Obstacles to Space Exploration: The Return

Image courtesy NASA and archives.gov

A couple of years ago I wrote a couple of articles for the BBC's Hitch-hiker's Guide to the Galaxy, a website based on the encyclopedia in the book of the same name by Douglas Adams. I wrote them a few weeks after getting to Japan, when I was desperate for any English interaction whatsoever, and they were pretty fun to research. I was soon waylaid by Fark and left the H2G2 site for good, though, and I never finished the second article.

Read the first article, if you like, but the English is difficult. I used academic/literature English with a dry style, so while it will be difficult to read, you can get a lot from it. It wasn't perfectly written, but it was my first real article, so I'm not embarrassed. The H2G2 site is excellent, and the book Hitch-hiker's Guide to the Galaxy is even better, for understanding a little bit about English humour.If you are interested in reading some interesting stories about the world, H2G2 is a good place to start. In a lot of ways it's better than Wikipedia (featured in this month's Surfin' English article), not the least of which is the fact that the articles tend to be pretty funny.

You will have questions about the grammar I used, and there will be many jokes that you don't understand. So don't hesitate to email me or comment in the section below.

Obstacles to Manned Space Exploration Part II: Life Support

How to eat, drink and make love in space.

There are five main items that we must address;

1. Food (Today's topic)
   
2. Air
3. Exercise and sleep
4. Waste Disposal and
5. Entertainment.

Without any of these five, a mission is doomed to disaster of the sort that makes the Titanic look like...erm...a really bad boat crash.

We will look at each of these in turn, discussing in each section three things;

1. The outline of the problem and how it affects the outcome of a mission
2. The state of present technology and whether it is suitable or not for the needs of the crew and
3. Possible solutions to the problem
   

Food: Where do we get it and what do we eat?

Sadly, the number of fast food restaurants and convenience stores in outer space has been dwindling since the Outer Space Nuclear Arms Treaty of January 27, 1967 and we are thereby required to find other food sources. The idea that food is an important aspect of manned space travel is essentially self-evident, but there are many problems associated with food, namely; where do we get it, what should we eat, how do we ensure that proper dietary requirements are met, what is the shelf-life of the food we take with us, and where do we store it?

If music be the food of life... (misquote, I know, but it works.)

It would be wonderful if the only thing one needed to survive was an old Led Zeppelin 4 cassette and a Sony Walkman, but sadly this is not true. Humans need food less ephemeral than rock and roll. For the sake of simplicity, let us assume that Earthly sustenance has two possible sources. The first is the friendly neighbourhood grocery store, where one can buy milk, bread, canned beans, and other items good for eating. The second is our garden, where we grow our vegetables, keep our chicken coops, and tie up the cow. We can make the same assumption about food in space. In essence, there are only two sources. We either have to bring our food with us after buying it in the shops, or grow it, breed it, and raise it on our ship. However, one item that allows for no debate about its source is water. We must bring water with us. There are no known intergalactic natural springs so we must take a good percentage of the water we will need with us. We will discuss the importance of this, and solutions to the problem, in a later article.

Packed sandwiches and a picnic cooler.

The great thing about bringing your own food with you is that you only need a microwave and water to prepare it. Freeze dried biscuits, ice cream, lasagna, and chow mein have all been created, most specifically for the space program. When one is hungry, one goes to the cupboard, takes out a package, opens the top and plunks it in the microwave with a few drops of water. Two minutes later, we can suck our beef bourgignon out of the convenient extra-wide straw in the top of the package. There are problems with this. Shelf-life, while incredibly long for freeze-dried items, is still limited. In the case of a trip longer than a year, this would become critical. The nutritional value of preserved foods drops off drastically after between six months and one year, while unpreserved foods are nutritious for even shorter periods. Nutritional supplements, like pills, creams, drinks, etc., can help but still will not supply everything the body needs.

While convenient in terms of what we will prepare for dinner each night, bringing our food with us is difficult because of the sheer mass of food required. On a short trip this is not a problem as you only need a few sandwiches, an apple, and a thermos of tea. On long trips, it becomes enormous.

Assume the average adult, in total, requires 2500 kilocalories of food and 2 litres of water a day.

Let's say that the 2500kCal makes up 2kg of food (not a bad guess).

That means that every day, for every person, we need 4kg of food and water (because 1L of water = 1kg).

For a 2.5 year mission, which is what some say is necessary for a Mars round trip, each person would require over 4 tonnes of food and water. Luckily, because half of that is water, which can be recycled (this will be discussed in the waste disposal article) with little loss, we can reduce the total required sustenance mass to, as a guess, 3 tonnes.

