It is a sealed container, 300mm wide and 450mm tall, designed to create an Earth-like environment in space, except without gravity.
Growing plants from seeds in space, where there is little to no gravity, is a big step for space research. It helps scientists figure out how to grow food in space and could support astronauts on long missions. Plus, it gives astronauts a fun and meaningful activity to do while they’re far from Earth.
CROPS, short for Compact Research Module for Orbital Plant Studies, is an experimental, unmanned module created to help ISRO learn how to grow and maintain plants in space.
The first CROPS mission (CROPS-1) aims to show that a seed can sprout and grow into a small plant with two leaves in space.
It is a sealed container, 300mm wide and 450mm tall, designed to create an Earth-like environment in space, except without gravity.
In CROPS-1, a special type of clay soil is used to help the seed grow. The soil is shaped into small pellets (tiny round pieces) and has tiny spaces, or pores, that can hold water and let air flow through. This makes it easier for the seed to absorb water and nutrients and allows its roots to grow properly.
The soil used in CROPS-1 can be cleaned by heating it to a high temperature. This process kills harmful microbes, fungi, and spores without damaging the soil’s ability to hold water, air, or support plant growth. This ensures the soil remains safe and effective for the seed to grow.
The soil is already mixed with a special type of fertilizer that releases nutrients slowly when it comes in contact with water. This ensures the plant gets the right amount of nutrients over time in a steady and controlled way, helping it grow properly.
The soil is divided into four chambers, and each chamber holds two seeds. The soil is packed tightly and covered with a layer of soft silicone foam. On top of that, there is a cover plate that presses down gently to keep the soil firmly in place. This setup helps create the right environment for the seeds to grow.
Each seed is pasted with a polypropylene tissue (a type of thin, flexible plastic sheet) using an organic gum (a natural, plant-based adhesive). This gum keeps the seed firmly in place until water is added. Once the gum gets wet, it softens, allowing the seed to start growing.
The seed needs to be properly cleaned with ethanol before it is pasted to prevent any contamination.
A piece of tissue ( (a small piece of plant material, such as a stem, leaf, or root)
is carefully placed into the soil by sliding it through a small opening in the silicon foam and the top cover. This setup helps keep the tissue in place and ensures it stays in contact with the soil for proper growth or testing.
This method of securing the seed helps it stay safe and protected from the strong vibrations and shocks that happen during a launch.
Additionally, CROPS-1 is equipped with special vibration isolators. These help protect the module by reducing the impact of vibrations and shocks that occur during launch, ensuring the system remains safe and stable.
The CROPS-1 container is carefully sealed in a clean and controlled environment after the tissue strips are placed inside. The chamber is designed to mimic Earth’s atmosphere, with 20.9% oxygen, 400–600 ppm of carbon dioxide, 50–60% humidity, and a temperature range of 25 to 30 degrees Celsius. This setup ensures the conditions are just right for the tissues to survive and grow.
In this chamber, the seed has everything it needs to start growing, except for water. Clean, filtered drinking water is stored in a small pressurized tank under the CROPS-1 module. An electric valve is used to keep the water separate from the soil until it’s needed.
Water flows from the valve into small metal tubes. These tubes have tiny holes all around them, allowing the water to slowly drip out and spread evenly. This ensures the water reaches the soil and the seed in a controlled way.
The water that comes out of the tubes gets soaked up by the porous soil. This happens because of a process called capillary action, where water moves through tiny spaces in the soil, almost like how a sponge soaks up liquid. This helps the water spread evenly to reach the seed.
Once the system is in orbit, the experiment begins when a command is sent from Earth. This command opens an electric valve, allowing water to flow into the soil. This step is essential to provide the seed with the water it needs to start growing.
The tissue strips in the system soak up water from the soil using capillary action. This means the water moves through tiny spaces in the material, just like how a paper towel absorbs liquid. As the water reaches the seed, the seed gets fully soaked, and this triggers the process of germination—the seed starts to grow.
During germination, tests done on the ground show that carbon dioxide levels begin to rise while oxygen levels decrease. This happens because, as the seed starts growing, it breathes in oxygen and releases carbon dioxide, just like humans do when they breathe. This is a natural part of the germination process.
The plants will stop growing if the carbon dioxide in the sealed chamber runs out, as they need it to grow. To monitor the conditions inside, the module has sensors that measure carbon dioxide and oxygen levels, as well as pressure, temperature, humidity, and soil moisture. These sensors help ensure the plants have everything they need to grow properly.
A high-resolution camera, along with its electronics, is placed at the top of the module to monitor the plant’s growth. The camera takes clear pictures of the plant at regular intervals, allowing scientists to closely observe how the plant is growing over time.
The CROPS-1 experiment was carried on the PSLV C60 mission as part of the POEM 4 payload. Its goal was to show that a seed could germinate and grow in space up to the stage where it develops two leaves, over a period of 5 to 7 days.
Cowpea was selected for the experiment after testing different types of seeds on the ground. It was chosen because it germinates quickly, making it ideal for the study.
After the launch and separation of the main satellite, the POEM platform was moved to a lower orbit, about 350 km above Earth. The CROPS-1 experiment was then turned on, and all systems were working normally. The temperature inside the module was carefully controlled, staying between 20 to 30 degrees Celsius. Around 90 minutes later, water was successfully added to the soil using an electric valve that was operated from the ground.
The next phase of the CROPS experiment will run for a longer period, lasting about 30 to 45 days. This phase aims to grow plants beyond the two-leaf stage. To support the plants’ growth, an advanced control system will be used to carefully maintain the right levels of carbon dioxide, oxygen, humidity, soil moisture, and temperature. This will ensure the plants can grow and thrive in the space environment.
(The author of this article is an award-winning Science Writer and a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach him at: girishlinganna@gmail.com)
