Artificial Gravity: punctuated gravity using a centrifuge

[nixter]

 Has it been considered that long term, low gravity induced problems could be addressed with punctuated high gravity using a small on-board centrifuge? It may be discovered that being subjected to very high G's for a short time every 24 hours may counter the effects of long-term exposure to micro gravity. One hour in a centrifuge at two G's would strengthen the body against the negative effects of micro-gravity. I know that the idea of on-board centrifuges is nothing new, but has the idea of brief punctuated bursts of high g’s been considered? The experience would probably be unpleasant and space travelers would learn to dislike them because high G’s are generally considered to be stressful and uncomfortable, but if some basic research on the ISS or elsewhere were to show that this works to counteract micro gravity, it might be worth it. I did a search on punctuated high gravity and did not find anything similar but I know that anything I can think of has probably already been thought of by several people, but I presented the idea here just in case it has not.
 Pre-conditioning space travelers in high gravity environments for some time before a mission begins would also probably help in resisting the negative effects of micro-gravity environments. Elon Musks Hyperloop technology could be used to make a very large centrifuge by constructing a large circular track with a ¹/₄ to1 mile diameter, people would live in these modules for long periods of time and the g's would be slowly increased incrementally as the occupants adjusted to the conditions. Athletes would use these as conditioning units for upcoming strenuous events and they would probably give them an advantage that would be eventually be considered unfair because of the results. It would be interesting to see how a human would adjust to the high G conditions after becoming conditioned to them and also interesting to see how they would feel and react when first reintroduced to one G conditions. I read somewhere that mice subjected to high G’s over long periods of time are at first unable to move around freely, but then they adjust and move about as they would under normal gravity. If this is true, humans should be able to adjust to these high gravity conditions also, especially if the process takes place over several weeks or perhaps even longer periods of time.
 

[speedevil]

Has it been considered that long term, low gravity induced problems could be addressed with punctuated high gravity using a small on-board centrifuge? It may be discovered that being subjected to very high G's for a short time every 24 hours may counter the effects of long-term exposure to micro gravity.

This isn't the sort of thing that can be actually tested without testing it in full-up tests.

You can't meaningfully extrapolate between intermittent high and 1G, and intermittent high and 0G meaningfully, when the behaviour you are interested in occurs pretty much only between 0 and 1G.

It's the sort of research that needs done, but the investment needed to do it is huge, and can mostly be hand-waved away as un-needed, given the effects of going from 0G for 6 months to a year to 1G are well known, and the reasonable assumption that Mars would be less bad.
For the return journey, pretty much all that needs to happen performance-wise to the crew is for them not to die.

[Slarty1080]

Why not just let them sleep in a 1g environment? Being fairly still and level they shouldn't suffer quite as many side effects from the rotation.

[guckyfan]

Why not just let them sleep in a 1g environment? Being fairly still and level they shouldn't suffer quite as many side effects from the rotation.

What would this be good for? Lying in bed on earth is used as a reasonable emulation of microgravity for medical tests.

Gravity needs to be used for exercise. Plus toilet facilities would profit a lot from it.

[dglow]

Why not just let them sleep in a 1g environment? Being fairly still and level they shouldn't suffer quite as many side effects from the rotation.

What would this be good for? Lying in bed on earth is used as a reasonable emulation of microgravity for medical tests.

Gravity needs to be used for exercise. Plus toilet facilities would profit a lot from it.

If spending 7-8 hrs/day in a centrifuge mitigated the vision impairment some experience, that alone would make it worthwhile.

[nixter]

This isn't the sort of thing that can be actually tested without testing it in full-up tests.
You can't meaningfully extrapolate between intermittent high and 1G, and intermittent high and 0G meaningfully, when the behaviour you are interested in occurs pretty much only between 0 and 1G.
It's the sort of research that needs done, but the investment needed to do it is huge, and can mostly be hand-waved away as un-needed, given the effects of going from 0G for 6 months to a year to 1G are well known, and the reasonable assumption that Mars would be less bad.
For the return journey, pretty much all that needs to happen performance-wise to the crew is for them not to die.

 Just as I thought, there may still be hope because space X has relatively unconventional research and development processes, they may find a way to invest in this type of research to determine whether or not it is viable.  It may be that the gravity environment on Mars is insufficient to support basic human health norms, if that is the case there will need to be some type of artificial gravity used on an ongoing basis to maintain bone health etc. etc.  if human beings are going to be traveling back-and-forth between Mars and earth in a continuous stream of missions, then our low gravity problems will have to be solved.  In the end most of these problems can be boiled down to one element, money. Space missions in general rarely have enough funding to provide truly robust, large space born equipment, one of the exceptions being the ISS. Perhaps with a planned space station between earth and the moon or a moon base, spaceX, utilizing the BFR will be able to assemble a large spaceship capable of having a huge built-in centrifuge like in 2001 a space Odyssey, that would solve the problem nicely.  This type of spaceship would always remain in space traveling between Mars the moon or the earth.  Of course this solution is obvious, but unattainable because of the lack of funding needed.

