Distillation in Space

I remember when I was very young watching my older brother in some sort of school play, where they were explaining why it’s hard work to boil an egg at the top of Mt Everest. I believe he was playing the part of Edmund Hillary, and after finding himself unable to have a soft-boiled egg at the summit, he was visited by some sort of gypsy ghost who gave a very brief summary of air pressure and it’s effect on boiling liquids. I may not be remembering it exactly how it went, but it was a memory that sprang forth while I was researching this next topic – can you distill spirits in space?

We previously covered the difficulties of making beer or carbonated drinks in a zero-gravity environment, and found the costs associated with weight, again, was a major issue. Remember, the point of this blog is to formulate a plan for a future when colonization of other planets and space tourism is a reality – if a beer costs $3000 USD a pint over a bar it is hardly going to drive trade is it? I know hotel bars are expensive but that is pushing it.

So, distillation in space – first off, if we are making it in space there is the issue of appellation controls; that is, any liquor which has regulations surrounding the production of said liquor, which states among other rules that the spirit must be made within the borders of a certain region. So we won’t be making tequila, cognac, scotch or bourbon in space, we will be limited by vodka, gin, brandies, rum and whiskey for our creations. There is an argument to be made over the vertical limits of a country’s borders, and whether or not you can claim appellation rights simply by staying in orbit over the region in question, however…

So firstly a quick primer on distillation: the term describes the action of separating one liquid compound from another by dissolving volatile compounds and re-condensing them into a separate vessel. While used for many practical applications (and for thousands of years in various forms all over the world), we are specifically looking at distillation for the purpose of creating (drinkable) alcohol.

The most common methods is heating a mash (a fermented combination of just about any biological matter with a high enough starch or sugar content) in a still until your alcohol evaporates, at which point it is collected in a condensing coil and chilled to turn back into a liquid. I am lucky enough to have lived for many years in a country where home distillation was legal, and spent many hours tending a friend’s 3-litre copper pot alembic still like the one pictured below, accompanied by a small tome called “Moonshine Made Simple” for inspiration, cultivating my mental image of myself as a modern-day rum runner or bootlegger. This was up until the point I realized wearing a fedora made me look like a twat.

However as any emphatically distiller will tell you distillation is not about just boiling a mash and hoping for the best. It is important to tend and cultivate your still as it is working, controlling temperatures to pull different flavors out of your mash into a final product. Even the shape and chemical makeup of the materials of your still affects the final product, but none of these factors really affected by atmospheric conditions.

Different types of alcoholic compounds evaporate at different temperatures, and these can have a negative effect on flavors and even your health - below is a quick chart of alcohol compounds and the temperatures they evaporate at.

Acetone                  56.5C (134F)

Methanol(wood alcohol)     64C (147F)

Ethyl acetate            77.1C (171F)

Ethanol                    78C (172F)

2-Propanol(rubbing alcohol)82C (180F)

1-Propanol                 97C (207F)

Water                     100C (212F)

Butanol                   116C (241F)

Amyl alcohol            137.8C (280F)

Furfural                  161C (322F)

Now you might recognize acetone as nail polish remover, proponal as hand sanitizer, butanol as a progenitor for butane (lighter fluid) and amyl alcohol as part of amyl nitrate, which you will probably recognize if you listened to a lot of house music in the '90s.

There are a lot of flavors you don’t want in your final spirit, your ethanol – so you want to have your mash aimed for the sweet spot of that 78 degrees Celsius. You’ll also want to discard an amount from above or below this point – the ‘heads’ and ‘tails’ of your distillate.

But wait, what was that about boiling an egg on Mount Everest? Well here is where it gets tricky. The boiling point of water is generally accepted to be 100 degrees Celsius, but that changes as altitude increases and atmospheric pressures drops. If there is zero pressure on the liquid’s molecules, no force exerted, then they will simply diffuse into a gas – which is fairly close to the definition of boiling. The action of a liquid boiling is created when the vapor pressure of the liquid is equal to the ambient atmospheric pressure – meaning there is enough energy to spontaneously break free into gaseous vapors.

But at a higher altitude, decreased air pressure means less energy is required to get a liquid to reach its phase transition – it’s “boiling point”. At the summit of Mount Everest, at 29,000 feet, it only takes around 69 degrees Celsius to “boil” water. Any energy added once a liquid is “boiling” is robbed via latent heat and vaporization into the atmosphere without increasing the actual heat of the water, regardless of your energy input. This means you physically can’t get water to the temperatures required to cook an egg, or anything else for that matter.

