Clay S.B.,U.S. Air force |
Knoth P.M.,Sierra Lobo, Inc.
Journal of Composite Materials | Year: 2017
The Air Force Research Laboratory led a research effort to benchmark the accuracy of static and fatigue predictions of several emerging composite progressive damage analysis techniques. The static portion of this technical effort is described in detail in a previous special issue of the Journal of Composite Materials. This paper provides the details of the fatigue experiments that were conducted to calibrate and validate the computational models. Initially, in-plane and out-of-plane S–N curves were generated through coupon tests that were performed on unidirectional laminae. The challenges experienced during fatigue testing of in-plane, matrix-dominated unidirectional coupon specimens are presented in detail. The higher fidelity test data from the fiber-dominated and out-of-plane experiments are also included in this paper. Following the calibration experiments, a series of tension–tension fatigue validation tests were conducted on open-hole coupons with three different stacking sequences. Each specimen was cycled to a pre-determined number of fatigue cycles, followed by static residual strength tests in both tension and compression. This paper provides the stress–strain responses of these validation tests as well as high-resolution X-ray computed tomography images of the subsurface damage as a function of cycles. Seven analysis teams used these test results to calibrate their models and to benchmark the accuracy of their predictions of damage and residual mechanical properties. © 2016, © The Author(s) 2016.
Clay S.B.,U.S. Air force |
Knoth P.M.,Sierra Lobo, Inc.
Journal of Composite Materials | Year: 2017
The Air Force Research Laboratory directed a research program to evaluate nine different composite progressive damage analysis methods under both quasi-static and fatigue loading. This paper describes the coupon tests that were performed at the Air Force Research Laboratory for calibration and validation of the methods under quasi-static conditions. The basic elastic and failure properties of unidirectional IM7/977-3 graphite/epoxy were first determined in order to properly calibrate the models. Validation tests were then performed on unnotched and open-hole coupons with three different laminate stacking sequences under both tension and compression loading conditions. This paper summarizes these experimental results and provides X-ray computed tomography images at subcritical load levels. © 2016 SAGE Publications.
Nawaz A.,Sierra Lobo, Inc. |
Santos J.A.,Sierra Lobo, Inc.
10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference | Year: 2010
Slug calorimeters are routinely used for characterization of arc-jet plasma conditions at NASA Ames Research Center facilities. The current model for evaluation of the temperature data from these measurements assumes no thermal losses when calculating incident heat flux. In order to investigate the importance of the losses, three different methods of evaluating slug calorimeter measurements are compared. The three methods were ASTM standard E 457-96, a finite element model and an analytical model. The latter two account for thermal losses, whereas the ASTM standard does not. In this study, data from arc jet tests, and, from a radiant heat source in a laboratory setting are evaluated. For the radiant heat source, the heat flux reaching the slug calorimeter was measured with a Kendall electric substitution radiometer with calibration traceable to National Institute of Standards and Technology (NIST). The results from all three methods of data analysis were compared to the value recorded by the electric substitution radiometer, which provides an absolute measurement of incident radiative heat flux. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.96K | Year: 2013
The proposed load-bearing, tank-applied, multi-layer insulation system consists of a set of highly reflective radiation shields made from 1 mil thick aluminized Mylar that is supported from a "pop-up tent like" support frame. In addition, the support frame carries the mass of an actively cooled shield and outer MLI blanket enabling ultra low heat leak storage of cryogenic fluids. The support frame is conveniently mounted to the top and bottom center tank penetrations, eliminating any direct supports to the cryogen tank itself, which reduces the heat leak to near the theoretical minimum. The novel design approach is significantly better than conventional MLI, which does not possess the required structural or thermal capabilities required. The technical approach is to integrate low-risk, high Technology Readiness Level (TRL) (TRL 7-9) components into a new and unique low-cost, light-weight, high-strength, thermally efficient MLI system. This approach enables the system to meet and exceed all requirements for reduced heat leak, low-mass, and high strength to withstand flight loads. The NASA Cryogenic Propellant Storage and Transfer Program will directly benefit from the development of the proposed MLI system.
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase II | Award Amount: 729.96K | Year: 2011
High-g testing through controlled deceleration has proven to be a key to the successful development of electronics that must survive gun launch. The need for this type of testing is expected to continue as the Army is driven to greater precision to reduce collateral damage, with several programs pursuing advanced Precision Guided Munitions (PGMs) and improved fuzing technology. The objective of this project is to develop Sierra Lobo"s magnetic capture technology to produce controlled deceleration events that meet the needs of the PGM test programs. Magnetic capture has the advantages of simplicity, low maintenance costs, high repetition rates, and predictable performance. This technology can improve the fidelity of testing and expand its applicability by enabling a deceleration profile to be conveniently programmed. In Phase I, modeling was used to verify applicability of the technology to the Army Research Laboratory"s (ARL"s) requirements, and a setup for developmental testing was designed and fabricated. During Phase II a magnetic capture system will be delivered to ARL. Extensive testing of the system before delivery will generate refined operating procedures that minimize both operating costs and the time that personnel must spend preparing for high-g simulations.
