THREE decades ago, when Alan Shepard was preparing to strap himself into a Mercury capsule and become the first American in space, NASA (National Aeronautics and Space Administration) needed a small, lightweight electrocardiograph.

Finding nothing of the sort in existence, NASA doctors and engineers did the only thing they could: they built on themsefees. That instrument the size of a pack of cigarettes, began an era of space medkal research that continues with the Space Shuttle Program and promises to be a centerpiece in NASA's efforts well into the 21st century.

In the early days of space flight, medical concerns were always at the fore. Each new milestone in space endurance-from Shepard's 15-minute suborbital hop to the two-week marathon of Gemini 7 in 1965-knocked down "straw men" hears that the human body would not function in space. But it was not until the early 1970s, after the Apollo inooitlanding program was over, that NASA started medkal research in orbit.

Three missions to the space station, lasting 28. 56, and 84 days respectively. amassed a mountain of data on human adaptation to weightlessness. Skylab crews underwent some disturbing changes including loss of muscle mass, bone demineralization and a decrease in red bkxid cells.

These adaptations to zerogravity would have to be understood and dealt with before permanent space stations and vistis to other planets could be feasible. But after Skylab. NASA settled into a king space flight hiatus while engineers developed a reusabk-Space Shuttle.

Only the joint Soviet-American misskHi in 19^5 broke the seven-year lapse. During NASA s hiatus, advances in miniaturization, computers and microelectronics developed for the spat e program were finding their way into the commercial medkal arena. NASA touted among such spinoffs" the tiny, implantable programmable . pacemakers derived from space

technology.

Space hardware can also be adapted for terrestrial research, such as the Bioreactor, a cell-culture device developed at the Johnson Space Center for Shuttle research. In ground-based tests, the Bioreactor has generated bits of human lung and small intestine tissue from normal primary cell cultures, apparently for the first tune in any laboratory. And w hile the Bioreactor is destined for space, part of the technology is applicable and will he marketed on Earth.

While Shuttle missions will continue to include medical activities, bigger opportunities for industry are on the horizon. For the rest of this century, NASA's focus will be on its permanently manned space station. Freedom.

It remains the centerpiece of NASA's prtKjram. Slated for habita tion by 1996, the space station will be home to as many as eight astronauts on tours of duty lasting from 90 days to six months or more. For the station, NASA needs a new generation of space medical hardware. The first priority will be to keep Freedom's crews healthy, and for that NASA is

creating the Crew Health (are Svstem (CHeCS).

This will let astronauts cope with anything from routine injuries to heart attacks. In the event of a medical emergency, the goal would be to stabilize a patient before putting him or her on a Shuttle for return to Farth.

in addition to an extensive phar macy. CHeCS will include such Limil iar items as a defibrillator and a ventilator. as well as innovations like an automated clinical chemistry analyzer and a digital x-ray camera that can transmit its pictures to doctors on Earth.

Also under consideration is a small ' CAT scanner to study how an astro-tuuts bone density changes in space. Once the station is operational, one main goal will be to pick up where Skylab left off, studying human adaptation to space flight

NASA hopes to have the space station, outfitted with the first components of CHeCS and Biomedical Monitoring and Counter-measures system, ready for its first visitors sometime in 1996. It will include equipments like gas chromatographs. EKG with Holter monitor, bioimpedance analyzer, centrifugal incubator, urinalysis system, osmometer ahd miniaturized flow cytometer.

Unlike space station crews able to return to Earth in an emergency. Mars astronauts will truly be on their own Autonomous medical care will be necessary. Computer aided diagnov tic systems may be included on the Mars ship.

Undoubtedly the astronauts will need the capability to dognajof surgery . The sheer lenph of the flights will require blood and pharmaceuti cab with extremely long shelf life. There is even a potential need for "telemedicine", giving doctors in mission control the ability'Io examine the astronauts using high resohttion television pictures and other data beamed to Farth.

I Itimately the most daunting challenges will be both medk al and psychological. "We've never done anything like this before. With talk like that, it's no wonder they call space "the final frontier ’