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Innovative Methods to Enhance the Combustion Properties of Solid Fuels for Hybrid Rocket Propulsion

1
Institute of Space Propulsion (ISP), School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
2
Department of Forensic Science and Technology, Jiangsu Police Institute, Nanjing, 210031, China
3
Space Propulsion Laboratory (SPLab), Department of Aerospace Science and Technology, Politecnico di Milano (RET), I-20156 Milan, Italy
*
Authors to whom correspondence should be addressed.
Aerospace 2019, 6(4), 47; https://doi.org/10.3390/aerospace6040047
Received: 8 March 2019 / Revised: 17 April 2019 / Accepted: 17 April 2019 / Published: 22 April 2019
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Abstract

The low regression rates for hydroxyl-terminated polybutadiene (HTPB)-based solid fuels and poor mechanical properties for the alternative paraffin-based liquefying fuels make today hybrid rocket engines far from the outstanding accomplishments of solid motors and liquid engines. In this paper, a survey is conducted of several innovative methods under test to improve solid fuel properties, which include self-disintegration fuel structure (SDFS)/paraffin fuels, paraffin fuels with better mechanical properties, high thermal conductivity fuels and porous layer combustion fuels. In particular, concerning HTPB, new results about diverse insert and low-energy polymer particles enhancing the combustion properties of HTPB are presented. Compared to pure HTPB, regression rate can be increased up to 21% by adding particles of polymers such as 5% polyethylene or 10% oleamide. Concerning paraffin, new results about self-disintegrating composite fuels incorporating Magnesium particles (MgP) point out that 15% 1 μm- or 100 μm-MgP formulations increase regression rates by 163.2% or 82.1% respectively, at 335 kg/m2·s oxygen flux, compared to pure paraffin. Overall, composite solid fuels featuring self-disintegration structure appear the most promising innovative technique, since they allow separating the matrix regression from the combustion of the filler grains. Yet, the investigated methods are at their initial stage. Substantial work of refinement in this paper is for producing solid fuels to fulfill the needs of hybrid rocket propulsion. View Full-Text
Keywords: hybrid; regression rate; self-disintegration; HTPB; paraffin; low-energy polymer; magnesium hybrid; regression rate; self-disintegration; HTPB; paraffin; low-energy polymer; magnesium
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Chen, S.; Tang, Y.; Zhang, W.; Shen, R.; Yu, H.; Ye, Y.; DeLuca, L.T. Innovative Methods to Enhance the Combustion Properties of Solid Fuels for Hybrid Rocket Propulsion. Aerospace 2019, 6, 47.

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