As the prospect of humans living on the Moon becomes increasingly likely, the question arises: what will they eat? Scientists are developing ways to create pasta and protein bars from thin air, but that's just the beginning.
The space race is accelerating. In the next two years, NASA plans to put astronauts back on the Moon. The International Space Station (ISS), designed to last for 15 years in orbit and now in its 26th year, will soon be replaced.
Scientists are looking at human missions to Mars and beyond. Add to that the rapidly growing space tourism industry, which takes paying customers to the edge of space, and the question becomes even more pressing: what will they eat?
"Food keeps astronauts sane. Having good, varied, tailored food that meets the individual needs of the astronauts is critical for mission success. I don't think people appreciate how important it is," says Dr Sonja Brungs, deputy head of the European Space Agency's (ESA) astronaut operations group.
Currently, astronauts eat prepackaged meals from specialist food producers that are freeze-dried, dehydrated or thermostabilised. The astronauts add water to heat or cool them. They are also allowed to take one 'comfort food' from home (again, this has to be carefully prepared and thermostabilised).
There are some foods that are off the menu: anything crumbly, such as bread, is a no-go in space as the crumbs can easily float off in the low-gravity environment, potentially getting inhaled or into vital equipment. Salt is restricted as the body retains sodium differently in space, leading to accelerated bone loss. Alcohol is also not allowed as it interferes with the water recycling system on the ISS.
"Variety is definitely an issue. Astronauts after only six months in space crave something crunchy. Variety in food texture is really important for mental wellbeing, and especially on longer-duration missions you need a variety of foods," says Brungs.
The ISS has a small on-board garden.
In 2021, NASA launched the Deep Space Food Challenge to explore ways of creating food with minimal resources, producing minimal waste and providing safe, nutritious and palatable food for long-duration missions in space.
Helsinki-based Solar Foods is one of eight companies that made it to the final stage of the competition. Their remarkable idea is to use space waste to create protein.
"We literally make food out of thin air," says Artuu Luukanen, Solar Foods' vice-president of space and defence. The company discovered an edible bacteria in the Finnish countryside that thrives on a diet of carbon dioxide, hydrogen and oxygen. The result is a bacterial protein.
The protein can be blended into different flavours and textures to create a range of nutritious foods, such as pasta, protein bars, meat substitutes and even egg replacements.
"In any habitat in space, you have two main waste products: hydrogen and carbon dioxide. So what we are talking about here is not only a space food production technology, but it will become an integral part of the environmental control and life support system," says Luukanen.
Solar Foods' protein can be extruded into a paste or powder, then mixed with flour and other regular food ingredients to create things like protein-rich pasta, energy bars and even chocolate. Experiments are ongoing to explore whether it can be mixed with oils and 3D-printed into steak-like textures.
Fresh food is another consideration: while vitamin pills can help, astronauts crave fresh produce. Experiments continue into how to grow vegetables in the unique zero-gravity, no-sunlight environment of space. The ISS has its own small on-board garden, where astronauts are studying how plants grow in microgravity.
Back on Earth, California-based start-up Interstellar Lab has developed a modular bioregenerative system for producing greens, mushrooms and even insects; it was also a finalist in NASA's Deep Space Food Challenge, along with Australia's Enigma of the Cosmos, which is working on ways to grow seedlings in space.
Fungi could be a likely future space food. Three of the six companies in the final of the Deep Space Food Challenge are exploring ideas around fungi. Swedish company Mycorena has developed a system that combines microalgae and fungi to create mycoprotein (a protein derived from fungi, often used in meat alternatives).
"Fungi is very versatile. It can grow on different substrates and it grows fast. It is possible to have a small, efficient system that produces enough food for a crew. It is also very robust, radiation-tolerant, easy to store and transport," explains Carlos Otero, research and development scientist at Mycorena.
As private companies become increasingly involved in the space race, so too does the opportunity for private chefs. Rasmus Munk, chef at the Michelin-starred Alchemist restaurant in Copenhagen, Denmark, is one of those preparing for lift-off.
Munk recently partnered with SpaceVIP to cater for the fine-dining experience on board Space Perspective's Spaceship Neptune, which costs £397,000 a head for a six-hour trip to the edge of space.
Munk is one of a number of chefs who see the potential in catering to wealthy space tourists on commercial flights into space. Yet while these developments might seem to be the preserve of the few who can afford such a trip (or are astronauts), the advances in space food are not just about what we will eat in zero-gravity environments, but also what we could be eating here on Earth.
NASA's Deep Space Food Challenge was also designed to create food production systems that benefit us on Earth, creating new ways to produce food in resource-scarce and harsh environments.
Phase three of NASA's Deep Space Food Challenge will take place this summer, further testing how these projects perform in space-analogue conditions.