Engineering test could help plant growth in space
Posted: April 2, 2002

The Biomass Production System is an engineering development unit for a future International Space Station plant habitat capable of supporting long-term plant growth and botanical experimentation in space. Photo: NASA-ARC
The engineering test of a plant-growth system to be launched on this week's space shuttle mission to the International Space Station also may reveal important clues about plant development in space.

The Biomass Production System (BPS) is an engineering development unit for a future International Space Station (ISS) plant habitat capable of supporting long-term plant growth and botanical experimentation in space. The STS-110 space shuttle mission, scheduled for launch April 4 from NASA's Kennedy Space Center, Fla., will deliver the BPS for in-flight operations aboard the ISS. The BPS and science samples will return to Earth on the STS-111 mission, currently scheduled for launch in late May.

"The BPS will allow us to test how best to grow plants in space over multiple generations," said Dr. Orlando Santos, chief scientist for the Space Station Biological Research Project (SSBRP) at NASA Ames Research Center in California's Silicon Valley. "The ability to carry out long-term experiments is a unique characteristic of the ISS facility that is critical for our understanding of the future of living things in the low-gravity environments of spacecraft, the moon or Mars." The BPS is one of several pieces of science hardware being developed by the SSBRP for use on the ISS.

The primary objective of the BPS is the technology validation test, which will evaluate hardware performance on orbit in order to select the best subsystems for design and development of a permanent plant research unit. Once developed, the plant research unit will be capable of supporting the continued growth and development of plant specimens and provide the capabilities necessary to perform scientific investigations for 90 days or more on orbit. The BPS also will support the Photosynthesis Experiment and System Testing Operations (PESTO), a study of the effects of microgravity on photosynthesis and metabolism in wheat plants. Some of the results from this study also will be used as part of the technology validation test.

The BPS is a powered hardware system that includes four independent plant growth chambers, a nutrient delivery system, a temperature/humidity control system, airflow and atmospheric control systems, a video system and a data-processing system. Each plant growth chamber has a growing area of about 42 square inches (260 square centimeters) and a height of over 6 inches (15 centimeters). The BPS was developed for NASA by Orbital Technologies Corp., Madison, Wisc.

The technology validation test will determine the ability of the BPS and its environmental control subsystems to support plant growth and development in microgravity. Researchers will study the health and growth of the plants, facility temperature and humidity controls, nutrient delivery, lighting, plant manipulation and sample retrieval, video and data acquisition, and performance of other operations and support systems.

The testing process will use two types of plants -- Brassica rapa and Apogee wheat. Brassica plants include such commonly grown vegetables as broccoli, cabbage, cauliflower, rutabaga and turnip. Brassica is a dicot, a plant with two cotyledons, or leaf-like structures, per seed, and exhibits multiple developmental stages (growth, flowering and seedpod production) in a short time. The growth of Brassica rapa seedlings will test the ability of the BPS to support the growth of a developmentally complex plant. Dr. Robert Morrow, Orbital Technologies Corp., Madison, Wisc., is the principal investigator.

Four-day-old Apogee wheat seedlings -- a monocot plant with one cotyledon, or leaf-like structure, per seed -- also will be exposed to a variety of temperature and humidity levels to test the ability of the BPS to control temperature and humidity set points. In addition, water utilization and plant photosynthesis will be measured. Plant tissue will be harvested and frozen or fixed when the plants are 21 days old.

PESTO will study the growth, photosynthesis, gas exchange and metabolism of Apogee wheat in microgravity. This experiment will determine the ability of wheat seeds to germinate, develop and grow in microgravity conditions, measure the growth of the seedlings, and determine the effects of microgravity on photosynthesis and transpiration. The PESTO principal investigator is Dr. Gary Stutte, Dynamac Corp., Kennedy Space Center, Fla.

Understanding photosynthesis is a critical component of plant-based atmospheric regeneration systems now under study for possible use in future long-duration space missions. By generating oxygen, removing carbon dioxide and purifying water, living plants could help maintain proper spacecraft atmosphere, and reduce the costs of air and water resupply on long-duration missions. This research also will have direct application to future production of crops that the ISS crew could eat, such as radishes, lettuce or onions.

The BPS testing and research are supported by NASA's Office of Biological and Physical Research, which promotes basic and applied research to support human exploration of space and to take advantage of the space environment as a laboratory.