apparently can trace a design lineage back to the very first solid-fuel radiation implosion device ever tested--the Shrimp--detonated in the Castle-Bravo Test. The Shrimp design was weaponized into the lighter and more compact MK-21. Later, an even smaller and lighter high yield weapon designated MK-46 was developed from the MK-21. After a test failure in Operation Hardtack I, the TX-46 secondary was redesigned and generated a high yeild on a retest. This revised design was assigned the designation TX-53, and developed into a deployed weapon. Although opportunity to test the production version of