For the first time since the end of NASA's Apollo missions to the moon, there is serious talk of sending humans beyond low earth orbit. NASA has been courting ideas for journeys to the moon and eventually Mars, while SpaceX is hell bent on being the first to get boots on the Red Planet. These ambitious plans present a host of technical challenges, however, particularly when it comes to food. This is why researchers at NASA's Kennedy Space Center in Florida have turned themselves into space farmers—without leaving Earth.
Up until 2015, the fare for astronauts aboard the International Space Station was limited to the dehydrated, freeze-dried foods that would be delivered aboard cargo resupply missions. Not only are these foods lacking in the taste department, but at $10,000 per pound, it's also incredibly expensive to ship freeze-dried spaghetti to low earth orbit. The goal, then, is to figure out how to produce food in space. This idea had its first proof of concept in August of 2015, when astronauts aboard the ISS were treated to a rare delicacy: fresh lettuce that was grown in space.
That lettuce was made possible by NASA's vegetable production system, otherwise known as Veggie, one of the handful of approaches the agency is taking to offset food transport costs and provide astronauts with a nutritious diet on long duration space missions. During a recent visit to Kennedy Space Center to view the SpaceX launch to the ISS, I stopped by NASA's labs to see how researchers are continuing to develop techniques to farm in microgravity.
My first stop was to visit Bryan Onate in his lab, where he is part of a team of researchers working on developing NASA's Advanced Plant Habitat. A prototype of the APH, which looks like a big, high-tech microwave, arrived at Kennedy last November and is basically the equivalent of MIT's food computer, but especially designed for the space requirements of the ISS.
Inside the habitat, a number of Arabidopsis, a type of flowering plant related to cabbage, were growing under an array of LED lights. The researchers are able to control a number of variables in the growing chamber, including oxygen and nutrient levels, and can even measure the temperature of the individual leaves of the plant. However the main perk of the APH is that the control of these variables is automated by a computer system the researchers have accurately, albeit awkwardly, named PHARMER—the Plant Habitat Avionics Real-Time Manager in Express Rack.
The APH is experimental—Onate described it as the "Veggie's big brother," and like the Veggie system that is currently on board the ISS, it is used to explore optimum growing conditions for various types of vegetables. The new advanced plant habitat will be sent to the ISS to take over for Veggie on two upcoming commercial resupply missions. According to Onate, one of the main goals of APH research on the space station is to recover some of the plants grown in space, bring them down to Earth, use their seeds to grow plants at Kennedy, and then ship seeds from those plants to the space station to see if they're still viable after the transition between terrestrial and microgravity environments.
The next stop was Kennedy's large environmental control chambers. These look like sterile walk-in refrigerators and are used to replicate all the environmental variables found on-board the ISS, such as humidity or CO2 levels—the only variable that can't be replicated is microgravity. These chambers served as a ground control for the vegetables that were grown on the ISS as part of the Veggie program so that the researchers could compare how microgravity affects the plant growth when compared with terrestrial conditions. I visited during the final hours before Friday's harvest of the Chinese cabbage, the fifth and most recent vegetable crop to be grown aboard the ISS.
According to researchers I spoke with on site, the experiment has so far been a resounding success. The astronauts on the ISS have been able to grow enough lettuce to make a small salad and the Chinese cabbage will likely be greeted with enthusiasm by the astronauts because it has more flavor than the red lettuce that had previously been grown.
"In microgravity, your taste sensation is dulled so astronauts like to have things a little bit spicier, sharper," one of the researchers told me. "So this is why we are growing Chinese cabbage: it grows fast, has great nutrient levels and also performed very well on our taste tests."
My final stop was to a small, unremarkable room with a metal work table in its center and potted plants crammed into small gaps of shelving space around the walls.
"What we're doing here is looking for the long duration aspects of food production, the next steps after veggie and APH," said Ralph Fritsche, the Kennedy food production project manager. "APH is really a research platform and Veggie was kind of the first steps of trying to grow crops, but the focus of the research in this room is to develop something that's actually going to supplement the crew's diet."
As Fritsche pointed out, growing small batches of lettuce on the ISS is great, but so far NASA hasn't managed to produce enough plant matter to really make eating lettuce anything more than a novelty for the crew. To actually produce vegetables that will supplement the crew's freeze-dried diet, both on the ISS and eventually on the surface of Mars, Fritsche and his colleagues have to figure out a way to mass produce vegetables in space.
This is trickier than it sounds for a number of reasons. In the first place, water flows differently in space. On earth, water will be pulled towards a plant's roots, but in space, water will ball up and not be distributed evenly for the plant. Also, since liquids tend to ball up in microgravity, this also prevents effective oxygen flow to the plant. According to Fritsche, NASA is working on a couple of solutions to this problem of oxygen and water systems for plants in microgravity. One is an active system which essentially pumps water to the desired locations within a grow area.
The other is passive and based on a 3D printed nylon substrate that NASA has developed with researchers at Utah State. This is basically a cube that is made up of a bunch of densely packed triangles. Seeds are then placed on top of this cube and water is allowed into the system. Nylon is hydrophilic so the structure attracts the water and because of the way the cube is designed, the water disperses to the corners of the triangles and is kept there by surface tension. This allows for even distribution of water droplets for the plant's roots, as well as allowing air to flow to the plant through the vacant space in the triangles that make up the substrate.
"If we get good results after testing this in parabolic or suborbital flight, we'll try to fly this to the space station," said Fritsche.
According to Fritsche, growing vegetables on the surface of Mars will be slightly less problematic than growing them in orbit. Even though Mars only has about a third of the gravity found on Earth, for the purposes of space farming and figuring out things like water flow, it is essentially the same.
Still, Fritsche and his colleagues want the most bang for their buck, which means figuring out how to maximize the amount of plant matter that can be grown in confined areas like those that are found on the space station and eventually, Martian greenhouses. This has led them to explore microgreens, which is an umbrella term for regular vegetables that are eaten long before they're mature, usually just a few weeks after sprouting. Since these vegetables are so small, grow relatively fast, are nutritionally rich and full of flavor, they make the most sense for supplementing astronaut's diets.
Fritsche imagined a future in which technologies like the 3D printed plant substrate and the APH automated farming system are combined to provide future Martians with a buffet of fresh microgreens. But despite the promise of combining NASA's farming technologies, he said it is unlikely that astronauts will ever be able to entirely ditch freeze-dried cuisine.
"I don't think we're going to get to a point that you're going to be able to offset the bulk of your nutrition with something you make on the way to Mars or the Moon," Fritsche said. "The key is that there are certain nutrients that degrade over time to the point you kind of have to make them along the way. Really what we're looking at is nutritional support, but I think it's likely that astronauts will continue to bring the bulk of food with them."
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