[guckyfan]

I have a different idea. Just go to Mars and see what happens. Make expensive plans when they are needed.

[Lampyridae]

Has it been considered that long term, low gravity induced problems could be addressed with punctuated high gravity using a small on-board centrifuge?

...
 

Yes, it has been considered. There are many studies on the topic stretching back to the 90s.

1997: (using intermittent standing, walking as a substitute for AG)
https://www.ncbi.nlm.nih.gov/pubmed/11540676

2018: (gender differences in reactions to intermittent short-radius centrifugation)
https://www.frontiersin.org/articles/10.3389/fphys.2018.00716/full

Basically, it works for a lot of things. Until we get some data from actual spaceflight though, we're not 100% sure how effective.

And as mentioned, centrifuge for toilets would also be great. Going to the loo in zero g is a nasty affair.

I'm not sure how this thread is SpaceX related, though. Unless you want to propose a centrifuge to stick inside a BFS perhaps.

[JulesVerneATV]

Immune System Changes During Space Travel Could Affect Aging on Earth

https://www.spacedaily.com/reports/Immune_System_Changes_During_Space_Travel_Could_Affect_Aging_on_Earth_999.html

[InterestedEngineer]

Immune System Changes During Space Travel Could Affect Aging on Earth

https://www.spacedaily.com/reports/Immune_System_Changes_During_Space_Travel_Could_Affect_Aging_on_Earth_999.html

I don't see how they controlled for lack of immune system stimulation.

The space station is a sterile-as-possible monoculture.

Lack of stimulation by new foreign agents is as bad for an immune system as lack of exercise is for muscles.

They have a mechanistic explanation on the change in immune cell shape, but I think they are missing something just as important as the difficulty of exercise in zero-G.

[edzieba]

Immune System Changes During Space Travel Could Affect Aging on Earth

https://www.spacedaily.com/reports/Immune_System_Changes_During_Space_Travel_Could_Affect_Aging_on_Earth_999.html

I don't see how they controlled for lack of immune system stimulation.

It's an in vitro study.

[punder]

I have a different idea. Just go to Mars and see what happens. Make expensive plans when they are needed.

Had this capability been developed 10 or 20 years ago, as Gary Hudson intended, it would have been quite useful. You’re correct—now, the intermediate data points on the g curve will come from surface stays on the Moon and Mars. Even if someone started a well-funded centrifuge program today, it’d be obsolete before its launch.

[StraumliBlight]

Had this capability been developed 10 or 20 years ago, as Gary Hudson intended, it would have been quite useful. You’re correct—now, the intermediate data points on the g curve will come from surface stays on the Moon and Mars. Even if someone started a well-funded centrifuge program today, it’d be obsolete before its launch.

Starlab (launching NET Late 2028) may incorporate a crew centrifuge, as its based on Airbus's modular LOOP concept.

[zubenelgenubi]

Topic moved to Advanced Concepts.

[mikelepage]

The reason I don't like the punctuated gravity idea is that it presumes that biomedical problems are the only ones we're solving with spin G.

Constant (or near-constant) spin G of some sort will save money by removing the necessity to redesign for microgravity, every machine or process which deals with any kind of fluid. The initial upfront investment is dwarfed by the ongoing development costs of not doing it. Plus, non-medical human factors issues are going to be the long pole in getting the general public to actually *want* to settle space.

[Lampyridae]

The reason I don't like the punctuated gravity idea is that it presumes that biomedical problems are the only ones we're solving with spin G.

Constant (or near-constant) spin G of some sort will save money by removing the necessity to redesign for microgravity, every machine or process which deals with any kind of fluid. The initial upfront investment is dwarfed by the ongoing development costs of not doing it. Plus, non-medical human factors issues are going to be the long pole in getting the general public to actually *want* to settle space.

Plus, some people just do not cope well with microgravity. Even a short-radius, low rpm centrifuge might be enough to relieve that.

[edzieba]

The reason I don't like the punctuated gravity idea is that it presumes that biomedical problems are the only ones we're solving with spin G.

Constant (or near-constant) spin G of some sort will save money by removing the necessity to redesign for microgravity, every machine or process which deals with any kind of fluid. The initial upfront investment is dwarfed by the ongoing development costs of not doing it. Plus, non-medical human factors issues are going to be the long pole in getting the general public to actually *want* to settle space.

The caveat there is that the rotation or spin system then becomes a critical system element. If the structure has to be spun down or rotation stopped, then those acceleration-dependant systems either need a microgravity-operation fallback mode (that incurs the costs you are trying to avoid), or a redundant microgravity backup system to be carried anyway.

