IC2, a pioneer in the development of micro-electromechanical systems (MEMS) based sensors for aerospace applications, today announced that the Air Force has awarded the company a new Phase II STTR contract to continue development work on a sapphire optical shear stress sensor for use in ultra-high temperature, high speed flows.

IC2 is developing ultra-high temperature capable shear-stress sensors using sapphire sensing heads and sapphire optical fibers.

Under this new 2 year contract, IC2 will be developing sapphire optical wall shear stress sensors and dynamic pressure sensors that can operate in hypersonic flow environments. Realization of these measurement capabilities will enable characterization of complex boundary layer flows in ground and flight test applications. The shear stress sensor consists of a miniature sapphire floating element sensor that uses an optical readout method for direct sensing of wall shear stress.  This MEMS-based sensor uses high temperature capable sapphire optical fibers for readout, enabling operation at up to 1700 ºF.  The optical fiber array can be several meters long, allowing for the electronics to be remotely located away from the high temperatures of the measurement model and facility. The advantages of the all-sapphire optical sensing scheme include: known, stable material properties; immunity to electromagnetic interference (EMI); resistance to cross-axis inputs (e.g., pressure and temperature); and a decrease in temperature sensitivity due to excellent thermal matching between sensor components.

In addition to the shear stress sensor, a robust high-temperature package for a sapphire optical pressure sensor will be developed. This pressure sensor also uses a sapphire optical fiber for readout, enabling operation in the same high temperature environments.

The time-accurate, continuous, direct measurement of fluctuating wall shear stress is currently not possible in high-speed flow applications. The realization of this capability not only benefits hypersonic vehicle development but also impacts fundamental compressible boundary layer flow physics research areas such as transition to turbulence and shock/boundary layer interactions.

The work will be carried out in conjunction with Innoveering and the University of Florida.