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010
The ability to restore large amounts of vented gaseous helium (GHe) at rocket test sites preserves the GHe and reduces operating cost. The used GHe is vented into the atmosphere, is non-recoverable, and costs NASA millions dollars per year. Helium, which is non-renewable and irreplaceable once released into the atmosphere, is continuously consumed by rocket test facilities at NASA centers such as KSC, SSC, and CCAFS at a rate of more than 6.6 Mscf per year. This use is projected to increase to more than 10 Mscf by the year 2018, assuming the same inefficient and costly operating procedures and facilities continue to be used. Given the decrease in the world's supply of helium, NASA is heading toward to an economic, operational, and programmatic disaster. New and highly innovative approaches are required to drive down launch operation life cycle costs. Scaling-up of existing systems to meet an increased demand of helium is not an option. Our team, Sierra Lobo, Inc. and University of Hawaii at Manao, proposes the use of PEM fuel cells to remove most of the impure oxygen and hydrogen in the helium gas stream. The small traces of oxygen and hydrogen impurities in the GHe will be removed by cryo-separation using commercial cryocoolers.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 94.48K | Year: 2011
NASA has identified in-space cryogenic fluid management (CFM) as a high priority for technology development because the construction of an in-space propellant infrastructure is anticipated to dramatically decrease costs across a broad spectrum of missions. This importance is reflected in the designation of CFM as a Flagship Technology Demonstration Mission (FTD-2) as well as a mission at the level of Crosscutting Technologies (CRYOTE). Sierra Lobo proposes to develop a CFM testbed at the scale of an Edison Demonstration Mission (CryoCube) that would serve as a platform for a series of flight tests of many major CFM technologies. The missions will be designed to be conducted as stand-alone satellites, without reliance on propellant transfer from an upper stage, in order to provide the greatest possible flexibility for launch vehicle selection. Follow-up missions using dedicated small satellite launch vehicles could take advantage of the technology demonstrated during this SBIR program, and could be performed as funding becomes available instead of depending on the allocation in a large block.
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 79.89K | Year: 2012
The Navy has stated a need for a backup cryogenic cooling method for shipboard superconducting systems. The cooling method must be as compact as practical and should operate without consumables even if power is lost for an extended period. Ideally, the backup cooling method should take advantage of the energy associated with a phase change. One known compound has a solid-to-liquid phase transition within the temperature range of interest (at 77 K) and remains a liquid up to and above room temperature. The compound presents no unusual hazards and is commercially available. Despite its apparent promise, the compound has not been previously explored for use in cryogenic applications. Sierra Lobo proposes to develop a backup Cryogenic Cooling Unit (CCU) using the compound. In the CCU, the energy storage medium is completely enclosed, does not need replenishment, and is storable at atmospheric pressure at room temperature. While power is available, helium gas is cooled to cryogenic temperatures by a dedicated cryocooler and circulated through tubes embedded in the energy storage medium. When power is lost, valves switch the flow through the heat exchanger from the dedicated cryocooler to the superconducting equipment"s cooling loop to deliver cooling power.
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase II | Award Amount: 674.94K | Year: 2011
GHe reclamation is critical in reducing operating costs at rocket engine test facilities. Increases in cost and shortages of helium will dramatically impact testing of rocket engines for launch vehicles and space propulsion systems as the global supply of this non-renewable element diminishes. Extremely large quantities of helium are being used during rocket engine testing each year at various test facilities. It is critical for program successes to minimize developmental and testing costs by reclaiming helium utilized in those programs and, equally important, to preserve this rare element for future generations. Phase I innovative solution efforts have proven the effectiveness of utilizing hydrogen (H2) Proton Exchange Membrane Electrochemical Cell (PEMEC) technology to purify an inert gas stream of helium (He) consisting of hydrogen contaminants in a cost-effective manner. This method allows in-situ, on-site helium re-utilization, returning the helium to cleanliness standards required for rocket engine test facility use. Phase I identified the challenges for dilute hydrogen operation of the PEMEC and provided viable solutions for improved efficiency, which allows the PEMEC's to provide high purity, 99.995% helium. Phase I also identified a possible configuration in which the exit stream of H2 can be added to a fuel cell operating in the galvanic mode to provide power back to the GHe reclamation system. Although Phase II efforts will not utilize that configuration, Phase I verified its feasibility and future system growth potential. Phase II efforts will build upon all the results of Phase I to deliver a fully functional prototype system for further evaluation in an operational environment. Technology Readiness Level (TRL) at the end of Phase I was five (5), while phase II will progress that level to six (6): System/subsystem model or prototype demonstration in a relevant environment.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 125.00K | Year: 2013
Sierra Lobo proposes to develop a technology that can provide both cooling and electric power generation using heat. When coupled with a radioisotope heat source, the technology is ideally suited to the needs of a long-lived Venus lander. The heat source powers Sierra Lobo's Thermoacoustic Stirling Heat Engine (TASHE), which is directly coupled to a Pulse Tube Refrigerator (PTR) in a duplex configuration. A linear alternator, also directly coupled, generates electricity. This configuration reduces the number of energy conversion processes and thus maximizes efficiency. The PTR cools a space called the coldbay that houses the linear alternator and scientific instruments. The only moving parts in the system are free pistons that tune the resonant frequency, which operate at Venus-ambient temperature, and the linear alternators that operate near Earth-ambient temperature.The system can potentially be used with the gas from the atmosphere of Venus, which is primarily composed of CO2, as a working fluid. This provides two key advantages: (1) The system can make the transit to Venus in a low-pressure state, which significantly decreases system mass, and (2) the effect of leakage during operation is minimized, providing confidence in long mission lifetime.