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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.

The jointly developed interlocking paver design consists of a molded solid material with tapered interlocking features that interface with features of an opposite gender in three orthogonal directions. This establishes a toleranced connection between the pavers that locks down six degrees of freedom. More specifically, the system consists of two types of pavers: polygon and spacer pavers. Both are symmetrical about the longitudinal and transverse axes and are designed to interlock securely with one another in a checkerboard pattern. The polygon paver features an octagonal top level and a rectangular bottom level with protrusions and recessed notches. The spacer paver has an elongated center portion with isosceles trapezoid extensions on the top level and a rectangular bottom level with protrusions and notches. The interlocking design locks down six degrees of freedom, providing enhanced stability and preventing the flow of exhaust gases between the seams to mitigate erosion of the underlying regolith. The pavers could be constructed leveraging in-situ resource utilization (ISRU). Lunar regolith has been identified as a potential construction material. Additionally, the pavers could be installed via robotic assembly, reducing the need for human labor in harsh environments.

This NASA-developed eVTOL UAS is a purpose-built, electric, reusable aircraft with rotor/propeller thrust only, designed to fly trajectories with high similarity to those flown by lunar landers. The vehicle has the unique capability to transition into wing borne flight to simulate the cross-range, horizontal approaches of lunar landers. During transition to wing borne flight, the initial transition favors a traditional airplane configuration with the propellers in the front and smaller surfaces in the rear, allowing the vehicle to reach high speeds. However, after achieving wing borne flight, the vehicle can transition to wing borne flight in the opposite (canard) direction. During this mode of operation, the vehicle is controllable, and the propellers can be powered or unpowered. This NASA invention also has the capability to decelerate rapidly during the descent phase (also to simulate lunar lander trajectories). Such rapid deceleration will be required to reduce vehicle velocity in order to turn propellers back on without stalling the blades or catching the propeller vortex. The UAS also has the option of using variable pitch blades which can contribute to the overall controllability of the aircraft and reduce the likelihood of stalling the blades during the deceleration phase. In addition to testing EDL sensors and precision landing payloads, NASA’s innovative eVTOL UAS could be used in applications where fast, precise, and stealthy delivery of payloads to specific ground locations is required, including military applications. This concept of operations could entail deploying the UAS from a larger aircraft.