[acksed]

This is a chance to mention a recent favourite finding in space medicine: take a bungee cord to simulate Lunar-gravity, and a 10m-wide, 5m-tall Wall of Death, to make a circular vertical track that would allow the runner to experience Earth-normal G-forces when running:

https://royalsocietypublishing.org/doi/10.1098/rsos.231906

Essentially, the high dynamic loading of the footstrike when a Lunar wall-runner makes contact reconditions the muscles and bones. They compare volunteers who, when confined to bed for 60 days, underwent 48 sessions of jump training over that time and managed to avoid most of the negative consequences.

The preliminary conclusion is that 8-9 laps of the track per day, split into two sessions, should be enough.

'Proper' centrifuges will need working out, but a circular hab with a running track on the wall could be built now.

[Twark_Main]

Again the "proper" effective solution for Mars or the Moon (vs a Starship or space colony) is just to use wearable weights.

And no, despite the prematurely confident objections of certain fiction writers, it doesn't really matter that weights don't perfectly reproduce 1 g exercise. It's "close enough," and at 1/1000th the cost of more....   fanciful approaches.   

Even on space colonies I expect — after humans get over our initial infragravity phobia — it will be common to see designs with something like 25-50% gravity, with the rest "made up for" (on an as-needed basis) by using wearable weights + more traditional exercise regimens similar to current countermeasures.

[Paul451]

Constant (or near-constant) spin G of some sort will save money by removing the necessity to redesign for microgravity, every machine or process which deals with any kind of fluid.

The caveat there is that the rotation or spin system then becomes a critical system element. If the structure has to be spun down or rotation stopped, then those acceleration-dependant systems either need a microgravity-operation fallback mode (that incurs the costs you are trying to avoid), or a redundant microgravity backup system to be carried anyway.

No. During despin, you only need lossy/storage-based short-duration zero-g life-support systems. Similar to what is on a capsule, say 5-7 day maximum duration. During spin, you have your long-term, low-loss, complex recycling/ & processing systems. The complex systems only need to have a shut-down state that is safe in zero-g, they don't need to operate in zero-g.

(And even the stored waste from the short-duration zero-g systems can be transferred into the more complex recycling systems, once back under spin.)

[Paul451]

after humans get over our initial infragravity phobia

What a bizarre comment.

[edzieba]

Again the "proper" effective solution for Mars or the Moon (vs a Starship or space colony) is just to use wearable weights.

And no, despite the prematurely confident objections of certain fiction writers, it doesn't really matter that weights don't perfectly reproduce 1 g exercise. It's "close enough," and at 1/1000th the cost of more....   fanciful approaches.   

Even on space colonies I expect — after humans get over our initial infragravity phobia — it will be common to see designs with something like 25-50% gravity, with the rest "made up for" (on an as-needed basis) by using wearable weights + more traditional exercise regimens similar to current countermeasures.

Unless you can add training weights to your eyeballs or to individual cells, that doesn't help all that much with the known microgravity health issues and introduces a whole slew of new problems (reduced 'weight' coupled with increased inertia).

The issues with 'just add weights' are well known and nothing to do with obliquely referred to 'fiction writers'.

[Twark_Main]

add training weights to your eyeballs

That's what the 25-50% gravity is for, obviously.   

I included large error bars because we don't (yet) know exactly what level of gravity is required to counter fluid effects.

a whole slew of new problems (reduced 'weight' coupled with increased inertia)

There are no "new problems" with inertia. As I said it's not an exact reproduction of 1g, but that's okay.

In some ways it's actually better that it's not a perfect simulation, because you don't need to alter your lean angle (which is very different on Earth vs the Moon!) when wearing vs not wearing the weights. This makes it less likely for "mode confusion" to cause stumbling and falling.

The issues with 'just add weights' are well known and nothing to do with obliquely referred to 'fiction writers'.

Don't tell me. Tell that to the person who "authoritatively" quoted a certain fiction writer (either Azimov or Clarke) the last time this came up. I don't have the link handy but you can search the forum.

[Twark_Main]

after humans get over our initial infragravity phobia

What a bizarre comment.

If you have any sort of argument, then please do make it.

The phobia I mention is very real, and it's on full display whenever the subject comes up here. Edzieba and his stealthily-made assumption above that "my eyeballs must need extra countermeasures for anything less than 99.9% gravity" is one example.  I think it's highly telling that his reply wasn't something like "hey I think you need 60% gravity for eyeballs instead of 50%," it was just an automatic freak-out absurd strawman the moment he saw anything lower than 1g. 

Last I checked the fluid effects are mitigated even at "merely" Mars gravity. By setting my error bars up to 50% I was being generous, actually. 


Anyway it's O/T for punctuated gravity, but I just want to give a little "fast forward" to the filthy impure compromise solution that's probably the ultimate winner (at least in certain space habitat niches). Carry on.

[Greg Hullender]

Rotating habitats are high on my list of technologies that I wish had more research funding. There are all kind of questions we needs answers to, including coping with instability, finding out how much gravity is really needed for long-term health and for reproduction, and how much Coriolis force people can handle without getting sick. There are clever ground-based experiments that give us some ideas, but we won't really know most of these until some experiments can be done in space.

