Introduction: Space Plant Assembly

About: I'm a Mechanical Engineering student at the University of Houston.

This submission is for the Collegiate category.

To survive in space for an extended period of time, we need food and the ability to grow that food. Great strides have been made in the science of botany in space. This project titled “the Space Plant Assembly (SPA)” will build on this effort in hopes of expanding some of the ideas toward make growing food in space a practical reality.

Step 1: Components and Measurements

The limits of the cube are 50x50x50cm, which when converted into inches became ~19.69x19.69x19.69in. The main components of my design are the plant pods, the drawer, and the shelf (Figure 1), which has 3/16in plexiglass in the "open" walls in the model. The smaller components are the lights, the compressor pump, the coded chip, and the various clips, mounts, and handles. On the inside of the box, the size that a ‘Outredgeous’ red romaine lettuce plant would grow was taken into account to accurately estimate the size needed for each one. According to LSU’s Planting Guide, lettuce should be planted between 4 and 12 inches apart. Middle ground was picked using 6 inches of space between each lettuce plant. Because ‘Outredgeous’ red romaine lettuce can grow to just under 12 inches and plants in space grow towards the lights, each plant was given just above 12 inches of upwards grow room. From these calculations, there is plenty of room for six plants to grow.

Step 2: Components and Measurements (cont'd)

The concept of plant pods (Figure 1) in this design is similar to that of what NASA is currently using, but with the ‘fabric’ encasement made of a non-degradable “teabag-like” fabric but thicker and more durable. The plant seeds will be pre-packaged in the plant pods for easier growing. Eventually the plants will need fertilizer to encourage growth, which can be mixed with the water to create a nutrient-filled solution.

Another thing to take into account is the lighting, which is attached to the box’s shelf, not the drawer. The lights modeled are simple grow lights that can be purchased anywhere and are self-powered by an inner battery. These lights usually shine out at an almost 90 degree angle, so one in each corner should light up the entire box, giving off plenty of light for all plants inside.

The box comes with a set of mounting brackets (Figure 2) used to secure the assembly which can easily be attached to the space station or folded out of the way. The top of the box has a handle (Figure 3) used to pull out the drawer containing the plants, which doubles as a type of halter to keep the water pouch tucked away once it is connected to the watering system. There are lid clasps (Figure 4) on both sides of the box to keep the drawer in place when not being used.

Step 3: Inner Workings

The irrigation system comes complete with inner connecting tubing and small vacuum pump which creates a slight negative pressure on the seed pods drawing the water to the soil within the pod. The water pouch is connected to the drawer’s lid, where it can then be tucked away (Figure 3). There are three pipes connected to the shelf’s innermost structure, which is a diamond shape for optimal plant room in mind. Two of the pipes go along opposite edges, while one larger pipe is inside the plant support itself. The outer pipes are for water to be pulled out of the bag, while the inner pipe is to pull the water from the outer pipes down into the plant pods for even watering throughout the pods. At the end of all three pipes is a vacuum pump, much like a small pump bought for an aquarium, which creates the vacuum.

The vacuum is what pulls water both along the outer pipes and into the pods to the inner pipe. The inner pipe is a larger opening (0.5 in.) so it will have a greater pull than the water pipes (0.4 in. each), which will stop water from travelling straight through the system. With these systems in place, the current usage of the water syringe inserted into the bag is no longer needed. The vacuum pump and other system power requirements will be design to meet ISS available power distribution. Vacuum pump, controls and power supply will be installed in the base of the plant support assembly. Manual and water sensing control will operate the vacuum pump.

Step 4: Conclusion

The Space Plant Assembly (SPA) will modify the way botany in space is achieved. The concepts of self-water system should free up astronauts to research and support other task with minimal effort given to plant care. The vacuum system will mitigate the chance if free water entering the enclosed environment of the ISS. And moisture in the system will be captured in a water reclaim system and the slight vacuum pump exhaust will be tubed to ISS air filter systems for clean circulation.

(The attached files are all parts in .ipt form and an animation of all parts separating from completion. InventorPro 2019 was used for modelling each part, assembly, and drawing.)

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