The U.S. space program should not "rush headlong toward Mars" but aim for the moon again and develop the technology and experience needed for an "orderly expansion outward from Earth," astronaut Sally K. Ride concluded in an 11-month study released yesterday.

The 63-page report unblinkingly portrays a fallen U.S. space effort and dampens the hopes of those who have pushed for a manned mission to Mars within the next 20 years. It also complicates the task of administration policymakers who have faced increasing charges recently of allowing the National Aeronautics and Space Administration to drift without long-term goals.

"Settling Mars should be our eventual goal, but it should not be our next goal," Ride said.

"It would not be good strategy, good science or good policy for the U.S. to select a single initiative, then pursue it single-mindedly," she cautioned. Instead, she recommends a selective strategy of "evolution and natural progression," in contrast to the spectaculars -- the Apollo moon program and the space shuttle -- that have characterized the U.S. approach so far.

In the report, entitled "Leadership and America's Future in Space," Ride said the space program "unfortunately lacks some fundamental capabilities," such as minimal Earth-to-orbit transportation.

The United States can no longer be the undisputed leader in all space endeavors but must pick its shots, according to Ride. The space program has already relinquished to the Soviets its leadership in two key areas -- the exploration of Mars and long-duration manned space flight -- she said, and is in jeopardy in others. "The Soviets are now the sole long-term inhabitants of low-Earth orbit," Ride said.

Spokesmen for NASA administrator James C. Fletcher, who has expressed support for a manned Mars mission as soon as possible, said the report will be used as a basis for further study and that the agency will not necessarily adopt all its recommendations.

The report, commissioned by Fletcher, parallels and often quotes a report completed more than a year ago by the congressionally mandated National Commission on Space to which the administration has not responded.

Ride, the first American woman in space, agreed to head a NASA team in preparing the study last year after participating in the Rogers presidential commission that investigated the Jan. 28, 1986, Challenger accident. She announced her resignation from NASA last May and is scheduled to leave the agency Sept. 26 to work at a research institute in California.

Ride was driving back to Houston's Johnson Space Center yesterday to wrap up her work with the space agency, a spokesman said, and was not available for comment. She has refused to hold a news conference to discuss the report, according to NASA spokesmen.

Her report assesses four poss- ible undertakings for the space agency: Mission to planet Earth, which would employ nine orbiting platforms to study and predict changes in the Earth's atmosphere, oceans and other life-support systems. "This initiative represents an important opportunity for the United States to exercise leadership in an increasingly significant area . . . . It shows a recognition of our responsibility to our home planet." Exploration of the solar system, including robot missions to a comet (Tempel 2), an outer planet (Saturn) and an inner planet (Mars). Ride, noting that she is adopting a strategy already proposed by a NASA advisory panel, said this initiative "offers opportunities to exercise leadership in the international arena . . . . Planetary exploration must be solidly supported through the 1990s." Outposts on the moon, an initiative that would "send the next generation of pioneers" to build on the legacy of Apollo, beginning with robotic exploration in the 1990s and landing astronauts on the lunar surface in the year 2000. They would construct an outpost that would evolve in size and capability, learn to "live off the lunar land" by extracting oxygen for propellants and life-support from the soil and learning to make construction materials.

"By 2001, a crew could stay the entire lunar night {14 Earth days} and by 2005, the outpost would support five people for several weeks at a time . . . . By 2010, up to 30 people would be productively living and working on the lunar surface for months at a time.

"It is not absolutely necessary to establish this steppingstone, but it certainly makes sense to gain experience, expertise and confidence nearer Earth first," the report said. Humans to Mars, a "quick-sprint" mission that would land Americans on that planet early in the 21st Century and produce an outpost there a decade later -- the only approach to a Mars mission she was asked to examine. Although it would be "a great national adventure," it would require a massive immediate national commitment and an approximate tripling of NASA's budget during the mid-1990s, possibly overwhelming other NASA projects such as the proposed space station during the next decade.

The report warns that such a fast-paced initiative could turn into another "one-shot foray or political stunt" that loses public support and leads nowhere in the same manner as the Apollo moon program -- something public hearings indicate the American people do not want and which most NASA personnel oppose.

In the wake of the Challenger disaster, Ride said, the space program is confronting two "fundamental, potentially inconsistent views" that reflect concern about the program's plight. On one side are those who are pressing for a "major, visionary goal" to galvanize public support and generate excitement. On the other are those focused on the shortcomings of the program that emerged in the investigation of the Challenger accident, who "believe that NASA is already overcommitted in the 1990s" and cannot handle another major program.

Both are partly right, she concludes. NASA needs long-term goals but cannot reach them without dealing with the shortcomings described in the Rogers commission report.

NASA alone cannot set these goals, but it "must lead the discussion," she said. She urges the agency to establish goals and pursue them by "articulating, promoting and defending them in the political and fiscal arenas."