[Twark_Main]

Rotating habitats are high on my list of technologies that I wish had more research funding. There are all kind of questions we needs answers to, including coping with instability, finding out how much gravity is really needed for long-term health and for reproduction, and how much Coriolis force people can handle without getting sick. There are clever ground-based experiments that give us some ideas, but we won't really know most of these until some experiments can be done in space.

I don't think anyone would argue with more funding.

But we should be clear — and I'm sure you understand this, but for the benefit of others — when we utter the requirement "without being sick," after it passes through the lens of real-world economics, it comes out the other side as "with you getting a little (non-zero amount of) sick, but not sick enough that the cost so incurred is greater than the cost of further reducing Coriolis forces."

We shouldn't expect perfection. We shouldn't expect utopia. We should expect a compromise solution that minimizes total cost.

[mikelepage]

after humans get over our initial infragravity phobia

What a bizarre comment.

If you have any sort of argument, then please do make it.

The phobia I mention is very real, and it's on full display whenever the subject comes up here. Edzieba and his stealthily-made assumption above that "my eyeballs must need extra countermeasures for anything less than 99.9% gravity" is one example.  I think it's highly telling that his reply wasn't something like "hey I think you need 60% gravity for eyeballs instead of 50%," it was just an automatic freak-out absurd strawman the moment he saw anything lower than 1g. 

Last I checked the fluid effects are mitigated even at "merely" Mars gravity. By setting my error bars up to 50% I was being generous, actually. 


Anyway it's O/T for punctuated gravity, but I just want to give a little "fast forward" to the filthy impure compromise solution that's probably the ultimate winner (at least in certain space habitat niches). Carry on.

Geez Twark, if you want people to give you credit for having nuanced thinking, you might give the same courtesy to others instead of being so quick to dismiss it as faith or phobia. The rationale for arguing for full gravity becomes clear through study of molecular biology or other biological sciences. Even the simplest bacterial cell is - objectively - many orders of magnitude more complex than any machine ever devised. When a complex system is in an equilibrium state, and is demonstrably prone to chaotic, emergent behaviour when pushed out of that state, it's not a leap of faith or phobia to make "let's just keep it in that state" your default hypothesis.

One can argue that a full 100% of G might be best whilst also accepting the economic rationale that partial-G spin gravity demonstrators will be more cost-effective in the near term. That said, I won't be surprised if the "most effective G level" - all costs considered - is a lot closer to 100% of G than most on this forum would believe or hope for.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G for many generations to come. Evolution is usually slow like that.

It makes sense to focus on the the mission/sortie level gravity spacecraft first though, for biomedical reasons, for critical equipment R&D reasons, and also for commercial/tourism reasons, so in the near-term I'll continue to argue for focussing on Mars-G level platforms in LEO.

[Twark_Main]

Geez Twark, if you want people to give you credit for having nuanced thinking, you might give the same courtesy to others instead of being so quick to dismiss it as faith or phobia. The rationale for arguing for full gravity becomes clear through study of molecular biology or other biological sciences. Even the simplest bacterial cell is - objectively - many orders of magnitude more complex than any machine ever devised. When a complex system is in an equilibrium state, and is demonstrably prone to chaotic, emergent behaviour when pushed out of that state, it's not a leap of faith or phobia to make "let's just keep it in that state" your default hypothesis.

Exactly, it's not a leap of faith. It's by definition phobia to make "zero risk or cost should be tolerable" the default. This design path is unlikely to be optimal because it's the most extremely conservative option along the entire design spectrum (see #8).

In around 1956 there were real scientific questions about whether cellular machinery would simply shut down in microgravity, and astronauts would spontaneously die. This risk was tested by launching various small animals on sounding rockets, and later on orbital flights.

There are biological impacts from spaceflight, but nowadays these are far better known than this chaos theory talk seems to suggest.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G

I actually agree with your conclusion, even if we may disagree on theory.  The total cost of motion sickness (in terms of lost business) is vastly greater on a 1,000-room LEO space hotel serving 200,000+ guests annually, as compared to a crew of 9 serving an 18-month maintenance deployment interval.

[edzieba]

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

[Twark_Main]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

[Twark_Main]

Unless by best practice you were referring to literally the best, ie luxury level accommodations.  In that case yes, you're going to pull out all the stop, and it will be priced to match!   

[edzieba]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

That's a lot of straw-manning there.

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there, rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

[Greg Hullender]

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there, rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

We also have lots of data about zero-g, which is short-term good but medium-term bad. Because we're looking at sending missions to Mars, it makes a great deal of sense to prioritize testing 1/3 g habitats. If there are long-term problems at 1/3 g, the sooner we know that the better.

I do think we can all agree that 1/3 g should be better than zero-g, right? (Assuming the Coriolis force isn't terrible.)

