If we want to live and work in space for long periods of time, we’ll need to conquer the
lack of gravity and its effects on the human body.
We’ll want to come up with some kind of artificial gravity.
Futurists imagine huge rotating space stations, but realistically there are strategies that
could provide artificial gravity for the times that we need it, and allow us to survive in
space forever.
Once again, science fiction has ruined our expectations about space exploration.
Star Wars, Star Trek, Aliens, you name it, they’ve got magic gravity holding their
feet to the floor.
Special nod to The Martian and Interstellar for trying to tackle it in a scientific way
with rotating structures.
But we don’t have magic, we’ve only got reality, and reality says that if you’re
in microgravity, you’re going to be floating around.
NASA Astronaut Scott Kelly spent 340 days on the International Space Station studying
the effects of long duration spaceflight.
When Kelly’s Soyuz capsule landed in the steppes of Kazakhstan, he was once again in
the gravitational embrace of Earth.
As he took his first few steps, it was clear that walking had become immensely difficult
for him.
His legs didn’t do what he needed them to do any more.
Over the next few hours, he became stronger and more coordinated, but still weak.
The lack of gravity had done a number on his sense of balance and coordination.
Thanks to the hours of daily exercise, Kelly had minimized the amount of bone and muscle
loss, but only gravity can prevent vision problems, an impaired sense of balance, and
redistribution of fluid in the body.
And when we travel to space to live, not just a for a year but for decades, and maybe even
generations, we’re going to need to supply our own gravity.
Until the Pandoran unobtanium mines are at full capacity, the only way we know to generate
artificial gravity is through rotation, thanks to centripetal force.
In fact, if you’ve ever ridden the Gravitron at the fair, you know what it’s like to
experience artificial gravity.
And if you’ve thrown up moments after getting off that nightmarish whirligig, you know full
well what the downsides can be.
What work is being done to figure out practical artificial gravity?
What kinds of structures make the most sense?
Do we need to go big?
Could we go small?
When you’re standing on Earth, you’re being accelerated downwards at 9.8 meters
per second per second.
Of course, the Earth itself is pushing back at you, so you don’t go anywhere.
That’s the force of gravity that you feel.
Rotation can provide the same force.
Think about what it’s like to be in a car going around a tight corner.
The car is turning, but you want to keep going in a straight line, so you feel a force pushing
you sideways.
You’re experiencing circular acceleration.
To experience artificial gravity, all you need to do is stand on the inside of a spinning
cylinder and let this circular acceleration mimic the force of gravity.
The distance from the center of rotation changes the amount of gravity you experience.
If the size of the rotating spacecraft is too small, then you’ll be experiencing different
gravity between your head and your feet.
And that’s where the nausea sets in.
Samantha Glassner recently wrote an article for Nu Sci where she crunched the numbers
for the Endurance spacecraft in Interstellar.
You know, that cool rotating wheel with all the modules on it.
According to Glassner, it has a radius of 29.3 meters.
If it was turning fast enough to give an astronauts 1g at their feet, they’d experience about
0.93g at their heads.
This would cause blood to flow from their head to their feet, and cause light headedness
and other problems.
You wouldn’t want to raise a generation of children in this kind of gravity.
You want to go bigger.
In 2001: A Space Odyssey, the rotating space station in the beginning of the movie is apparently
300 meters across, which means that it turns 1.7 times per second.
This would give inhabitants roughly 1g with minimal differences in gravity, from your
feet to your head.
The problem is, that space station is enormous.
To build structures like that would require a launch capacity we can barely comprehend.
Let’s do some quick mass.
According to a few sources, the mass of Space Station V is 68,000 tonnes.
The upcoming BFR will have the ability to put 150 tonnes into low Earth orbit.
In other words, you’d need about 450 launches of the BFR, to put the gear into orbit to
build the station.
And I know, we could get all that metal from asteroids, and the Moon, and so on, but this
is a long term goal after we’ve got a huge space infrastructure going.
Right now, we’ve got microgravity, and we know their are health downsides.
Can we improve on that?
Back in the 1960s, NASA’s Langley Research Center built the Rotating Space Station Simulator.
It was a 12-meter diameter ring that spun around between 3 and 10.5 rpm.
This gave subjects between 5 and 75% the force of gravity.
They were supported against the force of gravity by cables, and then asked to perform various
functions.
Above 0.3 g was uncomfortable with a big gravity difference between the head and the feet.
And over the next few decades, there were many papers produced on the subject, with
different ranges of suggested artificial gravities.
In general, though between 1 and 6 rotations per minute seemed to be the best speed.
Beyond 6 rotations a minute, there’d need to be too much vomit cleanup duty.
