We’ve spent a few episodes on the Guide to Space talking about just how difficult
it’s going to be to travel to other stars.
Sending tiny unmanned probes across the vast gulfs between stars is still mostly science
fiction.
But to send humans on that journey?
That’s just a level of technology beyond comprehension.
For example, the nearest star is Proxima Centauri, located a mere 4.25 light years away.
Just for comparison, the Voyager spacecraft, the most distant human objects ever built
by humans, would need about 50,000 years to make that journey.
I don’t know about you, but I don’t anticipate living 50,000 years.
No, we’re going to want to make the journey more quickly.
But the problem, of course, is that going more quickly requires more energy, new forms
of propulsion we’ve only starting to dream up.
And if you go too quickly, mere grains of dust floating through space become incredibly
dangerous.
Based on our current technology, it’s more likely that we’re going to have to take
our time getting to another star.
And if you’re going to go the slower route, you’ve got a couple of options.
Create a generational ship, so that successive generations of humans are born, live out their
lives, and then die during the hundreds or even thousands of year long journey to another
star.
Imagine you’re one of the people destined to live and die, never reaching your destination.
Especially when you look out your window and watch a warp ship zip past with all those
happy tourists headed to Proxima Centauri, who were start enough to wait for warp drives
to be invented.
No, you want to sleep for the journey to the nearest star, so that when you get there,
it’s like no time passed.
And even if warp drive did get invented while you were asleep, you didn’t have to see
their smug tourist faces as they zipped past.
Is human hibernation possible?
Can we do it long enough to survive a long-duration spaceflight journey and wake up again on the
other side?
Before I get into this, we’re just going to have to assume that we never merge with
our robot overlords, upload ourselves into the singularity, and effortlessly travel through
space with our cybernetic bodies.
For some reason, that whole singularity thing never worked out, or the robots went on strike
and refused to do our space exploration for us any more.
And so, the job of space travel fell to us, the fragile, 80-year lifespanned mammals.
Exploring the worlds within the Solar System and out to other stars, spreading humanity
into the cosmos.
Come on, we know it’ll totally be the robots.
But that’s not what the science fiction tells us, so let’s dig into it.
We see animals, and especially mammals hibernating all the time in nature.
In order to be able survive over a harsh winter, animals are capable of slowing their heart
rate down to just a few beats a minute.
They don’t need to eat or drink, surviving on their fat stores for months at a time until
food returns.
It’s not just bears and rodents that can do it, by the way, there are actually a couple
of primates, including the fat-tailed dwarf lemur from Madagascar.
That’s not too far away on the old family tree, so there might be hope for human hibernation
after all.
In fact, medicine is already playing around with human hibernation to improve people’s
chances to survive heart attacks and strokes.
The current state of this technology is really promising.
They use a technique called therapeutic hypothermia, which lowers the temperature of a person by
a few degrees.
They can use ice packs or coolers, and doctors have even tried pumping a cooled saline solution
through the circulatory system.
With the lowered temperature, a human’s metabolism decreases and they fall unconscious
into a torpor.
But the trick is to not make them so unconscious that they die.
It’s a fine line.
The results have been pretty amazing.
People have been kept in this torpor state for up to 14 days, going through multiple
cycles.
The therapeutic use of this torpor is still under research, and doctors are learning if
it’s helpful for people with heart attacks, strokes or even the progression of diseases
like cancer.
They’re also trying to figure out if there are any downsides, but so far, there don’t
seem to be any long-term problems with putting someone in this torpor state.
In a moment, I’m going to talk about a project that NASA is actually considering to test
out if this therapeutic hypothermia will be useful for long duration human spaceflight,
but first I’d like to thank Donald Jackson, Mike and Sherri Reed, Andrew Wasko, and the
rest of our 743 patrons for their generous support.
If you love what we’re doing and want to get in on the action, head over to patreon.com/universetoday
A few years ago, SpaceWorks Enterprises delivered a report to NASA on how they could use this
therapeutic hypothermia for long duration spaceflight within the Solar System.
