Before we can go to the stars we’ll need to build a robust infrastructure in our own Solar System. While most attention seems to be devoted to propulsion issues, I’m convinced that an equally critical question is how we can create and sustain closed-loop life support systems for such missions. Our point man on this is Ioannis Kokkinidis, who brings a rich background from his Master of Science in Agricultural Engineering (Agricultural University of Athens) and Mastère Spécialisé Systèmes d’informations localisées pour l’aménagement des territoires from AgroParisTech and AgroMontpellier, along with a PhD in Geospatial and Environmental Analysis from Virginia Tech. Here Dr. Kokkinidis discusses what has been done so far in the matter of growing foods in space, and takes us back to a mission that might have been, a manned flyby of Venus. As Ioannis notes, getting space foods up to the sumptuous standards of Greek cuisine will indeed be a challenge, but we’re at least making progress.
by Ioannis Kokkinidis
A few years ago the Greek press was buzzing with a story about the European Space Agency asking two French caterers to create a meal for Mars based on nine foods: rice, onion, tomato, soybeans, potatoes, lettuce, spinach, wheat and spirulina. The news story was the first time I was exposed to the ESA’s MELiSSA project, which aims to produce food through an artificial ecology for solar system colonization, including space stations and spaceships. A somewhat related American project to grow food in microgravity is the VEGGIE project, which has recently made headlines by growing several plants which were consumed by astronauts on the International Space Station. The subject of this post is to describe two leading edge projects to produce food in a space environment. I am not and have never been affiliated with either of the projects, I have never met any of the people associated with either project nor is anyone asking me to publicize these projects. I am simply a learned amateur, albeit one with graduate degrees in agronomy who is fascinated by the projects and their potential.
The Micro-Ecological Life Support System Alternative (MELiSSA) initiative is a European Space Agency project with almost 30 years of history behind it. Its origin lies in the flight of two tubes of nostoc algae in a recirculating system to space on the Chinese FSW-0 No 9 recoverable mission in 1987. In 1989 the MELiSSA Foundation was formed to create a closed loop artificial ecosystem for long spaceflights, based on aquatic ecosystems. MELiSSA aims to replace the current generation of mechanical Environment Control and Life Support Systems (ECLSS) with a new one based on biology, which will not only remove metabolic waste from the various streams (air, water) but also produce food in the process. The tool to accomplish this task is the MELiSSA cycle.
Fig 1: The MELiSSA cycle © ESA from http://www.melissafoundation.org/. The cycle has five compartments.
Compartment I: The liquefying compartment
This compartment gathers all the organic waste created in the spaceship and aims to convert it into ammonium, CO2, volatile fatty acids and minerals. For biosafety and efficiency reasons this compartment operates in thermophilic conditions (i.e. 55 C). The main biological functions involved are proteolysis, saccharolysis and cellulolysis. While saccharolysis is trivial, after all sugars are a main biological source of energy for most species, proteolysis and cellulolysis have proven more difficult to optimize, with proteolysis having an efficiency of 70% and cellulolysis of 44% in the cycle. Considering that despite billions in public and private investment in Europe and the United States to increase cellulolysis efficiency, cellulosic ethanol has not entered the market in meaningful quantities, these efficiency figures are pretty decent for the current state of technology.
Compartment II: The photoheterotrophic compartment
In this compartment volatile fatty acids, ammonium and minerals from component I are further broken down by Rhodospirillum rubrum bacteria into minerals and ammonium. The bacterium has proven very efficient in the process. For more, see this brief video.
Compartment III: The nitrifying component
This compartment has as feedstock urine from the crew, ammonium from compartment II and oxygen from compartment IV. It uses a mix of Nitrosomonas and Nitrobacter bacteria to oxidize ammonium into nitrates, which plants prefer as their nitrogen source
Compartment IV: The photoautotrophic compartment
This compartment is intended is to grow actual food and produce oxygen for the crew. It is divided into two parts: the algae compartment and the higher plant compartment.
- IVa: The algae compartment
In the current iteration of MELiSSA, the cyanobacterium Arthrospira platensis has been selected as the organism grown. This is one of two species (the other being Arthrospira maxima) that are known colloquially as spirulina. Several photobioreactors with this bacterium have been built and a predictive model has been created and validated experimentally.
