Spacecraft: Columbia
Launch Date/Time: 6/5/91 156:13:25:00
Landing Date/Time:
6/14/91 165:16:38:00
Duration:
9 days
Mission ID
STS-40
Spacelab Life Sciences 1 (SLS-1) was the first dedicated life science mission. This mission is of particular importance because of the numerous and varied alterations in the body's physiology and biochemistry associated with space flight. Exposure to microgravity leads to loss of calcium from bones, loss of muscle mass and body protein, changes in sensing body position and maintaining balance, loss of blood volume, and orthostatic intolerance upon return to Earth's gravity. Changes in the immune system have also been described. Understanding these various changes requires an integrated, comprehensive approach, where controlled measurements can be made preflight, inflight and postflight.
The orbiting laboratory where the experiments took place was the Spacelab. The Spacelab is a reusable laboratory carried in the Shuttle payload bay. To complete these experiments, equipment was mounted along the walls and floor of the cylindrical spacelab module. The module filled approximately one third of the space shuttle Columbia's payload bay. Crew members floated into the Spacelab through a tunnel adapter that ran from the airlock in Columbia to the Spacelab.
Primary Payload
The primary payload on this mission consisted of eighteen experiments, ten which studied changes in the crew members on the flight, seven which studied laboratory rats, and one which studied jellyfish (Aurelia). The ten human experiments involved research in the cardiovascular/cardiopulmonary, neuroscience, musculoskeletal, endocrine, hematology, cell biology and regulatory physiology disciplines. These experiments involved extensive preflight and postflight data collection, in addition to the information collected on the flight. The crew members participated as subjects throughout the experiments and were both subjects and operators inflight.
The crew followed a demanding pre and post flight testing schedule. They experienced 24 hours of head-down bed rest to test whether this ground-based analog of spaceflight produces the same cardiovascular effects as microgravity. A battery of vestibular tests were performed to test the crew membersĒ sensitivity to linear acceleration, and to examine changes in visual-vestibular interaction. Proprioception was also tested with the simple, but powerful, awareness of position test.
Along the way, the crew underwent the most comprehensive set of physiology studies since the Skylab program. Their responses to standing, lower body negative pressure and adrenergic agonists were recorded. Their pulmonary function was studied in detail. Measurements of renal blood flow, plasma volume, red cell mass, extracellular fluid volume, total body water, protein synthesis, aldosterone, ANP, renin, and catecholamines were made pre-, in- and postflight. Iron incorporation and red cell mass were determined before, during and after the flight. Protein synthesis and calcium excretion were measured. Responses to both submaximal and maximal exercise were determined. All these data show promise for allowing the most comprehensive, integrated understanding of human physiology during and after spaceflight.
The seven experiments which studied the laboratory rats were conducted in the preflight and post flight periods of the mission. Neuroscience, musculoskeletal, and hematology experiments were performed on the rats. The hematology studies used the same tracers and techniques as the human studies. These studies also included detailed examination of bone marrow and spleen samples. The neurovestibular studies and muscle studies required delicate dissections of the otoliths and muscles, to examine changes that occurred at the cellular level. Detailed studies of calcium balance and bone formation were performed on some rats, while others were studied to look at changes in myosin isozymes.
During the inflight period, an essential goal was to test and verify hardware protocols required to conduct biomedical research in the Spacelab. A Particulate Containment Demonstration Test (PCDT) was conducted on the General Purpose Work Station (GPWS). Successful operation was verified for the General Purpose Transfer Unit (GPTU), the redesigned Research Animal Holding Facility (RAHF), and the Small Mass Measuring Instrument (SMMI).
Biospecimen Sharing Program (BSP)
The Biospecimen Sharing Program was developed to ensure that valuable tissue samples not used by the primary investigators could be distributed to other interested investigators. The primary objective of this program was to maximize scientific return from the specimens flown on SLS-1, with the secondary objective of encouraging broader participation of the research community in the Life Sciences Flight Experiments Program. The SLS-1 BSP was initially an extension of the joint US/USSR studies conducted on Cosmos flights. Following the incorporation of the Soviet experiments, several additional foreign experiments were accepted, as well as experiments from NIH, NASA and various universities.
Spacelab Middeck Experiments (SMIDEX)
The SMIDEX facility flew for the first time on SLS-1. This Spacelab facility housed five experiments originally designed to fly in the Shuttle middeck. An advantage of flying SMIDEX on SLS-1 was that it offered additional flight opportunities for the backlog of experiments waiting to fly in the Shuttle middeck.
Detailed Supplementary Objectives (DSOs)
DSOs investigations are supplementary to the primary Shuttle payload, performed voluntarily by the crew and designed to require minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns and involve data collection before, during and after flight. Early DSOs focused on adaptation to microgravity and specifically space motion sickness. More recently, studies have been expanded to include cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry. Key hardware and procedures have been tested and verified as DSOs prior to use in support of more costly, complex life sciences investigations.
Detailed Test Objectives (DTOs)
At the beginning of the Shuttle Program, the Space Transportation System (STS) Program Office established a procedure for testing and refining Orbiter and subsystem performance capabilities, and for evaluation of new hardware and procedures. Procedures involving the Orbiter, its subsystems, and its support equipment were designated Development Test Objectives (DTOs). All other operationally relevant procedures were classified as DSOs.
Results
Spacelab Life Sciences 1 produced several remarkable findings. Contrary to expectations, central venous pressure was found to be reduced from preflight levels upon entering space. Inhomogeneities were found in ventilation and perfusion in the lung, despite what should have been a complete lack of gravitational gradients. Protein was lost on SLS-1, but surprisingly was shown to be more of a stress response, rather than a classic bed rest response. Ionized calcium was found to be unusually high. The otolith neuroepithelium was found to be altered, demonstrating neural plasticity in the peripheral nervous system. The balance between the visual and vestibular systems was changed considerably after the exposure to space. Bone formation was reduced. Red cell mass was reduced, but surprisingly iron incorporation was not diminished. In all, the findings on SLS-1 reveal that much remains to be learned about the complex physiological adaptations to spaceflight.