynamics of Rotating Machinery; May 08, 1994 - May 11, 1994; Kaanapali, Maui, HI; United States
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  • 6
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    Understanding the Space Shuttle Main Engine Hydraulic Actuation System and Reviewing Its Evolution (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-08-13
    Description: The complex engine start and thrust control requirements of the Space Shuttle Main Engine (SSME) require unique valve, actuator and control system hardware. The Hydraulic Actuation System (HAS) was designed, developed, and now operates to meet tight engine control requirement limits to assure safe, reliable and correct engine thrust at all times. The actuator is designed to be fail safe and fail operate in the areas where redundancy is important. The HAS has an additional pneumatic operating capability that insures a safe sequential closure of all actuators and propellant valves in the event of the loss of hydraulic system pressure or loss of electrical closed loop control of the actuator. The objective of this paper is to provide a complete description of the actuator s internal operating system, along with its interaction with all SSME system interfaces. Additionally the paper addresses the challenges, problems identified, and corrected, and lessons learned, during the course of the almost 35 years of engine operation.
    Keywords: Spacecraft Propulsion and Power
    Type: M10-0229 , 57th JANNAF Joint Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States
    Format: text
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  • 7
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    Identification of mission sensitivities for high-power electric propulsion systems (2005)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper presents the results of mission analyses that expose various mission performance sensitivities and system advantages of the ALFA technology for a small but representative subset of nuclear electric propulsion (NEP) missions considered under NASA's Project Prometheus.
    Keywords: Spacecraft Propulsion and Power
    Type: AIAA Paper 2005-3894 , 41st AIAA Joint Propulsion Conference; Jul 10, 2005 - Jul 13, 2005; Tuscon, AZ; United States
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  • 8
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    Verification of a Multiphysics Toolkit against the Magnetized Target Fusion Concept (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In the spring of 2004 the Advanced Concepts team at MSFC embarked on an ambitious project to develop a suite of modeling routines that would interact with one another. The tools would each numerically model a portion of any advanced propulsion system. The tools were divided by physics categories, hence the name multiphysics toolset. Currently most of the anticipated modeling tools have been created and integrated. Results are given in this paper for both a quarter nozzle with chemically reacting flow and the interaction of two plasma jets representative of a Magnetized Target Fusion device. The results have not been calibrated against real data as of yet, but this paper demonstrates the current capability of the multiphysics tool and planned future enhancements
    Keywords: Spacecraft Propulsion and Power
    Type: AIAA Paper 2005-4 141 , 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 10, 2005 - Jul 13, 2005; Tucson, AZ; United States
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  • 9
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    The role of radiation hard solar cells in minimizing the costs of global satellite communication systems (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: An analysis embodied in a PC computer program is presented, which quantitatively demonstrates how the availability of radiation hard solar cells can help minimize the cost of a global satellite communications system. An important distinction between the currently proposed systems, such as Iridium, Odyssey and Ellipsat, is the number of satellites employed and their operating altitudes. Analysis of the major costs associated with implementing these systems shows that operation at orbital altitudes within the earth's radiation belts (10(exp 3) to 10(exp 4)km) can reduce the total cost of a system by several hundred percent, so long as radiation hard components including solar cells can be used. A detailed evaluation of the predicted performance of photovoltaic arrays using several different planar solar cell technologies is given, including commercially available Si and GaAs/Ge, and InP/Si which is currently under development. Several examples of applying the program are given, which show that the end of life (EOL) power density of different technologies can vary by a factor of ten for certain missions. Therefore, although a relatively radiation-soft technology can usually provide the required EOL power by simply increasing the size of the array, the impact upon the total system budget could be unacceptable, due to increased launch and hardware costs. In aggregate, these factors can account for more than a 10% increase in the total system cost. Since the estimated total costs of proposed global-coverage systems range from $1B to $9B, the availability of radiation-hard solar cells could make a decisive difference in the selection of a particular constellation architecture.
    Keywords: Spacecraft Propulsion and Power
    Type: Space Photovoltaic Research and Technology 1995; 71-79; NASA-CP-3324
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  • 10
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    NASA spacecraft propulsion activities (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The NASA's activities in the development of spacecraft propulsion systems are reviewed, with emphasis on program directions and recent progress made in this domain. The recent trends towards the use of smaller spacecraft and launch vehicles call for new onboard propulsion systems. The NASA's efforts are conducted within the framework of the onboard propulsion program. The research and development work carried out in relation to the different propulsion system technologies are considered: electromagnetic systems; electrostatic systems; electrothermal systems; bipropellant systems; and monopropellant systems.
    Keywords: Spacecraft Propulsion and Power
    Type: ; 35-44
    Format: text
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