This article addresses the notion of buoyancy and why drinking beer in space (the ISS usually orbits in the thermosphere), or any carbonated drink for that matter, does not produce the known tingling sensation we can feel in our noses here on Earth.

So let’s first briefly consider what is buoyancy?
In simple terms, whenever an object is put into a fluid there are several forces that act upon it. The liquid exerts a force from the bottom upwards that tries to push that object up. Then there is the liquid force itself, let’s call it weight, that pushes an object downwards. However, because the liquid pressure increases the deeper you go down into the fluid, there will always be an upwards force bigger than the downward force.
This can be explained by looking at the formula for hydrostatic pressure:

In this formula, p is the density of the liquid, g is the gravitational force (9.81 m/s2) and h is the height of the fluid column measured from the surface. Keeping all the other parameters of the formula constant, the "h" at the bottom of a submerged object will be higher than the one at its top.
But we also have here another component: the "g". Well, there is practically no "g" in space, unless we artificially produce it. So, in this case, all the objects inserted or included into a fluid will just stay there.
Of course, there are many other factors that play a role here, for example the superficial tension of the fluids etc., however, for the sake of simplicity I am considering here only the buoyancy. So, nothing happens with the CO2 bubbles inside the fluid because they are no lighter than the fluid that surrounds them, perhaps looking something like in this photo:

This not mixing between the fluid and gases within creates a hard enough life for anyone who would like to enjoy a beer in space (hypothetically, at least as alcohol consumption is not permitted on the ISS), but let's also not forget the cabin temperature of roughly 20 degrees Celsius, which is way too high to enjoy an ice cold beer. If you want to cool it a bit forget leaving it outside too - just take a look at what the temperatures are "outside", unless of course you want to lick your beer like an ice-cream!

Nonetheless, let's suppose for a moment that an astronaut opened and drank a carbonated drink in space - the same physical properties are valid inside their belly. On Earth, most of the gas separates from the liquid before we drink it and then we simply burp to expel the rest. In space, the bubbles stay in the liquid so the astronaut consumes more gas, meaning a greater need to burp, but the gas would come up still surrounded by some liquid - a "wet burp" - seemingly very unpleasant. A frozen soft drink may be a pleasant alternative. Try pouring some of your beloved carbonated soft drink into a sealable plastic bag, freeze it, and see what you get - tasty, but no fizziness. Well, for everything in space…you need to adapt.

Setting aside the humour for now, this lack of buoyancy in space from a medical perspective can have very serious consequences. Just imagine an infusion bag where you cannot separate the air from the liquid.

It is not difficult to understand that medicine in space is a special endeavour, both in LEO and when we project forward to journeys into deep space. Even if the discovery of new propulsion technologies permit the prospect of a flight to Mars taking only one and a half months, every possibility and probability for the journey and arrival at the red planet must be considered. OK, so we set foot on Mars - oops, a wrong foot, a disaster happens and an astronaut now needs an infusion immediately - what do we do?

So much to think about, but until we figure it out, let's take a break and enjoy an earthly cold beer at sea level - cheers!

My name is Lucas, I am a doctor in the UK working in anaesthetics (or Anaesthesiology for any American readers) and intensive care medicine. I have had an interest in space medicine for over 10 years now, inspired by none other than Prof Thais Russomano who has mentored me over the years and still does. My Master’s dissertation (back in 2009) focused on CPR (cardiopulmonary resuscitation) methods in microgravity, with my continued research interest surrounding critical care in space. I am careful to say that I am a doctor with an interest in space medicine and physiology, as opposed to a ‘Space Doctor’ – as there are many individuals out there who have committed many more years than I have to this field and are vastly more experienced than I am! A club I aspire to join one day.

The idea of this blog, or series of blogs, is to look at some of the latest research in space physiology and space medicine, then consider how this will play out clinically. With a particular focus on critical care and potentially worst-case scenarios when in space (or microgravity environment). Something all doctors will have done in their careers; we are equipped with the skills to critically appraise papers and then ask if they are clinically relevant, or how will it change current practice.

​Over the last 60 (ish) years of human space flight, there is lots of evidence to show that there are many risks when the human body has prolonged exposure to microgravity, which can affect most body systems – eyes, brain, neuro-vestibular, psychological, heart, muscle, bone, kidneys, immune system, vasculature, clotting and even some that we haven’t fully figured out yet. But then what needs to be done is to tease out how clinically relevant are these from the research, how could that potentially play out if you were the doctor in space, then how to mitigate that risk and potentially treat it.