The defense secretary praised the 'readiness' of an attack submarine that hasn't been on a mission since 2015

Esper visited the Boise during a trip to Norfolk, where three Navy sailors assigned to the USS George H.W. Bush have died by suicide in the past two weeks.

"I wish I could tell you we have an answer to prevent future further suicides in the armed services," Esper told sailors. "We don't."

This year, suicides in the armed services have garnered significant attention, with the Air Force calling a one-day operational stand-down in August to address the number of suicides in its ranks.

The submarine Esper praised for its readiness has been out of action for four years and lost its certification to perform unrestricted operations in June 2016 as it awaited repairs, according to Navy spokesperson Cdr. Jodie Cornell.

"The Boise has been waiting for repairs since its last deployment ended in 2015, and become the poster child for problems w/ Navy maintenance," journalist Paul McLeary tweeted Wednesday.

The Boise and two other Los Angeles-class submarines have long awaited repairs that the Navy doesn't have the capacity to perform, so the service has contracted the labor to private shipyards.

Cornell told Insider that the Boise could go into repairs in spring 2020, but the contract for the private shipbuilder to perform the repair was still in negotiations.

Cornell told Insider that while there is indeed a full crew aboard the Boise, "the command has been executing an aggressive plan to send crew members to other submarines to both support the other ships, including deployments, and to gain Boise crewmembers valuable operational experience."

The Government Accountability Office (GAO) estimated in 2018 that attack submarines have spent 10,363 days in "idle time" — when they can't operate and are unable to get repairs — since 2008.

During that time, the Navy also spent an estimated $1.5 billion to maintain attack subs that weren't operational.