Ain't Nobody Pretty in Space

The first time I walked into the console room in the Erasmus center at ESTEC and watched crewmembers floating around in the Columbus module, I had two thoughts in quick succession. The first thought was, “Wow. I can’t believe I’m actually watching astronauts on the international space station live!” My second thought was, “What the hell is wrong with them?”

In movies about space, actors are always selected from that rarefied group of spectacularly-attractive people. And these gorgeous individuals continue to look beautiful whilst floating across the screen and dealing with space crises (think Sandra Bullock in Gravity, or Matt Damon and the porcelain-faced Jessica Chastain in The Martian). The selection criteria for astronauts is a little different than for actors – crewmembers are picked for their STEM educational backgrounds, and their technical skills and physical abilities. Appearance doesn’t really factor so much in to crewmember selection. Now, I’m not saying they’re ugly. These are nice looking folks (look up their pages on Wikipedia or profiles on your local Space Agency website if you don’t believe me). But here’s the secret nobody advertizes: ain’t nobody pretty in space.

Even extraordinarily attractive people - like the actors in Ridley Scott's The Martian would actually look a bit uglier in space. That's just how we roll in Microgravity (Source: IMDB)

Our cardiovascular systems evolved to feed blood to our hungry brains. Inconveniently, we carry our brains at the very top of our bodies. This means that all of our veins and arteries and the powerful pump of our heart has to work very hard to make sure we get precious oxygenated blood UP, all the while fighting gravity which is pulling that same blood DOWN. You’re starting to see the problem here, right? In space, there isn’t an UP or DOWN. But the heart doesn’t know that. It’s pumping faithfully along, pushing blood to the brain and, without the pull of gravity to countermand this pressure, a lot of blood gets driven into the head. If you’ve ever tried standing on your head for a goodly chunk of time, you have an idea of what this feels and looks like. Actually, go give it a try: stand on your head for as long as you can handle it – then take a good look in the mirror. I’ll wait while you do this.

What do you think? Pretty, eh? How about posting that selfie on Instagram?

You probably notice that your face is a bit redder than it ought to be, that your cheeks and eyelids are a bit puffier – actually, everything is a bit puffier. Also, maybe your head is a little uncomfortable. Did you start to get a headache? Do you have a little ringing in your ears? That’s what the astronauts on the Space Station have to deal with. Because of these fluid shifts, crewmembers have puffy faces and another effect we in the business professionally call “chicken legs” (This is something Hollywood may want to look into reproducing if they want to go for an authentic look!)

Expedition 63 Crew currently on board the ISS (Source: NASA.gov)

It doesn’t take a lot of math to figure out that extra pressure in the head might cause more than aesthetic challenges. For example, an astronaut’s vision can be affected: the eyeball can flatten, and the retina and optic nerve can be distorted. Hearing can also be damaged and the increased pressure may also affect the brain. In fact, a lot of research has gone into these fluid pressure issues. If you do a search of the Human Research experiments the Space Station Research Explorer on NASA.gov you’ll find about 60 different investigations studying intracranial pressure of ISS crewmembers and its effects. 

There are loads of different ways that researchers can look at pressure inside the head. Here are a few:

o   Blood Pressure & Heart Rate

o   Vascular Resistance. If blood vessels tighten or constrict, vascular resistance increases, and the heart must work harder to push the blood forward. If blood vessels dilate or relax, vascular decreases, reducing the amount of left ventricular force needed to open the aortic valve.

o   Magnetic resonance imaging (MRI) & Ultrasounds can be used to to measure the shapes and sizes and thicknesses of tissue, the veins and arteries, and the heart. Ultrasound measurements can be conducted on board the ISS because the equipment is relatively small. MRI machines are made of enormous magnets and are too big to go on the ISS. Therefore, all MRI measurements have to take place before or after a crewmember’s mission (such as the ESA experiment Brain-DTI, which I mentioned in my last post). 

o   Bioelectrical impedance analysis (BIA). In this measurement, a weak electrical current is passed through the body. Different types of tissue in the body will conduct or impede this current, so BIA measurements are used to look at body composition. Water in the body (typically stored in the muscles) is highly conductive, so higher amounts of body water will lead to a lower impedance.

o   Cerebral Cochlear Fluid Pressure (CCFP). This measures tiny displacements in the tympanic membrane (your eardrum).

o   Distortion-Product Otoacoustic Emission (DPOAE). Otoacoustic emmisions are sounds produced in the cochlea (the inner ear). This happens when the small hairs (or cilia) in the cochlea change their shape in order to amplify a sound and propagate it forward. These emissions can happen spontaneously (for example, in the case of tinnitus), or they can be evoked by an external sound. When the cochlea is stimulated simultaneously by two sound frequencies (whose ratio is about 1.2), a distortion-product optoacoustic emission is induced. This has to do with the shape of the cochlea (It’s spiralled around in a sea-shell configuration). When there is a large amount of intracranial pressure, this can affect the shape of the cochlea, and  this can reduce DPOAEs. (The Italian Space Agency, ASI, has an experiment called Acoustic Diagnostics that measures OAEs. I just watched ESA Astronaut Luca Parmitano and US Astronaut Andrew Morgan perform sessions for this experiment during Increment 61/62).   

