Posted: Oct 08, 2007 02:40 pm EDT
(Pythom.com) A Greek man once said that all the earth's oceans are connected. He claimed that Africa can be circumnavigated and that India can be reached by sailing westward from Spain. He stated that the earth is round and he even calculated its diameter to within an error of fifty miles. The big deal? <i>Eratosthenes</i> proposed all this around 200 BC, or almost 2000 years before Columbus voyage.

We know that we can go to Mars, and we have the technology to do it. Let's make sure that this time, it doesn't take another 2000 years before we leave. <cutoff>

<b>The options</b>

Previous entries in this series about our private mission to Mars examined the two essentials of any exploration journey - food and water. Today, we take a look at the third and final part of life support: Oxygen.

Burning candles, artificial gills, fern plants or maybe just some good old POISK are among the options on our mission to Mars.

We are hands-on explorers though, so before venturing too far Sci-fi, let's take a look at what's already out there and what has worked so far.

<b>Artificial air</b>

Mountaineers and scuba divers use pure oxygen, decompressed air or other gas mixtures carried in tanks. Hospitals and ill people use oxygen concentrators, compressed oxygen cylinders, and/or liquid oxygen. Miners, aircraft, and nuclear subs often opt for chemical oxygen.

In space, plants would be best as they both provide O2 as well as remove the bad carbon dioxide, but the greens simply refuse to grow in weightlessness; with the lack of gravity the sap doesn't know where to go, and that's just one of the problems.

<b>Manufacturing oxygen in Space</b>

On space stations ever since MIR, the Russian "Elektron" oxygen generator has been king. The Elektron produces oxygen via a simple electrolysis process: an electric current breaks water down into hydrogen and oxygen. The separated oxygen is released into the hab; while the hydrogen is dumped into space.

The Elektron, like most other gear on ISS, is controlled by laptops and the Elektrons manual controls. It's power hungry, and the filters tend to clog up, but it's the best we have.

This oxygen generator is now being supplemented by NASA with a second, upgraded version weighing close to 700 kg. Together, the two systems will help support six-person crews.

The main difference with the beefed up Elektron is that it uses a <b>solid</b> electrolyte, instead of the leaking, bubble-prone <b>liquid</b> electrolyte used by the Russian Elektron. In the weightlessness of space, gases/liquids behave funky so solids are more reliable.

<b>Space back-ups: TGK chemical oxygen generator, oxygen candles and cylinders</b>

Today, the ISS oxygen system consists of the Elektron unit (main source), and two back up options: the ISS guys have a supply of 100 days of bottled oxygen and solid-fuel chemical oxygen candles as a third option.

When the Elektron gave up on Mir, the crew relied on O2 tanks from the Progress, and the TGK chemical oxygen generator.

As mountaineers, we know O2 tanks well, but here's how the TGK chemical oxygen generator works:

A replaceable cylindrical steel cartridge holds two tablets of a solid oxygen compound in briquette form - the candle - and one igniter tablet with a flash igniter. The candles burn at a whopping 450-500 °C while the cartridge generates about 800W of heat (the outer surface however holds a bearable 50°C).

The fire separates the solid fuel into oxygen. With the fan running, it takes about 3 hours for the cartridge to cool down when the candles can be replaced. The oxygen is filtered and released into the space station.

At the time of the Elektron failure on MIR, there were 84 such candles on board; with 2 required per day for 2 crewmembers. The generator has since been improved with a safer solid compound, a fire safe outer shell and an electrically-fired igniter.

<b>Other uses for chemical oxygen</b>

Various types of chemical oxygen candles are used also by aircraft (in a drop-down system) and on subs. Most release oxygen at a fixed rate, have an indefinite shelf life if stored properly and produce oxygen for 15 to 20 minutes, or longer. They are heavy and contain a bulky filter for absorption of carbon dioxide. (1 kg to absorb about 0,5 kg of CO2).

In 1986, Everest expert Tom Holzel tried a closed circuit chemical oxygen system used already back in the 1930's and in 1951 & 53 by Everest climbers.

