Since November 2, 2000, the International Space Station has been continuously crewed meaning humanity has had a permanent presence in space. This importance of this station cannot be overstated—NASA has literally filled a book with all the ways the ISS has benefited humans on earth. It’s helped develop new cancer treatments, enhanced robotic surgery technology, improved data processing techniques, its benefits stretch far and wide. It is quite possibly the most significant science experiment humanity has ever undertaken.
It is also quite possibly the most expensive single item humanity has ever built at an overall cost, so far, of about $160 billion. Breaking that down, each day that each astronaut spends on the ISS costs about $7.5 million. The ISS is a joint project between Russia’s Roscosmos agency, Japan’s JAXA, Europe’s ESA, Canada’s CSA, and the US’ NASA. Physically, though, it’s split up into the Russian segment and the US segment with these two countries more or less taking responsibility for managing and supplying their side.
At over 350 feet or 110 meters long, the station is longer than a 747 and has more interior space than the average six-bedroom house. Space is still at a premium, though, as science experiments and equipment take up most of the room so normally there are only a maximum of six crew members on board at any given time. Back on earth, though, there are thousands of people working to support the activities of those six.
Now that the international space station is built and operating, the whole mission is basically a big logistics problem—it involves getting people, food, water, supplies, and experiments up and down from the station in a consistent, cost-effective, and safe manner.
Food, as an example, is one of the only completely non-renewable resources onboard the ISS. Water can be recycled, oxygen can be generated, supplies can be reused, but food is one-time use and then it's done. That means there has to be consistent shipments from earth to the station. About half the food is supplied by the Russians and the other half by the Americans.
There are a few constraints to space food—it has to be shelf-stable as there are no refrigerators on board, it has to last about two years as resupplies only happen a few times a year, it has to be light as weight is precious on the resupply rockets, and it has to be easy to prepare as astronauts’ time is valuable.
Within those parameters, the Russians use a system of canned food while the Americans use a system of flexible pouches which have the advantage of being lighter weight than the cans. This NASA food is produced at the Johnson Space Center in Houston, Texas.
Long before they launch, the astronauts do a taste test to determine which foods they like most and they express these preferences. Based on those, NASA will produce and load more of the best-liked foods. The astronauts can choose from hundreds of items—spaghetti and meatballs, barbecue beef brisket, Caribbean chicken, vegetable quiche, beef enchiladas, the options go on and on.
Somewhat surprisingly, the ingredients for the food are just purchased at a grocery store like any other meal. There is no special sourcing or special ingredients, although they do inspect the ingredients carefully after buying to be extra sure that they are safe. As far as we know, no astronaut has yet gotten food poisoning in space and NASA wants to keep it that way.
The food is then prepared fairly conventionally until the last step. Food is made shelf-stable and lightweight by one of two methods—thermostabilization or freeze-drying. With thermostabilization, heat is used to destroy microorganisms and enzymes that would cause food to spoil. With freeze-drying, the food is frozen and then almost all moisture is removed.
With this technique, there is nearly no water left in the food, which is normally the bulk of its weight, so a full serving of spaghetti, for example, weighs only one ounce or 28 grams. The space station has a water recycling system that recovers about 80% of the water onboard which means that, while they do occasionally have to resupply water from the earth, it’s more efficient to ship food up without water in it since the water onboard can be reused for multiple meals and that also helps keep it shelf-stable.
Overall, freeze-drying reduces the total food weight they have to take up. NASA currently pays about $29,000 per pound for shipment to the Space Station. Each gallon of water they bring therefore costs them about a quarter of a million dollars.mThat also means each of those one-ounce portions of spaghetti costs them about $1,800. They also typically include a few pieces of fresh fruit anytime a rocket goes up as a treat and, with these shipment costs, each apple is worth almost $10,000. This is why so much focus is put on minimizing weight.
In addition to the food they make, some foods are just shipped up as is. For example, if a crew member has a particular type of granola bar they like, the food preparation team will go out and buy some of those as a sample and perform some tests in their lab to figure out if it’s, as they call it, “flight compatible.” In that, they are basically looking to be sure that it’s not too crumbly as they don’t want crumbs floating around into all the nooks and crannies of the station, as well as being sure it’s not too liquidy, both for the purposes of weight and to be sure that it doesn’t cause free liquid to float around. Assuming it passes these tests, astronauts can pretty much bring what they want for snacks. It will be repackaged into NASA’s pouches, but there’s a surprising amount of simply store-bought food on the station.
Once all food is produced and packaged, it is shipped to one of four launch sites—either the Mid-Atlantic Regional Spaceport in Virginia where Northrop Grumman Cygnus resupply spacecraft are launched from. Cape Canaveral, Florida where SpaceX Dragon spacecraft are launched from. Baikonur Cosmodrome in Kazakstan where Russian Progress resupply and Soyuz crewed spacecraft are launched from; or Tanegashima Space Center in Japan where Japanese Kounotori spacecraft are launched from.
