ExWeb Special - Mars ho! Water, sweet water?

Posted: Jun 28, 2007 07:52 pm EDT

(Pythom.com) "Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." (Charles Darwin, Introduction to The Descent of Man, 1871)

Well, that would be us. Ignorance is exactly what "begets our confidence." Yet old Charles would be happy to know that the same confidence leads us to believe that all problems can be solved.

So on to our Mars mission. In order to pitch the sponsors, Amundsen would want to know the budget.

How much

In a Mars mission, the money will be determined by the following:

1. The rocket
2. The load
3. The landing

The kind of rocket we need, will be decided by the load we carry and what we want to do when we get there. It's fairly easy to just shoot by Mars and return to earth, but that would be like stopping 50 feet short of Everest summit. Our mission is to go there, land, explore and return to earth with goodies and wild stories.

Water, sweet water

Therefore, in order to establish the budget, we must begin with number 2 - the load.

The load will mainly consist of life support (fuel will be related to the weight we'll carry and whether or not we'll be landing, so let's get to that later). In unassisted polar exploration, alpine style high altitude ascents and lightweight ocean crossings - life support (water, food and oxygen) - compile 80% of the expedition weight and our Mars mission is no different.

The first key to any explorer's survival is water. Let's check our options.

How much do we need

About 60% of a fairly lean person's body weight consists of water. Fat people are down to 45%, fit people and kids store up to 75%.

A healthy person at moderate activity requires roughly 2 liters of water each day and recycles 100% of it.

At a temperature of about 20° C, out of 2300 ml of water intake, approximately 1400 ml is lost in urine, 100 ml in sweat and another 100 ml in faeces. The remaining 700 ml is lost by evaporation from the respiratory tract and by diffusion through the skin.

The major sources of our water intake are liquids, foods - and metabolic activity within the body (about 15%).

Metabolic water is produced as a result of energy production and that's why you get bloated after the gym. This water comes from breathing the air and carbohydrates broken down in the body for energy.

Cutting the weight

The problems of potable water are close to ocean explorers so let's take a look at what they are doing.

Seawater has a salinity of between 3.1% and 3.8%. Normal urine contains about 95% water and 5% solutes. Urine recycling machines are therefore somewhat related to ocean water makers. Any ocean rower will however tell you that save for the rudder; desalinators are the weakest link on their expeditions. Only this week, Ralph Tuijn reported that his water-maker stopped working several days ago, and he's been forced to pump a manual device for hours everyday since.

Sailboats experience the same thing and many therefore simply carry all drinking water with them. Could we cut the story short and do the same thing to Mars? We are two people and our expedition will last 1000 days. If we wanted to bring all our water, our first load would be roughly 4000 liters (1000 gallons) - not counting waste water (showers and such).

With the current payload cost at around $10k/lb; carrying 4000 liters of water to Mars would require a steep $88 Million of investment!

Recycling systems

Like it or not, we are back at the machines. It's clear that we lose most water through our urine, followed by sweat and breathing (we can do without the 100 ml in faeces). So we need some good recycling machines and air dehumidifiers.

While urine contains only about 5% solutes; the salt is not the biggest problem. It's the other organic compounds that mess things up, as they have vapor pressures similar to water which makes them hard to filter out in 0G. If left standing, the urea oxidizes and releases ammonia which, although great for cleaning windows, is even harder to remove.

No urine recycler has been used in space yet. It's another story with dehumidifiers; machines making water out of the air. Condensate from air was used already on Mir, although not for drinking water.

Current state of things

While the Russian air dehumidifier is said to have been beefed up since MIR to make some of the drinking water on ISS; the current people there have most of the water brought up.

In the March issue of NewScientist, it was reported that NASA will try their urine recycler on ISS in 2009. The system will recycle 93 per cent of all the water; a key part of the system is a process that can salvage about 85 per cent of the water in urine (0.3 liters water will however be used to flush each 1, 2 liters). Chemicals will be added to prevent smell, and then the weightless urine goes into a spinning distillation cylinder where it's heated at low pressure; and the water vapor is made to condense on the drum's outer surface. The resulting 'brine' is then recirculated through the distiller again and again until 85 per cent of the water in the urine is recovered.