"The oxygen was warm and moist, and the reaction is exothermic, which heated my sleeping bag," Tom reported. He also let a friend try it: "Dave rocketed up the flanks of Changtse right outside of ABC. He was breathing so effortlessly, he stopped for a moment, certain that the system had come open. As soon as he took it off to check, 'it was like throwing out anchors,' he remarked."

<b>The danger of chemical and other oxygen</b>

Sounds dangerous? It is.

In 1996, chemical oxygen caused the crash of a ValuJet DC-9 headed from Miami to Atlanta, Georgia. The plane's interior went on fire shortly after take off, and the plane crashed killing all aboard. Expired chemical oxygen generators were placed in the cargo compartment, without plastic caps covering the firing pins. Employees wrote the canisters were empty, when they were not.

In 1997, at the change of an air filter, one leaking solid oxygen canister went on fire for 14 minutes on the MIR station, spewing a torch-like jet of molten metal and sparks across the hab.

In March this year; an oxygen candle probably killed two British Navy sailors on a nuclear-powered submarine near the North Pole. Lucky enough, the explosion did not affect the ship's nuclear reactor. Part of the exercise was to measure ice thickness, which the Navy guys ended up doing in a big way: At the time of the accident, the submarine made an emergency surface straight through the ice cap.

Potassium superoxide was used as a chemical oxygen source on early manned USSR space missions. US shuttle and rocket crews simply bring oxygen tanks with them, and one such blew up on Apollo 13.

In Everest base camp, Russian Snow Leopard Valentin Bazhukov (72), tested liquid oxygen poured into old POISK bottles, and then evaporated. The system was said to be capable of putting more oxygen (125 %) in a standard bottle than other systems, at a lower price. But it proved a hard sell; "the volatility of this system is best shown by his half blown off mouth of a previous unit that malfunctioned on him, a climber reported.

<b>Oxygen and air pressure</b>

On Everest, most issues with supplementary oxygen have involved the cold (affecting the gear) and (less) the altitude (affecting the gas).

On climbing, lack of oxygen should in fact be labeled "lack of air pressure." Oxygen is still there, only the air is thinner. Already at 5000+ meters, your intake is only half that of sea level. At 8000+ you are down to a third. On Everest summit, we'd die after a short while unless we acclimatized.

When acclimatizing, you form more red blood cells. Those help you to better mine for the precious gas. As air pressure also varies with weather, your best bet is actually to climb when the forecasts announces high pressure. Not only will the weather be better, slightly more oxygen will be available to you in the denser air.

<b>What would happen if you didn't acclimatize?</b>

Many inexperienced Everest climbers underestimate the value of acclimatization time and the need to bring enough supplementary oxygen. Frostbite at best, brain/lung damage and death at worst follow such ignorance. Here are two early examples of the effects of high altitude:

In 1862, two Englishmen reached 8000 meters in a balloon. That's when all hell broke loose. One went partially blind, the other couldn't breathe. A cord was tangled and they couldn't abort the ascent. At 8,800 meters, one lost consciousness while the other, now partially paralyzed, was able to grasp the hydrogen release line with his teeth and the men landed safely after reaching about 9,000+.

Others were not so lucky. In 1875, two scientists decided to try an oxygen setup they had tested in a French decompression chamber. But the test would end tragically due to a human error one-two punch. The men brought too little of the oxygen, and were only acclimatized from the chamber.

At 8,784 meters, when the crew - the two scientists and a pilot - finally decided to nibble at the scarce O2, they found they couldn't get to it as they had lost the use of their limbs. Soon after, they became unconscious. The men had in addition thrown out too much ballast and now an uncontrolled climb followed. The pilot regained consciousness for a while; found that the balloon had started descending on its own and managed to bring it down. The balloonist was acclimatized from previous flights and survived, but the two inexperienced scientists died.

<b>What is air, exactly?</b>

On earth, the air is constituted by nitrogen (78%), oxygen (21%) and other gases (1%).

