A nuclear blast is measured in kilotons and megatons.
The Little Boy atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons of TNT (63 TJ), and the Fat Man atomic bomb dropped on Nagasaki on August 9, 1945, exploded with an energy of about 20 kilotons of TNT (84 TJ)
The Air Force’s ‘rods from god’ could hit with the force of a nuclear weapon — with no fallout
The 107-country Outer Space Treaty signed in 1967 prohibits nuclear, biological, or chemical weapons from being placed in or used from Earth’s orbit. What they didn’t count on was the US Air Force’s most simple weapon ever: a tungsten rod that could hit a city with the explosive power of an intercontinental ballistic missile
The rod itself would penetrate hundreds of feet into the Earth, destroying any potential hardened bunkers or secret underground sites. More than that, when the rod hits, the explosion would be on par with the magnitude of a ground-penetrating nuclear weapon— but with no fallout.
Such a weapon could destroy a target with 15 minutes’ notice.
One Quora user who works in the defense aerospace industry quoted a cost of no less than $10,000 a pound to fire anything into space. With 20 cubic feet of dense tungsten weighing in at just over 24,000 pounds, the math is easy. Just one of the rods would be prohibitively expensive. The cost of $230 million a rod was unimaginable during the Cold War.
These days, not so much. The Bush administration even considered revisiting the idea to hit underground nuclear sites in rogue nations in the years following 9/11. Interestingly enough, the cost of a single Minuteman III ICBM was $7 million in 1962, when it was first introduced ($57 million adjusted for inflation).
The trouble with a nuclear payload is that it isn’t designed to penetrate deep into the surface. And the fallout from a nuclear device can be devastating to surrounding, potentially friendly areas.
The long-rod penetrator rounds fired from the Abrams tank (and others) demonstrate the concept and effects, albeit on a microscopic scale.