Every nation that has contemplated sending humans into space has faced many challenges. One of the most pressing has been, "How does gravity affect and influence living systems, and, more specifically, our astronauts?" A newly developing division of life sciences called the space life sciences seeks to answer this question.

At the dawn of manned space flight, the fledgling space life sciences were concerned primarily with the safety and performance of astronauts. The launching of a monkey, named Albert, by the United States in 1948, and the rocketing of nine dogs by the former Soviet Union in 1952, were undertaken as test trials to study the effects of exposure to solar radiation at high altitude above Earth's atmospheric filter, and to see how, or if, animals could withstand the hazards of flight into the hostile environment in space. If human beings were to undertake a similar journey, it was reasoned, it would be necessary to create countermeasures to offset the anticipated life-threatening conditions they would most likely encounter when they were launched from the Earth's surface under high acceleration and faced unattenuated solar radiation.

The first orbital flight took place on October 4, 1957, when the former Soviet Union launched Sputnik 1. Sputnik 2 followed suit on November 3, 1957, carrying a dog named Laika ensconced in a pressurized compartment. Laika survived for one week in space, the rhythmic beating of her monitored heart proving that animals could survive the launch. Laika led the way for human exploration of space by disproving prevailing scientific wisdom that space flight would have been injurious to vital internal organs. The launching of Sputnik ushered in the Space Age and began much of what we take for granted today.

Four years later, Soviet cosmonaut, Yuri Gagarin, became the first person to orbit the Earth on April 12, 1961. From the United States, on May 5, 1961, the first piloted Mercury flight, Freedom 7, bore Alan Shepard into suborbital flight, making him the first American in space, and John Glenn rode Friendship 7 for three complete orbits of the Earth. Experiences from these and the three subsequent Mercury flights made it necessary for space scientists to develop countermeasures to the problems that faced man's existence in space.

The sixties saw the development of the famous Apollo program. With the Apollo missions came the first human lunar orbital flight, the first piloted flight to be influenced by the Moon's gravity, and of course, the first lunar landing. The saga of the famous Apollo XIII, however, reminded us how difficult it is to maintain a hospitable living environment in space. The Apollo missions demonstrated that humans could survive and work in the Moon's environment which has one-sixth the gravity of Earth. The astronauts' reports on two major changes that their bodies underwent in response to the microgravity - space motion sickness, and changes in their sleep patterns - generated long-term interest in the effects of microgravity on biological processes.

It was not until 1973, with the advent of NASA's Skylab program, that scientists were able to undertake experiments to investigate the individual body systems' responses to weightlessness. Skylab I was an unoccupied mission, however Skylab II, launched on July 28, 1973, carried Alan Bean (Commander), Jack Lousma, and Owen Garriott, Science Pilot, aboard. Their mission lasted 59 days, during which time they conducted many experiments, including a student-designed experiment to find out what kinds of webs spiders would spin in the weightless environment of microgravity. The scientific data from the Skylab missions remain a significant source of descriptive information that allows scientists to hypothesize about long-term physiological changes in space.

The Skylab missions set the stage for the current Spacelab era. Spacelab will represent an important step forward for the space life sciences and will make history when it returns to Earth with the Neurolab crew 1998, bringing back new information about how the brain and the nervous system respond to the microgravity environment of space.