Abstract In rocket engine failures of F-1 and Titan-II, chamber combustion instabilities (CI) caused damage, reflecting behavioral complexities at the component level. Combustion chamber walls with embedded acoustic nodes self-excited by the heat released to cause amplification of acoustic oscillations, showed increases in the thermo-kinetic related pressure. Although the causes of the failed launch were determined decades after the accident, the problem-solving process identified the CI problem domain with information describing the internal representation of the problem. Rocket engine complexity may be described by the high number of component parts contained; alternatively, of the constituent processes occurring. Interactive behaviors not accounted for, occur at the interface between the parts or result from coupling of different processes within the combustion chamber. Unlike monolithic systems, rocket engines exhibit performance behaviors emergent, unpredictable and uncoordinated. Over half propulsion technologies of prospective mission competence have a Technical Readiness Level (TRL) less than 5. However, operational risk needs mitigation through increased development of technological readiness related to not only structural performance but to processes enacted of their functions. Increasingly complex propulsion technologies and the thousands of stakeholder requirements needed for analysis are important for framing problems to be solved. The purpose of this paper is to correlate complexity of propulsion technology at the subsystem level with development of technological readiness for performance reliability. Nonlinear performance behaviors connote system complexity.

Launcher guidance and control (G&C) design is a very demanding process, most notably because mission requirements are known to compete against each other and strong couplings between different disciplines exist. These effects become even more impactful when it comes to reusable launch vehicles, many of which are currently under development. The main task of the G&C system is to generate and follow a trajectory to fulfil mission objectives. This is achieved using various actuator types, which typically include the main engine(s), thrust vector control (TVC), aerodynamic control surfaces and cold-gas thrusters of a reaction control system‎(RCS). The motion of these actuators introduces excitations of flexible modes and perturbations through the launchers’ structure which cannot be easily modelled since the mechanical properties are highly time-varying due to the propellant being burnt to generate thrust. External perturbations from aerodynamics or wind reinforce these effects. Furthermore, actuators and other subsystems are subject to faults and failures having multiple potential origins. All of these perturbations must be handled by the G&C system. In the current industrial approach, these multi-physics effects are tackled by separate teams using their own tools while G&C design is usually based on low-fidelity models that simplify the interactions between disciplines. The adoption of multi-physics acausal modelling approaches such as MODELICA and MATLAB Simscape is believed to enable a more efficient and accurate modelling of the multi-disciplinary interactions. This motivates the development of a dedicated multi-physics simulator for multi-actuated vertical take-off vertical landing (VTVL) vehicles based on MathWorks’ Simulink/Simscape. Setting up simulators is a crucial and time-consuming activity in GNC design. The openly distributable Rapid Reusable Launcher Simulation via Multi-physics Modeling (R2M2) tool is a multi-physics simulator framework that aims at reducing this modeling effort and enabling users to quickly and easily set up simulations of VTVL vehicles by only defining the required model parameters. This helps users to save time and resources and enables them to focus their research and development efforts on the GNC system. On the other hand, R2M2 provides the simulation environment to rapidly evaluate GNC approaches. In addition to simplifying the setup process, the R2M2 tool is also highly adaptable and able to simulate a wide range of VTVL mission scenarios, including different vehicle and actuator configurations and environmental conditions. Automated Monte Carlo routines are also provided to facilitate the investigation of the effects of wind disturbances and uncertain parameters. The tool is capable of modeling external influences such as gravitational and aerodynamic effects, as well as internal dynamics from time-varying and moving masses. Modeling of variable-mass dynamics is an essential component for launch vehicle simulations. Mass properties of launch vehicles are changing mainly due to the propulsion causing the ejection of combustion products through the engines’ nozzles. The varying mass influences not only the vehicle’s properties such as the center of mass and moments of inertia but also generates additional forces and moments for instance due to Coriolis effects [R1] [R2]. In addition, the tool can consider common actuator failure cases including the jamming of TVC actuators and aerodynamic control surfaces and degraded engine performance. Future implementations may extend the tool to being capable to consider sloshing effects and structural flexibility. This paper describes the design of the R2M2 tool and provides an overview of its functionalities and applications. The implementation within MathWorks’ physical simulation environments Simscape and Simscape Multibody is shown for all relevant subsystems and physical effects. Challenges and drawbacks using Simscape for flight mechanics m

Solid propellant grain, as a typical polymer, are the thrust generation devices and core load-bearing components of solid rocket motor (SRM) and are also known as SRM grain. They are constantly exposed to extreme service environments such as high temperatures, high pressures, and dynamic shocks, and have a relatively high failure rate in the field use of SRM. Its life and reliability are the shortcomings that restrict the improvement of weapons and equipment capability in China at present. This paper summarizes the typical fault types of SRM grain at present, and compares and analyzes the research progress of reliability design and analysis technology, reliability optimization technology, life test technology and reliability evaluation technology of SRM grain at home and abroad; This paper analyzes the deficiencies and reasons in the research and application of SRM grain reliability technology in China, and points out the technical difficulties and challenges faced by the integrated design of performance and reliability of SRM independent innovation design according to the needs of the forward research and development system of SRM. Based on the existing design level and industrial foundation in China, the basic research suggestions that should be carried out to consolidate the design ability of SRM grain in China are given.