4. PROGRAMS, MISSIONS, AND PAYLOADS

STS-51B/Spacelab 3

The STS-51B mission was launched onboard the Space Shuttle Challenger on April 28, 1985 and recovered on May 5, 1985. The mission was also called Spacelab 3 (SL-3), because it was the third Shuttle mission scheduled to use the Spacelab.

     Although the primary objective of the STS-51B mission was to conduct materials science experiments in a stable low-gravity environment, important research was conducted in life sciences, fluid mechanics, atmospheric science, and astronomy. Scientists from the U.S., France, and India carried out a total of 15 investigations in these disciplines. The Shuttle carried a crew of seven, including two payload specialists and three mission specialists.

     Several life sciences investigations using nonhuman subjects were conducted on the mission. This research was particularly significant because it involved the introduction and flight verification of the Research Animal Holding Facility (RAHF). The RAHF is a self-contained system that houses and provides life support for animals in space. Two RAHFs were flown on the mission, one contained 24 rats and the other contained 2 squirrel monkeys.

Life Sciences Research Objectives

The primary life sciences research objective of the mission was to evaluate the RAHF's capability to maintain animals in an environment comparable to a ground-based vivarium. This is vital to experiments conducted in space because uncompromised data on the physiological and behavioral effects of microgravity can only be obtained from healthy animals. In addition to fulfilling this objective, the mission provided valuable baseline data on various physiological parameters. The mission was also able to address the issue of possible risks to the crew's health and comfort. This was of some concern because for the first time, crew members and animals were confined together within the enclosed environment of the Spacelab.

     Specifically, the research objectives for the SL-3 mission were to: evaluate operations and procedures for in flight animal care; assess in-flight biocompatibility between the animals and the RAHF; gain mission operational experience; study the physiological, morphological and behavioral changes that occur in animals as a result of being contained in the RAHFs during space flight; and verify the principal hardware elements to be flown on later missions.

Life Sciences Payload

     Two adult male squirrel monkeys (Saimiri sciureus) were flown unrestrained in individual cages in the primate RAHF. The objective in flying these animals was to observe gross physiological and behavioral changes in response to space flight, and to evaluate the adequacy of the RAHF to house and support them in space.

     Both monkeys were free of various specified pathogens. Only six months prior to flight, it was decided that the monkeys should also be free of antibodies to the Herpes saimiri virus, because of crew safety considerations. Although the Herpes saimiri virus is not known to cause disease in either squirrel monkeys or humans that carry it, problems have been documented in other species. A worldwide search was initiated to find Herpes saimiri-free animals. Five were eventually located, but time limitations permitted only two of them to be trained for flight. Instruments were not implanted in the monkeys because of time constraints.

Rattus norvegicus, rat

     The rodent RAHF contained 24 individually housed male albino rats (Rattus norvegicus) that were certified free of several specific pathogens. Half of the rats were rapidly growing juveniles, weighing approximately 200 grams at flight. The remainder were mature 12-week old rats, weighing approximately 400 grams at flight. All rats were flown unrestrained. Before the flight, four of the rats were surgically implanted with biotelemetry transmitters.

     Each primate cage contained a removable solid window through which crew members could view the animal (Fig. 4-26). A perforated window beneath this allowed limited access to the animal. A temporary restraint system could be activated to restrain the animal in flight in the event of an emergency. Airflow directed urine and feces to absorbent, removable trays beneath the grid floor of the cage. Two infrared light sources and two activity sensors located at opposite sides of the cage were used to monitor animal movement. Periodic video recordings were made of the monkeys to evaluate their response to space flight.

Figure 4-26: Primate cage in the RAHF.

     Rodent cages were similar in design to the primate cages (Fig. 4-27). Two rats were housed in each cage, separated by a partition. A camera mirror system was installed to record the movements and behavior of four of the rats during launch and re-entry.

     The RAHFs were designed to provide life support in a manner comparable to vivarium housing on the ground. Besides providing access to food and water and effective waste removal, the facility also permitted environmental factors such as lighting, temperature, and humidity to be maintained within a specified range. An environment control system circulated conditioned air through the cages to control temperature and humidity, and facilitated air exchange with the Spacelab.

     Food and water consumption were monitored as an indicator of animal well-being and a measure of the normalcy of circadian periodicity. Water consumption was measured electronically when the Lixit reservoirs in the cages refilled after being emptied by the animals. Animals could manipulate a tap switch to activate feeders filled with banana pellets. A pellet counter monitored food consumption. Rodent food was presented in the form of a bar. The food bar advanced as the rodents gnawed on its end, and consumption was monitored by an event counter which sensed the forward movement of the bar.

