The versatility extends to the explosive power. Different variations produce different yields, the “dial-a-yield,” or DAY. Depending on the warhead, the president could choose an explosion slightly less powerful than the one that destroyed Hiroshima in 1945, or he could dial it up to a thermonuclear blast 30 times as strong.
The B61 can be dropped free-fall or with a parachute, detonated in the air or on the ground. Its Kevlar parachute, wrapped so tightly it is as hard as an oak tree’s trunk, can slow the bomb’s descent speed from 1,000 mph to 35 mph.
Five versions are still in service. The latest is the B61-11, activated in the mid-1990s as the only ground-penetrating nuclear weapon, known as the “bunker buster.” It is designed to reach hardened bunkers buried far underground and to detonate its nuclear payload on a time delay.
As the most modern version, the bunker buster will escape renovation. The other four models will be collapsed into a single version, an experiment never tried before, according to nuclear weapons experts.
Tight deadline for reinvention
Modernizing a nuclear weapon is not like upgrading any other machine. In the automobile industry, for example, cars are improved each year to reflect the latest technological advances and design changes. By contrast, few of the B61’s major components have been rebuilt to 21st-century, digital-age standards.
Most of the new components will not be replacements. They will be completely new, state-of-the-art versions, designed and built with equipment that did not even exist when the first iterations were turned out in the mid-1960s. “The entire arsenal was built with less computational power than what’s inside an iPhone,” one weapons manager said.
Arrays of supercomputers, advanced electronics and astonishingly detailed simulations will be used to renew the B61. The bombs will get new batteries, new neutron generators to ignite the thermonuclear explosion and new radar systems to signal when the bomb should detonate. New tail kits and special electronics will transform the B61 into the first precision-guided nuclear bomb, which means the designers can get rid of the parachute.
The first renovation must be completed within five years — a blink of an eye in the world of nuclear design and engineering — and all of them have to be done by 2022. If the work veers off schedule — something the Government Accountability Office and the Pentagon say they fear, given the NNSA’s record of delays and cost overruns — the life expectancy of the old bombs will expire and they will no longer be regarded as reliable.
Even if the work meets the deadline, the B61 faces an uncertain future outside the United States. Some NATO countries see nuclear weapons as the last remnant of the Cold War and face increasing calls from anti-nuclear and environmental groups to get them off their soil.
In Germany, popular support is growing for removing the B61s stationed at a German air force base near the village of Buchel in the western part of the country. Short of such a drastic step, the German government has not committed to paying for the expensive upgrades required to carry nuclear weapons when it replaces its aging fleet of Tornado aircraft with the new Eurofighter.
The plans of NATO allies are not the only threat to the B61. Some members of Congress have questioned the soaring cost of the redesign and the old bomb’s place in the modern arsenal.
The B61 traces its lineage to the first nuclear test, which occurred on the morning of July 16, 1945, in the desert near Alamogordo, N.M. The detonation of the first atomic bomb at the Trinity Site took place less than three weeks before the bomb called Little Boy was dropped on Hiroshima on Aug. 6, killing 70,000 people instantly and at least the same number from radiation exposure and injuries over the next five years.
In the years that followed, the United States conducted more than 1,000 nuclear tests as it perfected and expanded its nuclear arsenal during the arms race with the Soviet Union. Hundreds of tests also were conducted by other nuclear powers, including the Soviet Union, Britain, France and China. President George H.W. Bush called a halt to U.S. nuclear tests in 1992. His decision was reaffirmed in 1996 when President Bill Clinton signed the Comprehensive Test Ban Treaty. The Senate rejected the treaty in 1999 and has not voted on it again, but the ban has remained in place. Russia, Britain and France are among the 36 countries that have ratified the treaty.
Without the ability to test, the United States still must guarantee that its arsenal is reliable and safe. So nuclear physicists and computer engineers have turned to mimicking nuclear explosions through some of the world’s most sophisticated computer simulations.