Polar-Linear Displacement Torque Meter for Cryogenic Turbomachinery

Project Objective  

Develop and test a scalable torque meter capable of measuring speed, static torque, and rotating torque in cryogenic turbomachinery environments.

Project Description 

This project aims to create a novel torque measurement system for rocket engine turbomachinery that operates reliably under cryogenic conditions. Conventional methods estimate torque indirectly through enthalpy-based calculations, which involve multiple assumptions and intermediate steps. The proposed Polar-Linear Displacement Torque Meter - now being developed under the name TurboSense - measures torque by relating the radial displacement of specially designed polar‑linear disks to shaft twist angle, enabling precise determination of speed, static torque, and rotating torque. This approach improves turbomachinery performance characterization during testing and enables static calibration of torque sensors already integrated into a test assembly. 

The technology leverages displacement sensors optimized for cryogenic compatibility and high rotational speeds already used for turbomachinery speed and runout. TurboSense has long-term goals to couple displacement with clocking information for advanced rotordynamic analysis to support features such as damping seals and hydrodynamic/static bearings. Ultimately, this innovation will reduce testing complexity, enhance data fidelity, and support rapid prototyping of high-efficiency turbomachinery for advanced propulsion systems.

Project Results and Conclusions 

The project remains on track to deliver a cryogenic torque meter concept capable of meeting in-house turbomachinery testing requirements. Early static testing confirms strong potential to replace commercial speed/torque sensors that cannot operate at cryogenic temperatures or measure static torque.

FY25 provided seed funds to develop designs and test proof-of-concept. The team successfully advanced TurboSense from a concept to an in-house manufactured prototype. The team conducted multiple static tests on various shaft geometries to validate the relationship between radial displacement and torque. These tests confirmed that consistent and repeatable calibration curves can be obtained within the elastic range of the shaft. The static rig has since been adapted to enable coupling with a dynamometer and drive motor to perform dynamic testing. 

Lessons Learned

• Ambient-cryogenic thermal cycles cause displacement sensor drift, making live cryogenic calibration procedure essential for accurate data.
• Material strength and torsional capability must be re‑evaluated to support expected twist angles as early prototypes experienced plastic deformation at lower‑than‑expected torque loads.
• Sensor procurement lead times exceeded 3 months, and should be accounted for early

These findings will inform the next design and test cycle, which the prototype includes stronger shaft materials and updated geometry for a planned FY26 dynamic testing campaign.

Benefits to NASA Missions

• Improves characterization of cryogenic turbomachinery through direct torque and speed measurements.
• Reduces reliance on indirect thermodynamic estimation methods.
• Supports rapid prototyping and early development of advanced propulsion systems.
• Enhances Marshall Space Flight Center (MSFC) turbomachinery testing capabilities.

Benefits to the Commercial Space Industry

• Provides a cryogenic‑compatible torque measurement solution for high‑speed turbomachinery.
• Replaces costly off‑the‑shelf sensors that cannot operate in extreme environments.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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