One of the standard conditions for solidifying composite propellants consist of hydroxyl terminated poly-butadiene as a binder and ammonium perchlorate as oxidizer, is the curing process for certain time in a certain temperature. On this paper, the motives and reasons for the decreasing of this curing time were studied and discussed. The study and discussion include the productivity, cost, delivery, manpower, and maintenance points of view. By experiments and questionnaire work, it was seen that, all the previous points of view were affected positively. Generally, the productivity of the propellant was increased by 100%, the cost of curing process was decreased by 25% of the previous cost, the man power needed for the process of waiting and recording the readings was decreased by 50%, customer delivery process was fasted by 50% of the previous delivery time, and finally the maintenance processes due to equipment depreciation were improved by 50% from the previous. From the whole point of view, it was seen that, the decreasing of the curing time is very useful for the production of the propellant. Finally, it is observed that the decreasing of the curing time to the half time brought the same properties of the standard curing time, and then it is concluded that the deceasing of the curing time can be applied safely and usefully in the casting production line.
Propellant mixing and casting processes are the most complex and important operations in composite propellants manufacturing. They are affected by the rheological properties of the propellant. Casting process of composite propellants is influenced directly by its pot life. The short pot life of the propellant formulations can result in low reliability and increase the processing cost [1]. The propellant pot life is defined as the time available for accomplishing the processing steps of mixing and casting propellant before the propellant loses its fluid nature [2]. Different methods have been proposed for improving composite propellant process by extending its pot life using some affected chemical materials. This work concentrated on using the well-known antibiotic (tetracycline) to achieve this objective. When tetracycline added to the propellant formulation, the pot life was extended by a considerable time ranged between two and four hours. This extension referred to the solution which tetracycline offered to the problem that occurs from using transition metal materials (ferrocene compounds) in the propellant slurry to improve the burning rate. This addition of ferrocene compounds results in accelerating the curing reaction and so, shorten the pot life of the slurry. Tetracycline has good possibilities for metal complex formation and its activity depends on its metal binding function [3]. Moreover, tetracycline is cheap and available which let its use easier than other materials used for the same purpose. The results obtained from this work can help the manufacturer in filling big rocket motors by use of small mixers by applying the above method of extending the propellant pot life.
Composite propellants are energetic materials have ability to ignite, burn fast and cause several simultaneous exothermic chemical reactions which produce huge amounts of gases under high pressures and temperatures which can spread spontaneously. 1n the present study, the explosive material hexogen (Cyclo tri-methylene tri-nitramine) was used to improve the performance properties of composite propellants, especially the specific impulse. For several formulations of hexogen at different added percentages, the specific impulse was calculated using thermodynamic calculations program of composite propellants. The results given were compared with those formulations not including hexogen. It was seen that; hexogen caused a significant positive effect in the specific impulse. Accordingly, the energy of composite propellant was improved positively in the samples containing hexogen till 40% of the oxidizer ratio. Also, it was noticed that the specific impulse began to decrease gradually for the oxidizers containing more than 40% of hexogen which caused in a decreasing of composite propellant energy. Finally, it was concluded that, the use of some amount of explosive materials like hexogen can improve composite propellants energy successfully.
With the recent advances in technology, smart cities are rapidly earning momentum thanks to the quality of citizens' life that smart cities help improve. To provide better lives, smart cities should host several applications to increase the efficiency and accessibility of services. Since these services involve the conveyance of significant data among the smart cities' cloud and the dwellers over the Internet, security and privacy are critical. This paper proposes an authentication protocol with a full aggregation signature to secure the smart city applications. A certificateless aggregate signature (CLAS) is used for smart city real applications such as secure routing and database outsourcing. The proposed CLAS achieves message authentication, user anonymity, constant signature size, unlinkability, and is resistant to replay attacks. Also, we have proved that the proposed scheme is resistant to all malicious adversaries. Finally, the performance evaluation results show that the proposed CLAS performs better than existing relevant schemes.
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