Mrs. Lovell knew the rigors of the military life, having accompanied her husband, Capt. James A. Lovell Jr., on his assignments as a naval pilot and flight instructor before he joined NASA’s astronaut corps in 1962 and became almost single-mindedly devoted to training for a ride into space.

As Capt. Lovell flew on several Gemini missions with increasing responsibility, it fell to Mrs. Lovell to raise and discipline their four children largely by herself and endure the sexist coverage of the day. (“Marilyn Lovell is cute, active and efficient,” one profile noted. “She comes by the first two traits naturally.”)

Like other astronaut wives, Mrs. Lovell put her husband’s dream of going to the moon above all else. She hid a pregnancy from him for four months, fearing it might send him to the back of the line.

“The wives have it the roughest,” she told the Associated Press in 1968. “The guys get to take the ride.”

Capt. Lovell would let his wife know he was thinking of her in space. One Christmas while he was thousands of miles away, he sent her a mink coat. The card was inscribed, “To Marilyn — from the Man in the Moon.” Another time, he named a lunar mountain Mount Marilyn.

A few months before the Apollo 13 flight, Capt. Lovell took her to see “Marooned,” a fictional film about three Apollo astronauts who can’t return from space because of a catastrophic rocket failure. One of the crew members, like her husband, is named Jim. He gets sucked into space.

Mrs. Lovell identified other sources of impending doom. For one thing, there was the unlucky number 13. “It did bother me,” she told NBC News for a special program tied to the 40th anniversary of the mission. “And I said, ‘Well, what happened to 14?’”

Then, the day before blastoff, Mrs. Lovell was in the shower when her wedding ring slipped off and fell down the drain. “I just was terrified because, to me, it was like an omen that something really was going to happen,” she said.

She kept news of the lost ring to herself.

“For some reason or another the astronaut wives just never discussed anything that would worry their husbands before they went on a flight,” she told NBC News. “I mean, we kept everything to ourselves.”

Apollo 13, which launched on April 11, 1970, was not nearly as newsworthy as previous space missions. Television networks didn’t offer wall-to-wall coverage and none of them carried what was supposed to be a special live broadcast of the astronauts from space. (The Beatles’ breakup was the big news of the week.)

But on the third day of the mission — April 13, that unlucky number again — Mrs. Lovell’s phone rang. It was a friend at NASA. He sounded shocked.

“Marilyn,” the friend said, “I just want you to know that all these different countries have offered to help, you know, in the recovery and whatever.”

She had no idea what he was talking about.

“Have you been drinking?” she said.

NASA officials soon arrived to inform her that there had been an explosion on board. For the next four days, while the world watched as NASA raced to save the astronauts, Mrs. Lovell put on a brave face for television news reporters stationed outside her house.

“Would you like a ham sandwich?” she asked one reporter on her lawn.

But it was only an act. She prayed on the bathroom floor, out of sight from friends, family and the Lovells’ children. She pondered life raising their children alone.

On April 17, her husband and the other astronauts splashed down in the Pacific Ocean. Everyone survived.

“For four days,” she later said, “I didn’t know if I was going to be a wife or a widow.”

Director Ron Howard turned the episode into the hit movie “Apollo 13” (1995), helping immortalize the phrase “Houston, we have a problem,” even if that wasn’t exactly what the astronauts said following the explosion. (Capt. Lovell said, “Uh, Houston, we’ve had a problem.”)

Tom Hanks played Capt. Lovell. Kathleen Quinlan played Mrs. Lovell and was nominated for a best supporting actress Oscar.

Marilyn Lillie Gerlach, the youngest of five siblings, was born in Milwaukee on July 11, 1930. Her father owned a candy store, and she would sometimes slip into the store window to eat chocolate bunnies.

As a 13-year-old freshman at Juneau High School in Milwaukee, she exchanged shy glances with Lovell, who was two years older and worked behind the cafeteria counter to earn free lunch.

“The prom was coming and I had to invite some girl to the prom, you had to invite junior girls,” Capt. Lovell later told the Milwaukee Journal-Sentinel. “I invited a girl, but when she found out I wasn’t going to be prom king she dropped me like a hot potato. I didn’t have anyone else, so I invited Marilyn.”

They continued to date throughout high school. She attended Wisconsin State Teachers College in Milwaukee while he was at the University of Wisconsin, and she later transferred to George Washington University in Washington to be near Capt. Lovell while he studied at the U.S. Naval Academy in Annapolis.

They wed in 1952 after he graduated. In addition to her husband, survivors include four children, Barbara Harrison, James Lovell III, Susan Lovell and Jeffrey Lovell; 11 grandchildren; and seven great-grandchildren.

Mrs. Lovell was an active member of the Astronaut Wives Club, an informal group that counseled and supported other astronaut wives. But after the Apollo 13 incident, she would not allow him to travel into space again. Capt. Lovell worked in the telecommunications industry and ran a restaurant near Chicago.

Their marriage was one of the few astronaut unions to survive the stress of spaceflight. That April in 1970, Mrs. Lovell never gave up hope.

“I just knew he’d come back,” she said.