Project Title:

High-Performance Sapphire Windows

11.07-9806
912150
High-Performance Sapphire Windows
Advanced Fuel Research, Inc.
P.O. Box 380343
East Hartford
CT
06138-0343
Stephen C.
Bates
203-528-9806
LeRC
NAS3-26330
228

11.07-9806
912150

Abstract:

High-Performance Sapphire Windows
The environment in the combustion chamber of a liquid rocket is too extreme to allow
the use of large optical ports made from conventional materials. These ports are
crucial for the non-intrusive  measurements of combustion processes using advanced
laser diagnostics that require high-quality, wide-aperture access. Specially processed
and mounted sapphire windows will be developed to provide this optical access. Through
surface treatments and proper consideration of thermal stresses, single crystal sapphire
can be a mechanically equivalent replacement for high-strength steel. A prototype
sapphire window design will be developed that uses processing of the exterior sapphire
surface to achieve a reliable, large increase in mechanical strength. A simple high-pressure,
high-temperature window test facility will be assembled and used to test processed
sapphire samples and demonstrate the feasibility of the strengthening technique.
Coupling strengthened sapphire windows with high-temperature mounting techniques
will greatly expand capabilities for optical access to extreme environments, making
laser diagnostics more flexible and possibly leading to entirely new diagnostic applications.
Strengthened sapphire windows will lead to optical access for diagnosis of extreme
environments. This is an enabling technology for broad research in combustion that
has extensive commercial application for engines, burners, and furnaces.
single crystal sapphire, strengthening, window, optical access