Yes! It's easy indeed. We could test such a spacecraft with a simple inexpensive addition to the Soyuz launcher. At least inexpensive compared with typical costs for human spaceflight. Just adds kgs to the launch mass.
The key to this is the observation that every time we launch a spacecraft with humans on board - we also launch a final stage rocket - which also goes into orbit - for a while at least.
So - attach a tether to the final stage - and we already know how to do that - Joe Carroll who proposed the idea is responsible for many of the space tethers already sent up into space.
And set them spinning around a common centre of gravity and you get this:
And - remarkably - we could test this idea on the way to the ISS, with no extra fuel.
The idea behind this is - when you launch to the ISS - then you actually launch into a lower orbit first, a lower faster orbit - and - at least in the older missions - they used to spend several days "catching up" with the ISS in the lower orbit before they did the rendezvous.
And they still have enough supplies to do this as they were forced to do it earlier this year because of a mishap.
So - during those days when the Soyuz is playing "catch up" - you can tether it to the final stage - and instead of boosting it to a higher orbit - you do cleverly chosen rocket boosts at just the right point in the orbit and spin to spin it up more and more - while also boosting the orbit just enough to get it out of the lower Earth atmosphere.
And then - it turns out - remarkably - that you can recover all that fuel by releasing the tether at the right moment to go to the ISS.
The Soyuz then heads for the ISS - and the final stage goes to a controlled re-entry in the S. Pacific - another minor bonus as final stages don't have controlled re-entries at present - but just orbit until they re-enter - usually over the Northern Hemisphere (there isn't likely to be much left of them after re-entry so isn't a big deal but it is a nice minor bonus).
And - well they launch with a bit of extra fuel anyway to take account of weather conditions and unknowns - so when you get to orbit you might well have enough fuel left to do the entire experiment anyway even without that fuel recovery. So might do it so that you only actually do the experiment if you have that extra margin.
So that even if the tether broke at exactly the wrong moment (unlikely) sending the Soyuz back towards a lower orbit - it would still have enough fuel to make up those extra few meters per second again and rendezvous with the ISS.
For many details, including:
The big unknown here is, what spin rates can humans tolerate? And what "gravity prescription" do we need for health in space?
If we can tolerate quite fast spin rates in artificial gravity situations - then you could have a much shorter tether.
If we only need an hour or so of artificial g a day to be healthy - and can tolerate fast spin rates like 30 rpm for an hour - then you could even just have a spinning hammock type arrangement inside a spaceship to supply your artificial gravity.
Something like this (my own sketch)
Shows the two possible orientations for a hammock spinning for artificial gravity inside of a space station - if it turned out that this was enough for health and humans can tolerate the spin rate.
For some reason neither NASA, nor ESA, nor Russia have shown any interest at all in trying out these experiments in space - though there have been many ground based experiments.
Russia did do an experiment with rats in space - put them in a centrifuge - and it did improve their health - but for some reason - nobody ever followed that up with humans.
And Joe Carroll suggested his final stage tether spin experiment way back in the times of Space Shuttle. He eventually wrote his paper on the subject when he realised that NASA was not going to fly his experiment, probably never in his professional lifetime.
Perhaps when we get private space flight, they will be more adventurous and try out these ideas?
There are other ideas as well. Of course the big wheel shaped spaceships of science fiction. Also the Nautilus X sleeping compartment - it's the big wheel shaped area in this design - it's just large enough for a human in a spacesuit to crawl into it (for safety reasons for the early tests)
But all these ideas and designs - they are made on the basis of - not knowing much at all about
One uncontrolled experiment, a Gemini spin which you can see about 19 minutes into this video of the out of control Gemini 8
The astronauts did get sick after that - still - they survived - and you could probably learn to tolerate it with time - just as people get used to sea sickness. Ground experiments show that exposure to fast spins even just three sessions is enough to make a dramatic difference there.
And - nowadays (not then) they train astronauts to withstand spinning just in case anyone gets in a situation like that again
And as well as that there is evidence from the early SkyLab experiments - that our inner ears, which are what make us feel sick and giddy - they behave rather differently in space conditions - basically - because there is no constant pull of gravity acting along the spin axis as there is in e.g. horizontal centrifuges on Earth.
