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This paper presents experimental results for the performance effects of different converging- diverging graphite nozzle throat diameters on an in-house developed kerosenenitrous oxide liquid rocket test stand. The project aims to enhance the performance and efficiency of small-scale liquid rocket engines by experimentally investigating the effects of nozzle throat diameter on thrust and specific impulse. By confirming the correlation between nozzle geometry and the experimental data, it provides valuable insight for improving propulsion systems and components used in experimental rocketry such as sounding rockets. This study will evaluate two different nozzle throat diameters under varying propellant pressures and mass flow rates. The liquid rocket test stand consists of an external aluminum casing with a combustion chamber measuring 20” in length with an outer diameter of 76 mm and an internal diameter of 1.66”. The nozzle throat diameter tested will be 58/64” and 60/64”, each with a fixed exit diameter of 1.82”. Experimental results were collected over a range of total mass flow rates using data acquisition systems and analyzed using graphs and trend lines. The results indicate that as the throat diameter increases, the thrust output and specific impulse increase, although the results are inconclusive due to leaks and a back flame during testing, possibly skewing the results. The ablative wear was analyzed based on the nozzle throat size and mass flow rate. The knowledge gained from this study can be used to prevent future accidents for small-scale liquid rocket engine test stands and verify if the trends seen will be applicable to different nozzle materials and find the optimum nozzle throat diameter. 

Hydrogels from biopolymers are readily synthesized, can possess various characteristics for different applications, and have been widely used in biomedicine to help with patient treatments and outcomes. Polysaccharides, polypeptides, and nucleic acids can be produced into hydrogels, each for unique purposes depending on their qualities. Examples of polypeptide hydrogels include collagen, gelatin, and elastin, and polysaccharide hydrogels include alginate, cellulose, and glycosaminoglycan. Many different theories have been formulated to research hydrogels, which include Flory-Rehner theory, Rubber Elasticity Theory, and the calculation of porosity and pore size. All these theories take into consideration enthalpy, entropy, and other thermodynamic variables so that the structure and pore sizes of hydrogels can be formulated. Hydrogels can be fabricated in a straightforward process using a homogeneous mixture of different chemicals, depending on the intended purpose of the gel. Different types of hydrogels exist which include pH-sensitive gels, thermogels, electro-sensitive gels, and light-sensitive gels and each has its unique biomedical applications including structural capabilities, regenerative repair, or drug delivery. Major biopolymer-based hydrogels used for cell delivery include encapsulated skeletal muscle cells, osteochondral muscle cells, and stem cells being delivered to desired locations for tissue regeneration. Some examples of hydrogels used for drug and biomolecule delivery include insulin encapsulated hydrogels and hydrogels that encompass cancer drugs for desired controlled release. This review summarizes these newly developed biopolymer-based hydrogel materials that have been mainly made since 2015 and have shown to work and present more avenues for advanced medical applications.