Currently, a trip to Mars takes about 6-9 months.
And during that time, the human passengers are going to be using up precious air, water
and food.
But in this torpor state, SpaceWorks estimates that the crew will a reduction in their metabolic
rate of 50 to 70%.
Less metabolism, less resources needed.
Less cargo that needs to be sent to Mars.
The astronauts wouldn’t need to move around, so you could keep them nice and snug in little
pods for the journey.
And they wouldn’t get into fights with each other, after 6-9 months of nothing but day
after day of spaceflight.
We know that weightlessness has a negative effect on the body, like loss of bone mass
and atrophy of muscles.
Normally astronauts exercise for hours every day to counteract the negative effects of
the reduced gravity.
But SpaceWorks thinks it would be more effective to just put the astronauts into a rotating
module and let artificial gravity do the work of maintaining their conditioning.
They envision a module that’s 4 metres high and 8 metres wide.
If you spin the habitat at 20 revolutions per minute, you give the crew the equivalent
of Earth gravity.
Go at only 11.8 RPM and it’ll feel like Mars gravity.
Down to 7.8 and it’s lunar gravity.
Normally spinning that fast in a habitat that small would be extremely uncomfortable as
the crew would experience different forces at different parts of their body.
But remember, they’ll be in a state of torpor, so they really won’t care.
Current plans for sending colonists to Mars would require 40 ton habitats to support 6
people on the trip.
But according to SpaceWorks, you could reduce the weight down to 15 tons if you just let
them sleep their way through the journey.
And the savings get even better with more astronauts.
The crew probably wouldn’t all sleep for the entire journey.
Instead, they’d sleep in shifts for a few weeks.
Taking turns to wake up, check on the status of the spacecraft and crew before returning
to their cryosleep caskets.
What’s the status of this now?
NASA funded stage 1 of the SpaceWorks proposal, and in July, 2016 NASA moved forward with
Phase 2 of the project, which will further investigate this technique for Mars missions,
and how it could be used even farther out in the Solar System.
Elon Musk should be interested in seeing their designs for a 100-person module for sending
colonists to Mars.
In addition, the European Space Agency has also been investigating human hibernation,
and a possible way to enable long-duration spaceflight.
They have plans to test out the technology on various non-hibernating mammals, like pigs.
If their results are positive, we might see the Europeans pushing this technology forward.
Can we go further, putting people to sleep for decades and maybe even the centuries it
would take to travel between the stars?
Right now, the answer is no.
We don’t have any technology at our disposal that could do this.
We know that microbial life can be frozen for hundreds of years.
Right now there are parts of Siberia unfreezing after centuries of permafrost, awakening ancient
microbes, viruses, plants and even animals.
But nothing on the scale of human beings.
When humans freeze, ice crystals form in our cells, rupturing them permanently.
There is one line of research that offers some hope: cryogenics.
This process replaces the fluids of the human body with an antifreeze agent which doesn’t
form the same destructive crystals.
Scientists have successfully frozen and then unfrozen 50-milliliters (almost a quarter
cup) of tissue without any damage.
In the next few years, we’ll probably see this technology expanded to preserving organs
for transplant, and eventually entire bodies, and maybe even humans.
Then this science fiction idea might actually turn into reality.
We’ll finally be able to sleep our way between the stars.
Obviously, I’d like to know, would you do it?
Would you get into a device that allowed you to sleep through the journey to a distant
world or star system?
I’d love to know your thoughts in the comments.
In the next episode, we look at some newly announced missions to Uranus and Neptune.
That’s right, I’m going to talk about sending a probe to Uranus to study its gas.
Time for another playlist, so you can dig much deeper into this really interesting topic.
First up, a cool video about hibernating bears.
Not sure if it’s super useful, but aww, look at those baby bears sleeping.
An episode on the topic from SciShow.
A report from the Wall Street Journal about NASA’s hibernation plans.
And finally, two lectures from researchers in the field of human hibernation.
Would you get into a device that allowed you to sleep through the journey to a distant
world - oh, let's go back.