Feeding astronauts in space requires a sophisticated blend of food science, engineering, and logistics. For long-duration missions, the food system must be efficient, maximizing nutrition and safety while minimizing mass, volume, and waste. Food scientists develop meals that maintain their nutritional value and palatability for years, as resupply missions are not always possible on deep space journeys. This task demands advanced preservation techniques and packaging solutions to ensure every meal is safe and contributes positively to the crew’s physical health and mental well-being.
The Science of Space Food Preservation
The journey to making food mission-ready involves several specialized preservation techniques to ensure longevity and stability without refrigeration.
One prominent method is freeze-drying, also known as lyophilization, which removes nearly all the water content from a food item. In this process, food is flash-frozen and placed in a vacuum chamber where the frozen water sublimates, turning directly from ice into vapor. This technique drastically reduces the weight of the food by up to 90%, which is a significant advantage for space travel, and helps preserve the food’s original flavor and nutrient profile.
Another method is thermostabilization, which involves heat-processing foods to destroy all harmful microorganisms and enzymes. These cooked items are sealed in flexible, multilayered retort pouches or cans, similar to military Meals-Ready-to-Eat (MREs). Thermostabilized foods, which include wet-pack items like tuna or pudding, do not require the addition of water before consumption. This preservation method allows the food to remain shelf-stable at room temperature for extended periods, often for at least two years.
Irradiation is a third technique used primarily for meat items like beef steak and smoked turkey. The food is sterilized by exposure to ionizing radiation, eliminating spoilage-causing bacteria. Specialized packaging is also utilized, often involving flexible pouches made of laminated polyester and aluminum foil, which enhance the shelf-stability of the food and protect it from the harsh space environment.
Categories of Space Meals
Astronauts select their menus from a wide variety of meal types, each prepared using a different preservation method.
Rehydratable foods constitute a large portion of the menu, encompassing meals and beverages that have been freeze-dried or spray-dried. These items, which include scrambled eggs, mac and cheese, and powdered drinks, require the addition of hot or cold water before they can be eaten.
Thermostabilized foods offer an alternative that is ready to eat without rehydration, as they retain their moisture content. These wet-pack options are sealed in pouches or plastic cups and include items like canned fish, ravioli, or pudding. The packaging allows them to be consumed directly after being warmed.
A third category is natural form foods, which are items that can be eaten as they are, requiring no preparation other than being opened. These shelf-stable snacks are a favorite because they produce fewer crumbs than traditional bread, minimizing floating debris in the microgravity environment.
- Nuts
- Cookies
- Granola bars
- Tortillas
Limited quantities of fresh produce, such as apples and bananas, are also sent up on resupply missions, though these must be consumed within the first few days due to their short shelf life without refrigeration.
Onboard Preparation and Consumption
Eating in microgravity requires specialized equipment and procedures to manage food and prevent spills. The food preparation area, or galley, on the International Space Station (ISS) is equipped with a water dispenser that provides both hot and cold potable water. Astronauts use this dispenser to inject the precise amount of water needed into the rehydratable food pouches through a one-way plastic valve.
Once the water is added, the crew uses food warmers to bring their meals up to a more palatable temperature. The ISS utilizes both built-in and suitcase-like food warmers for various types of pouches and canned food. This heating process can take up to 30 minutes for some items to ensure they are adequately warmed through.
To consume the meal, astronauts cut open the food pouch and eat the contents directly with conventional utensils. Packages are secured to surfaces using hook-and-loop fasteners (Velcro) on trays or tabletops to prevent food from floating away. Liquids and condiments, like liquid salt and pepper, are kept in sealed pouches or bottles with specialized dispensing nozzles.
Menu Planning and Psychological Comfort
The planning of an astronaut’s menu is a deliberate process focused on meeting strict nutritional and logistical requirements while also supporting crew morale. Meals are designed to provide a specific caloric intake, often around 3,200 calories per day, and are analyzed to ensure a balanced supply of macro and micronutrients. Particular attention is paid to nutrients like calcium and vitamin D to support bone health, and the menu is carefully balanced to maintain overall physical performance in the space environment.
The food must also possess exceptional shelf stability, especially for long-duration exploration missions that may require a shelf life of up to five years. Beyond the technical requirements, food serves a psychological function in the confined and isolated environment of space. Astronauts are allowed to select a portion of their food choices from a catalog of over 200 items, and they often choose familiar meals or comfort foods to combat flavor fatigue and reduce stress. The ability to share a meal, sometimes including a small quantity of fresh food delivered by a resupply vehicle, provides a psychological benefit and helps maintain the crew’s well-being.