- IVb: The higher plant component
This component is intended to provide both food and water for the crew. While several crops have been evaluated in the course of the project, 8 have been selected: wheat, tomato, potato, soybean, rice, spinach, onion and lettuce. Currently the status of this component is far less mature than the algae component, they are still compiling the biomass production rates, nutrient and mineral compositions of the plants based both on outside work and their own research.
Component V: The crew component
This is simply the crew component of the spaceship, composed of the astronauts and cosmonauts who consume the food, produce CO2, urine and other waste which is sent to the components of the cycle.
Like all ESA programs, the intention of MELiSSA is not only to provide technology for space exploration but also for applications on earth. It has helped explored the concept of closed loop ecosystems, which are critical to colonize other bodies but also to help understand how earth ecosystems work. A pilot plant that uses rats as the trial crew (component V) has been running since 2009 at the School of Engineering of the Autonomous University of Barcelona. The greywater treatment plant of the Concordia station in Antarctica uses MELiSSA technology while a sensor for CO2 monitoring of sparkling wine has been commercialized. The BIOSTYR© bacterial support for wastewater treatment, commercialized by Veolia, has been derived from MELiSSA compartment III research. Andreas Mogensen conducted two MELiSSA related experiments during Expedition 44 to the ISS, consuming spirulina infused snack bars created by MELiSSA which he also shared with his fellow astronauts in the DEMES experiment, and keeping an eye on some micro-organisms and how they recycle our waste in space in the Bistro experiment.
The most recent news item associated with MELiSSA was the opening of a new facility called AlgoSolis to cultivate algae at an industrial scale in Saint-Nazaire in France. It seems that it is the intention of the project to construct a MELiSSA loop in the ISS or a future space station, though the concept still requires technological maturation. This is a very interesting project to follow in the future.
The Vegetable Production System (VEGGIE) experiment is an experiment of NASA’s Human Exploration and Operations Mission Directorate to grow salad crops in the International Space Station run by the Kennedy Space Center and Orbital Technologies Corporation (ORBITEC) of Madison WI, a subsidiary of Sierra Nevada Corporation. It is not the first plant growth experiment in space, the Bulgarian/Russian SVET SG (Space Greenhouse) experiment grew various plants on a series of experiments aboard the Mir space station in the 1990’s, several of those in partnership with NASA. These however were biological experiments intended to study plant growth in microgravity; cosmonauts were not supposed to consume the plants though some have admitted to nipping bits. The Veggie experiment intends to grow fresh food for astronaut consumption on the ISS. So far the experiment has had three phases, named Veg-01, Veg-02 and Veg-03 and has been conducted during Expeditions 35/36, 39/40, 41/42, 43/44, 45/46, 47/48 and 49/50.
VEGGIE builds on heritage from the SVET SG experiment on Mir, the Biological Production System of Expedition 4 and the failed efforts of Expedition 2 astronaut Jim Voss and Expedition 6 astronaut Don Pettit to grow plants on old food bags (see http://www.orbitec.com/documents/Veggie-APH.pdf). It is made of a plant growth chamber which is made of modular planting pillows, an LED bank for lighting and a fan for humidity control. It weighs 7.2 kg and has external dimensions 53 by 40 cm (=0.212 m2) with a root mat of 0.16 m2 and a growth height of 45 cm. It provides lighting and nutrients, having a 2 l fluid reservoir, but depends on the ISS ECLSS for temperature and CO2. It draws 115 Watts of peak power, is able to support different day/night lengths for experiments and contains a data logger that records temperature, humidity and pCO2 (see http://spaceflight101.com/iss/veggie/). The plants grow on the planting pillows, containing the substrate, fertilizer and seeds, which are of single use and arrive in ready-to-activate form from earth. It is deployed in an EXpedite the PRocessing of Experiments to Space Station (EXPRESS) Rack.
Veggie hardware validation test (Veg-01)
Veg-01 had a variety of goals including a shakedown of the system to see if the experimental apparatus works in space. VEGGIE was delivered to the ISS by the SpaceX CRS-3 mission launched on April 18 2014. Expedition 39 flight engineers Steve Swanson and Rick Mastracchio installed it at the European Columbus module on May 7 2014 and activated it the next day. They used 6 planting pillows of ‘Outredgeous’ red romaine lettuce, having a substrate of two different sizes of arcillite (3 of one and 3 of the other), a calcined clay media used on baseball fields that included fertilizer. Two sizes were used so as to compare root zones between the two media, so as to determine water and root distribution for future investigations.