Even Charles Darwin mentioned the phenomenon in his “Voyage of the Beagle”, where he encountered the problem en route to the Galapagos Islands:

“Having crossed the Peuquenes, we descended into a mountainous country, intermediate between the two main ranges, and then took up our quarters for the night[…]The elevation was probably not under 11,000 feet [...]. At the place where we slept water necessarily boiled, from the diminished pressure of the atmosphere, at a lower temperature than it does in a less lofty country[…]Hence the potatoes, after remaining for some hours in the boiling water, were nearly as hard as ever. The pot was left on the fire all night, and next morning it was boiled again, but yet the potatoes were not cooked.”

So if a liquid can reach its boiling point at lower points in decreased atmospheric condition (by extrapolation, ethanol would boil and vaporize at a mere 48 degrees Celcius!) what then will it do in the vacuum of space?

As said earlier – when there is zero force exerted on a liquid its molecules will naturally disperse via phase transition into a gas. So in a vacuum, a liquid will quickly “boil” into a cloud of vapor. But that’s not all, because of something extremely complicated called the “enthalpy of vaporization”. I won’t bore you with the particulars (this started off as a bartender blog, I’m sure of it. Don’t worry, we’ll be drinking soon. Grab yourself a drink now if you like, I’ll wait), but it is basically the energy required to turn a liquid into a gas.

So to turn itself into a gas the liquid has to expel all this energy – it’s what you can see when a pot of water is boiling. Next time you are making pot noodles be sure to tell someone about the enthalpy of vaporization, they will be well impressed.

But once the liquid is a vapor, it has used all its energy to get to this state – so it will very quickly go through a process called ‘desublimation’, which for all intents and purposes, is freezing.

The Edward's Vacuum pump in action, showing desublimation and freezing.

So in an absolute vacuum, a liquid will instantly boil and freeze!  How cool is that?

But it’s not so handy for traditional distillation, not if you hope to hit that sweet spot for the heart of your spirit. But distilling in a controlled vacuum is possible, through a process known as cold distillation. In fact there are benefits to this style, as you can avoid damaging any heat-sensitive ingredients in your mash. It’s also handy for avoiding cooking out lighter, temperature sensitive ingredients such as fresh plant materials and fruits. Overcooking these ingredients can release harsh, unpleasant organic compounds like chlorophyll or geosimin into your spirit.

There is now a commercially available (albeit prohibitively expensive) piece of equipment called a rotary vacuum evaporator, more commonly known as a rotovap, in which you can recreate the conditions needed for a low-temperature distillation.

 The rotovap in action

Another traditional type of distillation is freeze distillation, or fractional freezing. This technique is also known as the ‘Mongolian Still’, a mildly racist sounding term to describe the practice used in Central Asia to extract water content from an alcoholic solution, increasing the concentration of alcohol in the final solution. As water has a higher freezing point then ethanol, (0 C//-114 C), water and impurities freeze off, at which point the ice is removed and ethanol remains.

It was a popular way to turn cider or scrumpy into applejack in New Jersey, and surprisingly easy to do. I myself have actually experimented with creating my own applejack by freezing cider and straining the resultant mix and repeating the process to increase the alcohol content, as I couldn’t get my hand on any applejack myself. It became colloquially known as my “ghetto applecrack” around the bar. I might try it again as I know have access to some extremely sophisticated toys in the form of a real proper rotovap and flash freezers.

So I thought the process was very simple – but apparently I’m wrong, and the way I’ve described it to you is technically false false. Confused? So am I. But here we go.

As the freezing process begins at below zero degrees Celsius, the first material to freeze is not the water but a dilute of the water and alcohol. The liquid left unfrozen is higher in alcohol, and therefore subsequent freezing will take place at progressively lower temperatures. As freezing continues, the ice portion will slowly increase in its alcohol content, while always poorer in alcohol content then the concentrated liquid. Thermodynamic laws dictate that there will never be a true separation of water and ethanol in your concentrate, and at a certain point the entire mixture will freeze solid, instead of separating between the concentrated liquor and your ice and water frozen solution.

Because of this, the ratio of concentration comes down to the final frozen temperature of your liquid and not repeated cycles of distillation, unlike traditional heated distillation. Also, there is no way to separate out the bad alcohols from the good alcohols by this method – there is no way to control temperature or discard heads and tails. This means headaches abound for drinkers, as well as health risks like going blind from drinking methanol. So maybe better to stick to traditional distillation methods. Obviously a boiling, heated container filled with flammable liquid is a bad idea in zero gravity, so we are going planet-side to Mars next.

