NASA/Mir Phase 1A
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Mission Overview
Incubator, the first Fundamental Biology experiment on the Russian space station Mir, was performed during the first extended-duration stay of an American astronaut. The payload was flown to the station in April 1995 on Progress 227, a Russian supply ship. The Greenhouse 1 experiment was originally scheduled to be conducted along with the first Incubator experiment, but it was canceled because of repeated launch slips of the Russian vessel that would bring it to Mir. Only on-orbit facility modifications to the plant hardware were performed during that time.
STS-71
The historic STS-71 mission, the first docking of the U.S. Space Shuttle with Mir, was launched on Atlantis on June 27, 1995, from Kennedy Space Center. Atlantis carried the Spacelab module as well as a new orbiter docking system for connecting to Mir. During the ascent phase of the mission, the Shuttle flew seven crew members, including two Russian cosmonauts to replace the crew already on Mir. STS-71 marked the first time since the Apollo-Soyuz Test Project in July 1975 that Americans and Russians met in space.
The primary mission objectives were to transfer equipment, biomedical data, and specimens between the Shuttle and Mir, and to replace the Mir 18 crew, which had been onboard the station for more than 100 days. A number of microgravity and life sciences investigations were also flown to Mir on the STS-71 mission.
The launch of Atlantis had to be precisely timed in order for the Shuttle to rendezvous and dock with Mir. During the first three days of the mission, the Shuttle thrusters were fired periodically in order to bring it gradually to a position eight nautical miles behind Mir in its orbital flight. Mission control centers in Houston and Moscow monitored the complex rendezvous maneuvers of the two massive spacecraft. The crews of Atlantis and Mir were in contact by means of air-to-air radio during the final approach stage. Atlantis docked with Mir on the fourth day of the STS-71 mission and remained docked for nearly five days. During that period, the two Russians and one American onboard Mir conducted joint investigations with the Shuttle crew. On the tenth day of the mission, the Shuttle undocked from Mir and returned to Earth, carrying the samples from the first Incubator experiment. During the descent phase of the mission, Atlantis returned with an eight- member crew, including the three Mir 18 crew members.
The Mir 19 mission began with the undocking of Atlantis from Mir. Atlantis left behind the two cosmonauts who were to man Mir and several science experiments that were to be conducted before the docking of STS-74. These experiments included one managed by Ames Research Center, called Greenhouse 1, a joint project with Utah State University and the Institute of Biomedical Problems (IMBP) in Moscow.
After the departure of STS-71, a continuation of the Incubator experiment was delivered to Mir by another Russian transport vehicle. Incubator 1 and 2 were conducted on the Mir 18 and 19 missions along with the Greenhouse 1 experiment brought onboard by STS-71. Biological samples and data collected during Mir 19 were returned to Earth on STS-74. Engineering and operational experience gained from the STS-71 mission impacted planning for the STS-74 mission.
STS-74
Atlantis docked for a second time with Mir for the eight-day STS-74 mission, launched on November 12, 1995. The five-member crew included an astronaut from the Canadian Space Agency.
The primary objectives of STS-74 were to again successfully dock with Mir, to permanently install the Russian-built docking module onto the Mir Kristall module, and to conduct joint NASA/Russian Space Agency scientific experiments.
Atlantis docked with Mir on the fourth day of the mission and remained docked for three days. While docked, Shuttle and Mir crews performed collaborative science investigations. They also transferred supplies, equipment, and experiment materials to Mir for the upcoming Mir 20 mission. Experiment samples and data from the Mir 18 and 19 missions, equipment for repair and analysis, and products manufactured on the station were transferred from Mir to the Shuttle. STS-74 brought back quail embryos incubated and chemically fixed during the Mir 18 and 19 missions as well as plant samples and hardware from the Greenhouse 1 experiment.
Life Sciences Research Objectives
Earlier Russian avian embryology experiments on Mir showed that embryonic development and hatching do occur in space, but that the number of hatches is lower than on Earth. The Incubator experiment was designed to elucidate the nature of space flight effects on avian embryos and to determine whether gravity is required for normal avian embryogenesis and development. Studying such processes in birds allows researchers to better understand the effects that microgravity might have on human reproductive capabilities.
The Greenhouse experiment studied plant growth in space. Understanding how plants respond to space flight is important for conducting long-duration, manned space missions. As mission duration increases, it will become infeasible, for reasons of both weight and storage capacity, to carry sufficient food, water, and air supplies at launch. A solution to the problem is to develop recycling strategies using crop plants to generate food, water, and oxygen and remove carbon dioxide and excess humidity from the enclosed spacecraft environment (Fig. 17). The Greenhouse experiment focused specifically on how plants develop, metabolize, reproduce, and yield in microgravity. The experiment also served as an evaluation of the plant growth facilities on Mir. Unlike in previous U.S. space flight experiments, the plants brought to Mir on the STS-71 mission were allowed time to complete an entire life cycle in the space environment.
Life Sciences Payload
Organisms
Both Incubator experiments used fertilized eggs of the Japanese quail (Coturnix coturnix japonica), provided by IMBP. The quail is a widely used model organism in the study of embryogenesis. In addition, quail have been considered as a potential supplemental food source for long-duration missions, since they are smaller than the chicken and have a higher meat yield.
The Greenhouse 1 experiment used wheat plants (Triticum aestivum) of the Super-Dwarf variety. Wheat is an important agricultural crop and a likely candidate for a plant-based life support system to be used on long-duration missions.
