The Viability of Inducing Hibernation for Space Travel: An Exploration

Venturing into the vast cosmos beyond the Moon poses formidable challenges in terms of health, sustenance, and psychological well-being that we're just beginning to comprehend. 

In science fiction, a common solution to these issues is to place space travelers in a sleep-like state, akin to hibernation or torpor. This reduces metabolism and alleviates the tedium of enduring countless empty hours. 

Unlike concepts such as faster-than-light travel and wormholes, the idea of inducing astronauts into a form of hibernation seems attainable, so much so that even the European Space Agency is earnestly exploring the science behind it.

A recent study by a team of researchers from Chile, however, reveals a mathematical obstacle that may render the prospect of long-term human stasis unrealistic, possibly forever out of our reach. 

Roberto F. Nespolo and Carlos Mejias from the Millennium Institute for Integrative Biology, alongside Francisco Bozinovic from the Pontifical Catholic University of Chile, sought to decipher the correlation between body mass and energy consumption in hibernating animals. 

They found a basal metabolic rate that allows cells to survive in cold, oxygen-deficient conditions. For larger animals like humans, the energy conserved from entering a deep, hibernation-like state would be negligible. 

In fact, it might be more beneficial for us to simply nap in the traditional manner.

The term 'hibernation' typically conjures images of a bear ensconced in a den for a long winter's slumber. 

While bears do enter a dormant state for several frosty months, their torpor is dissimilar to the true hibernation seen in smaller creatures like ground squirrels and bats.

In these animals, body temperature, metabolism, heart rate, and breathing all decrease significantly, slashing energy usage by up to 98 percent in some cases, eliminating the need to expend energy hunting or foraging.

Nevertheless, even in this state, the animal can still lose over a quarter of its body weight as it depletes its energy reserves.

Applying the same mathematics to a hibernating adult human, a daily food consumption of roughly 12,000 kilojoules would be supplanted by a requirement for just a few hundred kilojoules of body fat.

In this scenario, our hypothetical space traveler, snuggled in their specially-equipped bed, would shed just over six grams of fat daily. Over a year, this would sum up to approximately two kilograms of weight loss.

This might be fine for a rapid journey to the Jovian moons, but if the average adult wants to survive decades floating through interstellar space to a nearby star, they'd need to pack on an additional few hundred kilograms of fat. That, or routinely wake to throw back a lard milkshake or three.

These back-of-the-envelope calculations rely on many assumptions, not least of which is how hibernation might scale. After all, there's probably a good reason behind the scarcity of massive hibernating mammals our size (or larger).

So the researchers carried out a statistical analysis across a variety of hibernating species, as detailed in previous studies.

From this, they concluded the daily energy expenditure of hibernating animals scales in a fairly balanced way, so a gram of tissue from a tiny mammal, like the 25-gram leaf-eared bat, consumes as much energy as a gram of tissue from an 820-gram hibernating ground squirrel.

We could assume that if we ever worked out how to hibernate as efficiently as a dormouse, every gram of our tissue would require the same energy as every gram of theirs.

It's a different story when mammals are active, however. The scaling of the relationship between active metabolism and mass produces a slightly different graph that reveals a point at which hibernating doesn't really save a great deal of energy for bigger beasts.

That point is near our own mass, implying our total energy needs while hibernating aren't going to be significantly different from those while we're merely at rest.

This could be why bears don't really hibernate in the same way smaller animals +ùdo. And it also means for us humans, going to all the risk and trouble of cooling our bodies, dropping our heart rate and breathing, and artificially depressing our metabolism just might not give us the results we'd hope for.

If we want to save our boredom and keep from munching through the ship's supply of freeze-dried ice cream, we might as well binge The Expanse, take a bunch of sedatives, and doze our way to Mars.

Forcing humans to hibernate just isn't going to be worth the hassle.