When the shuttle Challenger returns to space, it will, among other things, be an orbiting laboratory with some 22 scientific and engineering experiments aboard.
At this writing, the countdown was under way for launch at 7:33 a.m. Eastern daylight time Saturday from the Kennedy Space Center. The five-member human crew was going through final training for the six-day mission. But the crew of nonhuman astronauts - a colony of carpenter ants - was already in place in its GAS (Get-Away-Special) canister in Challenger's payload bay.
The ants, whose adaptation to weightlessness will be recorded by television and movie cameras, represent an experiment by students from Camden and Wilson High Schools in Camden, N.J. This is one of seven different experiments being carried in low-cost, self-contained GAS canisters.
They include a variety of crystal growth and other materials experiments for United States and foreign clients, studies of radish sprout growth by the California Institiute of Technology, and devices to measure the environment in the shuttle equipment bay.
However, by far the most significant experiment is mounted in Challenger's cabin where astronauts can service it. This is the electrophoresis system of McDonnell Douglas Astronautics Company. Electrophoresis is a tongue-twisting term for a process that uses electric forces to separate biological molecules, such as proteins, that are mixed together in solution. This promises to become the first commercial process to be implemented in a robot space factory. It is expected to be placed in orbit within the next five years.
McDonnell Douglas program manager David W. Richman explains that the process is worth taking into space in order to get away from gravity, which limits the technique's effectiveness on the ground. He told a meeting of the American Association for the Advancement of Science in Detroit last month that tests on two previous shuttle flights showed it possible to boost the yield and the purity of the product by several hundred percent.
On this flight, Dr. Richman says his team expects to verify the conditions under which the process best operates in space. Then his team plans to test a ''Production Prototype Unit'' during two shuttle flights in 1985 and 1986. If successful, this should lead directly to commercial production. While the first such space factory will be in an automated satellite, Richman says his team would like to move the unit to a manned space station, which it hopes will be available in the early 1990s. The National Aeronautics and Space Administration (NASA) timetable for such a station would have it in orbit by that time. However , the Reagan administration and Congress have yet to commit themselves to this project.
Such space manufacturing is expensive and thus is feasible mainly for products of high value that are used in small quantities - in this case pharmaceuticals. There is always the possibility that new ground-based processes would be better suited for the job. For example, techniques for producing pure biological materials using genetically engineered microbes might make the McDonnell Douglas space factory obsolete before it's launched.
Richman acknowledges this possibility. However, he says that his company considers the products currently being studied to be only the first of three to 15 possible space-produced materials to be developed by the year 2000. Speaking for NASA, Brian Pritchard, who heads the Space Station Task Force, has called the electrophoresis experiment ''the first success in terms of commercial objectives in space.''
The NASA-McDonnell Douglas experiment shares shuttle space with another, less advanced, commercially oriented unit. This is the ''Monodiserse Latex Reactor,'' aimed to produce uniform small spheres of latex. Flown three times before, the commercial future of the NASA-LeHigh University experiment is, at this stage, much less certain than that of the NASA-McDonnell Douglas unit.
Challenger is also carrying 17 US and foreign experiments on two special units that are a feature of the shuttle. A payload package fixed in the shuttle cargo bay carries six materials processing experiments - a joint project of NASA and the Federal Republic of Germany. Then there is the SPAS (Shuttle Pallet Satellite), which carries instruments and experiments into space outside the shuttle.