Plant Research Using Automation
There has been a great deal of research done on growing plants in space. For over 30 years NASA has been doing the research necessary to develop self-sustaining life support by studying crop growth systems. In 1982, the Soviet Union grew the first plant, Arabidopsis thaliana, in space aboard the Salyut 7 space station. In 2001, the Orbitec designed Biomass Production System was delivered to the International Space Station (ISS), where it operated for a year growing Brassica Rapa. Following this, Russian cosmonauts grew multiple plants, including dwarf wheat, leafy Mizuna, and dwarf peas.
The first system designed to grow edible plants at a larger scale on the ISS was Veggie, which was launched in 2014. This system grew red romaine lettuce and zinnia. Initially a self-irrigation system led to over-watering of the Zinna and under-watering of the lettuce, but a change to manual watering by the crew lead to health growth of the plants. After samples of the plants were returned for review, they were approved for astronaut consumption, leading to the lettuce being eaten by NASA astronauts on-orbit in 2015. For the zinnia, direct watering eventually led to fungal growth and other stresses, yet two of the plants went on to produce many flowers.
Following the first use of Veggie, the Veg-03 tests used a new pillow planting concept along with new fertilizers, plant species, and plant management protocols. In total, these changes reduced plant maintenance while maintaining energy consumption. Red romaine lettuce, extra dwarf Pak Choi, red Russian kale, and wasabi mustard were grown in two types of clay media. One of the key areas of research was observing the differences in root growth caused by different clay grain sizes.
The follow-on Veg-03 B and C experiments used the same hardware, but used Chinese cabbage. Together with the first Veg-03, the results showed that twice as much produce could be grown using same amount of starting materials. Veg-03 D-F tested mixed growth of three species of leafy greens and different harvest schedules. After Veg-03 F, Veggie PONDS (Passive Orbital Nutrient Delivery System) introduced new hardware features to mitigate micro-gravity effects on water distribution, increase oxygen exchange, and aid root growth. These changes were designed to improve on previous issues and establish support for larger leafy vegetables and fruit crops like tomatoes.
After the Veggie PONDS hardware was installed, Veg-03 G-I tests were performed. The Veg-03 G test included growth of red Russian kale and dragoon lettuce, planted by NASA astronaut Serena Auñón-Chancellor. The Veg-03 H test included a 30 day growth of both wasabi mustard greens and extra dwarf Pak Choi, planted by Canadian astronaut David Saint-Jacques.
After all the tests for Veg-03 were completed, a new project was carried out. The first phase grew Mizuna mustard during both a 28 day test (Veg-04A) and a 56 day test (Veg-04B). The second phase grew dwarf tomatoes (Veg-05). Different red-to-blue light recipes and fertilizer formulations were assessed on the ground ahead of time and two different treatments were applied on the ISS, with a duplicate ground-study on Earth that allowed comparison with plants grown on the ISS to understand how the plants were affected by the different environment. In addition to this study, crew members also took multiple surveys to test their mood response regarding the plants during growth and their experience when consuming them.
On April 18, 2017, the Advanced Plant Habitat (APH) test unit flew to the ISS and was positioned in an EXPRESS (EXpedite the PRocessing of Experiments to Space Station) rack in the Japanese Experiment Module Kibo. The APH joined the still active Veggie growth system, which was the first fresh food growth system on the station. The APH provided additional light spectra and output for plants, while containing about 180 sensors. The test unit was first used to grow Arabidopsis and Apogee wheat during its first experiment that started on January 22, 2018. A successful harvest was completed 30 days later. Compared to the Veggie system, APH was able to autonomously add water and make observations. The watering functionality used sensors to detect when the plant needed water and at what location. Observation functionality was provided by the PHARMER (Plant Habitat Avionics Real-time Manager in EXPRESS Rack) system that provided live data, remote command functionality, and photo down-link to Earth.
These tests helped learn how to optimize plant growth in space by monitoring growth progress compared to temperature, oxygen, and moisture. As the ability to grow food in space improves, it will be less essential to launch all necessary food from Earth. Since launching all the required food is expensive and logistically difficult, food is one of the factors that limits how far astronauts can travel in space and how long they can stay. Food resources must be grown in space to support long duration missions and allow visits to places like Mars.
The Advanced Plant Habitat (APH) is one step on the path to enabling increased plant yield of larger crops while requiring minimal crew time. Even though current crews must manually maintain and harvests plants, future systems will utilize robots to automate these steps. A recent partnership between Lockheed Martin and NASA Kennedy will test the technology and operation of one such autonomous in-space plant growth systems. Details of this work are not yet available, but this work will lead to autonomous systems needed to scale up plant growth operations in space. Once scaled up, the ability to grow plants at high volume in space will lead to mass production of space-grown produce that will gradually replace Earth launched food supplies. Ideally, this will provide a cheaper, healthier, and tastier food source for astronauts.
The study of in-space plant growth and use is an important part of developing Earth independent habitats. The production of food and biological life-support systems in space are two types of space resources that provide essential products that will play a central role in supporting habitation as part of our future space economy.