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  • Astrodynamics  (5)
  • Aeronautics (General)  (4)
  • Computer Systems  (4)
  • 2000-2004  (13)
  • 1960-1964
  • 1
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    A Direct Approach for Minimum Fuel Maneuvers of Distributed Spacecraft in Multiple Flight Regimes (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: In this work we present a method to solve the impulsive minimum fuel maneuver problem for a distributed set of spacecraft. We develop the method assuming a fully non-linear dynamics model and parameterize the problem to allow the method to be applicable to any flight regime. Furthermore, the approach is not limited by the inter-spacecraft separation distances and is applicable to both small formations as well as constellations. We assume that the desired relative motion is driven by mission requirements and has been determined a-priori. The goal of this work is to develop a technique to achieve the desired relative motion in a minimum fuel manner. To permit applicability to multiple flight regimes, we have chosen to parameterize the cost function in terms of the maneuver times expressed in a useful time system and the maneuver locations expressed in their Cartesian vector representations. We also include as an independent variable the initial reference orbit to solve for the optimal injection orbit to minimize and equalize the fuel expenditure of distributed sets of spacecraft with large inter-spacecraft separations. In this work we derive the derivatives of the cost and constraints with respect to all of the independent variables.
    Keywords: Astrodynamics
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  • 2
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    Deploying Object Oriented Data Technology to the Planetary Data System (2003)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: How do you provide more than 350 scientists and researchers access to data from every instrument in Odyssey when the data is curated across half a dozen institutions and in different formats and is too big to mail on a CD-ROM anymore? The Planetary Data System (PDS) faced this exact question. The solution was to use a metadata-based middleware framework developed by the Object Oriented Data Technology task at NASA s Jet Propulsion Laboratory. Using OODT, PDS provided - for the first time ever - data from all mission instruments through a single system immediately upon data delivery.
    Keywords: Computer Systems
    Type: Lunar and Planetary Science XXXIV; LPI-Contrib-1156
    Format: text
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  • 3
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    Optimal Orbit Design for the Magnetospheric Imaging Constellation (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The Magnetospheric Imaging Constellation (MagIC) is a NASA space science concept to study the Earth's Magnetosphere. The concept proposes to apply tomography techniques using an array of spacecraft to obtain three dimensional images of the Earth's magnetosphere. This paper presents an optimal orbit design to ensure that the constellation is in the desired region of the magnetosphere for maximum time. The solution is found using a steepest descent optimization algorithm that takes into account perturbations from the non-spherical Earth, drag, Sun, Moon and other significant bodies. The solution also satisfies constraints on maximum eclipse duration and geometry constraints to allow an adequate GPS navigation solution. We present three solutions depending upon the epoch of the primary science: vernal equinox, summer solstice, and a third midway between the vernal equinox and summer solstice. Orbit insertion is also considered. All spacecraft are assumed to be launched on a single vehicle into a nominal orbit and the (Delta)V's to achieve the nominal orbit are presented. After insertion into the nominal orbit, each spacecraft undergoes a phasing maneuver to place it in the appropriate position with respect to the rest of the constellation. We present a minimum fuel approach to maneuver each spacecraft from the nominal orbit into the desired final orbit.
    Keywords: Astrodynamics
    Type: 16th International Symposium on Space Flight Dynamics; Pasadena, CA; United States
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  • 4
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    A Preliminary Formation Flying Orbit Dynamics Analysis for Leonardo-BRDF (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: Leonardo-BRDF is a NASA mission concept proposed to allow the investigation of radiative transfer and its effect on the Earth's climate and atmospheric phenomenon. Enabled by the recent developments in small-satellite and formation flying technology, the mission is envisioned to be composed of an array of spacecraft in carefully designed orbits. The different perspectives provided by a distributed array of spacecraft offer a unique advantage to study the Earth's albedo. This paper presents the orbit dynamics analysis performed in the context of the Leonardo-BRDF science requirements. First, the albedo integral is investigated and the effect of viewing geometry on science return is studied. The method used in this paper, based on Gauss quadrature, provides the optimal formation geometry to ensure that the value of the integral is accurately approximated. An orbit design approach is presented to achieve specific relative orbit geometries while simultaneously satisfying orbit dynamics constraints to reduce formation-keeping fuel expenditure. The relative geometry afforded by the design is discussed in terms of mission requirements. An optimal two-burn initialization scheme is presented with the required delta-V to distribute all spacecraft from a common parking orbit into their appropriate orbits in the formation. Finally, formation-keeping strategies are developed and the associated delta-V's are calculated to maintain the formation in the presence of perturbations.
    Keywords: Astrodynamics
    Type: 2001 Flight Mechanics Symposium; 131; NASA/CP-2001-209986
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  • 5
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    A General Overview of the Data Acquisition and Controls Systems (DACS) of the E-Complex at NASA's Stennis Space Center (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The John C. Stennis Space Center (SSC) provides test operations services to a variety of customers, including NASA, DoD, and commercial enterprises for the development of current and next-generation rocket propulsion systems. Many of these testing services are provided in the E-Complex test facilities composed of three active test stands (E1, E2, & E3) and 7 total test positions. Each test position is outfitted with unique sets of data acquisition and controls hardware and software that record both facility and test article data and enable safe operation of the test facility. This paper addresses each system in more detail including efforts to upgrade hardware and software.
