Introduction

The Deep Space Hydroponics Module was designed to be our take on a compact, modular growth system for use during extended missions in zero-gravity environments. This project is being submitted at the Collegiate level.

The Design Process

Our team followed a 5 step engineering design process initially to address this challenge.

ASK: To start this project our team knew that we would need to spend time researching from a lot of perspectives. We researched how to successfully grow plants through hydroponics. For this we visited local hydroponics stores to see what products are on the market and what is current with technology in this area. We also researched what NASA is currently doing and ensured our design would align with the constraints of the ISS.

Also, we needed to understand how to create an Instructable and understand the submission process. Additionally, we did review submissions of others to Instructables to see what their point of view was for this challenge.

IMAGINE: After time was spent researching options and understanding how to proceed. Our team brainstorm possible solutions. We created hand sketches of possible designs. When reviewing these sketches we were able to do some continuous improvement as it was clear that our initial design could be approved upon to provide for more plants to be ready faster.

PLAN: Attached are our CAD designs. The below sections will highlight in more detail the materials needed to create this system. At a high level, we choose to use commonly found items so that it would be easier for others to duplicate our design. As well as a few 3D printed parts. Our design would also work on Earth, and as such we think that others may enjoy this Instructable for their usage so they can also have a lot of appealing plants. Our design is planned for lettuce and sized to accommodate their growth. It could easily be modified for other plants. This design holds 50 lettuce plants.

CREATE: At this stage, the testing we have done is with our CAD designs to see if all of our plans line up as expected. We have used average dimensions for lettuce to determine sizing; as we are trying to create a system that provides the most plants within the space limitations.

IMPROVE: When working through the initial design we thought initially that the water reservoir would be at the front of the enclosure. Upon more formal design, we realized that locating the water reservoir in the back of the structure allowed for the trays to be longer there for allowing for more room for plants. Originally we had planned to have our design configuration consist of 3 trays with seedlings, 2 for developing plants, and 1 for mature plants. We changed it to 1 tray for seedlings, 2 for developing plants and 2 for mature plants. This design change allows for more edible plants to become readily available faster.

Step 1: Structure

Knowing the size constraints of the project (50 x 50 x 50 cm3), we decided that a small, rigid frame made from extruded aluminum (in this case, Makerbeam) would be a perfect material to use. Makerbeam, as well as other extruded aluminum systems like Openbeam and 80/20, are easy to work with and configure using the T-slot system, where you can slide up and down and lock into different positions on the extrusions.

We also researched the potential testing location, the EXPRESS racks on the ISS (see pg.13 in ISS Reference Guide). In viewing the racks, we wanted to design for the entire system to be accessible from the front of the module, as well as any ports for power or other subsystems to be easily connectable. The EXPRESS racks can provide a steady source of power ranging from 3-12 kW, 114.5-126 voltage, DC. They also have an ethernet port and NTSC video feeds (for observation and monitoring). We have not accounted for the exact air mixture inside the module for this phase, however for specific situations there is also gas (nitrogen, carbon dioxide), temperature control, and vacuum. We initially wanted to have different sized areas for trays to install to in order to account for staging the plants, however given the average size of heads of lettuce (~15cm for fully grown Outredgeous lettuce) we decided to give each area an equal size. The system can be easily reconfigured for other plants or to stage for different germination periods.

Step 2: Interchangeable Trays

The system is designed to be flexible and adaptable to the development of the plants as they grow. Also to allow for highly flexible and versatile usage of the system. There are 5 total plant trays and 2 LED trays. By arranging the trays to hold plants on both sides, and also staggered along the pipes, the total plant throughput of this system can be up to 50 heads of lettuce in a 26-32 day period.

The trays are also designed to be removable, so that the process of harvesting and reseeding can be done as easily as possible.

Step 3: Lighting & Irrigation

Lighting

Since lettuce requires roughly 10-14 hours of direct light but it doesn’t have to be bright light. Lettuce can even grow under low light 24 hours. For this design, we have a LED grow panel on removable trays. For these panels we have a total of 30 LED strips with 22 LED’s per strip. There are 2 LED trays in our design and 5 fixed LED panels, similar to the above picture.

Note - to adapt this to other plants, consideration would be needed as to the lighting.

Irrigation Systems

On the front of the panel there is an access port where the astronauts connect up the water bags. These bags would be premixed with the specified nutrients. From there our system transfers the fluids in a parallel configuration to the trays. The system monitors the fluid levels to ensure the correct levels for the plants as specified through the user interface.

Step 4: Microcontrollers and Sensors

The core of the system is an Arduino Mega. Simple C code is used to control the IO. The LED panel are kept on at a low level brightness continuously since lettuce does not require a sleep cycle. The system will include fans to regulate temperature and to manage exhaust. Fans will cool the system and circulate air to ensure appropriate handling of the exhaust/carbon dioxide/oxygen replacement. The pumps for the irrigation system will be driven directly from the arduino as the signals from it are isolated.

Additionally, sensors would be added to the system to monitor environmental conditions such as temperature/humidity and moisture. The temperature sensor will determine if its too hot, if so it will turn on the fans. The moisture sensor would work together with the irrigation system to add water when the environment requires it. If a bag isn’t currently attached to the system, this can be accessed manually via the user interface.

User interface is a 3.5" TFT touch screen display and a small number of panel mount push buttons

Step 5: About Us

The Motor City Spectres (MCS) is a team of friends, mostly FIRST Alumni and Mentors, dedicated to sharing and promoting STEM initiatives and fun projects.

Team developing this module: Jared Coke / Heather Staley / Rich Lemmer / Patrick Tallman Additional to be listed later!