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  • Infinite server  (3)
  • Launch Vehicles and Launch Operations  (3)
  • 1
    Publication Date: 2019-08-13
    Description: The Ares I-X modal test program consisted of three modal tests conducted at the Vehicle Assembly Building at NASA s Kennedy Space Center. The first test was performed on the 71-foot 53,000-pound top segment of the Ares I-X launch vehicle known as Super Stack 5 and the second test was performed on the 66-foot 146,000- pound middle segment known as Super Stack 1. For these tests, two 250 lb-peak electro-dynamic shakers were used to excite bending and shell modes with the test articles resting on the floor. The third modal test was performed on the 327-foot 1,800,000-pound Ares I-X launch vehicle mounted to the Mobile Launcher Platform. The excitation for this test consisted of four 1000+ lb-peak hydraulic shakers arranged to excite the vehicle s cantilevered bending modes. Because the frequencies of interest for these modal tests ranged from 0.02 to 30 Hz, high sensitivity capacitive accelerometers were used. Excitation techniques included impact, burst random, pure random, and force controlled sine sweep. This paper provides the test details for the companion papers covering the Ares I-X finite element model calibration process. Topics to be discussed include test setups, procedures, measurements, data quality assessments, and consistency of modal parameter estimates.
    Keywords: Launch Vehicles and Launch Operations
    Type: LF99-9048 , NF1676L-10470 , 57th JANNAF Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|IMAC-XXVIII Conference and Exposition on Structural Dynamics; Feb 01, 2010 - Feb 04, 2010; Jacksonville, FL; United States
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  • 2
    Publication Date: 2019-08-13
    Description: The first test flight of NASA's Ares I crew launch vehicle, called Ares I-X, is scheduled for launch in 2009. Ares IX will use a 4-segment reusable solid rocket booster from the Space Shuttle heritage with mass simulators for the 5th segment, upper stage, crew module and launch abort system. Flight test data will provide important information on ascent loads, vehicle control, separation, and first stage reentry dynamics. As part of hardware verification, a series of modal tests were designed to verify the dynamic finite element model (FEM) used in loads assessments and flight control evaluations. Based on flight control system studies, the critical modes were the first three free-free bending mode pairs. Since a test of the free-free vehicle is not practical within project constraints, modal tests for several configurations in the nominal integration flow were defined to calibrate the FEM. A traceability study by Aerospace Corporation was used to identify the critical modes for the tested configurations. Test configurations included two partial stacks and the full Ares I-X launch vehicle on the Mobile Launcher Platform. This paper provides an overview for companion papers in the Ares I-X Modal Test Session. The requirements flow down, pre-test analysis, constraints and overall test planning are described.
    Keywords: Launch Vehicles and Launch Operations
    Type: LF99-9055 , NF-1676L-10483 , 57th JANNAF Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|IMAC-XXVIII Conference and Exposition on Structural Dynamics; Feb 01, 2010 - Feb 04, 2010; Jacksonville, FL; United States
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  • 3
    Publication Date: 2019-07-13
    Description: Ares I-X is a pathfinder vehicle concept under development by NASA to demonstrate a new class of launch vehicles. Although this vehicle is essentially a shell of what the Ares I vehicle will be, efforts are underway to model and calibrate the analytical models before its maiden flight. Work reported in this document will summarize the model calibration approach used including uncertainty quantification of vehicle responses and the use of nonconventional boundary conditions during component testing. Since finite element modeling is the primary modeling tool, the calibration process uses these models, often developed by different groups, to assess model deficiencies and to update parameters to reconcile test with predictions. Data for two major component tests and the flight vehicle are presented along with the calibration results. For calibration, sensitivity analysis is conducted using Analysis of Variance (ANOVA). To reduce the computational burden associated with ANOVA calculations, response surface models are used in lieu of computationally intensive finite element solutions. From the sensitivity studies, parameter importance is assessed as a function of frequency. In addition, the work presents an approach to evaluate the probability that a parameter set exists to reconcile test with analysis. Comparisons of pre-test predictions of frequency response uncertainty bounds with measured data, results from the variance-based sensitivity analysis, and results from component test models with calibrated boundary stiffness models are all presented.
    Keywords: Launch Vehicles and Launch Operations
    Type: LF99-9680 , IMAC-XXVIII Conference and Exposition on Structural Dynamics; Feb 01, 2010 - Feb 04, 2010; Jacksonville, FL; United States
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 8 (1991), S. 323-356 
    ISSN: 1572-9443
    Keywords: Infinite server ; batch arrival ; Markov renewal input ; customer dependence ; analytical result
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract An important property of most infinite server systems is that customers are independent of each other once they enter the system. Though this non-interacting property (NIP) has been instrumental in facilitating excellent results for infinite server systems in the past, the utility of this property has not been fully exploited or even fully recognized. This paper exploits theNIP by investigating a general infinite server system with batch arrivals following a Markov renewal input process. The batch sizes and service times depend on the customer types which are regulated by the Markov renewal process. By conditional approaches, analytical results are obtained for the generating functions and binomial moments of both the continuous time system size and pre-arrival system size. These results extend the previous results on infinite server queues significantly.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 22 (1996), S. 129-144 
    ISSN: 1572-9443
    Keywords: Infinite server ; batch arrival ; batch service ; analytical results
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Service systems with queueing often have both batch arrivals and batch services. This paper focuses on the number of busy servers and waiting customers in theGI X/MR/∞ system. For the number of busy servers, we obtain a recursive relation for the partial binomial moments in terms of matrices and explicit expressions for the marginal binomial moments. Special cases are also discussed to provide a more heuristic understanding of the model.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 2 (1987), S. 363-372 
    ISSN: 1572-9443
    Keywords: Infinite server ; impatient customers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract An infinite server queue is considered where customers have a choice of individual service or batch service. Transient results have been obtained for the first two moments of the system size distribution. Waiting time distribution is important in system evaluation and steady state results are obtained.
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