Space Food

Space food has changed a lot in the past few decades, and can now be quite similar to the food that you eat on Earth.  Whether you want to plan a space-themed picnic, or are just interested in the food technology, this article shows how you can eat like an astronaut with food bought from your local super market or online retailer.

Requirements

To get started, here is an excellent video describing some of the history and currently technology used in space food:

Based on the contents of that video, there are a few requirements that you want for the food:

• It needs to be “shelf stable” – which means that it can be stored at ambient (room) temperature.
• You should be ready to eat, or only require you to add water (either hot or cold).
• Some can be fresh, but most should have a long shelf-life.
• You want to consume it in a way that doesn’t lead to bits floating around.

There are also the requirements that you would have for any food – such as tasting nice and being nutritious.  A 2012 NASA report lists the categories of space food as: thermostabilised, irradiated, rehydratable, natural form, extended shelf-life bread products, fresh food, and beverages.  Examples of all of these are available in your local stores, and probably already in your cupboards.  The photograph below shows a selection.

Long-lasting foods that can be stored at room temperature. Most had best before dates around 9 months in the future. The sausage was 2 months, and the tinned fish was 18 months.

Your options include cereal bars, dried foods, sealed drinks, and anything you can eat straight from the can – such as fish (although probably not a popular choice on the ISS).  The video does say that the Russian canned food can be heated, but food that you can eat straight from the can is more like the “thermo-stabalised” food mentioned.

Freeze dried food

If you’re looking for something less ordinary, then freeze-dried food is probably the most ‘spacey’ you can get.  You add hot water to a packet, wait a few minutes, and then open it to reveal a fully prepared meal.  It’s a shame that if you search for space food, all that seems to come up is freeze-dried ice-cream.  Instead, if you want an equivalent to the freeze-dried food on the ISS, you’ll have to search camping stores.  There you’ll find packaged meals similar to that shown in the image below.

Cat approved freeze-dried food – scrambled eggs with ham and potato (the cat did not eat any)

When I cooked this one up I was impressed that the egg, ham, and potato did all regain their expected textures and flavours .  However, all of the pieces have to be fairly small to ensure even rehydration – large pieces could end up soggy on the outside and still dry in the middle – and personally I wasn’t keen on the small potato cubes.  Still, it’s easy to be picky when you’re surrounded by everything you need to prepare a fresh meal, and less so halfway up a mountain or floating in space.

So what is freeze-drying?  In this case the name pretty much says it all.  You freeze the food and then you dry it.  You’re probably used to associating heat with drying – such as hanging out washing on a warm day – so for freeze-drying we need a different process.  Shown below is the phase diagram for water – which shows how it changes between the states of solid, liquid and gas, at different pressures and temperatures.  All materials have a similar chart, but just switch between states at different values.

Water Phase Diagram – Creative Commons Attribution Share-Alike; based on a diagram by Eurico Zimbres.  Temperature is measured across the bottom in Kelvin.  Pressure is measured up the side in Pascals.

Our daily experience of water is shown in the outlined box. At the pressure you experience at sea-level, water turns solid at 0 degrees C and turns into a vapour at 100 degrees C.  In everyday language, if freezes into ice at zero, and boils into steam at 100.  If you live at high altitudes, and so lower atmospheric pressure, you will find that you can’t heat water to 100 degrees in an open pot.  The water will turn to vapour (steam) at a lower temperature and escape.

In a more extreme example, if you happen to be living on Jupiter’s moon Titan, then you’ll find seas of ethane, methane and propane.  What we normally think of as gases exist as liquids, because of the higher pressure and much lower temperature.

An important point on the graph is the “triple point”.  Note that for pressures above the triple point the region for liquids sits between solids and vapours.  If you want a solid to become a gas, you have to melt it into a liquid first.  However, note that for pressures below the triple point, a solid can change directly into a gas.  This is called sublimation, and is the process through which things are freeze-dried.  It mainly involves dropping the pressure and temperature below the triple point, and then only increasing the temperature.  It might be difficult to imagine, but you have probably seen dry-ice (frozen carbon dioxide) going straight from solid to gas at room temperature.  It’s the same process.

Why Freeze Dry?

Generally speaking, foods go ‘bad’ when microbes start eating them before you have a chance to.  Like us, microbes need food, oxygen, and water to live.  If they’re already on the food, then removing the water or the oxygen can be good ways of holding them back.  Freeze-drying, dehydrating, or salting removes the water.  Vacuum sealing or using an inert gas (like in crisp packets) removes the oxygen.  Both methods need good packaging to keep out oxygen or moisture from the air.

Another benefit for removing the water is that you reduce the weight.  For example, fruits can be in the region of 80 percent water, and so if you take the water out you reduce the weight significantly.  This benefit isn’t just used in space though; it is common practice to concentrate (i.e. remove water from) fruit juices on Earth before transporting them. You’ll regularly see fruit juices described as ‘from concentrate’.  You can take the water out at the source, transport the lighter material, and then add the water back in at the destination.  There is already water on the ISS, and the cost per kg to launch things on a rocket is very high, so what works on Earth just makes even more sense for space.

Packaging

If you watched the video then you’ll know how important the packaging is.  If you’re recreating the space food experience here on Earth then it’s equally important – not least because presentation makes all the difference.  Take some familiar food, package it in the right way, and it all adds to the illusion.

Firstly, try just removing the outer packaging.  Lots of foods already look spacey (vacuum sealed etc.) inside their glossy box.  Secondly, if the inner package isn’t spacey, then divide it up into individual portions – for example in Tupperware pots or zip-lock bags.  You can buy a relatively inexpensive vacuum sealer to go the extra mile, but if it’s just for looks then using a straw to suck the air out of a seal-able bag works reasonably well (see image below).

Vacuum sealed food with QR code – using zip-lock bag and straw technique

The rations on the ISS all seem to have barcodes on.  At the end of the day a barcode is just a representation of a number; and you need some sort of computer system that looks up what that number means.  Instead you can go even more futuristic and use QR (Quick Response) codes.  Just visit one of the online generators (such as http://www.qrstuff.com/ or http://goqr.me/), choose the text option, enter your text, and download the image.  You’ll need an app to read them, but just search the appropriate store for “QR code”.  You could of course just print out a text label (or write on it), but it isn’t quite the same.

And as a final note, don’t forget the tortillas!!