Mohammad Reza Palizvani - M. Sc. Student of Chemical Engineering, Imam Hossein Comprehensive University
Ali Akbar Jamali. - Ph.D of Chemical Engineering, Imam Hossein Comprehensive University.

Human spaceflight, space tourism, and the launch of microsatellites are all expected to grow in thefuture. In fact, with the recent increase of the satellite market, almost ۱۰۰۰ smallsats per year areforeseen to be launched over the next decade. Hybrid rocket propulsion has received significantattention for military and commercial applications due to its potential safety, throttleable, and restartability when compared with solid rockets, economicity, simplicity, and compactness features whencompared to liquid rockets. However, in order to make this new technology the future of the nextgeneration of rockets, some drawbacks of the heterogeneous combustion in hybrid rockets such as lowfuel regression rate and varying oxidizer-to-fuel ratio during the combustion process must be welladdressed. The diffusion-limited combustion in hybrid rocket motor is responsible for the lowregression and poor combustion efficiency of fuels such as Hydroxyl-terminated polybutadiene(HTPB), Poly methylmethacrylate (PMMA), and other polymeric binder-fuels. The paraffin-basedsolid fuel represents a potential solution to the slow regression rate of current solid polymeric fuels.However, paraffin-based fuels suffer from poor mechanical properties and rapid volatilization,preventing their full development and applications for a space mission. he low regression rate ofHybrid Rocket Engines (HREs) is one prominent characteristic that is addressed in most abstractsconcerning hybrid propulsion. Over the years, researchers developed and investigated numerous waysto tackle the low regression rate problem of HREs. This article is a collection and assessment of thesediverse methods and designs.

Hybrid propulsion, Regression rate, Combustion efficiency, Fuel additive, Paraffin wax