3 people X 3 tonnes = a lot of extra weight (otherwise known as 9 tonnes). How much space would that food take up? If the food was packed as densely as possible, and assuming the food had the same density as water (which isn't far off), we would need 9m³ of space to store all the food. That's a cube that's a little over 2m wide by 2m tall by 2m long. Doesn't sound like much, does it?

Consider that the volume of the Apollo capsule was about 7.7m³, one is better able to see why this is a problem.

As you can see from this picture, it would take the entire living volume of the Apollo capsule just to store the food for a Mars mission. And ours was a pretty liberal estimate that didn't include refrigeration systems, shelves, boxes, and silverware.

As mentioned in the previous installment of this series titled 'Propulsion', extra mass is a bad thing when designing space missions. The more mass you have, the more fuel you need, and the more fuel you have, the more mass you have. It's a vicious circle, and it requires a lot of math, so obviously we need a better solution.

Image courtesy http://homepage.mac.com/crmichaud/0504asma/0504asma.html, sorry for stealing it.

Grow-your-own

What seems to be the only other possibility is to grow our food as we go. The benefits of growing our own food are various and are laid out below.

Less total mass is brought along in the case of long-duration missions.

Although the mass of a hydroponic growing system would be high, compared to the total mass of the food one would need for a three year trip, it's negligible. We would need more water for growing food which increases mass again, and everyone would essentially become vegetarian which has its own problems, but there are many subsidiary benefits.

Food would remain fresh for the entire trip.

Fresh food makes for happy people. Crunchy lettuce. Orange carrots. If an astronaut wants an apple, she picks it off the hybrid ultra-multi-tree in the corner of the games room.

Freeze dried ice cream may be fun the first 43 times one eats it, but once the novelty has worn off, a simple crunchy carrot could potentially go a long way to aiding crew morale.

Image comes from howstuffworks.com

Nutritional value stays high.

This, more importantly than morale or mass concerns, is probably the greatest argument against bringing all the necessary food from Earth. The importance of good nutrition cannot be overemphasized, especially for a group of people who will be millions of kilometres from home.

Far from "just" making one physically healthy, nutritional levels have been shown to influence mood, sexual desire and ability, and intellectual capabilities.Very little would be more dangerous to the crew than a grumpy, foolish, space engineer who can't get it up.

Naturally, there are downsides to carrying a farm around.

Limited Variety

No matter how good a farmer one is, there is always a limit to the number of different crops one can grow on one field. If that field happens to be a 5cm deep swimming pool with nutrient rich water under UV lamps in the cramped back corner of a space ship, the choices are even more limited.

Also, as mentioned above, the crew would have to eat a vegetarian diet. There is no simple way to raise animals for protein, because they need way too much living space (unless you like veal), and have their own food requirements. So, to get the necessary protein (primarily from meat), calcium (from milk) and other minerals like iron, we need easily grown vegetable replacements.

Limited Volume

While packaged food may be heavy and eventually tasteless, a small farm is much less efficient in terms of calories per cubic metre. We can pack billions of calories into a space only 2m cubed with pre-packaged food, but a farm requires dozens of square metres of area in order to grow enough food for an entire crew (the increase can be mitigated by stacking, but then we get into other issues.) The farm itself may mass less, but the corresponding increase in the volume of the ship could easily outbalance the loss in total food mass.

Gravity

Boxed food doesn't care which way is up, but water does. To grow food in a hydroponic setup, we need something that keeps the water in one place. We can get that in two ways.

First, we can set the ship up so that it spins on its axis.

Image courtesy of the person at http://www.visual-memory.co.uk who stole it first

When a space ship spins, it creates an artificial gravity field. It's not real gravity, but it sure feels like it, and that's all that matters. If we have something like in the above picture, we don't have to worry about water floating all over the place. Setting a ship spinning is a pretty complicated procedure though, so it's not perfect.

Solutions and Conclusions

With what we have discussed thus far, we must come to the conclusion that though packaged food is a poor solution in a number of ways, it is probably the best for both short-duration and long-duration missions.

In order to have a farm, a ship would by necessity by two or three times bigger in volume just to have room for it or the big structure necessary to keep the ship spinning. This sort of requirement is beyond our ability right now, when we already have a suitable, though flawed, alternative in freeze dried food. A large volume craft is a waste of resources. There would have to be a much more pressing reason for including a farm on board a ship.

Luckily for the hydroponics industry, there are two reasons why we should have a hydroponic farm, and we will discuss them both in the next two sections. (As soon as I get around to them.)