Abstract
Hybrid rockets provide compelling features for use in atmospheric and space rocket propulsion. One of the prominent applications of hybrid rockets which foster on its characteristics is the propulsion of micro air launch vehicles. In this paper, a set of design options of a hybrid rocket motor is evaluated for propulsion of micro air launch vehicles. In order to evaluate the various design options of a hybrid rocket, we developed design and performance simulation codes. A simulation code is based on a legacy interior ballistic model. MATLAB® environment was used to develop the design and performance analysis codes and to visualize the temporal variation of performance characteristics and grain geometry during burning. We employ the developed codes to assess the replacement of solid rocket motors which are typically used in Air Launch Vehicles by hybrid rocket motors. A typical Micro Air Launch Vehicle mission to launch a 20-kg payload into a 400-km circular polar orbit is assumed. The results show that a hybrid rocket is a suitable candidate for micro air launch vehicles. The performance is improved in terms of specific impulse and thrust with smaller size in the same mission. Several design parameters of hybrid rocket motors were also evaluated and analyzed, including different fuel port geometry, type of fuels and oxidizers, number of ports, nozzle design and initial mass flux. These design parameters bring a significant effect on hybrid rocket performance and size.
Highlights
Hybrid rockets are featured with restarting capability, increased safety, high performance and relatively moderate cost
Studies showed that for short fuel grains, the boundary layer will not fully develop along the port longitudinal axis and some of the downstream parts of the fuel grain will gasify without complete burning while long grains, the entire oxidizer will be consumed before reaching the end of the grain (Kannalath et al, 2003)
We have shown the effect of varying design parameters which can continuously change the performance
Summary
Hybrid rockets are featured with restarting capability, increased safety, high performance and relatively moderate cost. There are few published propulsion system design codes available for the industry but many of them employ exhaustive searches in order to optimize continuous variables (Schoonover et al, 2000) During engine operations, both the exposed surface area and perimeter of fuel ports change with time, the mixture ratio will tend to shift even if the oxidizer mass flow is held fixed. This desire is restricted by the fact that efficient combustion may not be possible at these high mass fluxes and that mixtureratio shifts become more severe under these conditions (Vonderwell et al, 1995) We used another approach to examine the performance of a wheel-typed hybrid rocket motor through simulation of different design parameters.
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