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Green propellants based on cryogenic solids and the state of the art of CSPS using solid H2O2

: Lo, R.E.; Adirim, H.; Eisenreich, N.; Weiser, V.

Walker, C. ; European Space Agency -ESA-, Paris:
3rd International Conference on Green Propellant for Space Propulsion and 9th International Hydrogen Peroxide Propulsion Conference 2006. Proceedings. CD-ROM : 17 - 20 September 2006, Poitiers, France
Noordwijk: ESA Publications Division, 2006
ISBN: 92-9092-946-4
ISBN: 978-92-9092-946-8
Reportnr.: ESA-SP-635
International Conference on Green Propellant for Space Propulsion <3, 2006, Poitiers>
International Hydrogen Peroxide Propulsion Conference <9, 2006, Poitiers>
Fraunhofer ICT ()

Cryogenic Solid Propellants (CSP) are the propellants of choice when it comes to combining the advantages of solid and liquid propellants. CSP based solid rocket motors are as simple and as reliable as conventional solid monopropellant rocket motors while on the other side they deliver the same high specific performance that normally is only available when liquid bipropellants are used. The prize to be paid is of course that all the liquids have to be frozen and kept so until application. Most of High Energy Density Matter (HEDM) Propellants require permanent cooling anyway, rendering them as natural candidates for CSP technology. The paper focuses on Polynitrogens as examples of HEDM with chances of mid term application. The degree of "Greenness" of propellants can vary depending on various environmental and toxicological criteria. Using a figure of merit that combines these rather unrelated properties, the paper presents results of an evaluation of propellants that are more or less green with respect to these properties. For short term application, best bipropellants were based on H2O2 as the overall winning oxidizer along with storable fuels such as Polyethylene. The CSP bipropellant sH2O2 / Polyethylene was hence chosen for further experimental investigations towards a high thrust propulsion system. The SoA obtained by AI/ICT in this research under ESA and DLR contracts is well on its way from Technology Readiness Level 4 to TRL5. Recent advances are described in brief, including the successful feasibility demonstration using 1kg batches of modular disk stacks composed of up to 40 disks of frozen High Test Peroxide sH2O2 and Polyethylene. The bipropellant gas torches presently in use as igniters will have to be replaced by solid propellant cartridges. Under lessons learned are described problems that arose through the accumulation of explosive liquid HTP within the combustion chamber due to the horizontal test firing position. In the long run, CSP research must focus on HEDM development as the one and only break through visible in green high thrust earth-to-orbit propulsion.