I wouldn&#x27;t be surprised if the Soviets experimented with basalt fiber composite hulls at some point.  I think they used it in some ballistic missile cowlings, anyway.<p>Basalt fiber is similar to e-glass fiber, but has greater stiffness.<p>I&#x27;m guessing they made a few small fiber-wound spheres and did a crush depth test on them, but the results discouraged further experimentation.