RACIAL TENSION FEEDS the violence at Roosevelt Towers. Blacks are a small minority in the project. George Yuse, of the Cambridge Housing Authority, estimates that blacks are about 10 per cent of the project's population, while Cambridge is close to 7 per cent black. However, some public projects in black neighborhoods, like Putnam Gardens, are as much as 40 per cent black.

When asked why the Roosevelt tower is in worse shape than the low rises there, one white youth replied, "because the niggers live there."

Roosevelt Towers' blacks are concentrated in the tower building. Conditions in the tower make turnover there the highest, so vacancies are most likely to occur in it.

Yuse said last week that between 25 and 30 apartments are vacant in the project--about 20 of them in the tower.

The Housing Authority will be able to fill the vacancies, Yuse said, although newspaper publicity and the popularity of the city's rent subsidy program make the task more difficult. The subsidy program allows aid recipients to live in scattered privately-owned buildings instead of massing them into public projects.

Yuse attributes much of Roosevelt Towers problem to a change in the population living in the public housing. Complete families are moving out of the projects," he said. And families without male adults replace them. "Almost 80 per cent of our applicant pool is now broken families," Yuse said. "In Roosevelt Towers we are concentrating a group of low-income families in a small area."

Drugs share part of the blame for the project's problems. Many observers hold junkies responsible for much of the development's crime and vandalism. One resident claimed to know "four or five families" in the high-rise who "make their living selling the stuff."

Some Towers youths complain of harassment by police and security guards. One claimed that a security guard had cooperated with Cambridge police to trump up charges against a friend of his who the police "wanted to get."

A PERVASIVE DEFEATISM accompanies life in the Towers--a feeling, at least among whites, that conditions are steadily deteriorating. A resident who had lived in the project for nine years said that the rapid decline began "two or three years ago."

An old woman, a resident of the tower building for 15 years, shivered as she recalled what had happened in her home. "Things used to be better." Asked to explain why, she just repeats, "Things used to be better."

In 1950, Roosevelt Towers seemed to be an answer for a city crowded with homeless veterans. The main speaker at the Towers dedication ceremony was Congressman John F. Kennedy, a backer of the 1949 Federal Public Housing Act, which committed Federal money to public housing.

The subsidy program, which integrates the poor into existing neighborhoods, may be an answer to the problems of public housing. But no one has an explanation for the project's failure convincing enough to lead to the outline of a solution.

The project's general decline and the Tower's particular misery remain a mystery. The closing of the tower, while motels sprout near the Square, would be a chilling but not unique demonstration of urban failure.