The uniaxial compressive mechanical curves of nitrate ester plasticized polyether (NEPE) propellant under different temperatures and strain rates have been obtained with a universal testing machine and modified split Hopkinson pressure bar (SHPB). The experimental results show that the mechanical properties of NEPE propellant are both rate dependent and temperature dependent. With decreasing temperature or increasing strain rate, the modulus and rigidity obviously increase. Based on the previous models proposed by Yang and Pouriayevali, we propose a modified viscohyperelastic constitutive model which can describe the mechanical response over a large range of strain rates. Then we add a rate-dependent temperature item into the modified model to make a thermovisco-hyperelastic constitutive model. By comparing the experimental results with the model, we find that the thermovisco-hyperelastic constitutive model can correctly describe the uniaxial compressive mechanical properties of NEPE propellant at different temperatures and over a large range of strain rates from the static state to 4500 s⁻¹.

Gel fuel potentially combines the advantages of solid fuel and liquid fuel due to its special rheological properties, which have essential impacts on the application of gel fuel in propulsion systems. In this paper, we study the rheological property of organic kerosene gel through a series of measurements on its viscosity as a function of the shear rate, temperature, and shear history. The measured datasets are then fitted with constitutive relationships between the viscosity and shear rate at three different levels: the power law shear-thinning model, the power law dependency on both the temperature and shear rate, and the thixotropic property. It is found that intense pre-shear could exhaust thixotropy and reduce viscosity of the kerosene gel. For the power law shear-thinning model, the consistency index increases with the gellant mass fraction, whereas the power law exponent remains constant. The dependence of viscosity on temperature could be well approximated by an empirical power law relationship. As for the thixotropic property of the kerosene gel, the fitted second-order kinetic model corresponds accurately to the viscosity at different shear rates and shear times. The constitutive models fitted in this work at different levels are consistent with each other and provide useful tools for further applications of organic kerosene gel fuel.

The mechanical and thermal properties of the fabricated structures composed of lunar regolith are of great interest due to the urgent demand for in situ construction and manufacturing on the Moon for sustainable human habitation. This work demonstrates the great enhancement of the mechanical and thermal properties of CUG-1A lunar regolith simulant samples using spark plasma sintering (SPS). The morphology, chemical composition, structure, mechanical and thermal properties of the molten and SPSed samples were investigated. The sintering temperature significantly influenced the microstructure and macroscopic properties of these samples. The highest density (~99.7%), highest thermal conductivity (2.65 W·m⁻¹·K⁻¹ at 1073 K), and the best mechanical properties (compressive strength: 370.2 MPa, flexural strength: 81.4 MPa) were observed for the SPSed sample sintered at 1273 K. The enhanced thermal and mechanical properties of these lunar regolith simulant samples are attributed to the compact structure and the tight bonding between particles via homogenous glass.

Numerical simulations were performed to study the influence of the inside diameter of the pulse separation device port on the flow features and the local heat transfer characteristics in a dual pulse solid rocket motor. A lower–upper symmetric Gauss–Seidel implicit dual time-stepping method was applied to address the problem of unsteady flow. A high-resolution upwind scheme (AUSMPW+) and Menter’s shear stress transport turbulence model were employed to solve the Reynolds-averaged Navier–Stokes equations. The conjugate heat transfer strategy was realized by enforcing a common temperature and heat flux at the fluid–solid interface. After validating the accuracy and reliability of the numerical algorithm by comparison with experimental cases, the internal flow of a dual pulse solid rocket motor was simulated. The results show that the magnitude of the velocity, the wall shear stress, and the turbulent kinetic energy downstream of the pulse separation device port decrease with increasing pulse separation device port diameter. The local heat transfer coefficient increases sharply downstream of the pulse separation device port, reaching a maximum within 1–2 diameters downstream of the pulse separation device port, before relaxing back to the fully developed pipe flow value. The peak value of the local heat transfer coefficient reduces as the pulse separation device port diameter increases. Meanwhile with an increasing pulse separation device port diameter, the position of the peak local heat transfer coefficient moves upstream to the head of the first pulse chamber, and appears upstream of the position of the reattachment point by an average of about 28.6%.