    Keywords: Computer Systems
    Type: SSTI-2003-10-00099 , AIAA Paper 2004-2489 , AIAA Aerodynamic Measurement Technology and Ground Testing Conference; Jun 28, 2004 - Jul 01, 2004; Portland, OR; United States
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  • 6
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    Optimal Reconfiguration of Tetrahedral Formations (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The problem of minimum-fuel formation reconfiguration for the Magnetospheric Multi-Scale (MMS) mission is studied. This reconfiguration trajectory optimization problem can be posed as a nonlinear optimal control problem. In this research, this optimal control problem is solved using a spectral collocation method called the Gauss pseudospectral method. The objective of this research is to provide highly accurate minimum-fuel solutions to the MMS formation reconfiguration problem and to gain insight into the underlying structure of fuel-optimal trajectories.
    Keywords: Astrodynamics
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  • 7
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    Steady and Unsteady Flow Field Measurements Within a NASA 22-Inch Fan Model (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Results are presented of an experiment conducted to investigate possible sources of fan noise in the flow developed by a 22-in. (55.9 cm) diameter turbofan model. Flow diagnostic data were acquired to identify possible sources of both tone and broadband noise. Laser Doppler velocimetry was used to characterize the tip flows that develop within the rotor blade passages, the wake flow downstream of the rotor, and the shock waves that develop on the blades when operated at transonic relative tip speeds. Single-point hot-wire measurements were made in the rotor wake to determine the frequency content and the length scales of the flow unsteadiness. The results document the changes in the rotor wake flow with both rotor speed and axial distance downstream of the rotor. The data also show the tip flow development within the blade passage, its migration downstream, and (at high rotor speeds) its merging with the blade wake of the following blade. Data also depict the variation of the tip flow with tip clearance. LDV data obtained within the blade passages at high rotor speeds illustrate the passage-to-passage variation of the mean shock position. Spectra computed from the single-point hot-wire measurements illustrate how the energy in the flow oscillations is split between periodic and random components, and how this split varies with both radial and axial position in the rotor wake.
    Keywords: Aeronautics (General)
    Type: NASA/TM-2003-212329 , NAS 1.15:212329 , E-13924 , AIAA Paper 2002-1033 , 40th Aerospace Sciences Meeting and Exhibit; Jan 14, 2003 - Jan 17, 2003; Reno, NV; United States
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  • 8
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    Fan Noise Source Diagnostic Test: LDV Measured Flow Field Results (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Results are presented of an experiment conducted to investigate potential sources of noise in the flow developed by two 22-in. diameter turbofan models. The R4 and M5 rotors that were tested were designed to operate at nominal take-off speeds of 12,657 and 14,064 RPMC, respectively. Both fans were tested with a common set of swept stators installed downstream of the rotors. Detailed measurements of the flows generated by the two were made using a laser Doppler velocimeter system. The wake flows generated by the two rotors are illustrated through a series of contour plots. These show that the two wake flows are quite different, especially in the tip region. These data are used to explain some of the differences in the rotor/stator interaction noise generated by the two fan stages. In addition to these wake data, measurements were also made in the R4 rotor blade passages. These results illustrate the tip flow development within the blade passages, its migration downstream, and (at high rotor speeds) its merging with the blade wake of the adjacent (following) blade. Data also depict the variation of this tip flow with tip clearance. Data obtained within the rotor blade passages at high rotational speeds illustrate the variation of the mean shock position across the different blade passages.
    Keywords: Aeronautics (General)
    Type: NASA/TM-2003-212330 , E-13925 , NAS 1.15:212330 , AIAA Paper 2002-2431 , Eight Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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  • 9
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    Acoustic Benefits of Stator Sweep and Lean for a High Tip Speed Fan (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A model high-speed fan stage was acoustically tested in the NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel at takeoff/approach flight conditions. The fan was designed for a corrected rotor tip speed of 442 m/s (1450 ft/s), and had a powered core, or booster stage, giving the model a nominal bypass ratio of 5. The model also had a simulated engine pylon and nozzle bifurcation contained within the bypass duct. The fan was tested with three stator sets to evaluate acoustic benefits associated with a swept and leaned stator and with a swept integral vane/frame stator which incorporated some of the swept and leaned features as well as eliminated some of the downstream support structure. The baseline fan with the wide chord rotor and baseline stator approximated a current GEAE CF6 engine. A flyover effective perceived noise level (EPNL) code was used to generate relative EPNL values for the various configurations. Flyover effective perceived noise levels (EPNL) were computed from the model data to help project noise benefits. A tone removal study was also performed. The swept and leaned stator showed a 3 EPNdB reduction at lower fan speeds relative to the baseline stator; while the swept integral vane/frame stator showed lowest noise levels at intermediate fan speeds. Removal of the bypass blade passage frequency rotor tone (BPF) showed a 4 EPNdB reduction for the baseline and swept and leaned stators, and a 6 EPNdB reduction for the swept integral vane/ frame stator. Therefore, selective tone removal techniques such as active noise control and/or tuned liner could be particularly effective in reducing noise levels for certain fan speeds.
    Keywords: Aeronautics (General)
    Type: NASA/TM-2002-211345 , E-13143 , NAS 1.15:211345 , AIAA Paper 2002-1034 , 40th Aerospace Sciences Meeting and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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  • 10
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    A Distributed Data Architecture for 2001 Mars Odyssey Data Distribution (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Newer instruments and communications techniques have given scientists unprecedented amounts of data, more than can be feasibly distributed through traditional methods such as mailed CD-ROM's. Leveraging the web makes sense since it enables scientists to request specific data and retrieve products as soon as they're available. Yet defining the middleware system to support such an application has remained just out of reach, until Odyssey. For the first time ever, data from all Odyssey mission instruments were made available through a single system immediately upon delivery to the Planetary Data System (PDS). The Object Oriented Data Technology (OODT) software made such an application possible.
    Keywords: Computer Systems
    Type: International Conference on Space Mission Challenges for Information Technology; Jul 13, 2003 - Jul 16, 2003; Pasadena, CA; United States
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