I WANTED TO leave, to leave forever after the bombing of Hiroshima. I wanted to make up to the world in some way for the part I had in making those bombs possible.

Joan Hinton's decision, in 1947, to live in Communist China was a front page story. This heavy-set, healthy-looking woman was one of a handful of young American scientists to work on developing the atom bomb. Clippings of the time described her as a brilliant nuclear physicist who had worked on the Manhattan Project and had been one of a very few witnesses of the first nuclear explosions in the New Mexico desert. News stories decried her defection to China, picturing super secrets being carried to the enemy.

"What a silly fuss," says Hinton today. "When I arrived in the liberated area of China, they had nothing. We scoured the battlefields for old metal to make cooking pots. We walked along the roads searching for leftover Kuomintang materials to make nails. The last thing in anybody's mind was the development of an atom bomb. Our (Chinese) technology was so rudimentary that I thought I had made a breakthrough when I got a windmill to work, briefly, before the winds off the Gobi desert swept it away."

Hinton says, "The whole point in leaving the United States was to leave the science of destruction behind and try to help people make life better."

Hinton, 56, has been touring the United States recently for the U.S.-China People's Friendship Association. If her audience in Columbia, Md., made up of old friends, cousins and stragglers escaping the bitter cold of a winter Sunday, is an indication of her listenership, her description of China as an almost perfect society will be heard by quite a few.

Sitting in the poorly heated, aseptic Community Center of Whilde Lake Village, Hinton looked just about the same as she had in high school, robust, unlined, athletic. Her outfit of ill-cut green pants and loose white shirt was topped by a heavy green scottish sweater that I felt sure she had worn when she was my ski instructor in the late '30s, at the Putney School.

It was her mother, Carmelita Hinton, eminent American educator, who founded the co-educational Vermont boarding school that has become a model for progressive schools all over the country. It was Mrs. Hinton's basic assumption, then a revolutionary concept, that physical labor was as important as classroom instruction in the education of teen-age boys and girls. Thus it was that the adolescent Joan Hinton hauled manure, fed pigs, milked cows at Putney in what in hindsight turned out to be appropriate preparation for her life as a farm machinery technician in spartan China.

Mrs. Hinton believed and taught her students that anyone could do anything they wanted to do if they tried hard enough. Her favorite political comment was, "The world would be a much better place, a much fairer one if everyone put his shoulder to the wheel." She abhored laziness, "of the mind, the body or the spirit." She believed in succoring the oppressed, thus hired many teachers who were refugees from Franco's Spain and Hitler's Germany. She gave scholarships to young German Jews, Indians and blacks. She advocated simple living as a key to man's salvation. Her most active acolyte, her daughter, took these simple, although sometimes naive concepts to a real revolution. And has found that from her point of view they have mostly worked.

A generation has passed since Joan Hinton watched the first atomic explosion turn an arid but productive stretch of New Mexico into a wasteland. She is still the same person who, horrified by what she saw, packed a rucksack and set out to look for a better society. Hearty, optimistic, unruffled, her naivete combined with a highly skilled scientist's mind. She is surprisingly unchanged by years of hardship and the drama of being one of three or four young foreigners to be in the forefront of the Chinese revolution. Indeed, her pleasant, firm voice describes the hunger and deprivation of the early years in North China in just the same voice that had encouraged me down the icy New England slopes, firm but upbeat she was then and is now. She remains intellectually simplistic and at the same time highly skilled and competent.

Helping me with the sciences was easy for Joan Hinton. But the abstractions of literature bored her. For example, "Mrs. Dalloway," Virginia Woolf's convuluted, introspective, subtle view of the world, was not anything Hinton wanted to deal with, anymore than she currently wants to examine what is wrong with "the Gang of Four." China's latest group of disgraced former national heroes. She is content to say. "They are enemies of the people. They do not want what is best for China." Further questioning reveals no more.

I listened to Hinton talk enthusiastically about her first months in China when survival depended on her ability to scavenge, make do with scraps of food and patch her slim wardrobe. Listening, I remembered her, marooned with young students on a kayak trip. The white water had risen dangerously and she was responsible for our safety. It was a challenge she enjoyed. She plotted a cautious course. We would, she announced, wait for safer boating at the risk of some hunger. If those waiting for us became worried by the delay, well, that was their problem. She hoped they wouldn't panic. So with cheerful, calm and buoyant optimism we built fires, looked for berries, played games and waited until she determined the trip could be resumed without danger. Not one of us questioned her leadership. We had total trust in her competency. And still, she had no intimate friend among us.

As she stretched her scuffed boots out in front of a community hall chair, I thought of her standing in my family's elegant town house hall one Christmas vacation. There, in her blue jeans, ruddy and smiling, she looked completely miscast among urban comforts.

My father always made the same comment when Joan arrived to visit. "She would have been great on the Oregon Trail."

