HOUSTON -- Anyone who's read Tom Wolfe's "The Right Stuff" or seen the movie based on it knows about the mental and emotional stresses astronauts face as they train for space travel.

But those trying to explain the apparent breakdown of Lisa Nowak say the pressure can be even higher for female astronauts, who not only face the same work stresses as their male counterparts but often face high expectations at home.

"They made more sacrifices than the 'Right Stuff' guys," said Dr. Jon Clark, a former NASA flight surgeon who lost his wife, astronaut Laurel Clark, in the 2003 Columbia disaster. "They have to balance two careers -- to be a mom and wife and an astronaut. ... You don't come home at night, like most of the male astronauts, and have everything ready for you."

Clark said Nowak, charged with attempted murder and attempted kidnapping in what police depict as a love triangle involving a fellow astronaut, provided invaluable support to his family after his wife's death, even when it cost her time with her own husband and three children.

Nowak's background -- high school valedictorian, Naval Academy graduate, test pilot -- seemed to equip her for the challenge. Yet as she and some of her acquaintances acknowledged, the stresses on her and her family were extraordinarily intense.

On Wednesday, transformed from space hero to criminal suspect, Nowak returned to Houston for a medical assessment.

She was met on the tarmac by police and escorted into a waiting squad car after her release on bail. Her head was covered by a jacket. She faced a medical exam at Johnson Space Center and reporters from around the country were staking out her home.

NASA said it would revamp its psychological screening process in light of Nowak's arrest. The review will look at how astronauts are screened for psychological problems and whether Nowak's dealings with co-workers signaled complications.

Nowak has a teenage son and 5-year-old twin girls with her husband, Richard, who works for a NASA contractor. The couple separated a few weeks ago after 19 years of marriage.

"She was the epitome of managing a very hectic career, making sacrifices to accommodate her family," Clark said in a telephone interview. "All those stresses can conspire to be overwhelming. ... Clearly she suffered a lot of mental anguish.

"There is a lot of marital stress in the astronaut corps in general -- a huge amount," Clark said. "It's not unheard of for things to change into relationships that are beyond professional."

Clark expressed empathy with Richard Nowak.

"He was a real low-key, go-with-the-flow, unobtrusive person," Clark said. "You almost have to be to survive in the realm. ... It was hard on our marriage to have my wife gone all the time, and eventually have her career surpass mine."

Nowak's Road To Aeronautics

Nowak grew up in Rockville, Md., where she was co-valedictorian and a member of the track team in high school. She graduated from the Naval Academy in 1985. The class officers of her year said Wednesday in a statement released by Bryan Caisse, the class secretary, that Nowak was "a great classmate and friend."

"She never hesitated to lend a hand or assist someone in need. She has been an incredible role model as a Naval Officer, astronaut and mother, and has shared her success with many others," the statement said.

Nowak received a master's degree in aeronautical engineering, flew as a test pilot in the mid-1990s while caring for an infant son, and became a full-fledged astronaut in 1998.

"It's definitely a challenge to do the flying and take care of even one child and do all the other things you have to do. But I learned that you can do it," she said in a recent interview with Ladies Home Journal.

Last July, in the climax of her career, she flew on the space shuttle Discovery, helping operate its robotic arm and winning praise for her performance.

Signs Of Something Wrong

However, there were signs of turmoil in her life.

In November, a neighbor reported hearing the sounds of dishes being thrown inside Nowak's Houston home. And she had begun to form a relationship with William Oefelein, a fellow astronaut and father of two whose own marriage ended in divorce in 2005.

Police said Nowak told them the relationship was "more than a working relationship but less than a romantic relationship."

Charlene Davis, the mother of Oefelein's ex-wife, Michaella, said Wednesday that Nowak -- although friends with Oefelein for years -- had nothing to do with his marriage breakup.

"I think there were a lot of bad choices being made, and Lisa just made a horrible one," Davis said in a telephone interview. "And I just feel sorry for her. What the hell was she thinking?"

The final unraveling came this week when police arrested Nowak for allegedly trying to kidnap Colleen Shipman, an Air Force captain from Florida. Police said Nowak believed Shipman was her rival for Oefelein's affections.

Police charged Nowak with attempting to murder Shipman based on weapons and other items found with Nowak or in her car: pepper spray, a BB-gun, a new steel mallet, knife and rubber tubing. Nowak's lawyer, Donald Lykkebak, has said she only wanted to talk to Shipman.

Those who know Nowak away from the high-pressure atmosphere of NASA were stunned.

"I was very surprised... She always seemed very normal to me," said Candis Silva, who lives three houses down from the Nowaks. "She was a good role model for our daughters."

Thomas Nagy, a Palo Alto, Calif., psychologist who has studied the stresses facing dual-career couples, hesitated to offer any specific diagnosis of Nowak, but said such seemingly desperate acts could result from a chronic personality disorder or from a period of high stress that clouds one's judgment.

"When people are in that role of trying to do everything to the Nth degree, they don't get enough sleep, they don't do enough activities that are fun, they don't get enough exercise," he said.

"If we ignore those because we're trying to do it all, we pay a price -- more anxiety, more depression."