High-Performance Green Hydrazine-Based Propellant for Small Spacecraft

Whereas the last decade has seen a notable expansion in the number of small spacecraft on orbit, a lack of high-total-impulse chemical propulsion options continues to hamper their complete proliferation into mission arenas requiring dynamic maneuvering. This has been particularly true at the NanoSat/CubeSat scale, where volume limitations are most constraining. Because SmallSats are generally launched as secondary payloads, green ionic liquid propellants such as ASCENT and LMP-103S have been recognized as particularly advantageous in that they introduce minimal logistical impacts to primary payload integration workflow. However, despite the substantial packaging advantages conferred by their high impulse density, these propellants have nevertheless seen limited use on CubeSats owed the imparity of their very high reaction temperatures, high required preheat power, and high cost with the fundamental engineering constraints and objectives of CubeSat design. A new paradigm in high-performance hybrid hydrazine/ionic liquid propellants has been discovered presenting a previously-unexplored path to realize the same and greater benefits as high-TRL green ionic liquid alternatives while preserving the favorable properties of conventional monopropellant technologies. HyperflexTM Propellant, a representative formulation developed specifically as a drop-in replacement for monopropellant hydrazine but so-appellated in deference to its substantially broadened range of applicable propulsion technologies and mission classes, confers a number of physical and performance characteristics ideally aligned with the special needs of SmallSats and CubeSats, as follows: 27.5% greater density-specific impulse than conventional hydrazine Cold-startable in standard catalytic thrusters, with nominal preheat temperatures/power equal to conventional hydrazine Low 1100ºC flame temperature simplifies spacecraft thermal management Low vapor pressure/toxicity with an OSHA-defined vapor hazard ratio on par with vinegar Low -55C freezing point eliminates need for heating of propulsion system when not operating Potential path to reduced propellant manufacturing cost through the elimination of process-intensive distillation operations required for production of high-pure hydrazine Nonflammability, low impact/shock sensitivity, and high thermal stability facilitate ease of storage and handling Hot-fire and material compatibility test data continue to support Hyperflex™ Propellant as a candidate for integration in CubeSat missions with Aerojet Rocketdyne’s monopropellant thrusters. Hyperflex™ Propellant’s vapor pressure and high electrical conductivity also align it for use as an efficient electrospray propellant, enabling dual-mode systems to operate in both high-thrust and high-specific impulse operating modes via a single CubeSat-scale propulsion system. With a broad range of collateral uses, Hyperflex™ Propellant promises to empower a new era of even greater CubeSat/SmallSat proliferation into roles traditionally performed by larger spacecraft.