Fast-Acting, Deep-Throttling Hybrid Motor

Hybrid chemical motors offer an alternative to traditional liquid or solid motors for spacecraft, missiles, rockets, or other vehicles. The key advantage of a hybrid motor is the capability to throttle the motor via active control, which cannot be done in solid propellant motors. However, rapid throttling presents significant challenges to implement in practice. Here, NASA has combined a deep-throttling hybrid motor previously developed by Utah State University with a fast-acting digital valve design to produce a fast-acting, deep-throttling hybrid. Testing performed to-date using a prototype of the hybrid motor and digital valve design has shown the new hybrid motor to be capable of full-scale throttling twice as fast (1 second throttling compared to 2 seconds) as previous control valve designs. With optimization, there is potential full-range throttling may be further reduced to 0.5 second, a 4x improvement over previous control valve designs for hybrid motors. Additionally, smaller mid-range thrust changes have currently been measured in the <0.5 second range. With the throttling capability enabled by the implemented digital valves, it also becomes feasible to achieve thrust ratios of >40:1 for relatively small motors (<1000 N), opening up the opportunity to replace both the main propulsion system (MPS) and reaction control system (RCS) with a single, more efficient motor capable of meeting the needs of both on a spacecraft. The hybrid motor is at technology readiness level (TRL) 4 (component and/or breadboard validation in laboratory environment) and is available for patent licensing. NASA Marshall Space Flight Center and collaborators at Utah State University have developed a prototype for a highly efficient hybrid motor designed for spacecraft. This innovative motor addresses the need for both substantial propulsion during orbital maneuvers and precise control for attitude adjustments and stability. Hybrid motors offer a variety of advantages over traditional liquid and solid propulsion systems. Hybrid motor systems are significantly simpler than a liquid engine system, and offer safety gains and possible throttling capabilities compared to a solid rocket motor. However, the practical implementation of rapid throttling has presented significant challenges in the industry. The NASA motor tackles this hurdle by leveraging a digital valve technology, effectively reducing full-scale throttle time to one second or less and enabling the potential for rapid restart and short pulses of thrust. This hybrid motor technology holds promise for the future of space exploration and offers potential solutions for improved motors on low earth orbit spacecraft (commercial or government) as well as sounding rockets, missiles, and other systems.