Space shuttle Columbia's triumphant July 4th touchdown confirmed that America's Space Transportation System (STS) is ready and rugged enough to go into regular, cargo-carrying service.
This fourth and final test flight, a 2.8-million mile, 113-orbit trip around-and-around the world, had its problems - including a $36-million bill for the ''recoverable'' rocket boosters which sank in the Atlantic.
But the biggest blow to the STS program may come from STS-4's successes.
The nearly faultless mission demonstrated that the ship itself is space-worthy, even after going through stress tests designed to exceed anything expected on normal flights. And one of Columbia's packages of experiments showed that commercially profitable manufacturing in space may be within fairly easy reach. But, ironically, such achievements may make it difficult to raise additional federal money to expand the shuttle program.
National Aeronautics and Space Agency (NASA) officials want an extra $8 billion to build a manned space platform by 1990 and another $1 billion to increase the planned NASA shuttle fleet from four to five 100-mission orbiters.
NASA hoped to cap the STS-4 flight with a presidential endorsement of its expansionist ideas. Just as NASA planned, President Reagan did join a massive crowd at Edwards Air Force Base in California to welcome astronauts Thomas K. Mattingly and Henry W. Hartsfield home. And he did endorse the idea of ''establishing a permanent presence in space.''
But Mr. Reagan did not offer any additional funding. Instead, he outlined ways in which he expects the shuttle program to pay for itself.
''Beginning with the next flight, the Columbia and her sister ships will be fully operational,'' the President said at the nationally televised welcoming ceremony, ''ready to provide economical and routine access to space for scientific exploration, commercial ventures, and for tasks related to the national security.''
Mr. Reagan explained that the space program boosts the US standard of living by providing jobs and helps the cause of world peace by ''providing advanced methods for verifying strategic arms control agreements.''
Looking at space's money-earning potential, the President said the shuttle's success means that private industry can plan to ''use the near weightlessness and near perfect vacuum of space to produce special alloys, metals, glasses, crystals, and biological materials impossible to manufacture on earth.''
NASA officials and private experts agree with the President that space factories will be built and will be profitable. But the NASA view is that more public investment is needed to prepare for private industry's leap into space - just as on the ground, the government built the transportation networks needed to trigger industrial development.
But with or without extra money from Washington, NASA is determined to make its shuttle program a success. Already NASA has firm contracts with commercial customers and the Defense Department for flying 132 payloads on the next 62 scheduled shuttle flights. As well, NASA is considering a New Jersey firm's offer to provide a fifth shuttle in return for the right to market commercial cargo space for NASA flights.
Columbia's fifth flight, STS-5, in November will deploy two fare-paying commercial satellites. In addition to the shuttle's normal two-person flight crew, STS-5 will carry two ''mission specialists'' assigned to deal with any complex payload-handling requirements for customers.
NASA's Robert Bond, who heads the STS Effectiveness Office, explains that NASA is restructuring itself so that it can accomplish more even without extra funds.
Mr. Bond looks forward to ''the logical next step'' of building a manned space station ''now that we have a proven transportations system for bulk cargoes.'' He already sees the shuttle opening up a manufacturing potential by placing in space unmanned equipment for such tasks as growing giant crystals or forming perfectly spherical ball bearings. ''You simply allow the device to produce its product untended for as long as necessary,'' he explains, ''and then you revisit it briefly to gather the product and resupply the raw materials.''