[Paul451]

Pushing back towards the topic:

Does anyone know of any research (presumably animal research), that has tested for any benefits from "preloading" adaptation to hypergravity before a flight on Skylab/STS/MIR/ISS?

Example protocol: Throw batches of mice/fish/insects/whatever into a >1g centrifuge for 1, 2, 4 weeks before launch, along with a non-centrifuged control group. Fly all four groups to a space-station (or Shuttle "lab" mission), for a stay in micro-g, then return to Earth for comparison. Does "preloading" produce protection against micro-g-adaptation damage? Does it delay onset of micro-g damage? If either/both, does increases preloading time increase the protection/delay? Or does adaptation to higher-g just make adaptation to micro-g worse?

[Lampyridae]

One can argue that a full 100% of G might be best whilst also accepting the economic rationale that partial-G spin gravity demonstrators will be more cost-effective in the near term. That said, I won't be surprised if the "most effective G level" - all costs considered - is a lot closer to 100% of G than most on this forum would believe or hope for.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G for many generations to come. Evolution is usually slow like that.

It makes sense to focus on the the mission/sortie level gravity spacecraft first though, for biomedical reasons, for critical equipment R&D reasons, and also for commercial/tourism reasons, so in the near-term I'll continue to argue for focussing on Mars-G level platforms in LEO.

Instead of a linear curve, it's looking like a collection of peaks and troughs that are all over the place. It's exceedingly complex.

T cells respond within 20s to altered gravity by altering their gene activations.

A study using a random positioning machine to mimic microgravity, Moon and Mars gravity, plus irradiation (X-ray and/or carbon ion) showed wildly different results. They measured levels of IL-2, a key "alarm signal" protein for the immune system to respond to infection, as well as its genetic activation (ie its production capability) in T cells.

Without irradiation, the Moon showed less IL-2 gene activation than Mars. Weirdly, Moon and microgravity were shown as protective against X-rays compared to 1g. (The 1µM refers to the addition of 1µM of hydrocortisol as a simulation of stress)

edit: link and reference
https://www.mdpi.com/1422-0067/24/23/16943

Miranda S, Vermeesen R, Radstake WE, Parisi A, Ivanova A, Baatout S, Tabury K, Baselet B. Lost in Space? Unmasking the T Cell Reaction to Simulated Space Stressors. International Journal of Molecular Sciences. 2023; 24(23):16943. https://doi.org/10.3390/ijms242316943

[Lampyridae]

Pushing back towards the topic:

Does anyone know of any research (presumably animal research), that has tested for any benefits from "preloading" adaptation to hypergravity before a flight on Skylab/STS/MIR/ISS?

Example protocol: Throw batches of mice/fish/insects/whatever into a >1g centrifuge for 1, 2, 4 weeks before launch, along with a non-centrifuged control group. Fly all four groups to a space-station (or Shuttle "lab" mission), for a stay in micro-g, then return to Earth for comparison. Does "preloading" produce protection against micro-g-adaptation damage? Does it delay onset of micro-g damage? If either/both, does increases preloading time increase the protection/delay? Or does adaptation to higher-g just make adaptation to micro-g worse?

I do recall that there is research looking at rebound after long-term hypergravity exposure which seems to mimic micro- or partial gravity effects somewhat. In other words, it would just make the situation worse. Cellular adaptation to different g-loads happens within minutes, so that side of things wouldn't benefit. You effectively always get hyper-g loading before a transition to micro-g. (This might explain some short-term quirks of space adaptation)

[StraumliBlight]

NASA have put out a Request for Information for SpinSat.

SpinSat is a comprehensive and flexible approach to Mars-relevant science & technology development activities.

Goal: Develop beyond-LEO multi-payload platform to provide transit-to-Mars and Mars-surface gravity-plus-radiation environments for science experiments, model validation, technology development, & risk reduction. Objectives include:

Frequent access to Mars-relevant (BLEO) space via a launch-vehicle-and orbit-agnostic platform
Use of “cubesat standard” interfaces enabling broad participation in experiments by academics, commercials, and OGA

[Paul451]

Cool.

(Though more on-topic in the Testbeds thread.)

[Twark_Main]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

That's a lot of straw-manning there.

"Straw-manning is a synonym for miscommunication, except now it's your fault." 

Maybe consider the possibility that you are not fully understanding the other person's point,  Has the concept ever once had cause to cross your mind?  Or were you too busy reaching for your book "Debate Words For People Who Are Super Popular At Parties"? 

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there

Again, this is really "most timid practices." So it is indeed "best" in extremely risk-intolerant environments.  You're half right!

If the US with its current old guard is the leader in space, I do expect the field will remain extremely (paralyzingly?) risk intolerant. However it's a self-correcting problem, because it means we won't be the leader for long. 



Anyway, real space programs have proven to be far more risk tolerant than this thread would have you believe. Did you know they've sometimes been operating with (gasp!) no artificial gravity at all??  The horror!!!

