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NTN supplies bearings for H3 rocket turbo pumps

February 23, 2024

“H3 Launch Vehicle” ©JAXA

“H3 Launch Vehicle” ©JAXA

NTN has been supplying all the bearings for the turbo pumps of the engine of the second “H3 Launch Vehicle (H3TF2: Test Flight No.2)”, which was launched from Tanegashima Space Center at 9:22:55 JST on February 17, 2024. 

In order for a rocket carrying satellites or other objects to fly, it is necessary to burn liquid hydrogen and liquid oxygen at high pressure to inject a large amount of gas. Turbo pumps deliver liquid hydrogen fuel and liquid oxygen oxidizer to the engine’s combustion chamber by spinning an internal impeller at high speed. 

The bearings used in the impeller support the rocket’s ultra-high speed rotation, comparable to a jet aircraft with a DMN of approximately 2.8 million, even in the cryogenic environment of liquid hydrogen (-253℃) and liquid oxygen (-183℃). Since normal lubricants, including oil and grease, freeze at cryogenic temperatures, the bearings use NTN’s proprietary solid lubricant, which demonstrates lubrication performance even at cryogenic temperatures. In addition, the bearings use a high-strength retainer made of reinforced fiberglass to cope with this harsh environment. 

The H3 Launch Vehicle’s engine has a higher propulsive power than its predecessor, the H-IIA Launch Vehicle, to launch satellites of different sizes. As a result, each component is required to be highly rigid. The bearings for the H3 Launch Vehicle turbopumps are also designed with larger diameters to accommodate higher preload. As the diameter of the bearing increases, the centrifugal force of the balls used in the bearing also increases. For this reason, NTN uses ceramic rolling elements (balls) for bearings. This is the first time that ceramic balls have been used in commercial rockets manufactured in Japan. The use of ceramic balls, which are lighter than metal balls, suppresses the centrifugal force of the balls during rotation and achieves high-speed rotation performance with a dmn value of 2.88 million. 


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