Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 5 Articles
The author reviews the state of art of nonrocket launch assistance systems (LASs) for spaceflight focusing on air launch options.\r\nThe author proposes an alternative technologically feasible LAS based on a combination of approaches: air launch, high-altitude\r\nballoon, and tethered LAS. Proposed LAS can be implemented with the existing off-the-shelf hardware delivering 7 kg to low-earth\r\norbit for the 5200 USD per kg. Proposed design can deliver larger reduction in price and larger orbital payloads with the future\r\nadvances in the aerostats, ropes, electrical motors, and terrestrial power networks....
Aircraft routinely operate in atmospheric environments that, over time, will impact their structural integrity. Material protection\r\nand selection schemes notwithstanding, recurrent exposure to chlorides, pollution, temperature gradients, and moisture provide\r\nthe necessary electrochemical conditions for the development and profusion of corrosion in aircraft structures. For aircraft\r\noperators, this becomes an important safety matter as corrosion found in a given aircraft must be assumed to be present in all\r\nof that type of aircraft. This safety protocol and its associated unscheduled maintenance requirement drive up the operational\r\ncosts of the fleet and limit the availability of the aircraft. Hence, there is an opportunity at present for developing novel sensing\r\ntechnologies and schemes to aid in shifting time-based maintenance schedules towards condition-based maintenance procedures.\r\nIn this work, part of the ongoing development of a multiparameter integrated corrosion sensor is presented. It consists of carbon\r\nnanotube/polyaniline polymer sensors and commercial-off-the-shelf sensors. It is being developed primarily for monitoring\r\nenvironmental and material factors for the purpose of providing a means to more accurately assess the structural integrity of\r\naerospace aluminium alloys through fusion of multiparameter sensor data. Preliminary experimental test results are presented for\r\nchloride ion concentration, hydrogen gas evolution, humidity variations, and material degradation....
In the first section of this work, a suitable data reduction scheme is developed to measure the adhesive joints strain energy release\r\nrate under pure mode-I loading, and in the second section, three types of adhesive hybrid lap-joints, that is, Aluminum-GFRP\r\n(Glass Fiber Reinforced Plastic), GFRP-GFRP, and Steel-GFRP were employed in the determination of adhesive hybrid joints\r\nstrengths and failures that occur at these assemblies under tension loading. To achieve the aims, Double Cantilever Beam (DCB)\r\nwas used to evaluate the fracture state under the mode-I loading (opening mode) and also hybrid lap-joint was employed to\r\ninvestigate the failure load and strength of bonded joints. The finite-element study was carried out to understand the stress intensity\r\nfactors in DCB test to account fracture toughness using J-integral method as a useful tool for predicting crack failures. In the\r\ncase of hybrid lap-joint tests, a numerical modeling was also performed to determine the adhesive stress distribution and stress\r\nconcentrations in the side of lap-joint. Results are discussed in terms of their relationship with adhesively bonded joints and thus\r\ncan be used to develop appropriate approaches aimed at using adhesive bonding and extending the lives of adhesively bonded\r\nrepairs for aerospace structures....
The preliminary design of a jet aircraft wing, through the use of an integrated multidisciplinary design environment, is presented\r\nin this paper. A framework for parametric studies of wing structures has been developed on the basis of a multilevel distributed\r\nanalysis architecture with a ââ?¬Å?hybrid strategyââ?¬Â process that is able to perform deterministic optimizations and tradeoff studies\r\nsimultaneously. The particular feature of the proposed multilevel optimization architecture is that it can use different set of\r\nvariables, defined expressly for each level, in a multi-level scheme using ââ?¬Å?low fidelityââ?¬Â and ââ?¬Å?high fidelityââ?¬Â models, as well as\r\nsurrogate models. The prototype of the design environment has been developed using both commercial codes and in-house tools\r\nand it can be implemented in a geographically distributed and heterogeneous IT context....
Ballistic characterization of an extended group of innovative HTPB-based solid fuel formulations for hybrid rocket propulsion\r\nwas performed in a lab-scale burner. An optical time-resolved technique was used to assess the quasisteady regression history\r\nof single perforation, cylindrical samples. The effects of metalized additives and radiant heat transfer on the regression rate of\r\nsuch formulations were assessed. Under the investigated operating conditions and based on phenomenological models from the\r\nliterature, analyses of the collected experimental data show an appreciable influence of the radiant heat flux from burnt gases\r\nand soot for both unloaded and loaded fuel formulations. Pure HTPB regression rate data are satisfactorily reproduced, while the\r\nimpressive initial regression rates of metalized formulations require further assessment....
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