The scientific tourist #270 — the B61 nuclear bomb

This week you get the first in a series of images from the National Museum of Nuclear Science & History in Albuquerque, New Mexico.  This photo is of a B61 nuclear bomb, one of the main thermonuclear weapons still in service with the U.S. after the end of the Cold War (yes, this is just the casing).

B61 Nuclear Weapon

From the placard:

The B61 — 11′ 9.5″ (359 cm) long, 13.4″ (34 cm) diameter is a parachute-retarded or free-fall nuclear weapon. It can be dropped at high speeds from altitudes as low as 50 feet. In service with the U.S. since 1968, a variety of aircraft carry the B61 externally or internally.

On the floor next to the weapon is its parachute pack. The 24 foot (7.3 meter) diameter parachute decelerates a 710 pound (322 kg) B61 from 920 mph (1481 kph) to 50 mph (80 kph) in about one second. Repacked every 25 years, the 90 pound package is compressed to 43 pounds per cubic foot, about the density of an oak log.

One of the striking things about this weapon is the variety with which it has been fielded.  Nine versions of it have been produced since 1968 (four still in service), most with a selectable yield between 0.3 and 340 kilotons (for comparison, the bomb dropped on Hiroshima had a yield of about 16 kilotons).  Special versions have been produced for attacking fortifications (as a “bunker buster”), and more recently to fit it in the internal weapons bay of an F-35 Lightning II.  

The B61 became a lightning rod for controversy recently when $10 billion was requested for a Life Extension Program in order to keep the weapons operational until at least 2025.  It’s been reported, though, that the actual life extension (i.e., maintenance) segment of this funding would account for just 10% of the total — the rest of the money will / would give the gravity bomb a precision targeting capability.

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