The pillows then received about 100 milliliters of water each to initiate plant growth. 24 hours after activation on the ISS an identical VEGGIE experiment was activated on the ground at KSC to serve as control (see also http://spaceflight101.com/iss/veggie/). Steve Swanson, who by that time had become the commander of Expedition 40, harvested VEGGIE on June 10, 33 days after planting. The next day the control experiment was harvested on the ground. Two plants on the ISS experiment were lost due to drought stress. The tops of the surviving lettuce were cut away from the plant pillows and swabbed for microbial samples. The pillows and bellows also were swabbed.
The plants, sample swabs and a couple of the plant pillows were packaged and placed in the ISS’ minus-eighty-degree freezer for storage. The crop, along with the pillows and sample swabs were returned from the ISS on the SpaceX CRS-4 mission which splashed down on October 25 2014. The lettuce was analyzed for microbes on the ground and found to be within safe limits, for that matter it had a lower microbial count than what is usual for lettuce on the market. A second crop was activated in early July 2015 by Commander Scott Kelly, who had arrived on the ISS on March 28 2015. Thirty three days later they were harvested in turn, having lost only one plant and on August 10 2015 expedition 44 astronauts wiped the lettuce leaves with citric acid-based, food safe sanitizing wipes before consuming them raw. See http://www.nasa.gov/mission_pages/station/research/news/meals_ready_to_eat.
There is conflicting information online whether Veg-02 is just the zinnia experiment (described below), if it also included the second lettuce experiment mentioned in the previous section or for that matter if there even was a Veg-02 experiment, rather than skipping the number and moving directly from Veg-01 to Veg-03. In any case what follows is a detailed description of the zinnia experiments compiled from available online sources.
The planting pillows with the ‘Profusion’ zinnia seeds for the Veg-02 experiment were carried to orbit along with the rest of the VEGGIE apparatus on the SpaceX CRS-3 resupply flight. These plants received quite a bit of attention from Commander Scott Kelly during his Year in Space mission; he took care of the plants and tweeted about them several times. On November 16 2015 astronaut Kjell Lindgren activated the experiment, which was the first flowering plant experiment grown on the ISS, 3 days after activation of the control experiment at KSC. The experiment was composed of a total of four plants and lighting was set on a photoperiod of 10 hours day and 14 hours night in order to stimulate flowering.
The plants started to grow [http://www.nasa.gov/image-feature/first-flower-grown-in-space-stations-veggie-facility] but two weeks into their growth period, NASA astronaut Kjell Lindgren noted that water was seeping out of some of the wicks – the white flaps that contain the seeds and stick out of the tops of the plant pillows. The water partially engulfed three of the plants. Within 10 days, scientists noted guttation on the leaves of some of the plants. Guttation is when internal pressure builds in the plants and forces excess water out of the tips of the leaves. It occurs when a plant is experiencing high humidity.
Additionally, the zinnia leaves had started to bend down and curl drastically. This condition, called epinasty, can indicate flooding in the roots. The anomalies all pointed to inhibited air flow in the plant growth facility that, when coupled with the excess water, could have the potential to cause major problems to the crop. Commander Kelly, who took over the experiment after Lindgren returned on Earth December 10, noted that the plants had grown a mold. On December 22nd, after late night consultations with the ground crew, he cut the two affected plants off and put them in cold storage for return to Earth. Then he increased the fan speed to reduce humidity. Scott Kelly, though, reported on Christmas Eve that the reverse problem was currently happening, the plants were getting too dry. Watering was scheduled for December 27, but despite the advice of the ground crew, he decided to take the initiative and water them on Christmas Eve. He then tweeted one of his most memorable tweets.
By January 8 the flowers were on the rebound, leading to another tweet.
while on January 12 they had begun to flower. The zinnia plants on the ground were harvested on February 11 while those in space on February 14, Valentine’s Day. See http://www.nasa.gov/mission_pages/station/research/news/flowers.