     The crew evaluated general animal well-being through the viewing windows on the cages, and by monitoring food and water intake using the Spacelab computer. An onboard control panel could alert crew members to hardware malfunctions such as water leaks.

Figure 4-27: Rodent cage in the RAHF.

     An automated biotelemetry system (BTS) was used to monitor animal body temperature, heart rate, and electrocardiograms. The BTS consisted of a surgically implanted transmitter, an antenna on each RAHF cage, a receiver, and electronic interfaces with a dedicated computer. The output from the implanted sensors first went to an onboard computer, which reformatted the data and then transmitted it to the ground.

     There were four monkey cages in the primate RAHF equipped with BTS capability. However, physiological data was not obtained from the two flight monkeys because neither was outfitted with sensors. Physiological data was obtained from the four rats implanted with biotelemetry transmitters.

     Another measurement system, the dynamic environment measurement system (DEMS), recorded noise, vibration, and acceleration levels in the immediate vicinity of the RAHF during launch and re-entry. This data was expected to be important for designing future experiments and for interpreting results of studies affected by the environment outside the RAHF.

Operations

The execution of the mission involved simultaneous activities at three NASA centers: Hangar L at KSC in Florida, ARC in California, and the Payload Operations Control Center at JSC in Texas. Although the mission was successful, several obstacles had to be overcome at various stages during mission development and the in-flight period.

     Design, testing, and successful hardware integration required a major cooperative effort between the various NASA centers involved in the mission. The RAHF was originally designed as an animal transporter to be launched in the middeck of the Shuttle. It was to be installed in the Spacelab after launch. This concept was abandoned because it was difficult to move the bulky transporter down the tunnel connecting the middeck and Spacelab. The idea of mounting the transporter in the Spacelab aisle in order to maintain the vertical orientation of the animal cages at landing also turned out to be impracticable. The final design involved installing individual cages in the RAHF while the Shuttle was in its vertical position on the launch pad. This meant that the animals would be resting on the cage side at landing.

     A winch system, the Module Vertical Access Kit (MVAK), was designed to perform the complicated operation of loading animal cages and personnel from the middeck of the vertically oriented orbiter into the Spacelab below, while on the launch pad (Fig. 4-28).

Figure 4-28: The MVAK allows biological materials to be loaded into the Spacelab late in the STS launch sequence, after the spacecraft has been assembled and placed in vertical position: (a) orbiter middeck; (b) animal cage being lowered through tunnel connecting middeck and Spacelab; (c) Spacelab; and (d) RAHF.

     Mission operation procedures alsohad to be modified considerably to accommodate animal welfare and life sciences experiment requirements. Late loading of animals into the Spacelab before launch was vital because of animal welfare concerns and because this operation had to be performed during the light phase of the animals' light/dark cycle. Likewise, early removal after landing was necessary in order to conduct postflight studies on the animals before they readapted to Earth gravity.

     The main problem that arose during flight was the release of particulates from the animal enclosures into the Spacelab during maintenance operations. Despite the considerable publicity drawn to this problem, postflight analyses showed that neither the crew nor the animals were adversely affected. However, it was recommended that the faulty subsystems be redesigned before flying the hardware a second time. Malfunctions in the leak alarms for the water systems in the primate cages and in three of the rodent cages were also noted. The monkeys' drinking behavior pattern in space set off the leak alarms, pointing to a need for higher leak alarm settings in future missions. Fouling of activity sensors, viewing windows, and temporary restraint systems occurred because of the way in which the animals oriented themselves during waste elimination. No other significant problems were observed in flight, and the hardware was shown to be capable of being flown again after modification.

     The orbiter's landing site was changed from KSC to the Dryden Flight Research Facility in Southern California approximately two weeks before the mission. Postflight procedures had to be hastily revised to accommodate this change, but the animals were recovered without incident.

Results

The monkeys and rats were recovered in good condition, healthy and free of microbiological contaminants. Postflight tissue analyses were not performed on the flight monkeys. The flight rats were euthanized a few hours after recovery and their tissues subjected to a variety of tests. Control rats on the ground were euthanized and analyzed in the same manner shortly after. Several changes were noted in the flight animals as compared with ground control animals. These changes are summarized below. Detailed results of science studies are categorized by discipline and described in Appendix 1.

