Cold-Flow Testing of various injector designs for a novel hypergolic and green propellant combination developed at DLR Lampoldshausen
Creators: name:  ALBERTO SARRITZU 
name:   PHILIP TEUFFEL 
name:   ANGELO PASINI 
name:   FELIX LAUCK 
Publisher: name: Proceedings of the Aerospace Europe Conference - EUCASS - CEAS - 2023
Year: 2023
Subjects: GREEN PROPELLANTS
INJECTION
COLD-FLOW TESTS
ENERGETIC IONIC LIQUID
HYDROGEN PEROXIDE

description: In the field of space propulsion, the Green Propellants topic is a renowned recurrent trend. Between the many options available, a combination recently developed at DLR Lampoldshausen appears particularly promising, possessing most of the correct features to lead the switch to greener compounds: storability, reduced toxicity, good performance and especially hypergolicity. The propellant combination is an ionic liquid fuel, coupled with highly concentrated hydrogen peroxide as oxidizer, the so-called HIP_ 11. The present study describes various injection approaches, describing the multifaceted challenges encountered. The study is completed by a cold-flow test campaign that investigated the spray pattern of the various designs. 1. Green Propellants and the Hypergolic Combinations Hypergolic propellants have long been the preferred choice for the overall propulsion system of medium and large spacecrafts and upper stages, having been employed indiscriminately for both Main Engines and Attitude Control Systems for in-space applications. The versatility comes from their inherent ignition capability upon contact, which allows for reliable and instantaneous combustion. The utilization of hydrazine or its derivatives as the fuel and dinitrogen tetroxide (NTO) as the oxidizer has a heritage that goes back to the very beginning of space exploration with applications spanning from lunar module landings to deep space missions. Unfortunately, hydrazine and its derivatives, namely unsymmetrical dimethyl hydrazine (UDMH) and monomethyl hydrazine (MMH), are known to be toxic and carcinogenic substances and in Europe, hydrazine has been listed as a substance of very high concern under the REACH regulation, which may lead to its potential ban, regardless their current crucial role for present lunar missions, as exemplified by the European service module of the Orion spacecraft. The adverse properties of traditional hypergolic propellants necessitate extensive safety precautions during their handling and ground operations, including the use of self-contained atmospheric protective ensembles (SCAPE) suits. Consequently, the production, storage, transportation, and fuelling processes of these propellants incur substantial additional costs. The development of alternative green propellants aims to overcome the challenges associated with the dangerous and highly toxic nature of conventional propellants. By utilizing green propellants, it is possible to potentially reduce the extent of safety handling requirements, offering significant cost-saving opportunities. Many green alternatives exist, developed by numerous industries and research centres around the world, although only a few have reached a maturity level high enough to be considered widely available, with a growing difficulty into selecting the most adequate for different scenarios [ 1]. Them aturation of them ost promising alternatives is a crucial step to make them really appealing for the overall space market. 1.1 HIP 11 The department of Satellite and Orbital Propulsion at DLR\'s Institute of Space Propulsion in Lampoldshausen has a long heritage of research activities focused on the development and testing of environmentally friendly propellants for Copyright 2023 by First Author. Posted online by the EU CASS association with permission.