(in case it isn't obvious, what I'm saying is that your ultra-conservative risk posture in this thread is an extreme extreme outlier back in the real world)

rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

We seem to be talking about two different, but related, things.

You're talking about the process. "How do you get there from here?" You imagine a maximally timid path sure, but at least there's some arguable justification.

I'm talking about the result. "Where will we eventually end up?" We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

The idea that at the end of the process we will eventually end up at exactly 1 G (not even 90%, etc) is rather unlikely, regardless of whether you follow the reasoning.   

[Paul451]

Maybe consider the possibility that you are not fully understanding the other person's point,  Has the concept ever once had cause to cross your mind?  Or were you too busy reaching for your book "Debate Words For People Who Are Super Popular At Parties"? 

Is all this relevant to whether or not there's a benefit from punctuated gravity using a centrifuge?

[edzieba]

Pointless insults ignored.

So it is indeed "best" in extremely risk-intolerant environments.

Human spaceflight is such a risk-intolerant environment. Even SpaceX, the poster-child for moving-fast-and-breaking-things development, progress cautiously for their human spaceflight program. Lack of prudence in that environment is a good way to go from a rapid development programme to a stopped-dead development programme.

[Twark_Main]

So it is indeed "best" in extremely risk-intolerant environments.

Human spaceflight is such a risk-intolerant environment. Even SpaceX, the poster-child for moving-fast-and-breaking-things development, progress cautiously for their human spaceflight program. Lack of prudence in that environment is a good way to go from a rapid development programme to a stopped-dead development programme.

Anticipated and addressed. My very next paragraph was:

If the US with its current old guard is the leader in space, I do expect the field will remain extremely (paralyzingly?) risk intolerant. However it's a self-correcting problem, because it means we won't be the leader for long. 

Anyway, there's also a big difference between the kinds of (real) risks SpaceX is mitigating and the type of "risks" you're hand-wringing about in this thread. SpaceX is mitigating mountains, while you're moaning over molehills.

Astronauts will certainly be fine in 90% gravity, probably extending to <50% gravity, and perhaps punctuated gravity. Astronauts won't be fine if they blow up in a huge fireball on launch. SpaceX is very cleverly focusing on the latter, and avoiding wasted time on the former.

The same trade-off applies for punctuated gravity, hypogravity, or punctuated hypogravity. 

"In nature, the optimum is almost always in the middle somewhere. Distrust assertions that the optimum is at an extreme point." Constant 1G lies at one extreme end of the (biomedically motivated) AG spectrum.

[Coastal Ron]

...
I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children.

While I have no evidence to support my assumptions, what you articulated is my current assumption for what the predominate future rotating space station population will look like, and for the mission/sortie-level gravity I am gambling that Mars level gravity will become that standard, since if Elon Musk can start Mars colonization there will be a huge amount of medical science focused on keeping humans healthy in Mars gravity.

Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G for many generations to come. Evolution is usually slow like that.

Yes, as of today, for rotating space stations, I am assuming that Mars level gravity stations will be for work assignments, and Earth level gravity stations will be for long term living in space.

It makes sense to focus on the the mission/sortie level gravity spacecraft first though, for biomedical reasons, for critical equipment R&D reasons, and also for commercial/tourism reasons, so in the near-term I'll continue to argue for focussing on Mars-G level platforms in LEO.

I agree!

As for punctuated gravity for mitigating the effects of low gravity, I would suggest a second option. That instead of having a spin facility on a rotating space station that only produces far less than Earth gravity, you could have a second rotating "facility" stationed nearby where inhabitants of the rotating space station could go periodically for "gravity boosts".

And as already been stated, this idea might be worthy of testing out on a future artificial gravity testbed.

[Twark_Main]

Another part edzieba seems to have misclassified and forgotten to address (it's certainly no "insult"):

We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

Again the point I'm making applies to punctuated gravity, hypogravity, or a combination. In all cases you're trading off vehicle cost for the cost of accepting some biomedical impact, impact which can be compensated for in other (cheaper) ways  — eg scheduled exercise, body-worn weights, pharmaceuticals, etc

[Twark_Main]

As for punctuated gravity for mitigating the effects of low gravity, I would suggest a second option. That instead of having a spin facility on a rotating space station that only produces far less than Earth gravity, you could have a second rotating "facility" stationed nearby where inhabitants of the rotating space station could go periodically for "gravity boosts".

I don't get it.  If you need a second station anyway, why bother with low gravity at all? Just make it microgravity, instead of this "split baby" where you have all the design costs of spinning and you still need a second station with traffic between them. Seems like the worst (costliest) of both worlds.

Of course if you want, it's easy to have a higher-G "room" as part of a lower-G station. No centrifuge required. You just put your G Recovery Facility on the end of a long stick.   