After Putney, Hinton went to progressive Bennington College where she galloped through the science courses in a record three years. College contemporaries remember her as king, smiling and somewhat aloof. Her sister, Jean, and her brother Bill, who followed her to China and has subsequently written, "FanShen," the story of a Chinese village since the Revolution - a book widely recognized as the definitive one on current rural China.

Hinton almost made the first woman's American Olympic ski team and still counts those trial races as, "a high point in my life." After Bennington Hinton went to Wisconsin for her M.A. and on to the University of Chicago, where the world's first atomic bomb was begotten, for her Ph.D. Indeed her work on her doctorate brought her the singular distinction of becoming Enrico Fermi's assistant. From there she went to work in the labs at Los Alamos.

It was a long trip from New Mexico to China. It took Hinton over a year to reach the Red army in remote Shensi province. Passes from Chiang Kai-shek's part of China to Mao Tse-tung's in 1948, at the height of the civil war, were hard to get. "I had to join a kind of underground. I even tried to disguise myself," she explains. "And of course it was harder for me to melt in.

"I didn't have many thoughts about China when I left the States," she says, smiling. "I just knew that as an atomic scientist in America I would be involved in further refining the instruments of destruction. I knew I would have to sell my soul or quit. I had read Edgar Snow's, "Red Star Over China," and it made me think the Chinese were trying something worthwhile.

"Whose early years were certainly a challenge. The country was charred from years of war. No crops had been planted in the war areas. But we were always optimistic."

The first year was the hardest partly because the Chinese could not understand exactly how Hinton and the man she married in 1949, Sid Engst. a farmer from upper New York, happened to be there. "We would explain that we believed they were trying to make a better life for the millions of Chinese and we wanted to help. It didn't take long before we were completely accepted."

It's easy to understand why the Chinese so quickly adopted this indefatigable young American who happily went days without sleep, eating only occasional bowls of gruel in order to perfect a hog-feeding machine.

"We were under great pressure, not only because our own people needed things but because the Russians were insisting on repayment of their wartime loans. We all worked day and night. I was grateful," comments Hinton, "that I was able to develop a special expertise, to help make our farm a particular success."

Hinton and her husband worked on a state farm near Sian from 1951 to 1966. Engst, who had majored in animal husbandry at Cornell School of Agriculture, put his expertise to work in China. Over the years he has bred cattle, horses and hogs though he now works on farm machinery with his wife. Hinton describes her years in China as "productive." But in 1956, during the Cultural Revolution, the active Hinton was put in "a kind of limbo." All foreigners were gathered up, "for our own safety," lodged in a Peking hotel complex, which had originally been built by the Russians for their own personnel, and kept under close surveillance. "It was a period of waiting," says Hinton.

But by the early '70s Hinton was once again hailed for her inventive work on farm machinery. She and Engst had been moved to a Red Star commune, an hour's bicycle ride from Peking. The early years, even the virtually inexhaustible Hinton says, "were hard, no meat, no heat in the dormitories, very little clothing, not much medical care." But the miracle for Hinton is how much all that has changed. Adequate food for everyone, warm clothing, good rural medicine, fine schools and bit by bit the mechanization that is changing the back-breaking day of the rural Chinese.

"When we first started making farm implements we were thrilled to find the material just to make nails. Even hand plows were scarce. But by the year 2000 Chinese agriculture will be completely mechanized. You won't see anyone carrying those huge loads. People will be freed for other kinds of work."

Oil, grain and cotton are still rationed, but luxury goods like a wool coat can be bought off the ration. Both Hinton and her husband save most of their salary as they pay no rent for their three small rooms in a barracks like dormitory, which also houses a day-care center and women's dormitory. Food is either eaten in the communal dining room or purchased from the communal supply and cooked by a "grandmother" in their own apartments. It is cheap. There are no taxes. Medicine is free and since Hinton's energies are consumed by her job, she doesn't need money on leisure pursuits. Clothes present no temptation - her one set of underwear is washed out at night. She owns a bicycle but uses state-owned vehicles for any trips. Over the years she has acquired a few minimal comforts - three beds, four bureaus, six chairs, the use of a car or truck for business, a priority rating from time to time for a train ticket, a radio or a watch. Her special place in Chinese life can perhaps best be gauged by the attention given her mother when she fell desperately ill. A team of physicians was sent from Peking to the rural commune where Mrs. Hinton was visiting. The director of the team was Chou En-lai's own doctor. She recovered and credits her fine health to "such special care."

Hinton's reputation has made her a sought-after consultant all over China so she travels "a good deal." Her ability to understand drawings and make machinery is widely heralded. This, however, is her first trip home.

Home? Hinton stops herself in midsentence, "Of course China is home." But she has kept her American citizenship. Two of her three children speak no English and the third, a tall, handsome 25-year-old who is traveling with his mother sounds like a Chinese waiter but nevertheless, they, too, are American citizens. Why? She shrugs, smiles, "My family live here," comes the hesitant answer.