o   Optical Coherence Tomography (OCT) & MRI & Ultrasound. These are all different ways to make ocular measurements (measure the structure of the eye). When there is a lot of intracranial pressure, the eyeball can be flattened (called globe flattening), and alternating light and dark bands can form on the retina (called chorioretinal folds). The optic nerve can also be altered by this extra pressure. OCT and MRI of the eyes can be conducted when crewmembers are on the ground, but it’s possible to make structural measurements of crewmember’s eyes using Ultrasound equipment on the ISS.

As an example, here are just a few of the experiments that ESA and our partners are doing to look at intracranial pressure: 

NASA is currently conducting an experiment called Fluid Shifts – which is short for Fluid Shifts Before, During, and After Prolonged Space Flight and Their Association with Intracranial Pressure and Visual Impairment (Principal Investigators Michael B. Stenger,  Scott A. Dulchavsky, and Alan R. Hargens). This experiment has been running since 2015 and will finish up this year. Researchers are looking at how microgravity induced changes in cranial pressure affects the eyes of crewmembers. Researchers hypothesize that this fluid shift to the head increases pressure on the brain, which may push on the back of the eye and cause it to change shape. This investigation measures how much fluid shifts from the lower body to the upper body, in or out of cells and blood vessels, and determines the impact these shifts have on fluid pressure in the head, changes in vision and eye structures.

ESA Astronaut Luca Parmitano conducting a session of NASA's Fluid Shifts Experiment (Source: NASA.gov)

JAXA has an experiment called Cerebral Autoregulation (Principal Investigator Kenichi Iwasaki) which is short for Human Cerebral Autoregulation during Long-duration Spaceflight.  This experiment started in 2017 with increment 53/54 and is scheduled to run through April 2021, ending with Increment 64. This experiment builds on experiments conducted in the Space Shuttle’s Neurolab mission. The hypothesis is that the brain regulates bloodflow to itself – and that this capability will be improved the longer time the crewmember spends in space. Waveforms of arterial blood pressure in the finger artery, and blood flow velocity in middle cerebral artery, are measured before, during, and after long-term spaceflight using the Portable Doppler (PDOP). [The PDOP is European Space Agency (ESA) hardware that is used to obtain waveforms of blood flow velocity in the middle cerebral artery, and records this data by non-invasive measurement. Cardiopres is another piece of ESA hardware, used to obtain waveforms of continuous arterial blood pressure by non-invasive measurement.] 

ESA’s experiment Space Headaches (Principal Investigator Alla Vein) started in 2011 during Increment 29/30 and finished in Increment 55/56 with US Astronaut Scott David Tingle and Japanese Astronaut Norishige Kanai as the 23rd and 24th subjects. ISS Crewmembers are tough and don’t complain much – so we don't have a way of knowing whether or not they're floating around with killer headaches. But this experiment had crewmembers filling out weekly questionnaires  telling researchers how frequently they experienced headaches, and how intense these headaches were.  This will give us a better understanding of how badly this intracranial pressure hurts. 

The knowledge we gain from this research will be critically important as we expand human exploration through the solar system. I recently finished re-reading Andy Weir's book, The Martian (this is probably the reason I started thinking about this issue). If you're reading this blog, it means you're a space-nerd like me, so I don't need to tell you to read the book (but if you haven't, then  give it a look. It's a lot of fun). When the crew members of the Ares III mission decide to go back to Mars for Mark Watney,  they add more than another year onto their travel time - giving them more than 2 years in microgravity. With what we know about intracranial pressure, that's gotta hurt - and maybe cause some long-term damage.

Here's some real-world data for reference: To date, the longest number of consecutive days in space record holder is Russian cosmonaut Valery Polyakov who spent nearly 438 consecutive days aboard the Mir space station, from January 1994 to March 1995. Cosmonaut Gennady Padalka holds the record for most total days in space - with a little more than 878 days accrued over five spaceflights. That's almost two and a half years (2 years 4 months 3 weeks 5 days).

Of course the fictional spaceship in The Martian had some centripedal accelleration to simulate gravity - and this is probably something we'll need to consider if we want to have long spaceflight missions since this is the only effective countermeasure for the fluid shifts I describe here. However, this will present its own engineering challenges. Radial force due to centripedal motion is (mv^2)/r - so the speed of your rotating wheel will depend on how big your "r" is (for reference: the ISS is 109 meters [357 feet] end-to-end). If you have a spaceship built like a wheel - with a radius of 100 meters, you'd need to do about 3 revolutions per minute to simulate gravity. That's pretty darned fast.