The astronauts in Skylab were able to tolerate spinning and rocking motions that they couldn't tolerate on the ground either before or after their flight. But sadly - that was just testing short duration rocking motions and short spins rather than e.g. an hour or two of fast spinning of the type you'd need for a "personal centrifuge" inside of a space station.
So - personally I think it's reasonably promising that you might not even need to tether two spacecraft together - or a spacecraft with its final stage - but might just need spinning hammocks inside of a space station.
Oh and BTW there are a few people get born with a defect in their ear - which has no other effect except that they do not get dizzy or nauseous when they spin. So they at least could surely tolerate high spin rate short arm centrifuges for full gravity in space conditions.
Anyone like that could presumably go on long distance interplanetary flights with no more than a small spinning centrifuge in their spaceships for all their artificial gravity needs.
I think myself that probably many people will be able to learn to tolerate them - much like sailors learning to tolerate living permanently at sea which makes most people sea sick and most people also get over their sea sickness after a few days.
Whatever - we can only speculate at present as the experiment has never been done.
But - even if it turns out we need full gravity 24/7 - and need to have long multiple kilometer tethers - even that isn't hard to achieve. Doesn't even add that much mass to the mission. Kgs maybe tens or hundreds of kilograms, not tons.
I find it strange myself - that with so much data available that suggests that it is likely that artificial gravity could be an easy and inexpensive way to avoid zero gravity sickness - that for some reason - nobody has done the low cost experiments you need to do to test it.
We could have done these experiments any time from the late 1960s onwards. Could have done it before Apollo - and they were thinking at one point about maybe having spinning spacecraft for artificial gravity - but they found that astronauts could withstand a few days at least of zero g no problem so wasn't needed.
But technically - they had everything that was needed to do a tether experiment way back in the 1960s and certainly by the 1970s - they even did a couple of gemini tether experiments - but no follow ups on them - just showed that you can tether two spacecraft together and set them spinning - but only span them fast enough for a tiny amount of micro-gravity too little to have noticeable effects.
It would be easy for us to do it. The Gemini tether experiment was added to the next mission within a few months of thinking up the idea.
We could probably do a tether experiment based on Joe Carroll's idea on one of the next few human missions to the ISS - if there was the political will and interest to do it.
Of course there is always a lot of politics involved in human spaceflight. For something innovative like this I imagine there would be dozens of "hoops" to jump through before it gets approved, and lots of people to convince, somehow, that it is worth trying.
For some reason, human spaceflight has become rather unadventurous since Apollo. All they do is keep sending astronauts up to Low Earth Orbit over and over - and find out more and more data about how zero gravity affects humans.
And - had no missions to explore
It's not expense or difficulty or technical problems - I don't think that is really the handicap here.
For artificial gravity especially - that just needs a willingness to be adventurous and try out new ideas, these are probably amongst the lowest cost experiments you could do with the highest potential return relevant to the future of human spaceflight.
And for many years, it seems, there's just been no interest in doing them.
Crew Tether Spin For Artificial Gravity On Way To ISS - Stunning New Videos - Space Show Webinar - Sunday
Could Spinning Hammocks Keep Astronauts Healthy in Zero g?
And for background - and discussion of early ideas for spinning habitats see
USING FINAL STAGE AS COUNTERWEIGHT - OPPORTUNITY TO DO THIS ON EVERY HUMAN FLIGHT INTO SPACE
The key to this is the observation that every time we launch a spacecraft with humans on board - we also launch a final stage rocket - which also goes into orbit - for a while at least.
So - attach a tether to the final stage - and we already know how to do that - Joe Carroll who proposed the idea is responsible for many of the space tethers already sent up into space.
And set them spinning around a common centre of gravity and you get this:
And - remarkably - we could test this idea on the way to the ISS, with no extra fuel.
The idea behind this is - when you launch to the ISS - then you actually launch into a lower orbit first, a lower faster orbit - and - at least in the older missions - they used to spend several days "catching up" with the ISS in the lower orbit before they did the rendezvous.
And they still have enough supplies to do this as they were forced to do it earlier this year because of a mishap.
So - during those days when the Soyuz is playing "catch up" - you can tether it to the final stage - and instead of boosting it to a higher orbit - you do cleverly chosen rocket boosts at just the right point in the orbit and spin to spin it up more and more - while also boosting the orbit just enough to get it out of the lower Earth atmosphere.
JOE CARROLL'S CLEVER IDEA LETS YOU DO IT WITH NO EXTRA FUEL
And then - it turns out - remarkably - that you can recover all that fuel by releasing the tether at the right moment to go to the ISS.
