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The design of liquid propellant rocket engine (LPRE) is a very complicated process; this is due to two main concerns: First, the requirements to satisfy the issues of performance, stability and compatibility. Second, the complicated, interacting processes inside thrust chamber. In this paper, an attempt to illustrate the importance of different parameters affecting performance, stability and compatibility is performed, followed by extensive study of processes inside thrust chamber. The result of processes study is developing the concept of “rate limiting process” which means that the process that can be considered the most important hence the design can be done mainly by considering it alone. This is done by developing a 1D vaporization-controlled model with its application to two case studies to illustrate model validation and application. It was found that the 1D model is valid as long as the vaporization process is the slowest process in this case the error in computing chamber cylindrical length is ∼15%. However, if the mixing process is slow, or the reaction process in gas phase is slow as in the second case study of RFNA/Tonka250 case, the error grow and may reaches 50%

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The burning rate of solid propellants is an important factor for optimizing rocket motors and improving performance. The enhanced burning rate can increase thrust and reduce a propulsion system's overall size and weight. In this study, a novel nano-aluminum/THV composite additive was prepared and introduced into a solid ammonium perchlorate/polybutadiene composite solid rocket propellant to enhance its burning rate. The morphology of the composite particle additive and its effects on combustion were characterized. The use of small quantities (< 15 wt.%) of the additive resulted in a burning rate enhancement of up to 2.1 times that of the conventional coarse aluminized propellant with a specific impulse loss of only 3 seconds, and as much as 4.7 times enhancement with a predicted loss of 22 seconds in theoretical specific impulse. Some of this loss may be recovered by the improved combustion efficiency in smaller rocket motors because the additive was shown to significantly reduce the aluminum agglomeration at the propellant burning surface and reduce the size of reaction products which may reduce two-phase flow losses. The additive also provides wide burning rate tailorability, favorable for motor, grain, and thrust curve design. The burning rate enhancement mechanism is thought to be a physical cratering mechanism governed by the burning rate disparity between the binder/oxidizer system and the nano-aluminum/fluoropolymer additive and not a chemical catalytic effect.

One of the great challenges in designing tactical solid missiles is to achieve high acceleration in the boost phase then maintaining constant speed during the sustain phase. This could be achieved by using a dual thrust solid-propellant rocket motor. Many of these tactical motors use a combination of star, tubular or finocyl grains to achieve this profile. The present study uses two tandem star grains with different design parameters and different transition geometry. Previous researches had consistently shown that the main advantage of star grain is the potential higher volumetric loading in addition to high tailorability. The pressure-time curve for the designed grains is calculated using a zero-dimensional internal ballistic module and a small-scale test motor is used to verify the calculated pressure-time curve. Different transition geometries are compared. Tapered transition is shown to give a comparable performance with the sharp transition with the advantage of higher volumetric loading.

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Triethylamine borane (TEAB) and white fuming nitric acid (WFNA) is a promising hypergolic propellant combination being studied as an alternative to monomethyl hydrazine (MMH) and red fuming nitric acid (RFNA). Nitric acid and MMH are both known to be hygroscopic and their performance is affected by their water content. However, the effect of water on TEAB is yet to be determined. The goal of this research is to characterize the major consequences of water presence on the ignition and combustion performance of TEAB and to compare those results to MMH. TEAB samples are put through accelerated aging in humid and dry environments. Along with the aged TEAB, neat TEAB and neat MMH are used in drop on pool tests with WFNA. The drop tests are conducted by controlling the relative humidity to either below 25% or above 90% and the water concentration in WFNA to either 0% or 10% by weight. Ignition and combustion events are recorded using a photodiode, a microphone, a high speed camera, and a UV streak camera spectrometer. Statistical analysis is applied to the data to determine significant parameters and trends. While relative humidity does not appear to affect the combustion of TEAB with WFNA, water concentration in the oxidizer significantly weakens it. Relative humidity improves MMH ignition delay time and water concentration shows no effect. Nomenclature c* = characteristic velocity IDT = ignition delay time I sp = specific impulse MMH = monomethylhydrazine NTO = dinitrogen tetroxide PTFE = polytetrafluoroethylene RFNA = red fuming nitric acid RH = relative humidity TEAB = triethylamine borane WFNA = white fuming nitric acid = expansion area ratio  = density

One of the goals in solid rocket motor design is to have as large volumetric loading as possible keeping the basic requirements unaffected. Slotted grain can achieve this goal as it has the advantages of sliver-free and no stress-concentration regions that occur in other internal burning grains as star grain and wagon wheel grain. It has the disadvantage of exposing the motor wall to hot gases. In this paper, the geometry of slotted grain is discussed and the effect of design parameters (e.g., number of slots, dimensions of the slot, etc.) of slotted grain on grain burn back is explained. Also, a comparison between results and experimental data is performed.