     Both monkeys ate less food and were less active in flight than on the ground. One monkey adapted quickly to the microgravity condition. The other monkey exhibited symptoms characteristic of Space Adaptation Syndrome, consuming no food and little water during the first four days of flight. On the fifth day of flight, after being hand-fed banana pellets by the crew, its behavior became more comparable to that of the first flight monkey.

     Some of the changes seen in flight rats, such as absence of interferon production by spleen cells, lower plasma concentration of osteocalcin, and heightened marrow sensitivity to erythropoietin, may have been influenced by the 12-hour period between landing and sample acquisition.

     Postflight analyses of rat tissue indicated that the rats had not been exposed to prolonged or significant stress. Growth curves were parallel for all rats. The rats consumed more water during the mission, the circadian rhythm of food intake changed, and body temperature decreased during the animals' active phase.

     The rats had decreased muscle tone and muscle mass after flight. There was a shift from aerobic to glycolytic metabolism. More fast- twitch muscles were seen in the rats' soleus muscles after flight. Significant changes were also noted in the bone of the flight rats. Bone mass, and bending and tensile strength were reduced. Bone changes that occurred during this 7-day mission were found to be much greater than the changes noted in tail suspension studies (simulated microgravity studies) conducted for 28 days. Spleen cell production of interferon significantly decreased, which may be indicative of an impaired immune response.

     Metabolic changes noted included a shift from a lipid-based to carbohydrate-based metabolism. Changes were seen in brain metabolism and receptors and in the vestibular apparatus. Growth hormone synthesis was decreased. Thymus gland and testes weights were reduced after flight. In cardiac muscle, glycogen and lipid deposition increased and muscle cell microtubules decreased.

     In general, the postflight changes noted in rats were similar to the changes observed in humans, and were consistent with the findings of the Soviet Cosmos program.

     The life science research objectives of the SL-3 mission were accomplished in no small measure. Operations and procedures developed for mission care of the animals were satisfactory. These included the design modifications made to the RAHFs and the STS to accommodate the payload, the MVAK procedures, late and early access procedures to ensure animal welfare and uncompromised science results, and crew operations within Spacelab. Recovery of healthy unstressed animals demonstrated that the RAHFs were capable of adequately housing and supporting animals in space. The operational experience gained by the personnel involved was expected to be valuable for conducting more complex missions in the future. The amount of data gathered on the physiological, behavioral, and morphological responses of the animals to microgravity surpassed all expectations. The hardware being flight tested was verified from an operational and engineering standpoint and subsystems requiring modifications were identified.

Move to next section STS-51f/Spacelab 2

Additional Reading

Callahan, P.X., W.A. Lencki, and C. Dant. Spacelab-3 Ames Research Center Life Sciences Payload, Final Report.. Unpublished report, date unknown.

Callahan, P.X., W.A. Lencki, C. Schatte, G.A. Funk, R.E. Grindeland, G. Bowman, and W. Berry. Ames Research Center Life Sciences PayloadÑOverview of Results of a Spaceflight of 24 Rats and 2 Monkeys. AIAA Paper 85-6092, November 1985.

Callahan, P.X., C. Shatte, G. Bowman, et al. Ames Research Center Life Sciences Payload: Overview of Results of a Spaceflight of 24 Rats and 2 Monkeys. AIAA Paper 86-0583, January 1986.

Callahan, P.X., J. Tremor, G. Lund, and W. Wagner. Ames Research Center Life Sciences Payload Project for Spacelab Mission 3. SAE Paper 831094, July 1983.

Fast, T., et al. Rat Maintenance in the Research Animal Holding Facility During the Flight of Spacelab-3. Unpublished report, Abstract 83.2, 36th Annual Fall Meeting, American Physiological Society, Buffalo, New York, October 13-18, 1985, p. 375.

Fast, T., et al. Rat Maintenance in the Research Animal Holding Facility during the Flight of Spacelab-3. Abstract S-187-188, Proceedings of the 7th Annual Meeting of the IUPS Commission on Gravitational Physiology, Niagara Falls, New York, October 1985.

Fichtl, G.H., et al. Spacelab-3 Mission Science Review. NASA CP-2429, 1987.

NASA. Spacelab-3. NASA-EP-203, 1984.

Rasmussen, E. Life Sciences Payload Spacelab-3. NASA News, December 1984.

Schatte, C.L., et al. Spacelab-3 60-Day Report. Unpublished report, 1985.

Schatte, C., R. Grindeland, P. X. Callahan, G. Funk, W. Lencki, and W. Berry. Animal Studies on Spacelab-3. NASA TM-88212, January 1986.