 Figure 17. Bioregenerative life support systems represent a likely method for recycling waste and providing food, water, and oxygen on long-duration space flights. |
Quail eggs were kept in a Russian-designed incubator with a capacity of up to 80 eggs (Fig. 18). The incubator allows control of both temperature and humidity. A glove bag was provided for performing the fixations. Fixation bags used in the experiment contained either paraformaldehyde or an ethanol/glycerol solution. Since fixed eggs could be kept at ambient temperature, no refrigerator/freezer was needed.
Wheat plants were grown in the Svet, a plant-growth facility jointly developed by Russia and Bulgaria and sent to Mir in 1990. It comprises a plant growth chamber, a root module, a light unit, and a control unit. The Svet can hold about 100 wheat seedlings and accommodate plants that are up to 30 cm (16 inches) tall. Environmental monitoring systems developed by Utah State University were added to the Svet. Fluorescent lamps provide light that is about one-twelfth as intense as sunlightan amount that is marginally sufficient for adequate plant growth within the Svet. Wheat plants are grown in a solid zeolite substrate containing nutrients. Water is injected into the substrate material and transferred to the wheat seeds by means of a wick system. The U.S. environmental monitoring system, named the Gas Exchange Monitoring System, collects data on CO2, and water vapor in air entering and leaving the Svet, allowing calculation of photosynthesis, respiration, and transpiration.
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A harvest kit was used to collect plant samples from the Svet. The kit includes tools such as forceps, scissors, microscissors, and dissecting instruments. A portable glovebag, which prevents hazardous materials from coming into contact with the crew environment, was used to fix specimen samples. Preservatives for fixing samples were contained in a fixative kit, which includes chemical fixative solution in triple-sealed bags.
Operations
Preflight
For both Incubator experiments, the quail eggs were collected from IMBP over a period of days before flight and hand-carried to the launch site at ambient temperature. The eggs were then placed in a foam-lined metal box for transport to Mir on the Progress vessel. Two other groups of fertilized quail eggs from the same parents were used as controls. The asynchronous control eggs received the same pre-incubation time and temperature as the flight eggs. They were incubated in hardware similar to that on Mir, at similar temperatures. A laboratory vivarium control group also received the same pre-incubation time and temperature as the flight eggs but were incubated in a commercial incubator.
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The experiment plants for Greenhouse 1 were sent to Mir as seeds attached to a strip of plastic. A delayed synchronous ground control was conducted with temperatures, CO2 levels, light, and other environmental factors as close as possible to those reported from Mir.
Inflight
For both Incubator experiments, eggs were chemically fixed at various times to allow observation of different stages of development. The first set of eggs was fixed seven days after being placed in the incubator. Three more sets of eggs were fixed, at three intervals of three days each after the first fixation. Although the experiments remained on Mir for three months, the actual duration of each experiment was 16 days, after which fixed eggs were stored for return to Earth. The fixed samples were returned to Earth on the STS-71 and STS-74 missions.
Both control groups were fixed at the same time in the same solutions as the flight eggs.
Planting of wheat seed occurred after STS-71 undocked from Mir. During Mir 19, crew members monitored plant development by making daily observations and taking photographs. They also collected samples of plants at five different stages. The duration of the experiment was 90 days, from August to November. All samples were returned to Earth on STS-74 for postflight analysis.
Postflight
After the Shuttle landed, fixed quail egg and plant samples were distributed to the investigators.
 Figure 18. The Russian-built Incubator onboard Mir can provide temperature and humidity control for 80 avian eggs. |
Results
Quail Eggs Study
During Mir18/NASA 1, many of the embryos showed developmental abnormalities, and the mortality rate during the incubation period was high. Because of the possibility that unplanned temperature fluctuations in the incubator were the cause of the high mortality, none of the experiment objectives were satisfied by the data. During Mir 19, inflight development progressed to a further stage than in the Mir 18 experiment, but the fluctuation in incubator temperatures again could not be ruled out as the cause of mortality. No abnormalities in gross morphology were detected in the embryos. A third replicate of the experiment, performed during NASA 2 between STS-76 in March and STS-79 in September 1996, produced more viable embryos.
Wheat Study
Wheat plants grew for almost all of the 90 days of the experiment but exhibited poor growth. Inhibited growth was caused by the failure of four out of the six fluorescent lamps in the plant growth chamber and erratic moisture conditions in the soil. An unexpected result of the experiment was that the plants remained vegetative throughout the 90 days, never producing flowers in the form of wheat heads. Control plants were similar in appearance to the space plants but produced sterile (no seeds) heads. The lessons learned in this experiment were applied in 1996/97 by the same team with new equipment, and the Super-Dwarf wheat plants produced lush growth and about 280 wheat heads. However, all heads proved to be sterile. Ground studies have demonstrated that ethylene in the Mir cabin atmosphere caused the sterility. A subsequent Greenhouse experiment, conducted in 1997, which used mustard plant, produced the first successful seed-to-seed plant cycle in space. Another study on Mir that began in 1998, not sponsored by Ames Research Center, used Apogee, a strain of wheat more resistant to ethylene than Super-Dwarf wheat. The effort succeeded in producing some fertile wheat seeds.
Additional Reading
NASA. STS-71 Press Kit, June 1995. In NASA Space Shuttle Launches Web site: http://www.ksc.nasa.gov/shuttle/missions/missions.html.
NASA. STS-74 Press Kit, November 1995. In NASA Space Shuttle Launches Web site: http://www.ksc.nasa.gov/shuttle/missions/missions.html.