New motors for next-generation in-space servicing

The Precision Low Speed Motor Controller was designed as part of an OpTIIX telescope for the International Space Station. This technology is based on a precise current control loop and a high fidelity velocity measurement algorithm. The precise current loop uses a mathematical model of the electrical dynamics of the motor, custom electronics, and a PI controller to maintain a rapid response and smooth current control. The velocity measurement algorithm is embedded in the velocity loop that is wrapped around the current loop to provide a smooth low velocity control. Current motors are only capable of operating at approximately 15 rpm with a risk of excessive jitters. This technology reduces the responsive rpms by several orders of magnitude to approximately 0.025 rpms. This technology's capability has been integral to the success of several NASA projects, such as the OpTIIX telescope, the NASA Robonaut 2 robot , and the Modular Robotic Vehicle (MRV).

The HEMM is a is a wound-field partially superconducting machine that implements a combination of rotor superconducting and stator normal conductor elements, along with an integrated acoustic cryocooler, to achieve some of the benefits of a superconducting motor without the need for an external cryogenic system. The combination of the described elements allows a motor to be built which essentially operates like any other motor when viewed as a black box, but substantially enhanced performance can be achieved. The incorporation of superconductors on the rotor to create a high-level magnetic field results in a specific power and efficiency that could not be achieved any other way. The HEMM can achieve over 98% efficiency in a lightweight electric machine with an operating power greater than 1.4 MW, a specific power greater than 16 kW/kg (ratio to electromagnetic mass), and a rated operating speed of 6800 RPM. The HEMM can be used as both a motor or a generator, offering a wide range of applications including propulsion systems for hybrid aircraft, electric trains, hybrid cars, and turboelectric ships, as well as generator systems for wind turbines, power plants, or motors for other industrial machinery.

During SR-FSW, the wicking of substrate material into the gap between the crown shoulder and pin can lead to pinch load shifting–an increasing difference between the applied pin load and actual pinch load. NASA's IFR Tool mitigates pinch load shifting, enabling a more robust SR-FSW process due to better agreement between the applied pin load and the actual pinch load. As pinch loads are not dynamically measured during welding, NASA has relied on defect rates and pin tool ejection loads to demonstrate the value of the IFR Tool. Large-scale welds were performed with both the IFR Tool and a standard pin tool. Weld inspections found a 90% reduction in defect generation rate for the IFR tool, and the first defect in the standard pin tool sample occurred at 300" compared to at 900" in the IFR Tool sample. There was also a drastic improvement in mechanical properties variations along the weld. In another study, a series of 27.5' barrel welds were performed with both the IFR Tool and a standard pin tool. After welding, ejection forces required to remove the pin tools from their fixtures were measured. The standard pin tool ejection force was 9,400 lbs., nearly 5 times larger than that of the IFR Tool at 2,000 lbs . The large difference suggests that during welding, the standard pin tool would have been less responsive to substrate surface variations than the IFR Tool. Weld inspections supported this theory, as they found a significantly lower defect rate in the IFR Tool samples.

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 40:1 for relatively small motors (

Metal additive manufacturing may be limited by build volumes (i.e., it can be hard to make large parts), post-processing requirements, and upfront costs to buy capital equipment. The two NASA-developed technologies are add-on tools for FSW systems (reducing costs), do not require a printer or print bed, and produce parts with high quality surface finishes. The C-FSD attachment includes a non-rotating block through which the C-FSW rotating pin is threaded, and a containment plate to hold the plasticized metal within the system. In this technique, raw metal feedstock is fed into one end of the non-rotating block, is heated and plasticized by the C-FSW pin, and is driven out the other side of the block. The C-FSW pin is used to join the new material to the pre-existing layer. The B-FSD tool uses a dual-shoulder design to print outward from the edge of the base panel. The B-FSD process uses the same feed system as the C-FSD, but utilizes the bobbin/SR-FSW pin's dual shoulders (i.e., containing the metal on both the top and bottom) enabling more complex structures to be made, and the ability to print varying thickness depositions in a single pass. The Additive C-FSD and B-FSD end effector tools are both at technology readiness level (TRL) 4 (component and/or breadboard validation in laboratory environment) and are available for patent licensing.