The Soyuz then heads for the ISS - and the final stage goes to a controlled re-entry in the S. Pacific - another minor bonus as final stages don't have controlled re-entries at present - but just orbit until they re-enter - usually over the Northern Hemisphere (there isn't likely to be much left of them after re-entry so isn't a big deal but it is a nice minor bonus).
And - well they launch with a bit of extra fuel anyway to take account of weather conditions and unknowns - so when you get to orbit you might well have enough fuel left to do the entire experiment anyway even without that fuel recovery. So might do it so that you only actually do the experiment if you have that extra margin.
So that even if the tether broke at exactly the wrong moment (unlikely) sending the Soyuz back towards a lower orbit - it would still have enough fuel to make up those extra few meters per second again and rendezvous with the ISS.
DETAILS OF JOE CARROLL'S IDEA
For many details, including:
- Motivation for the mission - the zero g health issues
- How you make sure it gets enough solar power during the spin
- What happens if the tether gets broken by a micro-meteorite or space debris
- How to be sure that the mission is safe for crew and for ISS no matter what happens to the tether
WHAT IS THE GRAVITY PRESCRIPTION FOR HUMAN HEALTH - AND ACCEPTABLE SPIN RATES?
The big unknown here is, what spin rates can humans tolerate? And what "gravity prescription" do we need for health in space?
If we can tolerate quite fast spin rates in artificial gravity situations - then you could have a much shorter tether.
If we only need an hour or so of artificial g a day to be healthy - and can tolerate fast spin rates like 30 rpm for an hour - then you could even just have a spinning hammock type arrangement inside a spaceship to supply your artificial gravity.
Something like this (my own sketch)
HAS BEEN NO INTEREST AT ALL IN EXPERIMENTING IN ARTIFICIAL GRAVITY IN SPACE - EXCEPT FOR A SMALL EXPERIMENT DONE BY RUSSIA WITH RATS MANY YEARS AGO
For some reason neither NASA, nor ESA, nor Russia have shown any interest at all in trying out these experiments in space - though there have been many ground based experiments.
Russia did do an experiment with rats in space - put them in a centrifuge - and it did improve their health - but for some reason - nobody ever followed that up with humans.
And Joe Carroll suggested his final stage tether spin experiment way back in the times of Space Shuttle. He eventually wrote his paper on the subject when he realised that NASA was not going to fly his experiment, probably never in his professional lifetime.
WILL PRIVATE SPACEFLIGHT BE MORE ADVENTUROUS HERE?
Perhaps when we get private space flight, they will be more adventurous and try out these ideas?
OTHER IDEAS - NAUTILUS X
There are other ideas as well. Of course the big wheel shaped spaceships of science fiction. Also the Nautilus X sleeping compartment - it's the big wheel shaped area in this design - it's just large enough for a human in a spacesuit to crawl into it (for safety reasons for the early tests)
THINGS WE DON'T KNOW ANYTHING ABOUT
But all these ideas and designs - they are made on the basis of - not knowing much at all about
- What level of gravity is best for human health (full g, Martian g, Lunar g)
- How much gravity you need a day for health (one hour, several hours, a few minutes, has to be 24/7)
- What spin rates humans can tolerate (some say 1-3 rpm, some think you can tolerate 24 or 30 rpm at least for an hour or so a day)
THE UNCONTROLLED GEMINI 8 SPIN
One uncontrolled experiment, a Gemini spin which you can see about 19 minutes into this video of the out of control Gemini 8
The astronauts did get sick after that - still - they survived - and you could probably learn to tolerate it with time - just as people get used to sea sickness. Ground experiments show that exposure to fast spins even just three sessions is enough to make a dramatic difference there.
And - nowadays (not then) they train astronauts to withstand spinning just in case anyone gets in a situation like that again
EARLY SKYLAB EVIDENCE SUGGESTS WE MAY BE ABLE TO TOLERATE SPINNING IN SPACE BETTER THAN ON EARTH
And as well as that there is evidence from the early SkyLab experiments - that our inner ears, which are what make us feel sick and giddy - they behave rather differently in space conditions - basically - because there is no constant pull of gravity acting along the spin axis as there is in e.g. horizontal centrifuges on Earth.