There is an idea by which we could terraform Mars and make it suitable for human habitation popularized by the rubbish Val Kilmer film Red Planet. We would begin by detonating thermonuclear devices in low atmosphere orbit above the magnetic poles of Mars, where they have discovered the presence of ice. This detonation would melt the ice and introduce water onto the surface. At this point we would seed the plant from orbit with algae spores, and algae would grow as it does not need oxygen to spread, producing the gases necessary to form a sustainable atmosphere.

This would provide us with a survivable, breathable atmosphere. The low oxygen content would effectively mean any liquid would act like it would at high altitude on earth – that is, it would require less heat to reach its point of vaporization, less heat to get to a point where you could distill it.

A basic way of calculating what temperature you need to reach to extract ethanol is the following: You establish what ABV your mash is, that is the ratio of ethanol to water, then divide each by it’s specific boiling point, then add those figures to establish your ideal still temperature

(ratio x boiling point) + (ratio x boiling point) = still temperature.

For example, you have a 25%ABV mash –

so 75% water//25% various alcohols.

Boiling point of water at sea level: 100 C

                      .75 x 100c = 75.00c
Boiling point of ethanol at sea level: 78 C

.25 x 78c = 19.50c

Boiler temperature = 94.50c

But as that boiling temperature decreases in a thinner atmosphere, you have to apply less energy to get that ethanol to the point where it will vaporize. Remember distillation is not like cooking – you only want to reach the specific vaporization point so you can re-condense it into your distilled spirit.

Most of us live around sea level, where oxygen saturation in the atmosphere creates the optimal conditions for our bodies to function (making up around 20% of the air we breathe). At higher altitudes the chemical makeup of the air stays around the same, up until around 21,000 meters, but the density decreases as atmospheric pressure drops.

Human beings have demonstrated the ability to live for prolonged periods of time at what is defined as ‘high altitude’, with more than 140 Million people living above 2500 meters in the Andean regions and the Himalayas, with 5000m being around the limit to long-term human habitation and therefore the minimum atmospheric saturation we would look at before inhabiting another planet. If we assume a similar chemical makeup of air it would mean the boiling point of our mash on a terraformed Mars would be calculated as follows:

Boiling point of water at assumed atmospheric pressure: 95.12C

                            .75 x 95.12c = 71.34c
Boiling point of ethanol at assumed atmospheric pressure: 75 C

.25 x 75c = 18.75c

Boiler temperature = 90.09c

So not that massive a difference if you are looking at a future where we can inhabit the red planet and distill without having to live in atmospherically-controlled environments (see the academic work of Pauly Shore in Biodome for additional readings).

Again the issue we come to is weight – moving enough raw materials into space to make the alcohol. The standard formula of raw ingredient to spirit produced is the supremely unhelpful 2.5 gallons per bushel (look up the history of the bushel and it's definition for some "fun" facts on irrational numbers and taxation) - or around 15kg to make 9.5 liters. Plus, all that weight is then left over as waste at the end. Some distilleries are repurposing this waste as alternative energy fuel and that could be an exploitable avenue, but the prohibitive cost to get that raw material into space in the first place means a single 750ml bottle of spirit would cost around $122 - or a little over $406USD per bottle with standard industry markup. So while not as expensive as beer, spirits won't be cheap. 

Every single gram of cargo aboard a space craft costs a lot of money to get it from here to there, making production in space a costly endeavor given the current technology available to us. We could make it, but as earlier stated, this is about creating alcohol that is both practical and affordable.

Making alcohol in space is costly, shipping it to space is costly, so what is the alternative? Well after reviewing the options I would recommend freezing pure ethanol on earth and shipping it to be reconstituted as spirit once it arrives at it’s destination. Ethanol makes up around 40% by volume of any typical spirit, and it only has a density of 789grams per liter.

Once arriving at it’s destination the spirit would be cut with purified water (remember we have found ice on Mars and on other potentially inhabitable celestial bodies in our solar system, so this is within the acceptable parameters of the exercise) to create a neutral spirit. 

Running the spirit back to 40% means that 3 liters of pure frozen ethanol would make 10 750ml bottles of neutral spirit, making the cost of a bottle cost only $30USD and change, or around $100 with the markup.

So using this method we have a much cheaper alternative per bottle that making our own alcohol in space using raw ingredients. But drinking vodka for the rest of your life is a bit dull, isn’t it? So how do we turn this neutral spirit into something a bit more fun? Turn it into something resembling rum, gin, whiskey? Infuse it, age it, color it, flavor it?

Next up, stocking your space bar.