The XW-35 was designed from the outset as a

thermonuclear warhead A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...

for the first generation of

ICBM An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...

s. Development was driven by the development of the

Atlas missile The SM-65 Atlas was the first operational intercontinental ballistic missile (ICBM) developed by the United States and the first member of the Atlas rocket family. It was built for the U.S. Air Force by the Convair Division of General Dyna ...

, and when the accuracy of the Atlas was shown to be inferior to predictions the XW-35 design had to be altered to give a higher yield. By March 1958, the development of the XW-35-X1 was lagging. The XW-35-X1 was probably the device tested in the Koa shot of the

Operation Hardtack I Operation Hardtack I was a series of 35 nuclear tests conducted by the United States from April 28 to August 18 in 1958 at the Pacific Proving Grounds. At the time of testing, the Operation Hardtack I test series included more nuclear detonation ...

series (May 1958). Predicted yield was 1.75

megatons TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a m ...

; the actual yield was 1.37 megatons with the shortfall due to poor burning of the secondary. By this time the Air Force had designated the XW-49, a simple modification of the TX-28 already successfully tested during the Redwing series. By August 1958 the first dedicated missile warhead design, the W-35, had been cancelled in favor of the W-49.

References

* Hansen, Chuck,
Swords of Armageddon
(CD-ROM & download available). PDF. 2,600 pages, Sunnyvale, California, Chucklea Publications, 1995, 2007. (2nd Ed.) Nuclear warheads of the United States Abandoned military projects of the United States {{nuclear-weapon-stub