Mr. Perry, who will follow two highly accomplished physicists if confirmed, is far more familiar with issues involving the oil and gas industry. But weapons programs account for more than half of the Energy Department’s $30 billion budget.
The United States has not conducted a nuclear test since 1992, and some weapons experts believe that it has lost ground to Russia and China as they ambitiously improve their arsenals and delivery systems. Mr. Perry is certain to receive pressure to resume low-yield underground tests to ensure that existing weapons will function, and to help create new bomb designs, which have been off-limits in the Obama administration. How Mr. Perry responds to that pressure could define his tenure.
“Support from outside the Trump administration for testing will be robust,” said John Harvey, who from 1995 to 2013 held senior positions overseeing nuclear weapons programs in the Energy and Defense departments. “I don’t think they will be compelling in changing minds, absent a serious problem that we uncover in the stockpile,” he said.
But Mr. Harvey, who does not believe testing is needed for now, fears that those influences could break the bipartisan compromise in Congress that produced the nuclear “modernization” program: an expensive effort to upgrade nuclear delivery systems — bombers, missiles and submarines — and refurbish existing weapons in the arsenal. This program ensures both that the weapons can strike an enemy if necessary and that they work as designed.
“I think a strong push to do nuclear testing could upset the consensus,” he said.
Since 1998, when India and Pakistan conducted nuclear tests, provoking global condemnation, only North Korea is known to have undertaken tests. Some experts fear that if the United States began testing again, it would risk a new arms race by opening the door to testing for many other countries that want to improve or develop nuclear arsenals.
For that reason, testing would face opposition on many fronts. “It would be unbelievably stupid of us to start testing again,” said Burton Richter, a physics Nobel laureate and emeritus professor at Stanford who has advised presidential administrations since the 1970s.
Absent testing, the arsenal today is something like a 1967 Chevy that sits for decades without being driven, said Thomas Karako, a senior fellow in the international security program at the Center for Strategic and International Studies in Washington. “You have to have the confidence that if you have to crank the engine, it will turn on,” Mr. Karako said.
Still, people with intimate knowledge of the agency and the bomb program say that technical savvy alone will not make or break Mr. Perry’s ability to keep the stockpile in a state of readiness. Among those people is Steven Chu, who won the 1997 Nobel Prize in Physics and led the agency from 2009 to 2013.
“Everybody has a shot,” Mr. Chu said of Mr. Perry’s chance of success. Most important, Mr. Chu said, will be the willingness of Mr. Perry and his close technical advisers to press the weapons designers and stewards to explain their plans in plain enough terms to let the secretary make good decisions.
“If people are talking to a nonscientist, there might be a temptation to BS him,” Mr. Chu said. One advantage of being a scientist in those meetings, he said, was that “I refuse to be BS’ed.”
A spokesman for Mr. Perry referred questions about the former governor’s qualifications to his onetime chief of staff, Ray Sullivan. “As a former military officer and politician and governor, he dealt with a myriad of significant challenges that in many cases included unexpected or technical challenges,” Mr. Sullivan said. “At its heart,” he added, “it seems to me that this job is about managing and leading a very complicated organization and having the leadership qualities and ability to build a good team and to question that team, but lead it to a successful outcome.”
Mr. Trump and Mr. Perry attended the Army-Navy football game together on Dec. 10, and Mr. Trump announced his nomination several days later. The former governor’s positions on nuclear issues remain a mystery. Mr. Richter said he had questioned “technically oriented” members of the Republican hierarchy on where Mr. Perry stands. “Is he going in with a lot of fixed ideas?” Mr. Richter said. “They say they simply don’t know about Perry.”
Mr. Perry’s spokesman, Marc Palazzo, said that the Energy nominee was “deferring addressing specific policy issues until his Senate confirmation hearings.”
The current Energy secretary, Ernest Moniz, is a highly regarded physicist who succeeded Mr. Chu. But most other secretaries have not had such credentials. Bill Richardson, whose term has generally been praised, had been governor of New Mexico, and James D. Watkins was a retired admiral. James B. Edwards was a dentist turned politician who, when he resumed his practice, memorably said that he wanted to “get my hands in the saliva again.” Then President Ronald Reagan made him Energy secretary.
Some analysts say fears that Mr. Perry could fumble the nuclear program are overblown because that program is contained within the National Nuclear Security Administration, a semiautonomous agency inside the Energy Department that has its own director.
Franklin Miller, a principal at the Scowcroft Group who has warned that the Russians have started a new Cold War, said that dedication to the agency’s mission had always been more important than technical expertise at the top. Still, the agency has changed since the days of “shaking the desert” with underground tests in Nevada, New Mexico and elsewhere. The current way of certifying the stockpile, called science-based stockpile stewardship, is not only costly but also enormously complex, said John Pike, the director of the think tank GlobalSecurity.org and one of the most experienced security analysts in the field.
“There’s no end of mischief they could cause for the stockpile,” Mr. Pike said, referring to Mr. Trump and Mr. Perry, and pointing to the confusion and concern that followed the Twitter post by the president-elect.
Mr. Pike was withering in his criticism of Mr. Perry’s ability to act as a knowledgeable counterweight to Mr. Trump. “Perry’s got no idea which end the bullet comes out of,” he said. “He’s not somebody who’s going to say no to the president.”
In a yearly report, the heads of the weapons labs have certified that the stockpile is sound since the science-based program began in the 1990s. Those certifications have all been made without underground testing. “We don’t need it now,” said Steven E. Koonin, who was Mr. Chu’s under secretary for science and now serves on the Secretary of Energy Advisory Board. He added, “That’s not to say we might not need it at some point in the future.”
Mr. Koonin said he had not detected any disagreement on the issue from senior officials in the Obama administration. But the next administration will be pressed for changes on nearly every element of policy involving nuclear weapons. Some will not call for an immediate resumption of testing, but could lead down that path.
Others believe that the science-based approach, without testing, should be immediately re-examined. “It’s been horrifically expensive, and I don’t think we really know for sure that our weapons are as reliable as they were when there was testing,” said Kathleen Bailey, a senior associate at the National Institute for Public Policy, a conservative-leaning group in Washington.
There was always skepticism among some bomb designers and senior lab officials that the purely science-based approach would suffice. But C. Paul Robinson, who directed Sandia National Laboratory from 1995 to 2005, said the labs fell into line once the policy decision was made.
As for Mr. Perry, he was once involved in helping set up a technology transfer program between Sandia and the University of Texas, said Mr. Robinson, who worked with him on the effort and called him “a smart guy.”
“He’s a hard-working, competent guy,” Mr. Robinson said. He added that “this one gaffe that the papers keep writing about” — when Mr. Perry proposed eliminating the Energy Department but could not recall its name during a 2011 Republican presidential debate — “is certainly an aberration.”
Mr. Chu said that no judgment on the former governor’s ability to handle technical matters could be made until he had spent some time on the job. “I want Rick Perry to succeed,” Mr. Chu said.
Asked if he could recall a moment when his science background had helped him make a decision as Energy Secretary, Mr. Chu did not hesitate. “All the time,” he said.