On February 8, 2016, the OceanGate team conducted a second pressure test of a 1/3 scale model of the manned submersible, Cyclops 2.
The objective of this second pressure test was to validate that the carbon fiber cylinder that makes up the center of the pressure vessel is capable of withstanding an external pressure of 6,000 psi -- corresponding to operating in the ocean at a depth of about 4,200 meters (nearly 14,000 feet). See chart below for other pressure-to-depth comparisons.
Results of the test will be used in the final design of the full size pressure vessel for the 5-man submersible Cyclops 2.
Unlike the first pressure test where we tested a scale model with carbon fiber hemispheres on each end of the cylinder, for this test we replaced the hemispheres with 6" thick aluminum end plates in order to independently test the cylinder under pressure.
As with the first pressure test, the model was lowered vertically into the pressure test chamber and suspended in a harness. Lead weights were hung from the bottom of the model to prevent it from floating and contacting the pressure chamber lid when water is added to the chamber. The chamber was partially filled with water and the pressure test began.
The test was conducted as a series of steps where air was pumped into the chamber to increase the internal pressure to pre-set levels, and then held at each level for a period of time (dwell time) to monitor results. During the test, the pressure inside the model remained at 1 atmosphere (14.7 psi) -- the air pressure we experience at sea level.
During the test, we assess the effects of pressure on the model by monitoring strain data to detect any deformation of the carbon fiber.
After loading the model into the pressure chamber, the team calibrated sensors and completed the setup of the monitoring equipment.
10:05 am - The test commences and the pressure was raised to 1000 psi in the first of multiple step increases to eventually reach 6000 psi. These increases of 500psi or 1000psi increments each took from 2 to 4 minutes each. Upon reaching the next pressure level, the pressure was held at that level for up to 5 minutes as the team evaluated the affect on the model.
10:48 am - the pressure reached 5200 psi. This pressure is equivalent to a depth of 3700 meters (12,000 feet) -- the average depth of the ocean.
11:02 am - Success: the pressure was successfully raised to the target of 6000 psi -- the equivalent of a depth of 4200 meters (nearly 14,000 feet).
This test provides valuable proof that filament wound carbon fiber cylinders are viable to depths of 14,000 feet and demonstrates that the benefits of carbon fiber are real.
The next step in the development of Cyclops 2 is to complete the manufacture of two carbon fiber hemispheres and conduct a third pressure test.
The ocean covers about 71% of the surface of the earth with an average depth of about 3700 meters (12,000 feet).
The light blue area in the chart above illustrates the area of the ocean floor that the completed Cyclops 2 manned submersible will be able to descend to based on the results of this pressure test.
|Pressure||Equivalent Depth||Pounds on Hull|
|PSI||Bar||Feet||Meters||Scale Model||Full Size Hull|
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Weight: 275 lbs.
Displacement: 7.2 cu. ft.
The pressure vessel was designed and fabricated in collaboration with the University of Washington Applied Physics Lab Collaboratory, and Spencer Composites.
This pressure vessel model is approximately 1/3 of the size of the full sized vessel. The walls of the scale model are made of multiple layers of carbon fiber material and resin. The model is assembled from three main components: a center cylinder, and two 6" thick aluminum end plates. The full sized vessel will include a carbon fiber center cylinder and a hemisphere with viewport on each end of the cylinder.