SPACE AS A LABORATORY FOR THE LIFE SCIENCESBefore humans went into space, animals were sent up in rockets as surrogates to help us understand if a living being could withstand and survive a journey beyond the Earth's protective environment. The first successful space flight for live creatures came on September 20, 1951, when the former Soviet Union launched a sounding rocket with a monkey and eleven mice inside the nose cone of the rocket. This was not an orbital flight but instead an up-and-down rocket flight (similar to a very fast elevator ride up and down), and the animals survived. A few attempts to fly animals had been made previously (in fact, since 1948), but something always went wrong. These attempts were made with one purpose: to study the effect of exposure to solar radiation at high altitude, and to determine the effects, if any, of weightless flight.
While these animals were in space, instruments monitored various physiological
responses as the animals experienced the stresses of launch, reentry, and
the weightless environment. As scientists gained more experience with these
flights, animal space travelers were able to return to Earth in healthy
condition, refuting predictions that some vital organs might not function
in the low-gravity environment. This experience with animals paved the way
for human expeditions.
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first human to orbit the Earth. He rode Vostok 1 around the Earth (24,800 miles) and experienced weightlessness for 89 minutes. After one orbit he reentered the atmosphere and landed safely. Then on May 6th of that same year, astronaut Alan B. Shepard, Jr., rode in his Freedom 7 Mercury spacecraft for a 15-minute suborbital flight and was picked out of the water some 300 miles downrange. After Shepard, America's first astronauts completed solo flights of up to 2 days in the relatively small Mercury capsules. After the astronauts returned safely, medical scientists dismissed many of the concerns about the frailty of the human space explorer. However, the Mercury flights made it clear that the body undergoes some real changes during and after space flight, such as measurable weight loss and fluid redistribution.
Astronauts completed a more complex set of inflight medical studies during the Gemini missions, which served as precursors to the lunar missions. All the life sciences studies that had been carried out up to this point were important in preparing the space suit and equipment needed for survival on the first U.S. space walk, which occurred during Gemini 4 on June 3, 1965. Doctors observed additional physiological changes such as minimal loss of bone and muscle density, but discovered no substantial health problems that would prevent humans from traveling to the moon.
A total of eleven manned Apollo flights were launched between October 1968 and December 1972. Twelve astronauts worked on the lunar surface after Neil Armstrong first walked on the moon on July 20, 1969, during the Apollo 11 mission. The Apollo missions showed that astronauts could work quite productively on the moon in only one-sixth the gravity of Earth. While the Apollo missions included simple inflight physiological observations, doctors examined crew members primarily before and after each flight. During the flights, crew members reported a few minor physiological problems, such as space motion sickness, but once again humans were able to live and work effectively in space without experiencing any major physiological problems.
During these early missions (Mercury, Gemini, and Apollo), scientists began to learn about human responses to microgravity. However, the small Mercury, Gemini, and Apollo spacecraft had little room for research equipment (figure 2). All this changed in 1973 with the U.S. Skylab program, America's first space station (figures 3 and 4). At last, scientists were able to make more detailed measurements during three missions lasting 28, 59, and 84 days, each involving three human subjects. The most important contribution of these missions was the proof that people can live and work in space for several months.
Astronaut-scientists conducted investigations (experiments) onboard the large orbiting facility (about a five-room house), where there was more room for the research equipment needed to study the effects of living in weightlessness.
Skylab experiments gave scientists a basic picture of how individual systems of the body respond to weightlessness. But there was still no explanation for some responses and no complete picture of the relationships between different systems of the body. Like many pioneering efforts, Skylab left researchers with a multitude of new questions. Though initial progress was made, the real effort still lay ahead.
During the early evolution of human space flight, almost all the astronauts were male. The exception came when the first female to orbit the Earth, Valentina Vladimirnova Tereshkova, became the world's first cosmonette. She flew on the Russian spacecraft Vostok 6 during a three day mission that was launched on June 16, 1963. This was just before the U.S. Gemini flights began, and the event caught worldwide attention. It was not until almost exactly 20 years later that the first American woman, Sally Ride, flew in space. She flew on the seventh space shuttle mission (STS-7), launched on June 18, 1983. Women are now very active and, in fact, play important roles as astronauts in the U.S. space program, but since Tereshkova only one other woman (Savitskaya) has represented Russia In space.
On July 20, 1989, exactly twenty years after humans set foot on the moon, President George Bush challenged the nation to explore and build permanent communities beyond Earth: on the space station Freedom, on the moon, and on Mars. In so doing, he offered the opportunity for unparalleled discovery and created a blueprint for national excellence. Humans, the living element, are the heart of this venture, and the source of its greatest challenge and opportunity. Successful exploration of space depends on the health and well-being of the people who will travel to space and live and work there; successful exploitation of space to make our life on Earth richer depends on being able to do highquality laboratory research in space.
It is important to note that the historical summary included in this section primarily emphasizes the U.S. experience in space with the exception of a few examples of record-setting flights carried out by the former U.S.S.R. Appendix A, which shows a comprehensive list of all U.S. and U.S.S.R. human space flights through 1993, is provided so you can pursue any interest you may have regarding the complete history of human space flight experiences.
The National Aeronautics and Space Administration (NASA) has embarked on a series of shuttle missions dedicated to the space life sciences. Any space flight mission that involves a human has at least some point of biomedical interest attached to it (see appendix A), but certain dedicated missions have been designed to look more completely at human and animal physiology. These missions have sought to determine, in detail, how space Right influences living things, so that the health and productivity of space travelers can be maintained and so that lessons in medicine and physiology learned in space can be transferred back to Earth to enrich all our lives.
We will be looking at how the experiments that were flown onboard two particular dedicated life sciences missions were designed to provide an integrated story of human physiology in space. Before we examine these missions, however, look at how the spaceshuttle/Spacelab combination offers the science community a useful and accommodating environment that supports both normal living requirements and laboratory research requirements.