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Technology

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Hybrid Propulsion System

Hybrid propulsion is the subcategory of chemical propulsion that utilizes the combustion of a solid (state) fuel, and liquid (or gaseous state) oxidizer for creating a propulsive force. Since solid fuels are inherently non-toxic, non-flammable, and non-explosive, hybrid propulsion is the safest type of chemical propulsion.

In 2017, a JAXA Institute of Space and Astronautical Science (ISAS) Joint University Collaboration Center was established at Hokkaido University to accelerate research and development of hybrid propulsion for small satellites. This center would capitalize on the more than 25 years of research and development that had been conducted at Hokkaido University under the supervision of Letara's Co-founder, Professor Harunori Nagata.

Letara was established to commercialize this hybrid propulsion technology for small satellites and lead the industry towards safe and fast space transportation. Our first mission is to apply hybrid propulsion, which uses plastic as solid fuel and nitrous oxide as oxidizer, to small spacecraft requiring transfer and/or last-mile delivery from rideshare orbits.

Safe

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Only non-hazardous materials are used

Fast

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High thrust on demand for quick orbital transfer

Affordable

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Safety and ingenuity mean affordability

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2-0-0

Safety
NFPA704 Fire Diamond, #-#-#
toxicity-flammability-explosiveness
4 is most hazardous | 0 is completely safe

100

Thrust
Highly scalable, N
1 N-40 kN demonstrated in-house at Hokkaido University

320

Efficiency
Isp: Ideal Vacuum Specific Impulse, s

Performance Simulation

One of the most difficult issues in hybrid propulsion is nozzle erosion. Generally speaking, propulsion for small satellites requires longer combustion duration than is expected of chemical propulsion for Earth launch, because sub-G acceleration is most suitable for most maneuvers. The graphite nozzle throat (the smallest aperture of the nozzle) is eroded by the long combustion time, and the performance (thrust and specific impulse) is affected. We have developed an original analysis and prediction program to elucidate the unsteady nozzle erosion phenomenon, and have succeeded in high-precision analysis and prediction considering the nozzle erosion and the mitigation of its effects.

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Reignition System

IPropulsion systems for orbital transfer to non-intersecting orbits (e.g., Hohmann transfer), orbit insertion into orbits of other celestial bodies, or landing on gravitational bodies, require re-ignition capability. Hybrid propulsion, which is one of the safest types of chemical propulsion, is difficult to ignite compared with hydrazine-based propulsion, which is self-igniting (Hydrazine has an NFPA704 rating of toxicity-flammability-explosiveness of 4-4-3; where 4 is most hazardous). The safety of hybrid propulsion is related to the fact that it is not easy to ignite. That is why one of Letara's breakthrough technologies is our hybrid propulsion ignition technology. We are leading the way towards reducing reliance on hydrazine-based propulsion, and create the first safe AND fast spacecraft.

Optimum Design Program

Small satellites are launched into space either by piggybacking in the vacant space adjacent the main satellite, or by ridesharing, where multiple small satellites are transported together at the same time. Therefore, the space available for small satellites at launch is limited, and all components must be optimally placed in this limited envelope. We have developed a scalable and customizable optimization algorithm that can meet the performance requirements of the propulsion system and still fit within the envelope.