Discovery - the third United States space shuttle - is ready to undertake its maiden flight with a cargo of ''firsts'' on board. A defense communications satellite is to be deployed by a spring that will effectively toss it out of the shuttle like a Frisbee.
A 102-foot-long solar array will be deployed from within the shuttle cargo bay in an experiment that effectively uses the shuttle as a base for erecting and testing a space structure.
And, most significant of all, Discovery will carry the world's first nongovernmental, paying crewmember - Charles Walker, a private citizen working for McDonnell Douglas. He will operate, test, and, if necessary, repair the company's experimental equipment for producing exceptionally pure drugs by separating biochemicals under the weightless condition of orbital flight. Thus, a quarter of a century into the space age, the space frontier has begun to open for people other than official government space personnel.
At this writing, Discovery was being readied for liftoff from the Kennedy Space Center at about 8:43 a.m. Eastern Daylight Time Monday. After some 7 days, 52 minutes on orbit, it is scheduled to land at Edwards Air Force Base in California on July 2 at 9:35 a.m. EDT. The launch, orginally scheduled for June 22, was slipped to June 25 to allow time to replace one of the shuttle's three main engines.
It is a mission full of work-a-day routine for the six-member crew - no spectacular excursions with the jet-propelled backpacks, no dramatic rescues of ailing satellites. But it should demonstrate more of the shuttle's utility as an Earth-to-space bus and an orbital workhorse.
Indeed, mission commander Henry W. Hartsfield Jr. and pilot Michael L. Coats will have more the role of bus drivers than of intrepid space pioneers. Much of the mission work itself will be carried out by four specialists. Besides Mr. Walker, the paying passenger, these included Judith A. Resnik, the second US woman astronaut to orbit; Richard M. Mullane; and Steven A. Hawley, husband of Sally Ride, the first US space woman.
Ms. Resnik will help Walker do some of the more complex testing with his equipment. But, most of the time, he will be on his own, tending to the McDonnell Douglas/Johnson & Johnson experiment.
The experiment uses a process called electrophoresis. In this, electric fields are used to separate different molecules from one another in solution.
A mixture of proteins, for example, can be separated into streams of solutions containing the different proteins in highly pure form. On Earth, convection and other gravity-related effects make it difficult to obtain pure separations in this way. But, on orbit, a high degree of purity is possible.
The two companies are planning to make certain drugs with a high value per unit weight. The first of these, whose nature still is a company secret, now is ready for human testing.
The equipment has been modified to produce a quantity of the product for this purpose. Thus, it will need much more attention than has the equipment on earlier shuttle missions.
McDonnell Douglas is paying the National Aeronautics and Space Administration (NASA) $80,000 for Walker's ticket. This includes the small amount of astronaut training he has needed for the flight.
Meanwhile, the NASA astronauts will also be busy with a variety of experiments of their own, as well as launching the first of several LEASAT communications satellites. Hughes Communications Services Inc. is managing the LEASAT project for the Department of Defense.
The most spectacular experiment involves deployment of a new type of solar cell array 102 feet long - as tall as a 10-story building. This flexible power source may be used with future space stations. It folds up like an accordian.
The astronauts will erect and refold it several times and test its stability when erected. Instruments will check its performance as a power source, which should generate several times more energy per unit of surface than early arrays used, for example with the Skylab space station.
Discovery also is carrying a new stereo camera. Film in this large-format camera can capture an image of an area as large as the state of Massachusetts on a single frame. Yet the resolution is sharp enough (about 65 feet) to pick out individual houses. It should aid in geological mapping.
Discovery itself also is testing some innovations. New light-weight structural members have reduced its weight by several hundred kilograms. And, on parts of its surface, the protective thermal tiles have been replaced by a new thermal blanket that better withstands the rigors of launch and reentry.