The aim of the Veg-03 experiment is to build on the success of the previous VEGGIE experiments by growing ‘Tokyo Bekana’ cabbage along with ‘Outredgeous’ lettuce as food crops. Plants are again to be grown in two different sizes of arcillite substrate with specialized fertilizer. Eighteen planting pillows (12 of cabbage, six of lettuce) were prepared at Kennedy Space Center on early April 2016, by gluing the seeds using guar gum to the Teflon and Kevlar envelopes [https://blogs.nasa.gov/kennedy/2015/06/18/future-lettuce-planting-the-seeds-for-veg-03/]. They were then packed in gas-impermeable bags and then into cargo transport bags so as to be shipped on the ISS with the SpaceX CRS-8 mission to the ISS [https://blogs.nasa.gov/kennedy/2016/04/08/veg-03-plant-pillows-readied-at-kennedy-space-center-for-trip-to-space-station/]. First lady Michelle Obama planted cabbage seeds from the same batch that were shipped to her from KSC at the White House vegetable garden on April 5th 2016. She was assisted in that task by NASA Deputy Administrator Dava Newman, astronaut Cady Coleman, Brad Carpenter, chief scientist for space life and physical sciences at NASA, Gioia Massa, NASA Veg-03 science team lead at Kennedy and kids from Bancroft Elementary School and Harriet Tubman Elementary School [http://www.nasa.gov/feature/nasa-s-veg-03-seeds-planted-in-first-lady-s-white-house-garden]. SpaceX CRS-8 launched on April 8 2016, was captured on April 10 and the experiment is awaiting activation. Future plans for VEGGIE include growing dwarf tomato seeds in 2018.
Despite its modest size VEGGIE is the largest plant growth chamber ever launched to space. So far over three growth periods it has produced only one lettuce crop that was consumed by the inhabitants of the ISS following a 33 day growth period. Alas I did not find a news item on whether it was actually all consumed in one or several meals. If we wished to scale the experiment to producing a significant fraction of the food consumed by the astronauts and cosmonauts in space, as is the purpose of the MELiSSA experiment, we have the issue that the ISS is simply not big enough, despite being the largest space station in history. The complete length of the ISS modules from one edge to the other is 51 m. Assuming a 4 m average module diameter this would mean an opening area of 200 m2.
Under intensive agriculture we would most likely need on Earth around 250 m2 per inhabitant per year, though this needs to be validated in space conditions. But the ISS is three dimensional; we could say fit throughout the ISS modules enough VEGGIE modules to have sufficient growth area in the volume provided, if there were enough EXPRESS racks. Other issues would still need to be resolved. If a single 0.212 m2 VEGGIE module consumes 115 W of peak power, then 250 m2 of VEGGIE modules should consume 135,6 kW of power. The ISS power system produces, according to Wikipedia, between 84 and 120 kW of power on each orbit. Furthermore 1000+ Veggie modules would require quite a bit of astronaut attention and time that might not be available: Scott Kelly was aware of the rot issue in the zinnia experiment on the single Veggie module he was tending at least two days before he intervened, but he had to delay his intervention due to an unplanned spacewalk. Growing food in space requires very significant amounts of space and human resources, which is why so far space food has been grown, prepared and sent to space from Earth.
Cooking in Space
After growing food in space we would most likely need to cook it. While Veggie is intended to grow only raw food, MELiSSA intends to produce raw materials for balanced, cooked, or at least somewhat prepared, meals. This raises the issue of cooking in space, especially under microgravity conditions, which is still in a rather primitive form. Expedition 18 astronaut Sandra Magnus has produced a slideshow and an article of her cooking efforts in space. I admit that I am showing my cultural bias as a Greek here but with the exception of putting onions and garlic with olive oil at the Russian food warmers for several cycles, the rest of her cooking would not qualify as cooking in my book but rather as recombination of already partially prepared foods. Then again I have to admit that not everyone’s baseline for cooking is their grandmother spending two or three hours preparing lunch in the kitchen followed by a couple of hours of baking in the oven to cook it.
Moving from having raw produce to fully prepared cooked food requires several steps that have yet to be demonstrated in space. Let us assume that we have grown wheat and we wish to create a taco shell, a foodstuff quite popular with ISS astronauts and cosmonauts. We would need to separate and shell the wheat grains from the rest of the plant. Then we would need to mill the grains into flour which is a critical step in more ways than one: we depend on modern mills to separate several pathogens from the seeds and protect us from, say, ergotism. Then we would need to turn the flour into dough in microgravity, which is not very conductive to mixing materials that are in different phases. Next we would shape the dough and put it into an oven for cooking, which most likely would have to look like a toaster oven so as to avoid having the shaped dough wander inside the oven along with the convection currents. Then hopefully we would have a taco to fill with what we desire. As we can see we still need to prove that several of these steps can be achieved under microgravity conditions.
