DEEP SEA, DOWNHOLE & MARINE MOLDED GLASS DOME & MOLDED GLASS SPHERE

About 71% of the earth's surface is covered in water, most of which is at extreme pressures, all of which is inhospitable for humans and only accessible to AUV and ROV systems. For downhole (borehole) environments, extreme temperatures further impair access and observation. A properly designed pressure rated deep sea glass dome allows for safe, direct observation with AUV and ROV submersibles and downhole camera systems.

Thousands of years ago it was discovered that domes are the ideal structural shape for strength, second only to the dome's parent, the sphere *. No other non-spherical shapes come close to the natural strength of hemispheres (domes). The most important quality of high performance domes in hostile, high-pressure environments is symmetry, both in the shape, and the material homogeneity.

* A glass sphere is simply two hemispheric glass domes sealed together. A common practice in deep sea applications is to create semi-autonomous camera and electronic glass spheres with two Rayotek hemispheric domes with feed-through holes for electronics. Properly designed feed-through holes do not compromise the strength of the dome.

GLASS, STRONGER THAN STEEL FOR AUV & ROV ENVIRONMENTS:

Glass, as is used in a Rayotek molded glass dome, is by definition amorphous. What this means is good quality glass is naturally homogeneous and mechanically symmetric down to the atomic level. There are uniaxially stronger crystalline materials such as sapphire, but under the isostatic pressure conditions that AUV's and ROV's operate, crystalline materials are weaker for dome and sphere shapes. This is because crystalline asymmetric structures allow for premature buckling in the weaker axis. For metals and ceramics, grain boundaries must be considered because grains and grain boundaries are susceptible to uncontrollable creep and slippage. Therefore glass, specifically high quality, homogeneous glass like the glass used for Rayotek borosilicate glass domes is by far the superior material for high-pressure environments.

YOU GOTTA KNOW HOW TO HOLD THEM:

What makes a robust glass dome system once you've built a near-perfect optical glass dome out of high quality borosilicate glass? The best designed and manufactured glass dome is only structurally perfect in theory. Extensive work was performed on deep-sea glass domes in the 1960s with poor results, regardless of how perfect the actual domes were. A big reason: incompatible mounting systems due to incompatible bulk moduli. Bulk modulus is what determines how much a material will compress under pressure. Even so called "incompressible materials" like hydraulic fluid do shrink under pressure, as do glass, metal and all other materials. When a glass dome is mounted to a flange without the properly matched materials and correctly engineered interface, the glass will crack near the interface and the glass dome system fails, often catastrophically.

For more information on flange and thread mounted glass domes go to our sister company's Flanged Domes page at Rayoteksightwindows.com

RAYOTEK'S SUGGESTIONS FOR A ROBUST HIGH PRESSURE MOLDED GLASS DOME SYSTEM:

• Build the molded glass dome as dimensionally symmetric as possible. The more deviation from circularity and sphericity, the weaker the glass dome.
• Choose good quality glass, such as borosilicate glass, so the material homogeneity is good. Inhomogeneous glass compresses non-uniformly.
• Mount the dome properly. The ideal mounted dome behaves as if the glass dome is floating independently from the surface to which it is mounted
• Choose a company that can co-engineer and properly test your glass domes to insure they can handle the environmental conditions to which they will be subjected. Proper testing, including life testing, is critical to the safety of life, equipment, and your reputation.

Rayotek has decades of experience designing molded optical domes for the most extreme, hostile environments. There is a reason why Rayotek is the sole supplier for many military and commercial applications that use our optical domes and windows.