The astronauts in Skylab were able to tolerate spinning and rocking motions that they couldn't tolerate on the ground either before or after their flight. But sadly - that was just testing short duration rocking motions and short spins rather than e.g. an hour or two of fast spinning of the type you'd need for a "personal centrifuge" inside of a space station.
So - personally I think it's reasonably promising that you might not even need to tether two spacecraft together - or a spacecraft with its final stage - but might just need spinning hammocks inside of a space station.
PEOPLE WHO CAN'T GET DIZZY OR NAUSEOUS BECAUSE OF AN INNER EAR DEFECT
Oh and BTW there are a few people get born with a defect in their ear - which has no other effect except that they do not get dizzy or nauseous when they spin. So they at least could surely tolerate high spin rate short arm centrifuges for full gravity in space conditions.
Anyone like that could presumably go on long distance interplanetary flights with no more than a small spinning centrifuge in their spaceships for all their artificial gravity needs.
LEARNING TO TOLERATE HIGH SPIN RATES LIKE SAILORS GETTING USED TO ROCKING MOTIONS AT SEA
I think myself that probably many people will be able to learn to tolerate them - much like sailors learning to tolerate living permanently at sea which makes most people sea sick and most people also get over their sea sickness after a few days.
Whatever - we can only speculate at present as the experiment has never been done.
EVEN IF WE NEED FULL GRAVITY 24/7 - IS NOT DIFFICULT OR PARTICULARLY EXPENSIVE TO DO
But - even if it turns out we need full gravity 24/7 - and need to have long multiple kilometer tethers - even that isn't hard to achieve. Doesn't even add that much mass to the mission. Kgs maybe tens or hundreds of kilograms, not tons.
I find it strange myself - that with so much data available that suggests that it is likely that artificial gravity could be an easy and inexpensive way to avoid zero gravity sickness - that for some reason - nobody has done the low cost experiments you need to do to test it.
WE COULD HAVE DONE THESE EXPERIMENTS AT ANY TIME IN THE LAST 50 YEARS AND MORE
We could have done these experiments any time from the late 1960s onwards. Could have done it before Apollo - and they were thinking at one point about maybe having spinning spacecraft for artificial gravity - but they found that astronauts could withstand a few days at least of zero g no problem so wasn't needed.
But technically - they had everything that was needed to do a tether experiment way back in the 1960s and certainly by the 1970s - they even did a couple of gemini tether experiments - but no follow ups on them - just showed that you can tether two spacecraft together and set them spinning - but only span them fast enough for a tiny amount of micro-gravity too little to have noticeable effects.
EASY TO DO IT NOW, COULD DO IT WITHIN MONTHS IF THERE WAS THE POLITICAL WILL TO GIVE IT A GO
It would be easy for us to do it. The Gemini tether experiment was added to the next mission within a few months of thinking up the idea.
We could probably do a tether experiment based on Joe Carroll's idea on one of the next few human missions to the ISS - if there was the political will and interest to do it.
Of course there is always a lot of politics involved in human spaceflight. For something innovative like this I imagine there would be dozens of "hoops" to jump through before it gets approved, and lots of people to convince, somehow, that it is worth trying.
For some reason, human spaceflight has become rather unadventurous since Apollo. All they do is keep sending astronauts up to Low Earth Orbit over and over - and find out more and more data about how zero gravity affects humans.
And - had no missions to explore
- Closed system habitats - and using algae and plants to generate oxygen etc (Russia did experiments on algae for oxygen generation on the ground - and they were promising - got all the oxygen needed just from the algae - but never flew them into space).
- Artificial gravity - no serious attempt to explore this in space
- Travel further away from Earth than LEO - a mission to the L2 position at far side of the Moon for instance would be an interesting - not that demanding expedition for humans - very safe, easy to return to Earth - none of the hazards of a human landing on the Moon - but never been done. Never mind return to the Moon
It's not expense or difficulty or technical problems - I don't think that is really the handicap here.
For artificial gravity especially - that just needs a willingness to be adventurous and try out new ideas, these are probably amongst the lowest cost experiments you could do with the highest potential return relevant to the future of human spaceflight.
And for many years, it seems, there's just been no interest in doing them.
Crew Tether Spin For Artificial Gravity On Way To ISS - Stunning New Videos - Space Show Webinar - Sunday
Could Spinning Hammocks Keep Astronauts Healthy in Zero g?
And for background - and discussion of early ideas for spinning habitats see
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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