But maybe not, more on that in a minute.
The big question is, how much gravity do we need?
We know we evolved in Earth gravity, but can we handle less?
The bare minimum seems to be 20% to provide enough friction to be even able to walk around.
30% gives you the minimum amount of gravity to be able to pick up objects and move around
a work environment performing various tasks that astronauts would want to be able to do.
And over the decades, researchers have argued about exactly which of these is the right
amount for each task, whether it’s walking around, working, climbing ladders, operating
a P-5000 work loader, or fighting off xenomorphs.
If you wanted to actually generate full Earth gravity, where the space station is rotating
about twice a minute, you’d need a space station with a radius of about 225 meters.
Again, just for comparison, the orbiting ring in 2001: A Space Odyssey was 280 meters.
So that movie was surprisingly accurate.
The biggest version of this idea, is the O’Neill cylinder, proposed by the Physicist Gerard
K. O’Neill.
Built from material mined from the Moon and asteroids, O’Neill cylinders would have
a radius of 4 km, with a length of 32 km.
The whole cylinder would be set spinning, providing artificial gravity on the inside.
With a radius this large, very few people would experience any kind of motion sickness,
but you might be able to detect the rotation turning your head back and forth, or while
running around.
But again, if Space Station X would keep the BFRs at full capacity for the next few decades,
you don’t want to know how much it would take to make an O’Neill colony.
So let’s ask another question.
What will keep us healthy?
How much gravity do we need to survive for long periods in space?
Would we be willing to give up comfort for artificial gravity that helps us deal with
the health factors that only gravity can handle: vision, balance and fluid redistribution?
We’ll look at prototypes for that, but first I’d like to thank:
Tom Cliffe Torben Bellstrøm
Teton Saltes Joseph Hart
Jesús Bergasa López Jon Dillon
David Malone Ken Hodges
Mike Osbon
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Maybe we can’t live and work in full artificial gravity, but maybe we can spend some time,
to counter the negative effects of microgravity.
Space agencies have proposed tiny centrifuges that would provide periods of artificial gravity.
Right now, astronauts spend hours every day exercising.
Perhaps they could do both at the same time, experience artificial gravity while they work
out.
One idea that’s quite developed is called Nautilus-X, a module or even an entire space
station that would provide periods of artificial gravity for astronauts on long duration space
journeys.
The station would have a main module, 6.5 meters by 14 meters, similar to a module on
the International Space Station, But then it would be surrounded by a rotating habitable
centrifuge.
The astronauts would work in microgravity, but then spend time resting and sleeping in
the centrifuge, experiencing between 51 and 69% Earth gravity.
The initial proposal for a demonstration project would cost about $3.7 billion and could be
completed in 5 years.
Of course, the project was proposed back in 2011, and hasn’t gone any further since
then, which seems like a real shame to me.
This seems like a natural improvement to the Deep Space Gateway.
But recently, engineers from Boeing wondered, how small could you go?
Could you put people in just a chair, spin them up and prevent the dangers of microgravity?
First, they wanted to find out if humans could become accustomed to the nausea inducing effect
of differential gravity.
In other words, if you just spin and spin and spin, will you eventually stop feeling
sick?
At a test facility at University of Colorado Boulder, they trained subjects to adapt to
a spinning chair.
Over the course of 10 days, subjects went from 1.75 RPM to 17.8 RPM.
This corresponds to whirling around in a centrifuge with a radius of only 4 meters.
Which means that you could fit this module into various existing rocket fairings, like
the Falcon 9, and send a small module to the International Space Station.
With a radius this small, you could have a centrifuge with enough room for a rowing machine
or treadmill.
An astronaut would then be able to perform their daily exercise while also experiencing
artificial gravity.
They’d be doing 15 RPM to experience 1g, which the preliminary research showed that
astronauts should become accustomed to.
For a Mars mission, they proposed building a centrifuge with a 5-meter radius of rotation.
Two astronauts could be in the centrifuge at a time, balancing each other out.
To truly live and work in space for long periods of time, we’ll want to create comfortable
artificial gravity.
But to just survive and counteract the negative effects of weightlessness, it’s surprising
to see just how small a centrifuge is required.
It’s not hard to imagine every long duration space mission including a relatively small
centrifuge.
Even colonies on other worlds like the Moon or Mars could have a centrifuge that colonists
spend time in to help simulate the pull of gravity.
It might be a hassle, but it looks like practical artificial gravity is well within our reach.
And it’s a technology we’ll need to crack if we want to live and work in space for much
longer.
Well, what do you think, would you be willing to spend a few hours a day in the spin cycle
if that meant being able to live in space or on another world?
Let me know your thoughts in the comments.
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