The First International Microgravity Laboratory (IML-1) mission was the first in a series of international Shuttle flights dedicated to fundamental life and microgravity sciences research. The IML-1 crew was divided into the orbiter crew, responsible for the operation of the Space Shuttle and its systems, and the payload crew, responsible for conducting the experiments inside the Spacelab module.
IML-1 crewmembers were Commander Ronald J. Grabe, Pilot Stephen S. Oswald, Mission Specialists Norman E. Thagard, David C. Hilmers, and William F. Readdy, and Payload Specialists Roberta L. Bondar and Ulf D. Merbold.
A team of managers, scientists, engineers, technicians and support contractors worked together to plan, organize, develop and implement the IML-1 mission. NASA's Marshall Space Flight Center in Huntsville, Alabama, headed the management team for the IML-1 flight. The European Space Agency (ESA), Canadian Space Agency (CSA), French National Center for Space Studies (CNES), German Space Agency (DARA) and German Aerospace Research Establishment (DLR), together with the National Space Development Agency of Japan (NASDA), were partners in the development of hardware and experiments for IML-1. The IML-1 flight was funded by NASA, while the international partners funded the hardware development and supported the scientists. To minimize costs, scientists from different countries shared hardware and exchanged data.
Many of the 29 life sciences experiments conducted during the IML-1 mission were based on the results of previous investigations. Of great interest for researchers were the adaptation processes that the human body undergoes when exposed to microgravity. Reactions of the vestibular, nervous, circulatory, skeletal, muscle and metabolic systems were measured, providing important data necessary to develop countermeasures for potentially harmful responses of the human body to weightlessness.
Besides the investigations studying human physiology, 17 experiments focused on biology. Investigators studied the effects of microgravity and radiation on the development, behavior and reproduction of slime mold, yeast, hay-bacillus and Drosophila fruit flies, as well as its effects on different cell cultures from mammalian cells. Radiation levels were monitored to identify potential damage to living organisms by the harmful radiation of space.
Six life sciences investigations were sponsored by NASA: two human life sciences and four biology experiments. The human life sciences investigations were the Microgravity Vestibular Investigation (MVI) and the Mental Workload and Performance Experiment (MWPE). The Microgravity Vestibular Investigation contained several related studies, examining the effects of space flight on the human orientation system. The vestibular, visual and proprioceptive systems were interactively stimulated and the resulting perceptual and sensorimotor reactions were measured to study changes caused by adaptation to the microgravity environment. The Mental Workload and Performance Experiment examined the effects of microgravity on the ability of astronauts to perform tasks requiring interaction with a computer workstation. The results of this investigation were used to design more comfortable and efficient workstations for the International Space Station.
Other life sciences experiments performed during the STS-42 mission were those classified as Detailed Supplementary Objectives (DSOs). A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who serve as the test subjects. These studies are designed to require minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns, including space motion sickness, cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry.
The biology experiments sponsored by NASA investigated four different topics. The Gravity Threshold experiment studied the gravisensitivity and the threshold of the gravity-detecting mechanism of oat plants. The investigation Response to Light Stimulation: Phototropic Transients examined how wheat seedlings respond to light in microgravity, how it effects the growth pattern and autotropism of its stems. The experiment Genetic and Molecular Dosimetry of HZE Radiation examined how the cosmic rays and high energy and charged particles (HZE particles) cause mutation in the soil nematode (roundworm); and the experiment Chondrogenesis in Micromass Cultures of Mouse Limb Mesenchyme Exposed to Microgravity studied how embryonic limb bone cells (chondrocytes) produce cartilage under microgravity conditions.
The IML-1 microgravity science program gave investigators the chance to process materials in space under microgravity conditions that cannot be duplicated anywhere on Earth. Investigators grew several types of crystals using various techniques for later applications in computers, lasers and other optical and electrical devices that require near-perfect crystals. Other experimenters examined fluid processes that are masked or distorted by gravity, such as different kinds of convection; nearly every physical science depends on understanding these processes, and this basic knowledge is needed to produce advanced metals. During the IML-1 mission, a special accelerometer measured the accelerations inside Spacelab, screening any vibrations from Shuttle engine firings, crew motions or other instruments that possibly interfered with experiments.
The investigations conducted during the IML-1 mission added a large amount of scientific knowledge to life and microgravity science. The mission also created a strong foundation of mutual cooperation between six major international space agencies who went on to work together on the IML-2 mission, flown in July 1994, and will continue to work towards an International Space Station and other future endeavors.