Renewing her passport has been no trouble in the last few years. "Just a trip to Hong Kong to the American Consulate. The British were a little snippy about a passport that had expired 25 years ago but our people were just fine." Again the smile. "They wouldn't have been 10 years ago," she adds.

The high point of Hinton's American visit was a trip to see old friends at Los Alamos. She was specially touched that her old companions joined together to finance her plane ticket west and sponsor her lecture and slide show. She still loves and misses physics. "Pure science and original research," says her mother, "is what has always most fascinated Joan. It has been a real sacrifice for her to give it up. I don't think she has ever missed the creature comforts, indoor plumbing, or central heat or even the luxury of privacy. I know she has never missed pretty clothes. Indeed she might have been pleased to have so little choice and no indecisions about what to put on. But she has very much missed the companionship of other scientists. She has missed the lab."

Hinton says she has found it encouraging, "for the world, that American scientists are worried about the direction of science, disarmament, ecology, planning, all the kinds of things that disturb me about the American future."

How does America seem to an American who has chosen to spend 30 years in Communist China?

"Too much, too much of everything." She objects to the waste of buildings like the Dallas airport where size and commercialism seem to take the place "of planning for people," to the waste of food, "too much served and too much put in the garbage," over packaging, over selling, over throwing out. She remembers that at a recent stop her hostess was throwing out broken children's toys. "I could have fixed them," she says. She complains of a country that doesn't recycle human waste, or water, or paper or bottles, doesn't use all its manpower, encourages wide discrepancies between rich and poor.

She resents the cheery goodbye of the airline stewardess as "not sincere, pure commercialism." She dislikes all advertising, finds it " hard to believe anything anyone says about a product. Selling, not benefit for the people, is the important thing here," she says sadly.

China still looks like a much better society to her. One where an attempt is made to plan for a sensible technological future, without pollution, without unemployment. She points to, "wise prohibitions to increase the size of the cities and instead plan for mini-cities throughout the country. Most of all," she says, "the energy of the people. I believe the socialist road to progress is the fastest, certainly the faires t."

Hinton talks about, "Living happiness is work . . . to each according to his work which will ideally one day became each according to his need." For some of us the talk gets murky.

To a question about personal freedom her answer is direct. "It is more important to eat. But most of all it is more important to be part of a system that is working for everybody's good. I believe that the good of the community is more important than that of a single individual."

She gives complicated answers to such questions as, "Do you regret that your two oldest sons have no university, indeed, no professional training?" And the sum of 10 minutes discussion on how important it has been for them to work with factory groups is that Hinton is thrilled that under a new system of selection, based in the old academic achievement criteria, so long in disrepute, her 18-year-old daughter Karen has been chosen as a student at Peking University.

Her oldest son, Fred, strikingly handsome, with his mother's open smile, has been working in a Philadelphia steel mill since 1974. He seems to hang between the two societies. He says he will always be a foreigner in China. "The Chinese always think in terms of ancestors," he comments, "so you are always whatever your ancestor was, so inevitably I am always an American." Custom would frown upon his choice of a Chinese bride. But like his mother, Fred thinks the Chinese have found a more just way of life for the majority. His limited English makes his reasoning seem simplistic, on questions such as, "Having been exposed to a more open society, won't the regimentation of the newspapers, the kinds of goods available, bother you?" i.e. "It works out for the best that way . . . It is certainly better than the commercialism of American publications."

Both Hinton and her son are worried that personal rewards for extra work may spoil the spirit of the revolution. They fear that "Stakhanovism" may have the deadening influcence on the Chinese that it has had on the Russians. "Being paid by the piece is the antithesis of the Revolution," says Hinton. "The struggle in China that is coming up will be about the best way to tap the energy of the people. I hope that the leadership will understand that there is a vast reservoir of enthusiasm for working for the good of the whole. A spirit, a generosity that could be used with the same intensity as during the hard years."

Hinton looks forward to getting back to China, "as so much is going on, politically and other ways." It is, she says, "a society in motion." She particularly misses her part in the long debates about work on the commune farm. "Of course I wonder what decisons are being made about the farm machinery we will buy or build this spring. Since I will have to make it all work, I would love a chance to express my opinion! We have a participatory society and sometimes it is necessary to have a good strong voice," she says with a smile.

Hinton says that as the society becomes more mechanized, more sophisticated problems may arise that affect motivations. But again the broad smile, "I am sure that the soundness of basic thinking and the rightness of the people will make it all work out fine."

Even the Chinese atom bomb?

"I hope so," she answers.

And now she puts on her brown jacket and wool hat, her strainght blond hair peeking out from under. Her ruddy cheeks are aglow from the talk. She looks just like a Norwegian housewife off for a cross-country ski, but instead Joan Hinton is off to another town to give another eliptical talk on China. She is hopeful that there will be, "lots of people," but glad if even a few want to hear her, knowing that her welcome across the country would have been frostier 10 years ago."Some day people over here will understand how much the Revolution has done and how much the future holds for China," she concludes, smiling.