Johnson Space Center, Houston — Challenger, the new, improved, slimmed-down, souped-up sister ship to veteran space shuttle Columbia, lifted off smoothly from Florida's Kennedy Space Center at 1:30 Eastern time Monday afternoon.
The sixth Space Transportation System mission (STS-6) marks several firsts for a program already labeled ''operational,'' although in fact it remains experimental in many respects.
The chief objective of the five-day mission is to put the first tracking and data relay satellite (TDRS) into stable orbit 22,300 miles above Earth. This will set the stage for a new, space-based network that will vastly improve communications between Earth and orbiting spacecraft. If the first two TDRS satellites are launched successfully by this mission and August's STS-8, their first task will be to relay the tremendous volume of scientific data generated by the joint European-US ''Spacelab'' experiment scheduled for a nine-day flight in September or early October on STS-9.
Another key STS-6 objective is the shuttle program's first spacewalk, or extravehicular activity (EVA), set for Thursday. While mission commander Paul J. Weitz and pilot Karol J. Bobko watch from the shuttle's flight deck, mission specialists Donald H. Peterson and Story Musgrave will spend about 31/2 hours in the giant cargo bay. The spacesuits' complex life-support systems failed tests on the last shuttle flight and canceled a planned EVA. If the suits hold up this time, the April 7 spacewalk will include various tasks to test the astronauts' ability to work in the open cargo bay.
The greatest achievement of STS-6, however, may turn out to be its role in consolidating support for the shuttle program among space scientists and commercial shuttle customers. The scientific community has been sharply divided over the value of devoting $15 billion to create the National Aeronautics and Space Administration's (NASA) fleet of four or five reusable shuttles.
But with Challenger operational and two more orbiters under construction, space scientists appear to be shifting course. Instead of complaining about the money drained from scientific research to fuel an experimental shuttle program, scientists ranging from plant biologists to nuclear physicists and astronomers are welcoming the new research opportunities opened up by an operational shuttle system.
David Leinweber, a Rand Corporation research scientist, charges that shortcuts forced on NASA by years of underfunding have resulted in a ''less than ideal'' shuttle, being ''rushed into operation to generate revenue.'' He also regrets that diverting NASA's limited funds into the shuttle program has hurt other programs.
''Vital data from our planetary probes is spilling on the floor,'' Dr. Leinweber says, because there's no money in the budget for processing the data.
Yet Leinweber concludes that the space shuttle is key to maintaining US leadership in space and that ''the shuttle is the most advanced space vehicle ever to fly.'' He calls for additional funding to expand the shuttle program's usefulness by developing a variety of unmanned ''shuttle-derived launch vehicles.'' He says one unmanned version could increase cargo capacity from Challenger's 65,000-pound limit to perhaps 150,000 pounds by eliminating the orbiter's two-deck forward crew section. Such a giant space truck, he explains, would be the most cost-effective way to launch large space-station components.
Developing smaller, unmanned vehicles, powered by only one or two of the shuttle's normal three engines, would add to the program's versatility, Leinweber says. ''Having a stable of shuttle-derived vehicles both large and small, depending on what you will be launching,'' he explains, ''would lower the cost of the space-truck function and free up the manned shuttle for missions more appropriate for its unique capabilities.''
Physicist James L. Burch, who has been developing scientific experiments for the shuttle since 1974, says: ''The shuttle hasn't helped scientific research in the past because it has taken a lot of research money to get the shuttle operational.'' But he predicts that ''we are going to be making a lot of scientific breakthroughs thanks to the shuttle.''
He says one key advantage of the shuttle is its ability to put scientists into space along with their experiments. He adds that the shuttle also represents a major scientific advance ''because of its ability to carry huge payloads into space and provide large amounts of power for operating experiments.''
Dr. Burch, director of the Space Sciences Department of the Southwest Research Institute in San Antonio, says he hopes to see the shuttle used to assemble a permanently orbiting space platform.
He says that operating communications satellites have become commercially profitable already. ''Some type of permanent human presence or colonization'' will be the next step into space, according to Burch. A space platform could become the base for space-based manufacturing, for moon-mining operations, for a military defense system, or for a variety of other uses, he says.