If you are a scuba diver, you know nitrogen well. This is the gas that causes nitrogen narcosis and bends. Due to increased water pressure, somewhere below 30 m (100 ft) you feed your tank oxygen to the fish and think it funny. If you ascend too fast, you might suffer a stroke.

Air pressure affects the gas in the same way. In fact, to avoid bends, the guys at ISS spend an hour breathing pure oxygen before their space walks, to remove nitrogen from the body before pressure is reduced.

<b>Pure oxygen</b>

You don't have to breathe the exact mixture of earth air. You can reduce the amount of nitrogen and other gasses, but will have to adjust the pressure. Apollo spacesuits used low pressure pure oxygen.

But how safe is pure oxygen? Removing the buffer gas brings on a number of problems, such as drying of the lungs. While Apollo crews used pure oxygen on their week-long space missions, long-term effects of pure oxygen on the human body are unknown.

Apart from the drying effect, too much oxygen can cause DNA damage through the action of free radicals. This is a reality also on earth for extreme athletes - who "overload" on oxygen through rapid and deep breathing on exercise.

Athletes and health conscious people in general up their servings of spinach and other food items containing the nutrient folate in order to fight this potential risk for cancer as folate helps repair damaged DNA. While salad can be hard to get by in Space, the good news is that folate works well to take as a supplement.

Acclimatization and a mixture containing mostly oxygen at the right pressure seems optimal in space, as it also removes the need for airlock and allows lightweight spacesuits.

Mars atmosphere pressure varies with the season, ranging from 6 to 10 millibars, making it about 100 times thinner than Earth's. Space itself is not a perfect vacuum, although pretty close. If you just walked out into it unprotected, you would neither boil nor explode, but die by suffocation as the oxygen would immediately escape your blood and lungs. You would however not freeze to death. Space is cold but also mostly vacuum, a perfect insulator. The main temperature worry for space suits is in fact how to get rid of body heat.

<b>If all else fails - mining oxygen in space</b>

Oxygen can be found in Space, captured by the stars and planets. It can be found as rust on planets subjected to volcanic activity. Look for it the next time you go climbing, as the stuff (Ilmenite Titanium oxide) also is found in mountain ranges on Earth. A processor using electric current, heat, and gasses is needed to mine it.

On Mars, apart from looking for trapped underground water, another option is mining the carbon dioxide rich atmosphere for oxygen. To mine this oxygen, we'd need to use fuel cells and also be able to extract oxygen from the resulting water. The NASA MIP processor, scrubbed along with NASAs cancellation of the Mars Surveyor 2001 Lander, could be an idea to explore further.

Mining oxygen in Space has many advantages. The oxygen can be used for breathing, but also for rocket fuel. On our first Mars mission though, we'll need far simpler solutions.

<b>Summary</b>

All climbers and divers know how heavy cylinders of O2 and compressed air can be. An empty POSK 4-litre bottle weighs 2 kg and can hold 1,5 kg oxygen for a total weight of 3,5 kg - and that's light for portable tank O2. If cooled to below -118°C, oxygen will change to a liquid, taking much less space but becoming highly explosive.

Solid chemical oxygen candles produce 6.5 man-hours of oxygen per kilogram of the mixture. This would thus amount to about 4 kg/day each - or 8 kg/day for us both - or 8,000 kg of oxygen candles for the mission.

The new Elektron system provides approx. 6 kg of oxygen per day. 1 kg of water yields 25 L of oxygen per hour at a pressure of 760 mmHg, which is enough to support one crew member for one day. This means, that for 2 people on a 1000 day mission, a scaled down Elektron could weigh, say, about 500 kg, in addition to 2000 kg of water (if we don't recycle or pressurize to altitude).

It seems at this point that the best bet is to bring a smaller version of the Elektron, water, filters - and a back-up load of O2 tanks and chemical candles. So let's do the math:

Scaled down Elektron + filters: 500 kg
Water: 2000 kg
Backup chemical and bottled oxygen: 1000 kg
Total: 3500 kgs

Add food 1500 kg and drinking water 1000 liters (previous stories) and we have hit 6000 kg in payload on our Mission to Mars.

Next: The Hab.

<i>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.</i>

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