عنوان مقاله [English]
The principle goal of this paper is to present a methodology for a reliability based launch vehicle conceptual design (RLVCD). In this design methodology, launch vehicle reliability is determined based on customer needs. Then, a
multiple weighted criterion method, called the Analytic Hierarchy Process (AHP), is enabled to assess the reliability allocation of a launch vehicle subsystem, based on utilized technology, cost, complexity and operation time.
These criteria are selected to decide about the optimum reliability of each individual subsystem, such that the reliability goal of the launch vehicle can be achieved. This is a logical approach, because system reliability is the
product of subsystem reliabilities, and, therefore, if they are optimized and compatible, with respect to the mentioned criteria, system reliability will also be optimized and compatible. The aforementioned method utilizes the link
between the MATLAB code (evaluation of the inconsistency index of a matrix based on Eigen vector) and the EXCEL sheet (creation of the compared matrix of objective function, compared matrix of criterion and compared matrix of
alternative). In the RLVCD methodology, the Monte Carlo method is applied to launch vehicle reliability analysis and will also validate the launch vehicle subsystem reliability allocation. So, in the developed algorithm, mass-energy
coefficients and technology selection are affected by subsystem allocated reliability using a statistical process. In this paper, only the effect of engine modification in the design process on launch vehicle ballistic parameters will be considered, due to several problems, such as lack of data about other subsystems. There are some sub-cycles in the reliability based conceptual design of the launch vehicle, in which the algorithm iterates to meet the design requirements. Consequently, the RLVCD methodology is applied to an existing launch vehicle with different reliability. The obtained results show that the suggested methodology is an efficient method for reliability based design in the conceptual design phase.