Previous Blog Posts
Blog 1 - Challenge Overview + Plant Growth Factors
The Space Salad System Concept: Three Delicious and Nutritious Meals a Day
Having outlined how to grow plants in microgravity, I can now focus on what types of plants to grow as well as the spatial arrangement of the plants. The goal is to feed and nourish a rocketship crew so what came to my mind right away was salad! (Salad lettuce is a no-brainer because it is so easy and quick to grow!) I call my concept The Space Salad System. The Space Salad System offers three delicious and nutritious meals a day for a crew of two hungry astronauts.
Selected plants
Because I am aiming to develop a functional prototype within 10 weeks, I will only grow four types of plants and master cultivation of those types (but of course the chamber can accommodate other types of plants and more than just four types). I chose the following plants because they each represent a plant category and collectively, they make a great salad:
Spatial Arrangement
If possible, the chamber shall not only be microgravity-compatible, but also gravity-compatible such that it can continue to produce food after the crew has landed on Mars. Thus all plants will be oriented vertically. I will allocate approximately 75% volume to growing lettuce and 25% volume to the remaining plants.
- 7 columns each representing a day of the week when the lettuce is to be harvested
- 4 rows each accommodating a one-week growth phase such that one row in each column is available for harvest weekly (since lettuce has a four-week growth period)
- 5 plants in each row
- 3 indeterminate tomato plants which produce fruit constantly
- 12 (four around each tomato)
By staggering the growth phases of lettuce, I am able to accommodate a whopping total of 140 lettuce plants in the chamber. And by growing cherry tomatoes, walla walla onions, and cilantro, I can add tremendous flavor to the salad.
Here is an drawing I made to illustrate the spatial arrangement of the plants. (Note: I have omitted components such as LEDs because the purpose of this drawing is to validate the spatial arrangement of plants.) The chamber opens like a refrigerator from the left-hand side where the control panel is featured. Since my design is inspired by the layout of a refrigerator, accessing the crops are intuitive and easy. Tomatoes are positioned at the side of the chamber that swings open so that whenever the astronaut opens the chamber for the daily harvest, vibrations shake pollen from the tomato. This is a fantastic effect because this eliminates the need to manually tap each tomato for pollination. (Fruits require pollination, but there are no pollinator bees in space so astronauts are responsible for pollination!)
Here's the math: 1 meter = 100 centimeters. Lettuce head grows to approximately 15 cm in height and 15 cm in diameter after about four weeks of growth.
If we stagger the growth phases in a single column of lettuce so that we have 4 different heights, the heights are 4 cm, 8 cm, 12 cm, 16 cm = 40 cm total. (when 16 cm lettuce are harvested, move 12 cm lettuce to 16 cm, 8 cm to 12 cm and so forth. Plant a new lettuce at 4 cm. This happens every weekly since lettuce takes four weeks to grow and we have four lettuce.)
Each pot system is 10 cm in height so that's 40 cm.
Between LED strips and plants, there must be a minimum clearance of approximately 5cm so that light can reach each leaf; this also prevents plant stress due to heat emitted from LEDs. Each lettuce needs to be spaced 5cm away from the LEDs so that's 20cm.
40 cm total lettuce height + 40 cm pot system height + 20 cm LED spacing height = 100 cm height total. This makes full use of the height.
7 columns with each representing a day of the week. Since lettuce can be harvested every week in each column, and with a week's worth of columns (i.e. 7 columns) we have lettuce harvest daily. As for length of rows, we wish for lettuce to take up 75% volume or 75 centimeters. 5 lettuce x 15 cm = 75 cm. Perfect!
This covers fruit and vegetable food groups, but the salad is missing adequate carbohydrate, protein, and dairy, which altogether provide the necessary nutrients a person needs. (Granted, it is possible to grow carbohydrate-rich potatoes but since they take up so much volume and are difficult to grow in a constrained space, I choose not to grow such plants.) Realistically, we need to send some packaged food along with the crew:
- Carbohydrate - Quinoa
- Protein - Chicken
- Dairy - Cheese
The daily harvest will include 5 heads of lettuce, a couple of tomatoes, part of an onion, and a sprig of cilantro. When mixed in with quinoa, chicken, and cheese it becomes three nutritious and delicious meals per astronaut for that day.
In the next blog, I'll list out all the materials needed to make a prototype! Until then, keep learning and have fun! Click the arrow to navigate to the next blog.