The food will be carefully packed alongside everything else making the trip ensuring proper spacecraft balance. Thanks to all these weight-saving techniques, supplies for crew, including food, only represent a small portion of the overall weight of each launch. For example, on one SpaceX launch, crew supplies only represented 530 pounds or 240 kilograms of the 6,000 pounds or 2,700 kilograms of cargo. The rest of the launch capacity is dedicated to equipment and experiments.
Now, part of the difficulty of this supply chain is that launch dates change a lot. For example, the SpaceX resupply, CRS-16, was initially scheduled for August 2018, then it was pushed back till the 29 of November, then till December 4th, then again to December 5th when it finally launched.
These delays can come from quite mundane issues. The December 4th to December 5th delay, for example, came because it was found that the food loaded for lab mice who were making the trip was moldy and had to be replaced.
Even just getting a launch or landing date in the first place is difficult enough. Each site has its own set of constraints potentially preventing use. For example, Tanegashima Space Center in Japan can only be used for launch at certain times of year since, during fishing season, there are large numbers of ships offshore from the launch site which could be hit and damaged if a rocket exploded. Elsewhere, a Soyuz landing in Kazakstan had to be rescheduled as there was a G8 summit nearby which, for security reasons, imposed airspace restrictions that prevented spacecraft search and rescue aircraft from flying.
Even the angle of the sun relative to the ISS constrains when a spacecraft can dock. The other factor that can affect the supply chain is that rockets are imperfect. 5 of the 117 resupply missions to date to the International Space Station did not make it for one reason or another meaning there’s a failure rate of 4.3%.
There was even a nine-month stretch from 2014 to 2015 when three resupply missions failed. In times like these, it’s quite important that the ISS has plenty of backup food, water and supplies. While the astronauts would never starve, running out of food or water could mean that they would have to return to earth early potentially leaving the ISS un-crewed and therefore wasting many millions or billions of dollars.
When that third mission failed on June 28th, 2015, the station had enough food to last them for about another fifty days. In this case, even with three failed missions, they had plenty of food to last them especially considering the next resupply mission, a Russian Progress spacecraft, was scheduled just a week after the failure and it was successful.
There have been close calls, though. After the Space Shuttle Columbia disaster in 2003, astronauts had to cut their daily caloric intake and supplies got as low as 7 to 14 days of food. They were one resupply failure away from having to evacuate.
Sometimes, in order to stretch the food supply, NASA will have to extend the certified shelf life of food onboard. For this purpose, they keep a sample of each batch of food they make on earth, packaged and stored in the exact same conditions as on the ISS, so they can test if food is still fit for consumption and safe.
Assuming a rocket doesn’t have any issues, it will typically make it to the ISS in about two to three days. Once the spacecraft is near the ISS, the crew will spend almost a whole working day dealing with the docking process. Once that’s completed, either the same day or the next morning, they’ll open the hatch. Typically right at the hatch is the crew care package. This will include those fresh fruits and vegetables as well as some items sent up by the crew’s families.
One time, the crew care package even included real ice cream. While there isn’t normally a freezer on board, in this instance a portable freezer was sent up in order to transport samples from an experiment back to earth but, since it was empty on the trip up, the crew got this treat. Over the next few months, astronauts will go through their food one container at a time scanning a barcode each time they open one to let mission control know what their inventory level is like. That way, if the food is going quicker or more slowly than expected NASA can adjust future shipments.
Onboard, dehydrated food is heated up and hydrated using a food re-hydrator while other food can be heated up using another heater. The point of putting so much effort into food on the ISS is for the psychological well-being of the astronauts. With working long hours bottled up in a small space for up to a year, the mental stress of the job is enormous so any effort that can help reduce that is an effort worth doing.
As part of this, NASA puts a good amount of work into movie night. They have a large projector screen and, in addition to their onboard digital library of about 500 movies, the crew can download new movies. The ISS does have an internet connection and they’ve been known to get some movies, such as Star Wars: The Last Jedi, while they’re still in theatres. That same internet connection lets astronauts browse the web quite freely, even if it’s not quick. While the station does have 300 megabits per second of downlink capacity, the vast majority of it is dedicated to experiment and other data, but astronauts are able to regularly video call their families using it.
The unloading process of resupply vessels is quite a slow process, partially just because there isn’t much storage space onboard. Once a resupply vessel is unloaded, though, the crew will start loading it again with trash. The Northrop Grumman Cygnus, Russian Progress, and Japanese Kounotori spacecraft cannot return to earth so they just burn up in the atmosphere along with all the trash.
The SpaceX Dragon and crewed Russian Soyuz spacecraft do return to earth so they can bring back samples and experiments. Once ready, the spacecraft will undock and slowly drift away from the ISS until it disappears from view and at that point, the ISS is ready for another delivery of humans or cargo—one of the most unique regular deliveries in our universe.
