Annotation: Due to an increase of power of rocket engines, the high intensity sound field generated by the exhaust jets have become an important factor, which determines the success rate of a rocket launch. Ensuring a successful launch of a rocket system became harder due to new engineering problems. Identification and definition of acoustic sources structure within a complex supersonic jet, being a one of the most important scientific problems, which have to be solved to find the ways to control accoustic radiation. A three components of acoustic sources can be defined here – broadband signals from large and small components of of turbulent jet and tonal signals which usually being overlooked during the estimation of overall sound pressure level. The paper considers various aspects of acoustics of the launch of rocket systems, which includes characteristics of acoustic sources in supersonic jets, possibilities and physical limitation factors, under which it is possible to control the sound radiation. Among the possible ways to control the process of sound generation by a jet, a method of water injection in a jet is being studied. While saving the general thrust of the engine this method can not greatly reduce the sound radiation by a jet. It is recommended to use big amounts of water-air mix to protect the launch pad from damage. Significant progress on the topic of understanding the process of sound generation by supersonic jets can be achieved via mathematical modeling of sound radiation. The latest achievements of mathematical modeling of sound generation by supersonic jets being presented.

Annotation: Launch vehicle lift-off is one of the most critical phases of the whole mission requiring special technical solutions to ensure trouble-free and reliable launch. A source of increased risk is the intense thermal and pressure impact of rocket propulsion jet on launch complex elements and on rocket itself. The most accurate parameters of this impact can be obtained during bench tests, which are necessary to confirm the operability of the structure, as well as to clarify the parameters and configuration of the equipment and systems of complex. However, full-scale testing is expensive and significantly increases the development time of the complex. Therefore, a numerical simulation of processes is quite helpful in the design of launch complexes. The presented work contains simulation of liquid rocket engine combustion products jet flowing into the gas duct at the rocket lift-off, taking into account the following input data: the parameters of propulsion system, geometric parameters of launch complex elements, propulsion systems nozzles and gas duct. A three-dimensional geometric model of the launch complex, including rocket and gasduct, was constructed. The thermodynamic parameters of gas in the engine nozzle were verified using NASA CEA code and ANSYS Fluent. When simulating a multicomponent jet, the equations of conservation of mass, energy, and motion were solved taking into account chemical kinetics. The three-dimensional problem was solved in ANSYS Fluent in steady-state approach, using Pressure-based solver and RANS k-omega SST turbulence model. The calculation results are the gas-dynamic and thermodynamic parameters of jets, as well as distribution of gas-dynamic parameters at nozzle exit, in flow and in boundary layer at gas duct surface. The methodology applied in this work makes it possible to qualitatively evaluate the gas-dynamic effect of combustion products jets on gas duct for subsequent optimization of its design.

Annotation: The semi-empirical technique of evaluation of external acoustic loads during lift-off is a modification of the known NASA SP-8072 technique based on empirically determined universal dependencies of jet section acoustic power on normalized coordinate and frequency (Strouhal number). The proposed technique was updated in respect of evaluation of mechano-acoustic effectiveness of supersonic jet, determination of spatial scale of sound generating zone in jet, and formation of sound radiation direction towards rocket’s head module. A detailed presentation of the sequence of solving the task set is provided. A comparative analysis of the NASA SP-8072 technique and the proposed modification is made.

Annotation: The paper considers the main aspects of acoustic loads measuring during the rocket launch as well as problem of staff, equipment and environment protection from destructive effect of noise, generated by rocket’s engine. Proposed is the procedure of acoustic loads measurement and calculation of the minimal acoustic noise-safe launching rocket distance, at which it is safe to put equipment and operating personnel. This procedure is based on sharing of the numerical simulation of the exhaust jet in the ANSYS software system, engineering approaches in calculation of propagation and extinction of acoustic waves and measurement of the actual values of acoustic loads with the use of several noise meters. Effective sanitary standards of noise safety were taken to define the duration and power of acoustic loads safe for the personnel. As an example of use of this procedure, results of calculation of noise levels, provided by the sound attenuating chamber, and measurement data during the pulsed wind tunnel tests have been presented. As an outcome of calculations and measurements, done by the proposed procedure, outlines of the noise-safe zone were successfully defined and number of modifications suggested for the sound attenuating chamber to reduce the acoustic loads it generates.