[edzieba]

Another part edzieba seems to have misclassified and forgotten to address (it's certainly no "insult"):

We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

Again the point I'm making applies to punctuated gravity, hypogravity, or a combination. In all cases you're trading off vehicle cost for the cost of accepting some biomedical impact, impact which can be compensated for in other (cheaper) ways  — eg scheduled exercise, body-worn weights, pharmaceuticals, etc

Aircraft do not evacuate to altitude and then occasionally pressurise up to 1 Bar during flight. The fatigue cycles from ascent and descent pressurisation cycles are already the lifetime limiter for the airframe, so regular spinup/spindown would also apply new loads and lifetime fatigue constrains to space station structures.

[redneck]

Another part edzieba seems to have misclassified and forgotten to address (it's certainly no "insult"):

We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

Again the point I'm making applies to punctuated gravity, hypogravity, or a combination. In all cases you're trading off vehicle cost for the cost of accepting some biomedical impact, impact which can be compensated for in other (cheaper) ways  — eg scheduled exercise, body-worn weights, pharmaceuticals, etc

Depending on a lot of factors, it's possible that the exercise, weights, etc, could be more expensive than some level of spin gravity. What is the individuals time worth on that vehicle/station? Times how many man-hours per year for the extra workouts and such. Say thirty people times an extra hour a day for mitigation gets somewhere close to 10,000 man hours per year to offset the unfortunate effects. Probably still cheaper to have them doing the weights and exercise, but still a factor to consider.

I find it disturbing that the ISS crews have to spend so much of their time on maintenance of the station and themselves. It would seem to me that informed development going forward should have ships/stations with more focus on getting jobs done than just keeping it together.

[Lampyridae]

Another part edzieba seems to have misclassified and forgotten to address (it's certainly no "insult"):

We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

Again the point I'm making applies to punctuated gravity, hypogravity, or a combination. In all cases you're trading off vehicle cost for the cost of accepting some biomedical impact, impact which can be compensated for in other (cheaper) ways  — eg scheduled exercise, body-worn weights, pharmaceuticals, etc

Depending on a lot of factors, it's possible that the exercise, weights, etc, could be more expensive than some level of spin gravity. What is the individuals time worth on that vehicle/station? Times how many man-hours per year for the extra workouts and such. Say thirty people times an extra hour a day for mitigation gets somewhere close to 10,000 man hours per year to offset the unfortunate effects. Probably still cheaper to have them doing the weights and exercise, but still a factor to consider.

I find it disturbing that the ISS crews have to spend so much of their time on maintenance of the station and themselves. It would seem to me that informed development going forward should have ships/stations with more focus on getting jobs done than just keeping it together.

Not to mention making everyday tasks much simpler. Even with a small internal centrifuge, if you need to work on a piece of equipment you could do it there with a low spin setting. No need to find an anchor point to unscrew a panel. No need to worry about a loose bolt floating up your nose. No need to have velcro or duct tape everywhere to stick things to. I imagine it would increase productivity significantly.

[Twark_Main]

Another part edzieba seems to have misclassified and forgotten to address (it's certainly no "insult"):

We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

Again the point I'm making applies to punctuated gravity, hypogravity, or a combination. In all cases you're trading off vehicle cost for the cost of accepting some biomedical impact, impact which can be compensated for in other (cheaper) ways  — eg scheduled exercise, body-worn weights, pharmaceuticals, etc

Depending on a lot of factors, it's possible that the exercise, weights, etc, could be more expensive than some level of spin gravity. What is the individuals time worth on that vehicle/station? Times how many man-hours per year for the extra workouts and such.

"Some" level of gravity is what I advocate, yes. An informed and rational economic / engineering tradeoff, not a zealous compulsion to only accept solutions at one extreme of the spectrum.

I can see how the argument applies to scheduled exercise, certainly. I can't see how it substantially moves the needle on body-worn weights. That's one of their major advantages, in fact.


Without a time machine, in this thread we have two options: moan and lament the lack of biomedical data at punctuated gravity and/or infragravity, or speculate.  If intellectually risky and tenuous speculation (which accepts gravity lower than 1 G and punctuated instead of constant) is only met with conservativism and hand-wringing, might as well lock the thread now. 

[Paul451]

[...] not a zealous compulsion to only accept solutions at one extreme of the spectrum.
[...] is only met with conservativism and hand-wringing, might as well lock the thread now.

Jesus, dude, go outside.

[Twark_Main]

[...] not a zealous compulsion to only accept solutions at one extreme of the spectrum.
[...] is only met with conservativism and hand-wringing, might as well lock the thread now.

Jesus, dude, go outside.

Outside? Never heard of it. I live in Plato's Mom's Basement. With the ad hominem all settled, "Play the ball, not the man."

I didn't think "we should be allowed to actually discuss the thread topic instead of shutting down discussion in favor of constant 1G" would be so controversial. Let's discuss the topic rather than this.



...and don't call me Jesus!   

[mikelepage]

“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so. “ – Mark Twain

The great irony is that you're running afoul of your namesake's quote in this thread Twark.

The reason disproving a null hypothesis is part of standard scientific best practice, is because it forces you to prove first what you "know for sure". It's core tenet of modern scientific theory, so ignore it at your own risk.