Growing space food in perspective
One of the offshoots of the space race was the Apollo Applications Program (AAP), an effort to use the hardware developed during the Apollo program in other uses. It eventually studied three major applications: the Orbital Workshop, a permanent Lunar Base and a Manned Venus Flyby. A central concept of the AAP was the Wet Workshop: The upper stage of either a Saturn IB or a Saturn V (the S-IVB stage) would be launched to space, fire its engines to reach the appropriate trajectory, then the remaining fuel and oxidizer would be vented and the astronauts would move into the tanks after sealing them behind them using tools launched with them placed at the location where the Lunar Module would be during Apollo lunar missions.
In the end only the Orbital Workshop was launched in the form of Skylab, which was a Dry Workshop: It was launched already preconfigured as a habitat from Earth. Skylab can be seen as a prototype for the Manned Venus Flyby spaceship, which after all has been called “Skylab to Venus”. It is unfortunate that in the 5 decades since, very few spaceship plans can claim to have reached the level of maturity that Manned Venus Flyby reached with the launch of Skylab. Only the Soviet Mars Train, released a few years before the collapse of that country, can also claim to be based on space tested systems, more specifically the Mir Space Station and the Russian segment of the ISS which was based on Mir/Mars Train designs. While some of the NASA Mars plans have talked about the use of Destiny derived modules, so far only the Manned Venus Flyby has had a plausible plan using existing hardware in production at the time of its planning. For a review of Mars plans see http://history.nasa.gov/monograph21.pdf.
Skylab holds to this day the record for food weight and portions packed in a single launch. Skylab, like the first generation Salyut stations, lacked the ability to receive unmanned resupply missions and while some food was carried along with the crews, most of the food consumed aboard was carried to space during the launch of the Space Station. More specifically, Skylab was launched with approximately 2500 lbs of food packages and another approximate 350 lbs were launched along with the astronauts, mostly with Skylab 4. I use imperial units in this section because that was what NASA used at the time in the documentation.
The workshop included 5 freezers each weighing about 60 lbs (without the food inside them), 22 unrefrigerated food assemblies at 90 lbs each and 3 overage containers at 30 lbs each (see http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760011703.pdf). Adding all these numbers up totals 2850 lbs of food and 2370 lbs for the containers, and a system total of 5220 lbs. Considering that the total weight of Skylab without the Apollo CSM at launch was 150,350 lbs, the mass fraction of the food system was 3.5% of total weight, including the food that was later launched. Food without the support equipment was 1.9% of total Skylab weight. Originally Skylab food was packed for 140 days of operation; in the end the three manned missions lasted 171 days and they kept a 10 day contingency margin of food for the last flight in case weather delayed the return of the last crew. My understanding is that when Skylab 4 landed only the contingency food was left on board the station.
The Manned Venus Flyby spacecraft was to last for 400 days. The planners allotted 1800 lbs for the food for the 3 astronauts, a figure that does not include the weight of its containers. Furthermore, the thrown weight of the whole MVF assembly stack was 106,775 lbs of which 37,710 was for the Environmental Support Module and 34,600 for the S-IVB stage and the Instrument Unit [https://www.devin.com/cruft/19790072165_1979072165.pdf]. This would give a food fraction of 1.7%, as opposed to Skylab’s 1.9%.
Now on Skylab the Orbital Workshop weighed 62,500 lbs, IU 4,600 lbs with a total weight (including the 22,200 lbs Apollo Telescope Mount but not the Apollo CSM carrying the astronauts) of 150,300 lbs. If for 181 days of food supplies Skylab need 2850 lbs of just food, for 400 days of supplies they would need 6300 lbs. While it is true that when MVF was studied we had little idea how much food astronauts and cosmonauts needed in space, the differences in mass between the MVF plans and what was their equivalent weight on Skylab offer a cautionary tale on planning without having built any actual equipment. It is rather difficult to find figures online on how much weighs the food that each ISS astronaut or cosmonaut consumes every year, but my understanding is that since the 1970’s actually food weight consumed is more or less the same but packing material weight has significantly decreased.
My foray into the Apollo/Skylab era is intended to show just how small a fraction of spaceship weight is taken by the food system. I have not performed this sort of analysis with later spaceship plans, assuming they were ever that detailed, but even for a two year trip in space (say to Jupiter) food weight should not be a showstopper. Growing food would still be beneficial for psychological reasons and to supply vitamins in a more pleasant form than pills. For long term interstellar travel, when we surpass a trip length of a decade, which is generally the maximum that canned foods survive, growing food will become critical. The projects mentioned in this post will probably be among the ancestors of the systems and their designed used on these starships.