In an open letter to President Joe Biden and Congress, the Union of Concerned Scientists (UCS) argued that the new intercontinental-range ballistic missile system, known as Sentinel, was “expensive, dangerous, and unnecessary.”

The Department of Defense on Monday certified the continuation of the project, releasing the results of a review that was legally required when the cost estimate ballooned to “at least” $131 billion earlier this year, which drew the scrutiny of some Democrats in Congress, according toThe Hill.

The Defense review found that Sentinel was “essential to national security,” but the scientists disagreed with the assessment.

“There is no sound technical or strategic rationale for spending tens of billions of dollars building new nuclear weapons,” Tara Drozdenko, director of UCS’ global security program, said in a statement.

Nobel Prize-winning physicist Barry Barish, a signatory to the letter, was also harshly critical of the Pentagon’s approach.

“It is unconscionable to continue to develop nuclear weapons, like the Sentinel program,” he said.

700+ scientists & experts are calling on President Biden & Congress to cancel the Sentinel program and retire the US land-based missile force. Doing so would save Americans more than $100 billion and make the world safer.

Learn more: https://t.co/5dQCOUKnQ3 pic.twitter.com/UxtHV9TSod

— Union of Concerned Scientists (@UCSUSA) July 8, 2024

The soaring costs of Sentinel, which is overseen by the defense contractor Northrup Grumman, have been the subject of media attention. The program will cost an estimated $214 million per missile, far more than originally expected, Bloombergreported on Friday.

However, the cost is hardly the only reason to cancel the program, UCS scientists argue. The silos that house the nuclear missiles, which are found in North Dakota, Montana, Wyoming, Colorado, and Nebraska, are vulnerable to attack—in fact, they are designed to draw enemy weapons away other U.S. targets, according toScientific American. Such an attack would expose huge swaths of the American population to radioactive fallout.

Because they are a likely target, the siloed missiles are kept on “hair-trigger” alert so the U.S. president can launch them within minutes. This “increases the risk of nuclear war” that could start from false alarms, miscalculations, or misunderstandings, the UCS letter states.

The scientists further argue that there’s no need for a land-based nuclear weapons system given the effectiveness of nuclear-armed submarines—one of the other parts of the nuclear triad, along with bomber jets. Such submarines are “hidden at sea” and “essentially invulnerable to attack,” according to the letter. Moreover, the submarine missiles are just as accurate as land-based missiles, and already have “destructive capability than could ever be employed effectively,” it states.

The submarine system is also being overhauled, as is the ‘air’ component of the nuclear triad. In total, the U.S. military plans to spend more than $1 trillion over 30 years on renewing the nuclear arsenal, according to the Arms Control Association.

The U.S. leads the way in a surge of global spending on nuclear arms, according to two studies published last month, one of which found that nearly $3,000 per second was spent in 2023.

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