This distillate is mixed with other waste water, and then filtered. Salt is removed by an ion-exchange resin, and then the lot is reheated to 130 °C, injected with oxygen gas, and run through more ion-exchange beds to remove volatile organics and kill bacteria, fungi and viruses.

The machine can purify nearly 6 liters per hour and is built for a crew of 6 using 4.4 liters of water each. To make sure that gases and liquids moved through the components as expected they were tested in 0G on a vomit comet and shuttle tests checked out well in terms of launch redundancy.

Yet when we saw the machine last year, it was huge and looked like a mechanic's nightmare. Even if we could get our hands on a smaller version, say the size of a dishwasher, any explorer will cringe at all the parts involved. Filters ruin and centrifuges break. Which leads us to the number one keyword in all exploration - backup - and a ride straight into a dark side of humanity.

The secret gold

We'd heard about 'golden showers' but had no idea what an exact science urine fetish actually is. Likeminded people throwing such parties avoid certain foods such as asparagus, as these give an inpolite flavor.

Drinking urine is however a surprisingly wide practice. From Egypt in 1000 B.C. and over Hippocrates some 500 years later; 'urine therapy' is used to this day by a number of cultures as well as in homeopathy to cure allergies, increase fertility, clear the skin, heal cuts and get a long life in general. Himalayan climbers might be aware that Tibetan monks collected and drank the urine of Dalai Lama. Hindu yogic do it, and some Russians mix it with certain mushrooms - a practice also adapted by western drug addicts.

If consumed within 15 minutes, urine is sterile for the producer's own body. Viruses or bacteria have already been filtered out. People trapped in deserts and under debris in earthquakes have survived by drinking their own urine. In a natural recycling process, the fluid gets cleaner by each ingestion. Urine can more than double your survival from 2 days up to 5, when there's simply no urine left (you've lost too much water sweating).

But urine is also one of the body's methods of getting rid of waste products and chemicals. Drinking all of your own urine, you're accumulating your own refuse. Over a long time, this could have the same effect as would kidney failure.

Tests have shown that drinking your own urine is safe up to three months, but nobody knows what happens over three years. Urine therapy is new to us and so the question is; how safe is it to consume substantial amounts of it and for how long?

An acceptable back-up

As a last resort though, especially if diluted by clean water from the dehumidifier; our urine could save our lives on a Mars mission in case of recycling failure. With an acceptable back-up to the iffy system, we can risk to bring it.

The conclusion for our Mars mission is therefore: With the help of a dehumifier and a urine recycler; the latter simplified to clean personal urine only, we should be able to recycle about 75% of our water. That means that we'll have to bring only about 1000 liters with us; including an estimated recycling system weight of - say - 50 kg.

Yet plans are only words, and words are cheap. On his Atlantic crossing in an inflatable in the 1950s'; Alain Bombard demonstrated that survival is possible drinking only seawater (along with collecting rain), provided it's digested in small amounts over regular intervals throughout the day. That's what explorers do. When finishing this entry, it dawned on us that if we are serious about our Mars mission we must be able to demonstrate our back-up plan. Tina was selected guinea pig and the images tell the rest of the story.

ExplorersWeb founders, US residents Tom and Tina Sjogren are planning a private mission to Mars. The expedition preparations have a hands-on, simple exploration approach and are openly disclosed.
#Mountaineering #Polar #Space #Mountaineering #Oceans






Stepping up to the plate, Tina does her first field test of Mars emergency hydration: "People sometimes think that Tom is the front man on our expeditions, but this is the reality of it."
It's sterile, supposedly good for you and tastes like lukewarm water. Pinching your nose helps eliminating the smell. "It didn't taste bad but the recollection of what I'd just done made me puke 5 minutes later," Tina reported.
...NASA have a better idea, they say. While being fine tuned for ISS, their water recycling unit currently purifies water for villagers in Kendala, Iraq - the guys are reportedly drinking clean water for the first time in years thanks to this space technology. Image of NASA's urine recycler, ExplorersWeb (click to enlarge).