I don't usually play the "I have a phd" card, but maybe in this case it will help - if only to give an example of how badly it can bite you in the ass when you ignore this principle. For me, it was having my phd take over a year longer than it really needed to, because we saved money by not testing the thing we were sure we knew. Long story short: our friends and colleagues gave us the wrong reagent - one that was *so* similar to the one we were expecting that we only found out later when we finally put it through a mass spec after over a year of weird results. That's when our colleagues had their wtf moment - realised all *their* stocks had been accidentally switched - and took another 8 months to remake it from scratch and send us a new batch.

In that case it was human error as a root cause of the weirdness, but it's not like nature isn't capable of giving us weird results all by itself (see the results Lampyridae linked above). The point stands regardless: the scientific validity of an approach - test the thing you think you know first - is a standard approach for good reasons, and answers a qualitatively different question from those considered in a trade study, like cost. It's why you get so many news headlines of scientists "proving" obvious things, to which the usual response is "well duh!" - the obvious thing is never the actual point of the study.

One important exception to this rule is when the initial trades make it clear that this approach is so expensive, that it's the difference between whether the experiment gets done at all or not. That's the only reason why I'm pushing the Mars-G approach first. If the entire history of science is any guide, we will get weird results we weren't expecting, and the definitive interpretation of those results will only come once we build the 1G control^#, but with some luck by that stage we'll be much faster/better/cheaper at building spin-G habitats, and we'll have made some money and answered some interesting questions in the smaller model.

^#Technically the perfect control would be a crewed space habitat that could implement *linear* 1G acceleration for weeks or months at a time, (allowing us to properly control for the difference between the space environment and Coriolis effects) but good luck with that 

[Twark_Main]

“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so. “ – Mark Twain

The great irony is that you're running afoul of your namesake's quote in this thread Twark.

The reason disproving a null hypothesis is...

This is basically the same misunderstanding I had with edzieba:

You're talking about the process. "How do you get there from here?"

I'm talking about the result. "Where will we eventually end up?"

The first is necessarily rigid, while the second is necessarily speculative.

One important exception to this rule is when the initial trades make it clear that this approach is so expensive...

My thinking precisely. It's weird that you're so vehemently...  agreeing with me.   

I too expect that Mars-G is probably a bit too low. Here I have been predicting (so please, no letters on epistemology or dead authors  ) that most cost-forward designs (which is the majority of all real-estate!) will eventually settle around 50% Earth gravity, with appropriate hybrid mitigations to match.

But I am confident that exactly 1 g is unlikely to be used for health reasons (other than the early experimental stations as mentioned), for the same boring rational economic reasons that commercial planes don't pressurize to the air pressure on the ground. There's always a trade-off.

^#Technically the perfect control would be a crewed space habitat that could implement *linear* 1G acceleration for weeks or months at a time, (allowing us to properly control for the difference between the space environment and Coriolis effects) but good luck with that 

True. The closest economical control environment would use an extremely long radius centrifuge, which is cheapest to build as a barbell (or even a tomahawk).

[mikelepage]

One important exception to this rule is when the initial trades make it clear that this approach is so expensive...

My thinking precisely. It's weird that you're so vehemently...  agreeing with me.   

That's the thing Twark, we're *all* largely on the same page regarding the pragmatic approach, but you've been misconstruing people's assertions that *ideally* we should start with a 1G control as saying that we *have* to do this, then combatively labelling it as hand-wringing and "infragravity phobia". Hence the complaints of straw-manning, and me calling you out on a lack of nuanced reading.

I'm just requesting better forum etiquette out of you really.

[Twark_Main]

you've been misconstruing people's assertions then combatively labelling it as "infragravity phobia".

Speaking of poor reading comprehension, my comment about "infragravity phobia" wasn't directed at any specific assertion made in this thread. I suggest going back and reading it again to understand the point I was making (vs your strawman).

And "hand-wringing?" That's because....  edzieba was hand-wringing. I stand by my accurate description.   


For the edification of any residual hand-wringers out there, here's a spoiler alert:

Will working in space destroy your body in the long-term? Yes.

Will we tolerate that? Yes. We'll tolerate it for the same reasons we tolerate it today with roughnecks on an oil derrick, roofers, plumbers, etc. These jobs already destroy your body, and working in space will be no different. Don't like this harsh reality? Tough. Not everyone can be born with "The Right Stuff."

Living in space is, of course, another matter. Then it simply boils down to how much you can afford. The equivalent of Elysium will be very nice, I'm sure.


This is why we shouldn't let perfect be the enemy of good when it comes to intermittent gravity. One day in the future we'll have all the biomedical data in front of us, and on that day we won't be choosing "there can be exactly zero health risks" for our final designs. In other words, the presence of non-zero biomedical risk is not a show-stopper, and we shouldn't treat it like one.

Hopefully it's clear now.  Let's move on, but we should keep this last point in mind.